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I had a debate with a person who believes in some kind of creativism, let's call it that way.
And in the middle of the "debate", an interesting question popped up.
What are evidences of "transition between species". Is there a fossil record that shows us the "transition". I googled it and it was pretty obscure subject.
I would like to answer that question and really it "hits" my beliefs.
People who think in creationism or think about species rigidly might have a bit problem with that, so let me describe an example:
When are humans "adult"? Legally, at 18 (or your national equivalent). However, everyone understand that people are becoming adult gradually. Sometimes, they "age" very quickly after some harsh experience (16 years old student who parties all days because parents pay for it vs 16 years someone whom father died and he has work to help feed his small sisters as family did depend on father's wage).
Now imagine that you don't have all this information, but very incomplete "images" or "screenshots" of this kind of development. There would be quite a mess from it. You have image of one kid at 13 who is still young, another kid at 19 who is partying, single image of this 16 year old adult who has to feed his family and image of 48 year old gentleman.
If you go with this mindset that most of species that ever lived you can't get and you are just guessing something from a few snapshots that are themselves incomplete as well (e.g. we often don't have whole skeleton but just single bone from a lot of species), your idea on what to expect will change. This is a first step. Then you need to realize that most of fossils that shows some transition do not form lineage, but instead branches that are related. Finally, when you understand this (and modify your expectations and "what to look at", you can take any relatively complete and well-studied set of fossils like human ones. On human lineage (with great apes), we can see gradual increase of brain and in the case of human, gradual decrease in size of jaw. Development of hip bone is nice as well as it shows gradual process of adaptation to upright walking.
Another line of examples, but again, you need to redefine your expectations, is to point on dogs. If we had dogs in our fossil records, there would be large amount of species, instead of one "dog" species.
Or you can just point out at plants and say that "species" does not really mean anything.
Evidence of Species Relations: Biology Lesson Plan Essay
Introduction:The topic of the lesson in Biology is “What Evidence Shows that Different Species Are Related?”. It is designed to support teachers and students through an educational process by providing clear instructions, objectives, material, and activities that can help 14-15-year-old students learn better the world of Biology and the variety of species that exist around.
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Key Concepts: Evolution, a variety of species, differences and similarities, the relationship between species, fossils.
Objectives:Students should demonstrate their communicative skills and abilities to comprehend how different species can be related students learn more about the evidence for evolution and discuss the material that has to observe students try to share their opinions and compare them before and after new material is offered students compare their predictions and analyze the results got.
Material: a video presentation is taken from youtube.com (11min, 21 sec) a table with a list of evidence for the connection between species several books that are required for reading, the cards with the evidence for evolution list.
Activities, Instructions, and Expectations: The following table introduces the activities that can be offered to students.
|Welcome to Evolution: Students are introduced with a topic||Students share their thoughts about evidence for evolution, what they know about evolution, which species they can identify.||Students develop their creative skills and clarify what they know and what they want to know.|
|Differences of Species: A teacher identifies the main aspects of the topic||Students listen to the teacher and make notes about evolution and a variety of species.||Students underline the main issues that can be discussed.|
|Evidence for Evolution: Part I: Students watch a video (“What Is the Evidence for Evolution”)||Students should make some notes to remember the main points in the list of evidence for evolution||Students listen to the information carefully and learn new simple facts about evolution.|
|Evidence for Evolution: Part II: Students discuss a video||Students share their opinions about the video watched and answer simple teacher’s questions.||Students demonstrate their analytical skills and their abilities to analyze new material in groups.|
|Cards with evidence:Students work with cards about evolution evidence||A teacher divides students into several groups and asks to introduce two different animals from different epochs that can be compared and related.||Students learn how to work in groups and develop their required portion of collective skills and share their knowledge on a topic.|
|Discussion||A teacher asks what has been studied and what students want to know more. Students share their opinions and repeat the main concepts learn during the class.||Students know how to use new material and analyze the teacher’s instructions.|
|Test||Students are offered to pass a quiz to check the level of understanding of a new topic.||Students learn from their mistakes and comprehend their weak and strong points.|
Assignment Details:At the end of the class, a teacher gives clear instructions for students to be followed. Students get their homework and the assignment to read several chapters from different books. Besides, it is offered to prepare a project on the basis of the evolution topic and the differences between species and the possibility to relate them. Students are divided into groups of two and develop projects on different animals that can be related.
Outcomes:Students have to be motivated to study deeper the process of evolution. There are many animals that can be compared and related. The question of evolution is open today, and students have to contribute to this question as well. A teacher is not only a guide. He/she is a mentor and a facilitator in a learning process.
Common Core Standards:These standards are created to provide students with help on how to learn the required skills and use them properly. The current lesson plan is developed for 9 th -grade students. It is possible to apply the standards that are developed by the California Department of Education in 2013. There are several standards that can be used in the plan under consideration.
- Students have to develop an explanation on the basis of evidence
- Students should create models to illustrate the organization of interacting systems
- Students should apply statistics and probability to support their explanations
- Students need to create simulations with the help of which they can test their solutions and understand the impact of biodiversity.
This information is analyzed and taken from “HS-LS4 Biological Evolution: Unity and Diversity” (California Department of Education, par.4).
Evidence of species transitions - Biology
NO EVIDENCE FOR EVOLUTION
Scientists' Research and Darwinism
Edited by Emerson Thomas McMullen, 2002
Science has many limitations, but probably its worst shortcoming involves history. For example, if scientists did not know about the Battle of Waterloo, a turning point in history, what could they tell us? If we showed them the battleground, they could dig up bones, teeth, spent bullets, some corroded weapons, and other miscellaneous items to analyze. But they could not tell us much about the battle itself. They could only guess at the most important thing: who won it. Similarly, in the Battle of Midway, a turning point in the Pacific War, four Japanese carriers were sunk: the Akagi, Hiryu, Kaga, Soryu, and one American: theYorktown. In 1998, Robert Ballard, the explorer who found the Titanic, searched for these carriers. All he found was the Yorktown. Based on this evidence, and without knowing any history, one might wrongly infer that the United States lost this battle.
These examples show just how poorly science handles history. The beginning of life and the origin of living things are historical events. They are not happening now and scientists cannot observe them. We have no time machine to ascertain what really occurred. Yet we find evolutionists claiming to have the correct insights into these important historical events. Many assert that we came from chemicals and evolved from a common ancestor. Are these assertions based on science, or a naturalistic worldview?
For a list of well-known scientists who dissent from Darwinism, click here: 100 dissenting scientists. Scientists on this list include Russell W. Carlson, Prof. of Biochemistry & Molecular Biology, U. of Georgia Jonathan Wells, PhD Molecular & Cell Biology-U.C. Berkeley Dean Kenyon, Prof. Emeritus of Biology, San Francisco State Marko Horb, Researcher, Dept. of Biology & Biochemistry, U. of Bath Tony Jelsma, Prof. of Biology, Dordt College Siegfried Scherer, Prof. of Microbial Ecology, Technische Universität München Marvin Fritzler, Prof. of Biochemistry & Molecular Biology, U. of Calgary, Medical School Lennart Moller, Prof. of Environmental Medicine, Karolinska Inst., U. of Stockholm Matti Leisola, Prof., Laboratory of Bioprocess Engineering, Helsinki U. of Technology Richard Sternberg, Invertebrate Zoology, National Museum of Natural History, Smithsonian Institute (2002).
Let us first consider the origin of life. It is not happening today. If life arose in the past only from various chemicals, we have to ask two questions: 1. "How did a very complex molecule, DNA, occur when the best that can happen naturalistically is for chemicals to form amino acids?" 2. "Even given DNA, how did we obtain the intricate genetic information it contains from chemicals, which have no genetic information at all?" How does something come from nothing? Are evolutionists calling for miracles here, under the name of science? There is no genetic information in chemicals to mutate and no genetic information to undergo natural selection - mutation and natural selection being two mainstays of current evolutionary thinking. Also, there is no process that scientists know of, whereby amino acids naturally form DNA. Given these considerations, how can any clearly thinking person claim that we came from only chemicals? Yet some people do, so it would seem that their faith in a naturalistic worldview overrides reason. For more on this click here: Problems with Chemical Origin of Life Theories.
Now let us consider the origin of living things. In evolution, the debated issue is the idea of descent from a common ancestor. Suppose we are given a simple common ancestor as a starting point. What is the source of the new genetic information for the alleged advance to more complex life forms? A mutation or adaptation just shuffles around the existing information that already resides in the DNA. Thus, we might find a two-headed snake (a shuffle of information), but never a winged snake (new genetic information). That is why there are no fish with feet in the fossil record. Fish carry no genetic information for feet. The idea of descent from a common ancestor predicts fish with feet, but there are none in reality. Scientists have found millions and millions of fossil fish, but not one with feet.
What we have noted about fish applies to other animals as well. It is no wonder that, amongst the billions of fossils we know about, scientists have found no clear-cut transitional forms. The idea of descent from a common ancestor is testable, but is found wanting. Again, evolutionists are calling for a miracle in the name of science and their faith overrides their reason. At present, there are two types of evolutionary ideas, Neo-Darwinism and Punctuated Equilibrium.
Many evolutionists today are Neo-Darwinists and so this article deals mostly with them. However, a few subscribe to Punctuated Equilibrium, an evolutionary theory proposed by Niles Eldredge and the late Stephen J. Gould. Here is two scientists' criticism of Punctuated Equilibrium:
In the past 25 years, Eldredge and Gould have proposed so many different versions of their theory that it is difficult to describe it with any accuracy. If a scientific theory is to be of any value as a tool for exploring the real world, it must have some stability as a set of propositions open to empirical test. Punctuated equilibrium has undergone so many transformations that it is hard to distinguish its core of truth from the "statement that morphological evolution sometimes occurs episodically."
The above quotation by Jerry A. Coyne and Brian Charlesworth, Department of Ecology and Evolution, University of Chicago, appeared in Science, Volume 276, Number 5311, 18 April 1997, pp. 337-341. Their point is that Punctuated Equilibrium is not testable. One criterion of science is that theories have to be testable, otherwise they are not scientific. So according to this criterion and to Coyne, Punctuated Equilibrium is not a scientific idea.
Simply stated, Neo-Darwinism is the gradual origin of species from a common ancestor by natural selection of chance mutations. (Theistic evolution introduces God into this otherwise naturalistic process.) The idea fails because of the fossil record shows none of the predicted transitional forms but rather reveals the complexity and diversity of the early animal forms. Additionally, these forms have no precursors according to the fossil record. This has always been a problem for Darwinism and Neo-Darwinism from its inception until now. The following are what scientists have said about this in somewhat reverse chronological order:
Some General Examples
Paleontologist Alan Cheetham, a gradualist evolutionist, summed up decades of his own research: "I came reluctantly to the conclusion that I wasn't finding evidence for gradualism." Reported by R.A. Kerr in "Did Darwin Get It All Right?" Science 276:1421, 10 March 1995.
". . . no human has ever seen a new species form in nature." Steven M. Stanley, The New Evolutionary Timetable (New York: Basic Books, Inc., 1981), p. 73.
"There are no fossils known that show what the primitive ancestral insects looked like, . . . . Until fossils of these ancestors are discovered, however, the early history of the insects can only be inferred." Peter Farb, The Insects, Life Nature Library (New York: Time Incorporated, 1962), pp. 14-15
."Thus so far as concerns the major groups of animals, the creationists seem to have the better of the argument. There is not the slightest evidence that any one of the major groups arose from any other. Each is a special animal complex related, more or less closely, to all the rest, and appearing, therefore, as a special and distinct creation." Austin H. Clark, "Animal Evolution," Quarterly Review of Biology, Vol. 3, No. 4, December 1928, p. 539.
"When we descend to details, we can prove that no one species has changed nor can we prove that the supposed changes are beneficial, which is the groundwork of the theory [of evolution]." Charles Darwin, The Life and Letters of Charles Darwin, Vol. 2, editor Francis Darwin (New York: D. Appleton and Co., 1898), p. 210
No Transitional Forms
"But the curious thing is that there is a consistency about the fossil gaps: the fossils go missing in all the important places. When you look for links between major groups of animals, they simply aren't there at least, not in enough numbers to put their status beyond doubt. Either they don't exist at all, or they are so rare that endless argument goes on about whether a particular fossil is, or isn't, or might be, transitional between this group or that." [emphasis in original] Francis Hitching, The Neck of the Giraffe: Where Darwin Went Wrong (New Haven Ct,:Ticknor and Fields, 1992) p. 19. (See my articleThe Coelacanth, Living Fossils, and Evolution).
There is no fossil record establishing historical continuity of structure for most characters that might be used to assess relationships among phyla." Katherine G. Field et al., "Molecular Phylogeny of the animal Kingdom," Science, Vol. 239, 12 February 1988, p. 748.
Evolutionists believe that amphibians evolved into reptiles, with either Diadectes or Seymouria as the claimed transition. Actually, by the evolutionist's own time scale, this "transition" occurs 35 million years (m.y.) after the earliest reptile, Hylonomus (a cotylosaur). A parent cannot appear 35 million years after its child! The scattered locations of these fossils also present problems for the evolutionist. [See Steven M. Stanley, Earth and Life Through Time (New York: W.H. Freeman and Co., 1986), pp. 411-415. See also Robert H. Dott, Jr. and Roger L. Batten, Evolution of the Earth, 2nd edition (New York: McGraw-Hill, 1976), p. 311.
"And let us dispose of a common misconception. The complete transmutation of even one animal species into a different species has never been directly observed either in the laboratory or in the field." Dean H. Kenyon (Professor of Biology, San Francisco State University), affidavit presented to the U.S. Supreme Court, No. 85-1513, Brief of Appellants, prepared under the direction of William J. Guste, Jr., Attorney General of the State of Louisiana, October 1985, p. A-16.
"The fact that all the individual species must be stationed at the extreme periphery of such logic [evolutionary] trees merely emphasized the fact that the order of nature betrays no hint of natural evolutionary sequential arrangements, revealing species to be related as sisters or cousins but never as ancestors and descendants as is required by evolution." [emphasis in original] Michael Denton, Evolution: A Theory in Crisis, London: Barnett Books, 1985, p. 132
". . . there are no intermediate forms between finned and limbed creatures in the fossil collections of the world." G.R. Taylor, The Great Evolution Mystery, ( N.Y: Harper and Row, 1983) p. 60.
". . . the gradual morphological transitions between presumed ancestors and descendants, anticipated by most biologists, are missing." David E. Schindel (Curator of Invertebrate Fossils, Peabody Museum of Natural History), "The Gaps in the Fossil Record," Nature, Vol. 297, 27 May 1982, p. 282.
"Gaps at a lower taxonomic level, species and genera, are practically universal in the fossil record of the mammal-like reptiles. In no single adequately documented case is it possible to trace a transition, species by species, from one genus to another." Thomas S. Kemp, Mammal-like Reptiles and the Origin of Mammals (New York: Academic Press, 1982), p. 319.
"Modern apes, for instance, seem to have sprung out of nowhere. They have no yesterday, no fossil record. And the true origin of modern humans - of upright, naked, tool-making, big-brained beings - is, if we are to be honest with ourselves, an equally mysterious matter." Lyall Watson, "The Water People," Science Digest, May 1982, p. 44.
"At any rate, modern gorillas, orangs and chimpanzees spring out of nowhere, as it were. They are here today they have no yesterday, unless one is able to find faint foreshadowings of it in the dryopithecids." Donald Johanson and Maitland Edey, Lucy: The Beginnings of Humankind (New York: Simon and Schuster, 1981 reprint edition, New York: Warner Books, 1982), p. 363.
It is true that the skeletal features of some amphibians and some reptiles are similar. However, huge differences exist in their soft internal organs, such as their circulatory and reproductive systems. For example, no evolutionary scheme has ever been given for the development of the many unique innovations of the reptile's egg. [See Denton, pp. 218-219 and Michael Pitman, Adam and Evolution (London: Rider, 1984) pp. 199-200.]
"In fact,the fossil record does not convincingly document a single transition from one species to another." Steven M. Stanley, The New Evolutionary Timetable (New York: Basic Books, 1981) p. 95
"Well, we are now about 120 years after Darwin and the knowledge of the fossil record has been greatly expanded. We now have a quarter of a million fossil species but the situation hasn't changed much. The record of evolution is still surprisingly jerky and, ironically, we have even fewer examples of evolutionary transition than we had in Darwin's time. By this I mean that some of the classic cases of Darwinian change in the fossil record, such as the evolution of the horse in North America, have had to be discarded or modified as a result of more detailed information - what appeared to be a nice simple progression when relatively few data were available now appears to be much more complex and much less gradualistic. So Darwin's problem has not been alleviated in the last 120 years and we still have a record which does show change but one that can hardly be looked upon as the most reasonable consequence of natural selection." David M. Raup, "Conflicts Between Darwin and Paleontology," Field Museum of Natural History Bulletin, Vol. 50, No. 1, January 1979, p. 25. (He says a similar thing on p. 50.)
Dr. Colin Patterson, a senior paleontologist at the British Museum (Natural History), was asked by Luther D. Sunderland why no evolutionary transitions were included in Dr. Patterson's recent book entitled Evolution. In a personal letter, Patterson said:
"I fully agree with your comments on the lack of direct illustration of evolutionary transitions in my book. If I knew of any, fossil or living, I would certainly have included them. You suggest that an artist should be asked to visualize such transformations, but where would he get the information from? I could not, honestly, provide it, and if I were to leave it to artistic licence, would that not mislead the reader?. . . Yet Gould and the American Museum people are hard to contradict when they say that there are no transitional fossils. As a palaeontologist myself, I am much occupied with the philosophical problems of identifying ancestral forms in the fossil record. You say that I should at least `show a photo of the fossil from which each type organism was derived.' I will lay it on the line - there is not one such fossil for which one could make a watertight argument." Copy of letter, dated 10 April 1979, from Patterson to Sunderland.
"Surely the lack of gradualism - the lack of intermediates - is a major problem." Dr. David Raup, as taken from page 16 of an approved and verified transcript of a taped interview conducted by Luther D. Sunderland on 27 July 1979.
". . . there are about 25 major living subdivisions (phyla) of the animal kingdom alone, all with gaps between them that are not bridged by known intermediates." Francisco J. Ayala and James W. Valentine, Evolving, The Theory and Processes of Organic Evolution (Menlo Park, California: The Benjamin Cummings Publishing Co., 1979), p. 258.
The following was based on an interview with Dr. Niles Eldredge, an invertebrate paleontologist at the American Museum of Natural History.
"But the smooth transition from one form of life to another which is implied in the theory is . . .not borne out by the facts. The search for `missing links' between various living creatures, like humans and apes, is probably fruitless . . . because they probably never existed as distinct transitional creatures. This oddity has been attributed to gaps in the fossil record which gradualists expected to fill when rock strata of the proper age had been found. In the last decade, however, geologists have found rock layers of all divisions of the last 500 million years and no transitional forms were contained in them. If it is not the fossil record which is incomplete then it must be the theory." "Missing, Believed Nonexistent," Manchester Guardian (The Washington Post Weekly), Vol. 119, No. 22, 26 November 1978, p. 1.
"The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches the rest is inference, however reasonable, not the evidence of fossils . . . . We fancy ourselves as the only true students of life's history, yet to preserve our favored account of evolution by natural selection we view our data as so bad that we never see the very process we profess to study." Stephen Jay Gould, "Evolution's Erratic Pace," Natural History, Vol. 5, May 1977, p. 14.
"New species almost always appeared suddenly in the fossil record with no intermediate links to ancestors in older rocks of the same region." Ibid., p. 12.
"All paleontologists know that the fossil record contains precious little in the way of intermediate forms transitions between major groups are characteristically abrupt." S.J. Gould, "The Return of Hopeful Monsters," Natural History, Vol. 86, June-July 1977, p. 23.
"Most orders, classes, and phyla appear abruptly, and commonly have already acquired all the characters that distinguish them." Ibid., p. 266.
"The absence of any known series of such intermediates imposes severe restrictions on morphologists interested in the ancestral source of angiosperms and leads to speculation and interpretation of homologies and relationships on the basis of the most meager circumstantial evidence." Charles B. Beck, Origin and Early Evolution of Angiosperms (New York: Columbia University Press, 1976), p. 5.
"The geological record has so far provided no evidence as to the origin of the fishes . . . ." J.R. Norman, A History of Fishes, 3rd edition (New York: John Wiley & Sons, 1975), p. 343.
"All three subdivisions of the bony fishes first appear in the fossil record at approximately the same time. They are already widely divergent morphologically, and they are heavily armored. How did they originate? What allowed them to diverge so widely? How did they all come to have heavy armor? And why is there no trace of earlier, intermediate forms?" Gerald T. Todd, "Evolution of the Lung and the Origin of Bony Fishes - A Causal Relationship?", American Zoologist, Vol. 20, No. 4, p. 757.
"Despite the bright promise that paleontology provides a means of `seeing' evolution, it has presented some nasty difficulties for evolutionists the most notorious of which is the presence of `gaps' in the fossil record. Evolution requires intermediate forms between species and paleontology does not provide them." David B. Kitts (School of Geology and Geophysics, University of Oklahoma), "Paleontology and Evolutionary Theory," Evolution, Vol. 28, September 1974, p. 467.
"The transition from insectivore to primate is not clearly documented in the fossil record." A.J. Kelso, Physical Anthropology, 2nd edition (New York: J.B. Lippincott Company, 1974), p. 141.
". . . experience shows that the gaps which separate the highest categories may never be bridged in the fossil record. Many of the discontinuities tend to be more and more emphasized with increased collecting." Norman D. Newell (former Curator of Historical Geology at the American Museum of Natural History), "The Nature of the Fossil Record," Adventures in Earth History, editor Preston Cloud (San Francisco: W.H. Freeman and Co., 1970), pp. 644-645.
"A person may choose any group of animals or plants, large or small, or pick one at random. He may then go to a library and with some patience he will be able to find a qualified author who says that the evolutionary origin of that form is not known." Bolton Davidheiser, Evolution and Christian Faith (Phillipsburg, New Jersey: The Presbyterian and reformed Publishing Company, 1969), p. 302.
"There is no more conclusive refutation of Darwinism than that furnished by palaeontology. Simple probability indicates that fossil hoards can only be test samples. Each sample, then, should represent a different stage of evolution, and there ought to be merely `transitional' types, no definition and no species. Instead of this we find perfectly stable and unaltered forms persevering through long ages, forms that have not developed themselves on the fitness principle, but appear suddenly and at once in their definitive shape that do not thereafter evolve towards better adaptation, but become rarer and finally disappear, while quite different forms crop up again. What unfolds itself, in ever-increasing richness of form, is the great classes and kinds of living beings which exist aboriginally and exist still, without transition types, in the grouping of today." [emphasis in original] Oswald Spengler, The Decline of the West, Vol. 2 (New York: Alfred A. Knopf, 1966), p. 32.
But whatever ideas authorities may have on the subject, the lung-fishes, like every other major group of fishes that I know, have their origins firmly based in nothing, a matter of hot dispute among the experts, each of whom is firmly convinced that everyone else is wrong . . . . I have often thought of how little I should like to have to prove organic evolution in a court of law." [emphasis in original] Errol White, "A Little on Lung-Fishes," Proceedings of the Linnean Society of London, Vol. 177, Presidential Address, January 1966, p. 8.
". . . to the unprejudiced, the fossil record of plants is in favour of special creation. If, however, another explanation could be found for this hierarchy of classification, it would be the knell [the death signal] of the theory of evolution. Can you imagine how an orchid, a duckweed, and a palm have come from the same ancestry, and have we any evidence for this assumption? The evolutionist must be prepared with an answer, but I think that most would break down before an inquisition. Textbooks hoodwink." E.J.H. Corner, "Evolution," Contemporary Botanical Thought, editors Anna M. MacLeod and L.S. Cobley (Chicago: Quadrangle Books, 1961), p. 9
."The [evolutionary] origin of birds is largely a matter of deduction. There is no fossil evidence of the stages through which the remarkable change from reptile to bird was achieved." W.E. Swinton, "The Origin of Birds," Biology and Comparative Physiology of Birds, editor A.J. Marshall (New York: Academic Press, 1960), Vol. 1, Chapter 1, p. 1. See my article Did Birds Evolve from Dinosaurs? Latest Research Says No!
"When and where the first Primates made their appearance is also conjectural. . . . It is clear, therefore, that the earliest Primates are not yet known. . . ." William Charles Osman Hill, Primates (New York: Interscience Publishers, Inc., 1953), Vol. 1, pp. 25-26.
"As our present information stands, however, the gap remains unbridged, and the best place to start the evolution of the vertebrates is in the imagination." Homer W. Smith, From Fish to Philosopher (Boston: Little, Brown, and Co., 1953), p. 26.
"It may, therefore, be firmly maintained that it is not even possible to make a caricature of an evolution our of palaeobiological facts. The fossil material is now so complete that it has been possible to construct new classes and the lack of transitional series cannot be explained as due to the scarcity of the material. The deficiencies are real, they will never be filled." Nilsson, p. 1212
"In spite of the immense amount of the paleontological material and the existence of long series of intact stratigraphic sequences with perfect records for the lower categories, transitions between the higher categories are missing." Richard B. Goldschmidt, "Evolution, As Viewed by One Geneticist", American Scientist, Vol. 40, January, 1952, p. 98.
"There is, however, no fossil evidence bearing on the question of insect origin the oldest insects known show no transition to other arthropods." Frank M. Carpenter, "Fossil Insects," Insects (Washington, D.C: U.S. Government Printing Office, 1952), p. 18.
"It has long been hoped that extinct plants will ultimately reveal some of the stages through which existing groups have passed during the course of their development, but it must be freely admitted that this aspiration has been fulfilled to a very slight extent, even though paleobotanical research has been in progress for more than one hundred years. As yet we have not been able to trace the phylogenetic history of a single group of modern plants from its beginning to the present." Chester A. Arnold,An Introduction to Paleobotany (New York: McGraw-Hill, 1947), p. 7.
"When a new phylum, class, or order appears, there follows a quick, explosive (in terms of geological time) diversification so that practically all orders or families known appear suddenly and without any apparent transitions."Ibid., p. 97.
"This regular absence of transitional forms is not confined to mammals, but is an almost universal phenomenon, as has long been noted by paleontologists. It is true of almost all orders of all classes of animals, both vertebrate and invertebrate. A fortiori, it is also true of the classes, themselves, and of the major animal phyla, and it is apparently also true of analogous categories of plants." George Gaylord Simpson, Tempo and Mode in Evolution (New York: Columbia university Press, 1944), p. 107.
". . . the geologic record did not then and still does not yield a finely graduated chain of slow and progressive evolution. In other words, there are not enough intermediates. There are very few cases where one can find a gradual transition from one species to another and very few cases where one can look at a part of the fossil record and actually see that organisms were improving in the sense of becoming better adapted." Ibid., p. 23.
Complex and Diverse Early Animals
Developmental biologist Rudolf Roff of Indiana University concludes from the fossil evidence from Canada, Greenland, China, Siberia, and Nambia of a Cambrian explosion of life: "There must be limits to change, after all we've had these same old body plans for half a billion years." Reported by J.M. Nash in the cover story, "Evolution's Big Bang: New discoveries show that life as we know it began in an amazing biological frenzy that changed the planet almost overnight," Time Magazine, 4 December 1996, p. 74. (See my article, The Implications of the Cambrian Explosion for Evolution).
"Vertebrates and their progenitors, according to the new studies, evolved in the Cambrian, earlier than paleontologists have traditionally assumed." Richard Monastersky, "Vertebrate Origins: The Fossils Speak Up," Science News, Vol. 149, 3 February 1996, p. 75.
"Evolutionary biology's deepest paradox concerns this strange discontinuity. Why haven't new animal body plans continued to crawl out of the evolutionary cauldron during the past hundreds of millions of years? Why are the ancient body plans so stable?" Jeffrey S. Levinton, "The Big Bang of Animal Evolution," Scientific American, Vol. 267, November 1992, p. 84.
"The most famous such burst, the Cambrian explosion, marks the inception of modern multicellular life. Within just a few million years, nearly every major kind of animal anatomy appears in the fossil record for the first time . . . . The Precambrian record is now sufficiently good that the old rationale about undiscovered sequences of smoothly transitional forms will no longer wash." Stephen Jay Gould, "An Asteroid to Die For," Discover, October 1989, p. 65
."If there has been evolution of life, the absence of the requisite fossils in the rocks older than the Cambrian is puzzling." Marshall Kay and Edwin H. Colbert, Stratigraphy and Life history (New York: John Wiley & Sons, 1965), p. 103
."There are no fossils known that show what the primitive ancestral insects looked like, . . . . Until fossils of these ancestors are discovered, however, the early history of the insects can only be inferred." Peter Farb, The Insects, Life Nature Library (New York: Time Incorporated, 1962), pp. 14-15.
". . . it is well known that the fossil record tells us nothing about the evolution of flowering plants." E.J.H. Corner, "Evolution?" in Macleod and Cobley, eds., Contemporary Botanical Thought (Chicago: Quadrangle Books, 1961) p. 100.
"Granted an evolutionary origin of the main groups of animals, and not an act of special creation, the absence of any record whatsoever of a single member of any of the phyla in the Pre-Cambrian rocks remains as inexplicable on orthodox grounds as it was to Darwin." T. Neville George (Professor of Geology at the University of Glasgow), "Fossils in Evolutionary Perspective," Science Progress, Vol. 48, No. 189, January 1960, p. 5.
"One of the major unsolved problems of geology and evolution is the occurrence of diversified, multicellular marine invertebrates in Lower Cambrian rocks on all the continents and their absence in rocks of greater age." Daniel I. Axelrod, "Early Cambrian Marine Fauna, " Science, Vol. 128, 4 July 1958, p. 7.
"There is another and allied difficulty, which is much more serious. I allude to the manner in which species belonging to several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks." Darwin, The Origin of Species, p. 348.
"The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several palaeontologists - for instance , by Agassiz, Pictet, and Sedgwick - as a fatal objection to the belief in the transmutation of species. If numerous species, belonging to the same genera or families, have really started into life at once, the fact would be fatal to the theory of evolution through natural selection." Ibid., p. 344.
"To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the Cambrian system, I can give no satisfactory answer." Ibid., p. 350.
"The case at present must remain inexplicable, and may be truly urged as a valid argument against the views here entertained." Ibid., p. 351.
What are transitional fossils and why are they important to the fossil record?
Transitional fossils are believed to be the preserved evidence of transitional forms of organisms, the so called missing links which provide support to the theory of descent with modification.
A transitional fossil is a term used to describe a fossil that shows a transitional form of two different species. The transitional fossil will show a combination of traits from the species that preceded it and the species that followed it. One of the best example of a transitional species is Archaeopteryx, which shows the transition from dinosaurs without feathers to modern birds.
Transitional fossils are predicted by the Darwinian theory of evolution. This theory also known as descent with modification states that all life started from a common cell and has gradually changed to all forms of life present on earth today. The transitional fossils predicted by descent with modification have not been found.
As the theory states that organisms have gradually changed from one from to another form transitional fossils should be found that show evidence of the transitional forms of the organism. In using the fossil record to support the Darwinian theory of evolution finding these transitional fossils is important. There are Questions about the truth of the Darwinian theory of evolution because of the lack of transitional fossils showing gradual changes from one form to another form.
Problem 5: Abrupt Appearance of Species in the Fossil Record Does Not Support Darwinian Evolution
Editor’s note: This is Part 5 of a 10-part series based upon Casey Luskin’s chapter, “The Top Ten Scientific Problems with Biological and Chemical Evolution,” in the volume More than Myth, edited by Paul Brown and Robert Stackpole (Chartwell Press, 2014). The full chapter can be found online here. Other individual installments can be found here: Problem 1, Problem 2, Problem 4, Problem 5, Problem 6, Problem 7, Problem 8, Problem 9, Problem 10.
The fossil record has long been recognized as a problem for evolutionary theory. In the Origin of Species, Darwin explained that his theory led him to believe that “[t]he number of intermediate varieties, which have formerly existed on the earth, [must] be truly enormous.” 65 However, he understood that the fossil record did not document these “intermediate” forms of life, asking, “Why then is not every geological formation and every stratum full of such intermediate links?” 66 Darwin’s answer showed the tenuous nature of the evidence backing his ideas: “Geology assuredly does not reveal any such finely graduated organic chain and this, perhaps, is the most obvious and gravest objection which can be urged against my theory.” 67
Today, some 150 years later, out of thousands of species known from the fossil record, only a small fraction are claimed to be candidates for Darwin’s intermediate forms. Fossil evidence of evolutionary intermediates is generally lacking, as the late evolutionary paleontologist Stephen Jay Gould admitted: “The absence of fossil evidence for intermediary stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution.” 68
Darwin attempted to save his theory of gradual evolution by maintaining that intermediate fossils are not found because of “the extreme imperfection of the geological record.” 69 Even Gould noted that Darwin’s argument that the fossil record is imperfect “persists as the favored escape of most paleontologists from the embarrassment of a record that seems to show so little of evolution directly.” 70 But in the last few decades, this excuse has lost credibility.
Paleontologists today generally recognize that while the fossil record is imperfect, it is still adequate to assess questions about evolution. One study in Nature reported that “if scaled to the … taxonomic level of the family, the past 540 million years of the fossil record provide uniformly good documentation of the life of the past.” 71 Another paper in Paleobiology evaluated our knowledge of the fossil record and concluded that “our view of the history of biological diversity is mature.” 72 Paleontologists now increasingly recognize that “jumps” between species, without intermediates, are not simply the result of an incomplete record. Niles Eldredge, an evolutionary paleontologist and curator at the American Museum of Natural History, puts it this way with Ian Tattersal: “The record jumps, and all the evidence shows that the record is real: the gaps we see reflect real events in life’s history — not the artifact of a poor fossil record.” 73 This conclusion did not come easily, as one scientist who studied under Gould felt the need to implore his colleagues that “[e]volutionary biologists can no longer ignore the fossil record on the ground that it is imperfect.” 74
A Pattern of Explosions
The eventual realization that the fossil record is not entirely incomplete has forced evolutionary biologists to accept that the record shows a pattern of explosions, not gradual evolution of living organisms. One biology textbook explains:
Many species remain virtually unchanged for millions of years, then suddenly disappear to be replaced by a quite different, but related, form. Moreover, most major groups of animals appear abruptly in the fossil record, fully formed, and with no fossils yet discovered that form a transition from their parent group. 75
Probably the most famous instance of abrupt appearance is the Cambrian explosion, in which nearly all of the major living animal phyla appear for the first time. An invertebrate biology textbook explains:
Most of the animal groups that are represented in the fossil record first appear, “fully formed” and identifiable as to their phylum, in the Cambrian, some 550 million years ago. These include such anatomically complex and distinctive types as trilobites, echinoderms, brachiopods, molluscs, and chordates. … The fossil record is therefore of no help with respect to the origin and early diversification of the various animal phyla… 76
Evolutionary scientists acknowledge that they cannot explain this rapid appearance of diverse animal body plans by classical Darwinian processes, or other known material mechanisms. Robert Carroll, a paleontologist at McGill University, argues in Trends in Ecology and Evolution that “The extreme speed of anatomical change and adaptive radiation during this brief time period requires explanations that go beyond those proposed for the evolution of species within the modern biota.” 77 Another paper likewise maintains that “microevolution does not provide a satisfactory explanation for the extraordinary burst of novelty during the Cambrian Explosion” and concludes “the major evolutionary transitions in animal evolution still remain to be causally explained.” 78 Likewise a 2009 paper in BioEssays concedes that “elucidating the materialistic basis of the Cambrian explosion has become more elusive, not less, the more we know about the event itself.” 79
But the Cambrian explosion is by no means the only explosion of life recorded in the fossil record. Regarding the origin of major fish groups, former Columbia University geoscientist Arthur Strahler writes that, “This is one count in the creationists’ charge that can only evoke in unison from paleontologists a plea of nolo contendere [no contest].” 80 A paper in Annual Review of Ecology and Systematics explains that the origin of land plants “is the terrestrial equivalent of the much-debated Cambrian ‘explosion’ of marine faunas.” 81 Regarding the origin of angiosperms (flowering plants), paleontologists have discovered a “big bloom” type of explosion event. As one paper states:
In spite of much research and analyses of different sources of data (e.g., fossil record and phylogenetic analyses using molecular and morphological characters), the origin of the angiosperms remains unclear. Angiosperms appear rather suddenly in the fossil record… with no obvious ancestors for a period of 80-90 million years before their appearance. 82
In a similar way, many orders of mammals appear in an explosive manner. Niles Eldredge explains that “there are all sorts of gaps: absence of gradationally intermediate ‘transitional’ forms between species, but also between larger groups — between, say, families of carnivores, or the orders of mammals.” 83 There is also a bird explosion, with major bird groups appearing in a short time period. 84 One paper in Trends in Ecology and Evolution titled “Evolutionary Explosions and the Phylogenetic Fuse” explains:
A literal reading of the fossil record indicates that the early Cambrian (c. 545 million years ago) and early Tertiary (c. 65 million years ago) were characterized by enormously accelerated periods of morphological evolution marking the appearance of the animal phyla, and modern bird and placental mammal orders, respectively. 85
Of course there are a handful of examples where evolutionary scientists believe they have found transitional fossils documenting gradual Darwinian evolution. The origin of whales has been called a “poster child for macroevolution,” 86 where it is believed that around 55 million years ago, certain land mammals lost their hind-limbs and evolved into fully aquatic whales. In particular, it is claimed there are fossil land-mammals with ear-bones similar to whales, and fossil whale-like mammals that retain their hindlimbs.
Even though vertebrate and whale expert Phillip Gingerich admits that we only have “fossils illustrating three or four steps that bridge the precursor of whales to today’s mammals,” 87 let’s assume for a moment that a full sequence of fossils exists. Is this enough to demonstrate that this transition occurred? Even if there are fossils that look like potential intermediate forms, if the overall evolutionary story does not make sense, then the fossils cannot be transitional. In this case, the Darwinian evolution of whales from land-mammals faces serious mathematical challenges from population genetics.
Many changes would have been necessary to convert a land-mammal into a whale, including:
- Emergence of a blowhole, with musculature and nerve control
- Modification of the eye for permanent underwater vision
- Ability to drink sea water
- Forelimbs transformed into flippers
- Modification of skeletal structure
- Ability to nurse young underwater
- Origin of tail flukes and musculature
- Blubber for temperature insulation 88
Many of these necessary adaptations would require multiple coordinated changes. But as we saw in Problem 3, such simultaneous mutations require extremely long periods of time to arise via the Darwinian mechanism. Whale evolution now runs into a severe problem. The fossil record requires that the evolution of whales from small land mammals would have to have taken place in less than 10 million years. 89 That may sound like a long time, but it actually falls dramatically short, especially given that whales have small population sizes and long generation times. 90 Biologist Richard Sternberg has examined the requirements of this transition mathematically and puts it this way: “Too many genetic re-wirings, too little time.” 91
Whale origins thus provides an interesting case study of evolutionary transitions: On a rare occasion where there actually are fossils that potentially show intermediate traits, unguided neo-Darwinian evolution is invalidated by the short amount of time allowed by the fossil record. If this “poster child” of macroevolution doesn’t hold up to scrutiny, what does this tell us about other cases where evolutionists tout supposed transitional fossils?
Human Origins and the Fossil Record
Indeed, the public is commonly told that there are fossils documenting the evolution of humans from ape-like precursors, but a closer look at the technical literature tells a different story. Hominid fossils generally fall into one of two groups: ape-like species and human-like species, with a large, unbridged gap between them. In 2004, the famed evolutionary biologist Ernst Mayr recognized the abrupt appearance of humans:
The earliest fossils of Homo, Homo rudolfensis and Homo erectus, are separated from Australopithecus by a large, unbridged gap. How can we explain this seeming saltation? Not having any fossils that can serve as missing links, we have to fall back on the time-honored method of historical science, the construction of a historical narrative. 92
In light of such evidence, a paper in the Journal of Molecular Biology and Evolution called the appearance of Homo sapiens “a genetic revolution” where “no australopithecine species is obviously transitional.” 93 The lack of fossil evidence for this hypothesized transition is confirmed by Harvard paleoanthropologists Daniel E. Lieberman, David R. Pilbeam, and Richard W. Wrangham:
Of the various transitions that occurred during human evolution, the transition from Australopithecus to Homo was undoubtedly one of the most critical in its magnitude and consequences. As with many key evolutionary events, there is both good and bad news. First, the bad news is that many details of this transition are obscure because of the paucity of the fossil and archaeological records. 94
As for the “good news,” they still admit: “although we lack many details about exactly how, when, and where the transition occurred from Australopithecus to Homo, we have sufficient data from before and after the transition to make some inferences about the overall nature of key changes that did occur.” 95 In other words, the fossil record provides ape-like australopithecines (“before”), and human-like Homo (“after”), but not fossils documenting a transition between them. In the absence of intermediates, we’re left with “inferences” of a transition based strictly upon the assumption of Darwinian evolution. One commentator proposed the evidence implies a “big bang theory” of the appearance of our genus Homo. 96 This does not make for a compelling evolutionary account of human origins. 97
Rather than showing gradual Darwinian evolution, the history of life shows a pattern of explosions where new fossil forms come into existence without clear evolutionary precursors. Evolutionary anthropologist Jeffrey Schwartz summarizes the problem:
[W]e are still in the dark about the origin of most major groups of organisms. They appear in the fossil record as Athena did from the head of Zeus — full-blown and raring to go, in contradiction to Darwin’s depiction of evolution as resulting from the gradual accumulation of countless infinitesimally minute variations. . .” 98
This poses a major challenge to Darwinian evolution, including the view that all animals are related through common ancestry.
[65.] Charles Darwin, The Origin of Species (1859), p. 292 (reprint, London: Penguin Group, 1985).
[68.] Stephen Jay Gould, “Is a new and general theory of evolution emerging?” Paleobiology, 6(1): 119-130 (1980).
[69.] Charles Darwin, The Origin of Species (1859), p. 292 (reprint, London: Penguin Group, 1985).
[70.] Stephen Jay Gould, “Evolution’s erratic pace,” Natural History, 86(5): 12-16, (May, 1977).
[71.] M. J. Benton, M. A. Wills, and R. Hitchin, “Quality of the fossil record through time,” Nature, 403: 534-536 (Feb. 3, 2000).
[72.] Mike Foote, “Sampling, Taxonomic Description, and Our Evolving Knowledge of Morphological Diversity,” Paleobiology, 23: 181-206 (Spring, 1997).
[73.] Niles Eldredge and Ian Tattersall, The Myths of Human Evolution, p. 59 (New York: Columbia University Press, 1982).
[74.] David S. Woodruff, “Evolution: The Paleobiological View,” Science, 208: 716-717 (May 16, 1980).
[75.] C.P. Hickman, L.S. Roberts, and F.M. Hickman, Integrated Principles of Zoology, p. 866 (Times Mirror/Moseby College Publishing, 1988, 8th ed).
[76.] R.S.K. Barnes, P. Calow and P.J.W. Olive, The Invertebrates: A New Synthesis, pp. 9-10 (3rd ed., Blackwell Sci. Publications, 2001).
[77.] Robert L. Carroll, “Towards a new evolutionary synthesis,” Trends in Ecology and Evolution, 15(1):27-32 (2000).
[78.] Jaume Baguña and Jordi Garcia-Fernández, “Evo-Devo: the Long and Winding Road,” International Journal of Developmental Biology, 47:705-713 (2003) (internal citations removed).
[79.] Kevin J. Peterson, Michael R. Dietrich and Mark A. McPeek, “MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion,” BioEssays, 31 (7):736-747 (2009).
[80.] Arthur N. Strahler, Science and Earth History: The Evolution/Creation Controversy, pp. 408-409 (New York: Prometheus Books, 1987).
[81.] Richard M. Bateman, Peter R. Crane, William A. DiMichele, Paul R. Kenrick, Nick P. Rowe, Thomas Speck, and William E. Stein, “Early Evolution of Land Plants: Phylogeny, Physiology, and Ecology of the Primary Terrestrial Radiation,” Annual Review of Ecology and Systematics, 29: 263-292 (1998).
[82.] Stefanie De Bodt, Steven Maere, and Yves Van de Peer, “Genome duplication and the origin of angiosperms,” Trends in Ecology and Evolution, 20:591-597 (2005).
[83.] Niles Eldredge, The Monkey Business: A Scientist Looks at Creationism (New York: Washington Square Press, 1982), 65.
[84.] See Alan Cooper and Richard Fortey, “Evolutionary Explosions and the Phylogenetic Fuse,” Trends in Ecology and Evolution, 13 (April, 1998): 151-156 Frank B. Gill, Ornithology, 3rd ed. (New York: W.H. Freeman, 2007), 42.
[85.] Alan Cooper and Richard Fortey, “Evolutionary Explosions and the Phylogenetic Fuse,” Trends in Ecology and Evolution, 13: 151-156 (April, 1998).
[86.] J.G.M. Thewissen and Sunil Bajpai, “Whale Origins as a Poster Child for Maccroevolution,” BioEssays, 51: 1037-1049 (December, 2001).
[87.] Philip Gingerich, “Fossils and the Origin of Whales,” ActionBioScience.org (December, 2006), http://www.actionbioscience.org/evolution/gingerich.html
[88.] List provided courtesy of Dr. Richard Sternberg.
[89.] Alan Feduccia, “‘Big bang’ for tertiary birds?,” Trends in Ecology and Evolution, 18: 172-176 (2003).
[90.] See Walter James ReMine, The Biotic Message: Evolution Versus Message Theory (Saint Paul: MN, Saint Paul Science, 1983).
[91.] Private communication with Richard Sternberg.
[92.] Ernst Mayr, What Makes Biology Unique?, p. 198 (Cambridge University Press, 2004).
[93.] John Hawks, Keith Hunley, Sang-Hee Lee, and Milford Wolpoff, “Population Bottlenecks and Pleistocene Human Evolution,” Journal of Molecular Biology and Evolution, 17(1):2-22 (2000).
[94.] Daniel E. Lieberman, David R. Pilbeam, and Richard W. Wrangham, “The Transition from Australopithecus to Homo,” Transitions in Prehistory: Essays in Honor of Ofer Bar-Yosef, p. 1 (John J. Shea and Daniel E. Lieberman eds., Oxbow Books, 2009) (internal citations removed).
[96.] “New study suggests big bang theory of human evolution,” (January 10, 2000) at http://www.umich.edu/
[97.] For a more detailed discussion of the fossil evidence and human origins, see Casey Luskin, “Human Origins and the Fossil Record,” pp. 45-83 in Science and Human Origins (Discovery Institute Press, 2012).
[98.] Jeffrewy Schwartz, Sudden Origins: Fossils, Genes, and the Emergence of Species, p. 3 (Wiley, 1999).
Image by Whit Welles Wwelles14 (Own work) [GFDL or CC BY 3.0], via Wikimedia Commons
Thanks to Rob Foley, Marta Lahr, Chris Stringer and Lawrence Martin for the invitation (to W.H.K.) to participate in the Royal Society Discussion Meeting in honour of Richard Leakey, and for their forbearance during the preparation of the manuscript. Thanks are due Carol Ward, Fred Spoor, Bernard Wood, Gen Suwa, Luke Delezene and Dave Strait for discussion about the issues at stake in thinking about early Homo. The manuscript also benefitted from the constructive comments of two anonymous referees.
# Possible Causes of the Cambrian Radiation: What Lit the Fuse?
Numerous hypotheses exist for the geologically rapid diversification of invertebrates in the Cambrian, proposing various key evolutionary innovations or environmental triggers. Critical levels of ecological or behavioral complexity may also have stimulated diversification. At the molecular level, organisms may have reached a key threshold of genetic organization or evolved a key gene.
A number of important environmental changes occurred in the late Precambrian and in the early Cambrian that likely had important consequences for the early evolution of metazoans. Near the end of the Precambrian there were several episodes of nearly global glaciation in which sea ice and continental glaciation extended to the equatorial regions. The last of these “snowball Earth” episodes was about 635 million years ago.1 This time just precedes the earliest fossil evidence of metazoans. The major changes in ocean temperature and chemistry associated with the transition from a snowball Earth to a greenhouse world would likely have had profound effects on life. In particular, isotopic data indicates that the oceans became increasingly oxygenated after the end of the last of the global glaciations. 2 Higher oxygen levels would have been critical for aerobic respiration and the evolution of larger body sizes.
The advent of mineralized hard parts was an important part of the Cambrian “explosion.” The ability of organisms to secrete hard parts had important consequences for both metazoan evolution, and for the preservability of these organisms in the fossil record. Much of the rapid increase in fossil diversity during the early Cambrian is among organisms with resistant hard parts. Changes in seawater chemistry may have played an important role in permitting or stimulating mineral precipitation by marine organisms. With the right concentrations of certain ions, normal physiological processes, such as respiration or photosynthesis, may cause precipitation. Such biomineralization could then be modified through natural selection. In addition, hard parts represent a handy way to store useful ions, or remove toxic ones. Carbonate and phosphate ions, present in most skeletons, are also good buffers against pH changes. Recent work on seawater chemistry during the latest Proterozoic and early Cambrian has indicated a major change in calcium ion concentrations between 544 and 515 million years. 3 This time interval coincides with the onset of widespread biomineralization in the fossil record.
The rise of hard parts would likely have had important behavioral consequences. Hard skeletons provide firm attachments for muscles, enabling various activities and motions not otherwise possible, and skeletons would have helped to support larger and more complex bodies. Hard parts also would provide a protective armor against predators, and evidence for predation is found almost as early as the first skeletal elements appear in the fossil record. Predator-prey interactions seem particularly effective at producing an evolutionary escalation, with the prey evolving defenses and the predator evolving ways to overcome them. Animals with mineralized armor would promote selection for harder jaws and claws in the predators. The more effective predators would in turn increase selective pressure for more resistant skeletons in the prey.
Changes in animal behavior can also change the physical environment. A major environmental change in the early Cambrian came as a result of increased complexity and intensity of bioturbation (burrowing, digging, or other moving and mixing of the sediment by organisms). Burrowing can be a response to escaping predation or seeking out food resources. These evolving behaviors also disrupted the existing seafloor habitat. For much of the Precambrian and into the early Cambrian, microbial and algal mats largely covered the seafloor. These mats provided a stable base for sessile animals and kept mud out of the water, making it easy for filter feeders to obtain relatively high amounts of food and low amounts of sediment. The advent of algal grazers, extensive burrowing and other bioturbation disrupted these mats. This created problems for animals adapted to the old seafloor pattern, but provided a new habitat of muddy seafloors. 4 Additionally, the constant burrowing unearthed buried nutrients, making them accessible to animals at the surface of the sediment.
Available food resources and ecological roles were also altered with the appearance of planktonic or swimming metazoans in the early Cambrian. Prior to the Early Cambrian, there is no evidence for macroscopic zooplankton or swimming animals. However, in the Cambrian several actively swimming, plankton-feeding animals appeared. At the same time, many kinds of planktonic algae became extinct and the surviving forms were much smaller. Evolution of swimming and plankton-feeding ability leads to the diversification of plankton feeders, but it also affects the bottom-dwelling organisms. 5 Both the fecal material and the carcasses of these animals would have fallen to the bottom, moving large quantities of nutrients from the water column, where they were previously inaccessible to animals, to the sea floor. Even today, most of the nutrients in the deep sea come from these sources.
This brief survey of possible factors in the Cambrian explosion illustrates how ocean chemistry, environment, ecology and animal behavior are complexly intertwined. Complex positive and negative feedbacks make it very difficult to tease out which factor was most critical to the rapid diversification of metazoan life at the end of the Precambrian and early Cambrian. However, evidence from multiple sources strongly suggests that several significant changes in the world’s ocean environment conspired to light the fuse of evolutionary innovation.
How does Biogeography provide evidence for evolution? 5 Things to Know…
1. Species of a particular region share a common lineage
Biogeography supports the theory of evolution and describes the distribution of lifeforms over various geographical areas, both in the past and the present times.
It states that the species of a particular region share a common lineage (ancestry). This means that the ancestral species of a particular region have evolved to the many present-day descendent species over the course of evolution.
The biogeographical distribution states that closely related species are usually found in close physical proximity to one another and that fossils from these regions resemble modern organisms of that region.
If speciation was random, the distribution of species would be expected to be scattered all around. This suggests that these species from a particular region share a common lineage.
For example, it is seen that most of the Australian mammal species are marsupials (carry young ones in a pouch), while most mammal species found elsewhere in the world are placental (nourish young ones through a placenta).
This happened because Australia was isolated by water for millions of years, and so these species were able to evolve without competition from (or exchange with) other mammal species elsewhere in the world.
The marsupials of Australia due to their excessive presence have evolved themselves to create a diversity of various marsupial mammal species than the placental ones.
And so, it literally proves that species of a particular region share a common lineage which is evidence of biogeography.
2. Evidence from historical biogeography
Historical biogeography is a discipline of biogeography that is concerned with the origins and evolutionary histories of species on a long time scale in a particular geographical region.
Historical biogeography describes how, and when the species of a particular region have evolved and have lead to the creation of new species over time.
Various factors of microevolution and macroevolution that has occurred due to genetic drift, natural selection, adaptive radiation, etc. are all responsible for the speciation (creation of new species from ancestral species) in a particular geographical region.
Studying those factors of microevolution and macroevolution can provide us with clues and evidences from historical biogeography which had leads to massive evolution in the ancestral species.
Historical biogeographers depend heavily on evidence from other disciplines like fossil records, body anatomy, embryology, molecular biology to provide a large part of the information needed to determine distributions and past interactions.
Historical biogeographers also make use of a tool called an area cladogram which is actually a branching diagram showing the cladistic relationship between a number of species to find how those species are biogeographically related.
Thus historical biogeography allows scientists to determine how the differences in a particular geographical area and its environments affected the evolutionary history of different species of common origin.
For example: Evidence from historical biogeography shows that most modern marsupials (almost 70% of the extant species) are found exclusively in Australia. Australia has only a few placental mammals compared to South America, even though environmental conditions are similar between the two regions.
3. Evidence from ecological biogeography
Ecological biogeography helps in explaining and examining the distribution patterns of the various plants and animals from the viewpoint of their physiological needs and shows how they were related long ago, and is still related to their ecological niches.
Understanding the ecological along with the historical causes of present distribution patterns can help us to predict how the ancestral floras and faunas responded long before their evolution, and how their descendant species will respond to factors in the environment after their huge evolution and specialization, and thus help us to conserve their biodiversity.
Environmental factors such as temperature, humidity, salinity, predation-prey relationships, etc. are all considered as key elements in the ecological biogeography of many species.
When describing the ecological biogeography we also talk about the organism’s tolerances and responses to changes in moisture, temperature, soil chemistry, illumination, and other factors.
And it is seen that not many species share the same ecological niche, and as only a few of the species that will ever share the same ecological niche, evolution will tend to separate them.
This shows why the ancestral species have highly adapted to the change in its ecological and environmental factors due to natural selection over time and has lead to the present formation of many new-related species.
The evidences of the evolution of ecological biogeography can also be explained from factors like molecular homology, convergent and divergent evolution, etc.
For example, broad groupings of organisms that had already evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) tend to be distributed worldwide. In contrast, broad groupings that evolved after the breakup tend to appear uniquely in smaller regions of Earth.
It is because of how their ecological factors forced them to better adapt themselves through natural selection which can be explained by the various ecological-biogeographical evolutionary studies.
4. Evidence from Island or Continental biogeography
One of the most significant pieces of proof for evolution comes from the study of island or continental biogeography. This is explained by how the evolutionary and plate tectonics theory influences biogeography.
Plate tectonics is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of Earth’s lithosphere that occurred on Earth between 3.3 and 3.5 billion years ago.
Due to plate tectonics, many regions of the earth that previously had almost the same kind of related species were now isolated from each other due to the formation of many islands, and huge continents.
So, as a result, each of the islands and continents showed a huge variety of adaptations overtime in its inhabiting species with no occurrence of migration from one island/continent to another because each one was isolated from the other.
For instance, in the Finches on Galapagos islands, you will see that those species that eat large seeds tended to have large-tough beaks, while those that eat insects have thin-sharp beaks. All have originated from their ancestral seed-eating finches.
Island or continental biogeography in these remote locations like the Galapagos islands which was formed due to plate tectonics, Darwin noticed that there were unique species not found anywhere else.
Darwin observed that the species on both islands appeared to be closely related to the species on the nearest continent.
He concluded that the animals on these isolated islands must have been originated from the nearby continent, but because they were separated from the other species on the continent, they gradually evolved into something different over thousands of years.
Darwin’s observation showed that these finches were not found in similar climatic zones elsewhere on Earth but especially in the Galapagos Islands. This literally proves how island or continental biogeography led to the evolution of the finches.
5. Comparative biogeography as evidence of evolution
Comparative biogeography is the comparative study or comparison between two or more different biogeographical areas and comes to a conclusion on how evolution has occurred over time in contrast to these different biogeographical areas.
Comparative biogeography aims at identifying biologically meaningful areas, called “endemic areas” and at organizing them in a classification scheme according to their relationships.
In terms of evolution, comparative biogeographical studies show that how an ancestral species population of a particular area gets separated and isolated into various sub-populations in different-different areas, and later on, with the advancement of time these sub-populations adapt themselves into their type of environment of their particular area.
For instance, Darwin observed that the species on different Galapagos islands appeared to be closely related to the species on the nearest continent.
He concluded that the animals on these isolated islands must have been originated from the ancestral species of the nearby continent. But because they were separated from the other species on the continent, they gradually evolved into something different over thousands of years of evolution.
Another example of comparative biogeography is the lack of mammals on islands like Canary Islands or the Galapagos Islands.
It’s because the mammals that were present in these islands were not able to better adapt and so they got extinct over time.
Moreover, it was very unlikely for the other large mammals to travel over hundreds of miles of ocean water to reach such isolated islands from the nearby continent. And so, no mammals are still seen in these islands.
A few other transitional fossils of interest. This is, obviously, not a sequence. Images and diagrams of the fossils here.
- Aardonyx, a proto-sauropod dinosaur that, though bipedal, could probably also walk on all fours (Yates et al, 2009). Contrary to what you might expect, in this case bipeds evolved to become quadrupeds.
- Amphistium, an early flatfish, with eyes intermediate in position between an ordinary fish and a modern flatfish (Friedman, 2008).
- Claudiosaurus, an early relative of marine reptiles like plesiosaurs, but the limbs are not very specialised for swimming (Prothero, 2007).
- Darwinopterus, a pterosaur, has the advanced skull and neck of the Pterodactyloidea group, but other traits (e.g. its long tail) are like the primitive Rhamphorhynchoid group (Lu et al, 2009).
- Enaliarctos, an early seal, but with more primitive skull and feet (Prothero, 2007).
- Eocaecilia, an early caecilian, but with limbs (Jenkins and Walsh, 1993).
- Gerobatrachus, a transitional fossil between frogs and salamanders (Anderson et al, 2008).
- Haikouella, perhaps the earliest known chordate (Coyne, 2009).
- Najash, an early snake. Had two hind limbs (Apesteguia and Hussam, 2006).
- Odontochelys, an early turtle with "half a shell" and a long tail (Dawkins, 2009).
- Pezosiren, an early manatee, but with legs rather than flippers (Prothero, 2007).
- Protosuchus, a crocodile precursor but "smaller and much more lightly built" than modern crocodiles (Prothero, 2007).
- Seymouria, a "mosaic of primitive tetrapod [i.e. amphibian] and advanced amniote [i.e. reptile] characters" (Prothero, 2007).
- Sphecomyrma, an early ant, with primitive features (Coyne, 2009).
- Triadobatrachus, an early frog, but with more vertebrae, and possessing ribs, which modern frogs don't have (Benton, 2005).
There was a section on ichthyosaurs (a group now extinct) on this site, but I wasn't entirely satisfied with it. We don't yet have anything as good as Tiktaalik or Ambulocetus for ichthyosaurs. Still, fossils like Mixosaurus can be considered transitional between early eel-shaped ichthyosaurs, and later dolphin-shaped species.
Transitional fossils are fossils of organisms that have characteristics of their ancestors’ species and their descendants’ species. why do you think these fossils are important to the study of evolution? do you think the word transitional is a scientifically appropriate description for these fossils?
1. Transitional fossils tells a story of the relationship between the ancestors and the descendant, this allows scientists to determine or study the common pattern in development. This fossils are also used to prove the Darwin theory of evolution.
2. Yes the synonym of transitional is 'midway' and/or middle'. Transitional fossils are fossils that have traits of their ancestor and descendant. Thus these fossils exist between (middle) of their ancestor and descendant.
3. No, I don't think it is possible for all species that ever existed, because some fossils exist in places that humans cannot reach.
1. Why do you think these fossils are important to the study of evolution?
Ans. Fossils are the preserved remains or traces of animals, plants, and other organisms from the past. Fossils are important evidence for evolution because they show that life on earth was once different from life found on earth today.
2. Do you think the word transitional is a scientifically appropriate description for these fossils?
Ans. A transitional fossil is a term used to describe a fossil that shows a transitional form of two different species. . As the theory states that organisms have gradually changed from one from to another form transitional fossils should be found that show evidence of the transitional forms of the organism.
3. Knowing how fossils form, do you think it’s likely that humans will ever piece together a complete fossil record for every species that ever existed on Earth? Why or why not?
Ans. The fossil record is somewhat like an enormously complex jigsaw puzzle with many pieces still missing. Our interpretation of this record has been biased by differential preservation. Some species are underrepresented or have not yet been found. We are left with a somewhat blurred picture of portions of the past, especially the early past. Despite these realities, we have been able to piece together a remarkable understanding of the evolution of life on our planet.
Biologists Uncover Darwin's Missing Evidence for Divergence of Species in a Warbler's Song
Biologists at the University of California, San Diego have demonstrated, in a study of the songs and genetics of a series of interbreeding populations of warblers in central Asia, how one species can diverge into two.
Their description of the intermediate forms of two reproductively isolated populations of songbirds that no longer interbreed is the "missing evidence" that Darwin had hoped to use to support his theory of natural selection, but was never able to find.
"One of the largest mysteries remaining in evolutionary biology is exactly how one species can gradually diverge into two," says Darren E. Irwin, a biologist at UCSD who headed the study, detailed in the January 18 issue of the journal Nature. "This process, known as speciation, is very difficult to study because it can take a great deal of time to occur."
Biologists have generally learned about the divergence of species by comparing many different species at various stages of speciation. But in their study of the greenish warbler, a songbird that breeds in forests throughout much of temperate Asia, Irwin and his colleagues—Trevor D. Price, a biology professor at UCSD, and Staffan Bensch, a former postdoctoral student at UCSD now at Sweden’s Lund University—discovered a rare situation known to biologists as a "ring species."
"Ring species are unique because they present all levels of variation, from small differences between neighboring populations to species-level differences, in a single group of organisms," says Irwin, a former student of Price who is in the process of beginning his postdoctoral work with Bensch at Lund University.
In the case of the greenish warbler, Phylloscopus trochiloides, the scientists discovered a continuous ring of populations with gradually changing behavioral and genetic characteristics encircling the Tibetan Plateau, which is treeless and uninhabitable. This ring is broken by a species boundary at only one place, in central Siberia, where two forms of the songbird coexist without interbreeding.
"This creates a paradox in which the two co-existing forms can be considered as two species and as a single species at the same time," says Irwin. "Such ring species are extremely rare, but they are valuable because they can show all of the intermediate steps that occurred during the divergence of one species into two."
In their paper, the scientists show how they discovered a gradual variation in the song patterns, morphology and genetic markers of 15 populations of the greenish warbler. At each end of the ring of interbreeding populations, which extend around each side of the Tibetan plateau and through the Himalayas, the scientists found that the two distinct, non-interbreeding forms of the bird do not recognize each other’s songs, which are critical in the selection of their mates. They determined this from experiments in which they played recordings of male greenish warbler songs and judged the response of other birds in the trees.
"In the greenish warbler, as in most songbirds, males sing to attract mates and to defend territories," says Irwin. "The greenish warblers living in the Himalayas sing songs that are simple, short and repetitive. As you go north along the western side of Tibet, moving through central Asia, the songs gradually become longer and more complex. On the eastern side of the ring, moving northwards through China, songs also become longer and more complex, but the structure is different than on the western side. Where the birds meet in Siberia, their songs are so different that they do not recognize each other as mates or competitors. They act like separate species, and the genetic evidence supports that conclusion.
"Apparently, as the birds moved north along two pathways into the forests of Siberia, their songs became longer and more complex, perhaps because females in the north rely more strongly on song when choosing a mate. But the forms of complexity differed between west and east Siberia, because there are more ways to be complex than simple.
"The greenish warbler is the first case in which we can see all the steps that occurred in the behavioral divergence of two species from their common ancestor. These results demonstrate how small evolutionary changes can lead to the differences that cause reproductive isolation between species, just as Darwin envisioned."
The study was financed in part by the National Science Foundation and National Geographic Society.
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