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How many neurons do we have in our forearm?

How many neurons do we have in our forearm?


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I am developing a neural interface, getting signals from the forearm and mapping them to hand gestures. The question we have at the moment is what is the upper bound of information bandwidth that we could tap into, meaning if we were to engineer an electrode so small that we could listen to every single neuron in the forearm, how many neurons could we listen to?


How do we get so many different types of neurons in our brain?

SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.

Neurons are cells inside the brain and nervous system that are responsible for everything we do, think or feel. They use electrical impulses and chemical signals to send information between different areas of the brain, and between the brain and the rest of the nervous system, to tell our body what to do. Humans have approximately 86 billion neurons in the brain that direct us to do things like lift an arm or remember a name.

Yet only a few thousand genes are responsible for creating those neurons.

All cells in the human nervous system have the same genetic information. But ultimately, genes are turned "on" or "off" like a light switch to give neurons specific features and roles.

Understanding the mechanism of how a gene is or is not turned on -- the process known as gene expression -- could help explain how so many neurons are developed in humans and other mammals.

"Studies like this are showing how by unique combinations of specific genes, you can make different specific neurons," said Adam D. Norris, co-author of the new study and Floyd B. James Assistant Professor in the Department of Biological Sciences at SMU. "So down the road, this could help us explain: No. 1, how did our brain get this complex? And No. 2, how can we imitate nature and make whatever type of neurons we might be interested in following these rules?"

Scientists already have part of the gene expression puzzle figured out, as previous studies have shown that proteins called transcription factors play a key role in helping to turn specific genes on or off by binding to nearby DNA.

It is also known that a process called RNA splicing, which is controlled by RNA binding proteins, can add an additional layer of regulation to that neuron. Once a gene is turned on, different versions of the RNA molecule can be created by RNA splicing.

But before the SMU study was done, which was published in the journal eLife, it was not exactly clear what the logistics of creating that diversity was.

"Before this, scientists had mostly been focused on transcription factors, which is layer No. 1 of gene expression. That's the layer that usually gets focused on as generating specific neuron types," Norris said. "We're adding that second layer and showing that [transcription factors and RNA binding proteins] have to be coordinated properly.

And Norris noted, "this was the first time where coordination of gene expression has been identified in a single neuron."

Using a combination of old school and cutting-edge genetics techniques, researchers looked at how the RNA of a gene called sad-1, also found in humans, was spliced in individual neurons of the worm Caenorhabditis elegans. They found that sad-1 was turned on in all neurons, but sad-1 underwent different splicing patterns in different neuron types.

And while transcription factors were not shown to be directly participating in the RNA splicing for the sad-1 gene, they were activating genes that code for RNA binding proteins differently between different types of neurons. It is these RNA binding proteins that control RNA splicing.

"Once that gene was turned on, these factors came in and subtly changed the content of that gene," Norris said.

As a result, sad-1 was spliced according to neuron-specific patterns.

They also found that the coordinated regulation had different details in different neurons.

"Picture two different neurons wanting to reach the same goal. You can imagine they either go through the exact same path to get there or they take divergent paths. In this study, we're showing that the answer so far is divergent paths," said Norris. "Even in a single neuron, there are multiple different layers of gene expression that together make that neuron the unique neuron that it is."

Norris used worm neurons because "unlike in humans, we know where every worm neuron is and what it should be up to. Therefore, we can very confidently know which genes are responsible for which neural process.

"The very specific details from this study will not apply to humans. But hopefully the principles involved will," Norris explained. "From the last few decades of work in the worm nervous system, specific genes found to have a specific effect on the worm's behavior were later shown to be responsible for the same types of things in human nerves."


Do octopuses' arms have a mind of their own?

Often described as aliens, octopuses are one of most unusual creatures on the planet, with three hearts, eight limbs and a keen intelligence. They can open jars, solve puzzles and even escape from their tanks, aided by their eight ultra-flexible and versatile arms. But determining how exactly octopuses control all eight limbs is a puzzle that scientists are still trying to crack.

"Octopus arms are completely unique. First off, there are eight of them, each with over 200 suckers that can feel, taste and smell the surroundings. And everything is moveable. The suckers can grasp, and the arms can twist in an almost limitless number of ways," said Dr. Tamar Gutnick, an octopus researcher formerly at the Okinawa Institute of Science and Technology Graduate University (OIST). "So this raises a huge computational issue for the brain and their nervous system has to be organized in a really unusual way to deal with all this information."

Octopuses have an extensive nervous system, with over 500 million neurons, similar in number to that of a dog. But unlike dogs and other vertebrates, where the majority of neurons are in the brain, over two thirds of the octopuses' neurons are located within their arms and body.

With such a strangely-built nervous system, scientists have long suspected that octopuses' arms may have a mind of their own and act autonomously from the central brain. Research has shown that octopuses' arms use reflex loops to create coordinated movements, and some octopuses can even distract predators by discarding limbs that continue to move for long periods of time.

"Some scientists think about octopuses as nine-brained creatures, with one central brain and eight smaller brains in each arm," said Dr. Gutnick. But her new research, published in Current Biology, suggests that the arms and the brain are more connected than previously thought.

Dr. Gutnick and her colleagues have shown that octopuses are capable of learning to associate inserting a single arm into a specific side of a two-choice maze with receiving a food reward, even when neither the reward nor the arm in the maze are visible to the octopus. But crucially, while the learning process takes place in the central part of the brain, the information needed for the brain to choose the correct path is detected only by the arm in the maze.

"This study makes it clear that octopus's arms don't behave totally independently from the centralized brain -- there's information flow between the peripheral and central nervous system," said Dr. Gutnick. "Rather than talking about an octopus with nine brains, we're actually talking about an octopus with one brain and eight very clever arms."

Navigating the maze

The scientists tested whether single arms were able to provide the brain with two different types of sensory information -- proprioception (the ability to sense where a limb is and how its moving) and tactile information (the ability to feel texture).

Humans have a strong sense of proprioception. Sensory receptors located within skin, joints and muscles provide feedback to the brain, which stores and constantly updates a mental map of our body. Proprioception allows us to walk without looking at our feet and touch a finger to our nose with our eyes closed.

But whether octopuses have the same ability is not yet proven.

"We don't know whether an octopus actually knows where its arm is, or what its arm is doing," said Dr. Gutnick. "So our first question was -- can the octopus direct its arm, based only on sensing where its arm was, without being able to see it?"

The researchers created a simple Y-shaped opaque maze and trained six common Mediterranean octopuses to associate either the right or left path with a food reward.

Rather than slowly exploring the internal shape of the maze, the octopuses immediately used fast arm movements, pushing or unravelling their arm straight through the side tube into the goal box. If they pushed their arm into the right goal box, they could retrieve the food, but if their arm entered the wrong goal box, the food was blocked by a net and the scientists removed the maze.

Five out the of the six octopuses eventually learned the correct direction to push or unroll their arm through the maze in order to get the food.

"This shows us that the octopuses clearly have some sense of what their arm is doing, because they learn to repeat the movement direction that resulted in a food reward," said Dr. Gutnick. "It's unlikely to be to the same extent as humans have with our mental maps and the representations we have of our body in the brain, but there is some sense of self-movement from the arms that is available to the central brain."

The team then explored whether octopuses were able to determine the correct path when using a single arm to sense the texture of the maze.

The researchers presented another six octopuses with a Y-shaped maze where one side tube was rough, and the other side tube was smooth. For each octopus, picking either the rough side or the smooth side of the maze led to a food reward.

After many trials, five out of the six octopuses were able to successfully navigate the maze, regardless of whether the correct texture was located on the left or right side tube, showing that they had learnt which texture was correct for them. This time, the octopuses opted for a slower searching movement inside the maze, first determining a side tube's texture and then deciding whether to continue down that side tube, or to switch sides.

Importantly, the team found that for both types of mazes, once octopuses had learnt the correct association, they could successfully navigate the maze using arms that hadn't been used before. "This further rules out the idea that each arm could be learning the task independently -- the learning occurs in the brain and then the information is made available to each arm."

But where this information is stored within the brain, Dr. Gutnick isn't sure, and is a question left for future experiments.

"The brain of octopuses is so different -- it's still a black box to us really," she said. "There's so much more to learn."


Do octopuses' arms have a mind of their own?

The researchers taught octopuses to insert their arms down the left or right side tubes of Y-shaped mazes. Both sides of the maze were baited with food, but food on the incorrect side was blocked by a net. Here, an octopus correctly picks the right side tube and grabs a food reward. Credit: Dr. Tamar Gutnick

Often described as aliens, octopuses are one of most unusual creatures on the planet, with three hearts, eight limbs and a keen intelligence. They can open jars, solve puzzles and even escape from their tanks, aided by their eight ultra-flexible and versatile arms. But determining how exactly octopuses control all eight limbs is a puzzle that scientists are still trying to crack.

"Octopus arms are completely unique. First off, there are eight of them, each with over 200 suckers that can feel, taste and smell the surroundings. And everything is moveable. The suckers can grasp, and the arms can twist in an almost limitless number of ways," said Dr. Tamar Gutnick, an octopus researcher formerly at the Okinawa Institute of Science and Technology Graduate University (OIST). "So this raises a huge computational issue for the brain and their nervous system has to be organized in a really unusual way to deal with all this information."

Octopuses have an extensive nervous system, with over 500 million neurons, similar in number to that of a dog. But unlike dogs and other vertebrates, where the majority of neurons are in the brain, over two thirds of the octopuses' neurons are located within their arms and body.

With such a strangely-built nervous system, scientists have long suspected that octopuses' arms may have a mind of their own and act autonomously from the central brain. Research has shown that octopuses' arms use reflex loops to create coordinated movements, and some octopuses can even distract predators by discarding limbs that continue to move for long periods of time.

"Some scientists think about octopuses as nine-brained creatures, with one central brain and eight smaller brains in each arm," said Dr. Gutnick. But her new research, published in Current Biology, suggests that the arms and the brain are more connected than previously thought.

Dr. Gutnick and her colleagues have shown that octopuses are capable of learning to associate inserting a single arm into a specific side of a two-choice maze with receiving a food reward, even when neither the reward nor the arm in the maze are visible to the octopus. But crucially, while the learning process takes place in the central part of the brain, the information needed for the brain to choose the correct path is detected only by the arm in the maze.

"This study makes it clear that octopus's arms don't behave totally independently from the centralized brain—there's information flow between the peripheral and central nervous system," said Dr. Gutnick. "Rather than talking about an octopus with nine brains, we're actually talking about an octopus with one brain and eight very clever arms."

The scientists tested whether single arms were able to provide the brain with two different types of sensory information—proprioception (the ability to sense where a limb is and how its moving) and tactile information (the ability to feel texture).

Humans have a strong sense of proprioception. Sensory receptors located within skin, joints and muscles provide feedback to the brain, which stores and constantly updates a mental map of our body. Proprioception allows us to walk without looking at our feet and touch a finger to our nose with our eyes closed.

But whether octopuses have the same ability is not yet proven.

In the experiments that tested for proprioception, the octopuses tended to use "straight" movements, aimed at either the left or right side of the maze. In the experiments that tested for tactile discrimination, the octopuses chose to use slower "search" movements. Credit: Reproduced with permission from Elsevier. Originally published 10 Sep 2020 by Current Biology in "Use of Peripheral Sensory Information for Central Nervous Control of Arm Movement by Octopus vulgaris"

"We don't know whether an octopus actually knows where its arm is, or what its arm is doing," said Dr. Gutnick. "So our first question was—can the octopus direct its arm, based only on sensing where its arm was, without being able to see it?"

The researchers created a simple Y-shaped opaque maze and trained six common Mediterranean octopuses to associate either the right or left path with a food reward.

Rather than slowly exploring the internal shape of the maze, the octopuses immediately used fast arm movements, pushing or unraveling their arm straight through the side tube into the goal box. If they pushed their arm into the right goal box, they could retrieve the food, but if their arm entered the wrong goal box, the food was blocked by a net and the scientists removed the maze.

Five out the of the six octopuses eventually learned the correct direction to push or unroll their arm through the maze in order to get the food.

"This shows us that the octopuses clearly have some sense of what their arm is doing, because they learn to repeat the movement direction that resulted in a food reward," said Dr. Gutnick. "It's unlikely to be to the same extent as humans have with our mental maps and the representations we have of our body in the brain, but there is some sense of self-movement from the arms that is available to the central brain."

The team then explored whether octopuses were able to determine the correct path when using a single arm to sense the texture of the maze.

The researchers presented another six octopuses with a Y-shaped maze where one side tube was rough, and the other side tube was smooth. For each octopus, picking either the rough side or the smooth side of the maze led to a food reward.

After many trials, five out of the six octopuses were able to successfully navigate the maze, regardless of whether the correct texture was located on the left or right side tube, showing that they had learnt which texture was correct for them. This time, the octopuses opted for a slower searching movement inside the maze, first determining a side tube's texture and then deciding whether to continue down that side tube, or to switch sides.

Importantly, the team found that for both types of mazes, once octopuses had learnt the correct association, they could successfully navigate the maze using arms that hadn't been used before. "This further rules out the idea that each arm could be learning the task independently—the learning occurs in the brain and then the information is made available to each arm."

But where this information is stored within the brain, Dr. Gutnick isn't sure, and is a question left for future experiments.

"The brain of octopuses is so different—it's still a black box to us really," she said. "There's so much more to learn."


The Enteric Nervous System: The Second Brain in Your Gut

The human gut has been referred to by some scientists as the "enteric nervous system." The enteric nervous system is widely-regarded as our second brain. It consists of a sophisticated network of 100 million neurons fixed in the walls of our guts.

Bacteria in the gut produce neurochemicals like serotonin that the second brain utilizes to control basic physiological processes and cognitive functions. Serotonin is a chemical that influences the digestive processes and mood states. The second brain in our gut produces over 90% of the chemical that exists in our entire bodies.

Our gut is versatile in its ability to cooperate with the brain. This realization along with knowledge of our brain&aposs capacity to regulate external dangers led researchers to the gut-brain connection. Gastroenterologist Emeran Mayer, MD, Director of the Center for Neurobiology of Stress at the University of California, Los Angeles, believes that, "it&aposs almost unthinkable that the gut is not playing a critical role in mind states."

The ENS and Emotions

The enteric nervous system could be responsible for mood swings experienced by people experiencing stomach issues. Researchers previously thought that anxiety and depression were to blame for issues like constipation and bloating. However, studies have found evidence of a two-way exchange in which digestive issues may also be to blame for signaling the central nervous system to trigger mood changes.


Biological and artificial hardware

Most of us forget that the human brain and artificial neural networks today are based on completely different sets of materials and chemical elements.

Brains are made of cells, and microchips are made in silicon and metal

If you only have cells immersed in a conductive ionic medium, transmitting electrical signal is hard for sure! Yet biological brains evolved to do just that. The had no other way to send signals across long distance but to do so with pulses. We talked about this a lot here and here. So that is really why biology uses spiking neural networks (1-bit signals, if you will). If it could signal with continuous levels without being swamped by noise, it would have! Because it would save a lot of energy.

In one sentence: biology has leaky squishy fluidy tubes used as wires, while silicon has metal wires with nice insulation. And this is the crux of the problem and the main difference of why one system has evolved in this way.

On the other hand electrical circuits used in todays computers are all digital and multi-bits. We started with analog signals too, just the old biological brains (and our eyes), because an analog signal has in theory infinite number of values (symbols) it can transmit. But then all infinite possibilities are narrowed to a few because of electronic fundamental noise, in the same way that electrical noise in biological medium forced it to become 1-bit pulses.

If you have 1-bit, how can you use it to represent many values? Time between pulses on one neuron or a group of many neurons of 1-bit can represent larger ensembles like in digital circuits.

You see: when you have neurons their output can have any number of bits you can afford in your system: 1-bit if you have to, or 4 or 8 or 16-bits if you can. And since many 1-bit neurons can represent larger bit numbers, then effectively you can decide:

do you want more 1-bit neurons or less multi-bit neurons?

The balance depends on which technological medium you use and all its parameters.

Remember back-propagation works better with many bits, as its neurons needs to store smaller and smaller numbers while back-propagating over many layers. Today, we can back-propagate with just 8–9 bits per neuron (and another 8 in common across a group of neurons).

Learning is of course also vastly affected by the medium at your disposal. In artificial neural networks signal can travel further and with more noise immunity, so multi-bits and less neurons are the way to go. Learning also can use these properties to afford algorithms such as back-propagation and more global optimization as opposed to local rules dominated by short-range signals in a leaky medium.

An biological brain evolved over millions of years by making the same mistakes many times and replicating solutions in many places with many differences that are more the product of random search than intelligent design (with this I mean a global system design that predated the actual realization). lol.

Do we have the best digital circuit we can have? It can always get smaller. One day transistors may be just a few atoms, if we find ways to combat thermal noise and scaling. And there are new materials and new silicon devices coming up. One thing is sure: it will be hard to swerve away from silicon-based technology given our investment over the last 60 years. I have no crystal sphere here, so time will tell.

Often we heard that comparison about bird wings: how in biology we have flapping wings and in airplanes we do not. Most here forget to take into account the differences in size and also in materials used in both system. Small wings made of feathers are light and easy to activate by muscles, but large metal wings are not easy to move and the material may not be able to withstand the large forces of motion because of material properties. These two are in fact so different that it almost makes no sense to compare them! This is really the same in case of neuron and synapses: their structure and operation make sense in one domain, but not necessarily in others.

cells and silicon each have paths of their own


The Biology of Human Uniqueness

As humans we tend to think of ourselves as rather unique in the created order of things. As Christians, we understand ourselves to be created in the image and likeness of God as we learn in Genesis 1:26. But what does this really mean? Certainly being made in God’s image does not refer to our physical construction God is spirit and therefore does not have a physical body. But God’s plan from the beginning was to rescue us from our sin through the incarnation, God becoming man. Jesus was and is the Son of God, Messiah, the God-Man. Therefore it is not a stretch to suggest that our bodily make-up is meant to be the unique earthly home of Jesus and His Spirit within us. Therefore, I suggest that our biological make-up is unique in the animal kingdom since no other animal is made in His image.

But what does this really mean? I am going to borrow from several sources, principally Michael Denton’s Nature’s Destiny , to discuss the biological uniqueness of humans. The Discovery Institute is also in the process of producing a film series based on Denton’s work, titled Privileged Species: How the Cosmos is Designed for Human Life.

We are able to point out numerous qualitative abilities in the human species found nowhere else in the animal kingdom. I will discuss these in detail below, but I’ll provide a brief overview now to whet your appetite.

First, I’ll be discussing our unique intelligence. Humans’ ability to think abstract thoughts appears to be absolutely unique. It is difficult to arrive at a selective advantage in an evolutionary sense to this type of thinking, so where did it come from?

Second, and related to our intelligence, is our unique language capability. Most animals communicate with their own species, but no other species, including primates, actually use language. As toddlers we accumulate language by simply being around it. Chimps and gorillas have to go through painstaking trial and error and still can’t communicate as a three-year-old does.

Third, our excellent vision allows us to use our intelligence, language and other capabilities to manipulate our surroundings in precise and advantageous ways.

Fourth, our excellent manipulative tool, the hand, is unsurpassed in other primates. We have both strength and fine motor control in our hands, allowing us to combine a strong grip and delicate finger movements that allow a wide range of movements. This, combined with our upright stance, provides an ability to restructure our immediate surroundings as no other species can.

We are also a highly social species which allows for quick distribution of ideas to everyone’s benefit. And all these combine to allow us to be the only species to use and manipulate fire, which brings a host of unique abilities.

Human Intelligence and Language

As I mentioned above, our intelligence separates us from any other primate species. Our brain is three times the size of the brain of a chimp. But beyond that, the number of neurons and connections between neurons far surpasses any other mammal. Michael Denton cites that in each cubic millimeter of the human cortex, are 100,000 cells, about 4 kilometers of axonal wiring and 500 meters of dendrites, and around 1 billion synapse connections between neurons. We have 10 million more of these synapses than a rat brain.

The size and scope is one thing, but our mental capabilities are indeed unique. As mentioned above, humans are capable of abstract and conceptual thought. No other primate exhibits any signs of this capacity. In addition, our mathematical reasoning is completely other compared to other animals. You might suspect that some animals can count. But it is a learned response attached to reward. We don’t really suspect the rat/horse/chimp knows what they are doing. Comparing calculus to simply counting bananas is just no comparison at all.

When you stop to consider our appreciation of the arts, there is no place to go but humans. James Trefil is a physicist fascinated by biology and evolution. But when considering the arts he says, “No matter how hard I try, I can’t think of a single evolutionary pressure that would drive the ability of humans to produce and enjoy music and dance. . . . This has always seemed like a serious problem to me—perhaps even a more serious problem than that perceived by most of my colleagues.”

When we turn to language, our uniqueness is informed even further. Plants and animals all communicate in one form or another, but not by language as humans communicate. We communicate both new information and abstract concepts, something other species don’t even approach. We possess the proper equipment to both produce and receive language and speech. And by proper equipment I mean both the brain processes and the anatomical necessities for actual speech (e.g., teeth, tongue, voice box, etc.). There is also a social ability that can utilize these upper levels of communication.

But we’ve heard about chimps and gorillas learning language. Kanzi, a bonobo chimpanzee, learned words and even symbolic use of a keyboard. Kanzi also learned through hearing the use of new words. But that is where it stopped.

To quote James Trefil again, “If we take the claims being advanced for Kanzi at face value, where are we? We have a member of the most intelligent primate species, a veritable Shakespeare of non-human animals, raised under special and unusual conditions, performing at the level of a human child of two and a half. But remember that in humans, real language begins just after this age. . . . Then we have to conclude that even in this optimal case, animals other than humans cannot learn real human language.”

Human Vision and the Hand

Now I’d like to introduce two features we can easily take for granted, our hands and our eyes.

Ordinarily we don’t think of our hands as being anything special. But just try to think of any other creature that can do the many and diverse things we can do with our hands. The closest match is the hand of a chimp. But
chimp hands are larger, stronger, and even clumsy. Simple things like using all ten fingers to type, peel an apple, or tie a knot are beyond what chimps can do.

The strength in our fingers comes from larger muscles in the forearm and the fine manipulative control comes from much smaller muscles in the hand itself. Our ability to manipulate our environment with our hands is unparalleled. Using our intelligence we even devise additional tools for our hands to further extend our mastery of the world around us. Full use of our hands comes about from our upright and bipedal gait, allowing our hands the freedom not found in any other mammal.

In his book Nature’s Destiny Michael Denton asks about the human hand “whether any other species possesses an organ approaching its capabilities. The answer simply must be that no other species possesses a manipulative organ remotely approaching the universal utility of the human hand. Even in the field of robotics, nothing has been built which even remotely equals the all-around manipulative capacity of the hand.”

But in order to even use our hands well, we need exceptional vision to be able to detect all the little things our minds notice to manipulate. Given the physics of visible light and the dimensions and molecular process of detecting light in our eyes, the resolving power of the human eye is close to the optimum for a camera-type eye using biological cells and processes.

Some animals such as high-flying hawks and eagles detect motion from far greater distances that we can, and some organisms see much better in the dark than we do, but for all-around color vision, detail and resolution, our eyes seem to be the best there is. Combined with our highly interconnected brain, our upright gait for easily seeing straight ahead, a swiveling neck to see side to side, and our overall size, our eyes open the world to us as for no other species.

Developing science and technology, communicating to thousands and even millions through the written word, and simply exploring the world around us, are only possible through an integrated use of our unique intelligence, social structure and speech, hands and vision.

The Use of Fire

As I have explored the biology of human uniqueness, I have focused on some of our individual capacities such as our intelligence, speech, our marvelous hands, and our unique all-around color vision. I have used throughout, the wonderful book by Michael Denton, Nature’s Destiny. Now I’m looking at one of our key distinguishing characteristics which combine all of these. Humans are the only biological creatures that have mastered the use of fire. If you think for a minute, every other animal has nothing but fear when it comes to fire. We are also fearful of fire and the damage it can do, but we have also managed to harness it and use it.

There are a couple of obvious advantages for the use of fire. First it provides additional light after sundown that extends our activity into the evening. Second, fire provides additional warmth in the evening and allows us to venture into colder climates. Third, fire allows us to cook food, particularly meat which is a very significant source of fat calories and protein. Cooking our food certainly distinguishes us from any other creature and has allowed us to add the necessary energy to fully use that big brain of ours which is a major drain on our energy stores, even at night.

But beyond these, if we never harnessed the energy and power of fire, we would not have been able to develop tools involving metal. Using heat to forge ever more powerful hand tools and weapons revolutionized human culture. Without fire we could not have developed any form of chemistry and especially the use of electricity. Electricity has revolutionized human existence in the last 100 years. Fire is an influential and powerful tool indeed.

But how have we been able to do this? First, we need to take advantage of our intelligent capability for abstract thought and reasoning. As I said earlier, we too fear fire, but we need to be able to think about it and be curious enough to not only rationalize that we might be able to harness its power, but that it would also be useful. This ability to deduce the control and use of fire requires high-level reasoning.

Denton also points out that for a fire to be sustainable it needs to be at least 50 centimeters across (or about a foot and a half). To create a fire of this size we need our upright stance to walk the distance to gather the right amount and size of branches. That means that our upright stance, free arms, the manipulative tools of our hands, and our discerning vision work together to allow us to create a sustainable fire.

Therefore, the control and manipulation of fire requires a combined use of most of our unique biological capacities. Think about this the next time you sit around a campfire or grill your supper on a warm summer day. It’s part of what makes us human!

Human Anatomy and Genome

In this article I have been focusing on aspects of human biology that make us unique in the universe of living organisms. I discussed in some detail our unique intelligence, allowing us complex and abstract thought. We have a unique ability to communicate audibly and through a symbolic written word. These combine with our stereo vision and unique manipulative tool the hand, to allow us sole possession of the ability to use and manipulate fire. All of these capabilities are made possible by several unique aspects of our anatomy.

Humans have the largest brain of any primate species. Whales, dolphins, and elephants have larger brains, but size is not the main distinctive. Our human brain is structured like no other. If you were to open up just one cubic millimeter of our brain you would find over 100,000 cells with 4 kilometers of cell wiring and 1 billion connections between neurons. The structure and organization of our brain is definitely without parallel. Studies of our entire genome compared to chimpanzees indicate vast differences in non-coding sequences that influence the production of brain proteins. These changes are in the thousands.

In 1999, famous MIT linguist Noam Chomsky, reflected that “Thus, in the case of language, . . . (new research) is providing interesting grounds for taking seriously an idea that a few years ago would have seemed outlandish: that the language organ of the brain approaches a kind of optimal design, that it is in some interesting sense an optimal solution to the minimal design specifications the language organ must meet to be usable at all.” Without our unique brain structure, our language ability would not be forthcoming.

When comparing our skeletal structure to those of our supposed closest ancestors according to an evolutionary explanation, there are major changes that would have been needed to be accomplished in a relatively short time. Casey Luskin from the Discovery Institute does an admirable job digging into these differences and makes some sweeping conclusions. Numerous studies indicate that between the lineage of Australopithecus and Homo there would need to be significant changes in shoulders, rib cage, spine, pelvis, hip, legs, arms, hands and feet. But of these major transitions, the fossil record is silent.

Luskin also refers to a study by Durrett and Schmidt in 2007 that estimates that a single-nucleotide mutation in a primate species would take 6 million years to become fixed. But what is needed are multiple mutations in multiple segments of the skeletal system and in the physiology of the brain. Homo sapiens are far more unique than many have suspected. The more we learn, the more unique we become.

Since humans are created in the image of God, we expect human biological uniqueness. Even more significantly, bearing His image indicates an affinity for humans by the Creator we cannot fully comprehend.

1. Michael Denton, Nature’s Destiny: How the Laws of Biology Reveal Purpose in the Universe (New York: The Free Press, 1998).

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Where did we come from? Heather Zeiger uses Stephen Meyer's book Signature in the Cell to logically show that the best answer is an intelligent cause&mdashGod&mdashrather than natural causes. Where&hellip

Dr. Ray Bohlin explains how the Discovery Institute's book "Science and Human Origins" reveals why evolutionary theory cannot account for human origins. Just What Needs to be Accomplished From Ape-like&hellip

Dr. Ray Bohlin

Raymond G. Bohlin is Vice President of Vision Outreach at Probe Ministries. He is a graduate of the University of Illinois (B.S., zoology), North Texas State University (M.S., population genetics), and the University of Texas at Dallas (M.S., Ph.D., molecular biology). He is the co-author of the book The Natural Limits to Biological Change, served as general editor of Creation, Evolution and Modern Science, co-author of Basic Questions on Genetics, Stem Cell Research and Cloning (The BioBasics Series), and has published numerous journal articles. Dr. Bohlin was named a Research Fellow of the Discovery Institute's Center for the Renewal of Science and Culture in 1997, 2000 and 2012.

What is Probe?

Probe Ministries is a non-profit ministry whose mission is to assist the church in renewing the minds of believers with a Christian worldview and to equip the church to engage the world for Christ. Probe fulfills this mission through our Mind Games conferences for youth and adults, our 3-minute daily radio program, and our extensive Web site at www.probe.org.

Further information about Probe's materials and ministry may be obtained by contacting us at:


How Many Cells Are In Your Body?

A simple question deserves a simple answer. How many cells are in your body? Unfortunately, your cells can't fill out census forms, so they can't tell you themselves.

A simple question deserves a simple answer. How many cells are in your body?

Unfortunately, your cells can’t fill out census forms, so they can’t tell you themselves. And while it’s easy enough to look through a microscope and count off certain types of cells, this method isn’t practical either. Some types of cells are easy to spot, while others–such as tangled neurons–weave themselves up into obscurity. Even if you could count ten cells each second, it would take you tens of thousands of years to finish counting. Plus, there would be certain logistical problems you’d encounter along the way to counting all the cells in your body–for example, chopping your own body up into tiny patches for microscopic viewing.

For now, the best we can hope for is a study published recenty in Annals of Human Biology, entitled, with admirable clarity, “An Estimation of the Number of Cells in the Human Body.”

The authors–a team of scientists from Italy, Greece, and Spain–admit that they’re hardly the first people to tackle this question. They looked back over scientific journals and books from the past couple centuries and found many estimates. But those estimates sprawled over a huge range, from 5 billion to 200 million trillion cells. And practically none of scientists who offered those numbers provided an explanation for how they came up with them. Clearly, this is a subject ripe for research.

If scientists can’t count all the cells in a human body, how can they estimate it? The mean weight of a cell is 1 nanogram. For an adult man weighing 70 kilograms, simple arithmetic would lead us to conclude that that man has 70 trillion cells.

On the other hand, it’s also possible to do this calculation based on the volume of cells. The mean volume of a mammal cell is estimated to be 4 billionths of a cubic centimeter. (To get a sense of that size, check out The Scale of the Universe.) Based on an adult man’s typical volume, you might conclude that the human body contains 15 trillion cells.

So if you pick volume or weight, you get drastically different numbers. Making matters worse, our bodies are not packed with cells in a uniform way, like a jar full of jellybeans. Cells come in different sizes, and they grow in different densities. Look at a beaker of blood, for example, and you’ll find that the red blood cells are packed tight. If you used their density to estimate the cells in a human body, you’d come to a staggering 724 trillion cells. Skin cells, on the other hand, are so sparse that they’d give you a paltry estimate of 35 billion cells.

So the author of the new paper set out to estimate the number of cells in the body the hard way, breaking it down by organs and cell types. (They didn’t try counting up all the microbes that also call our body home, sticking only to human cells.) They’ve scoured the scientific literature for details on the volume and density of cells in gallbladders, knee joints, intestines, bone marrow, and many other tissues. They then came up with estimates for the total number of each kind of cell. They estimate, for example, that we have 50 billion fat cells and 2 billion heart muscle cells.

Adding up all their numbers, the scientists came up with … drumroll … 37.2 trillion cells.

This is not a final number, but it’s a very good start. While it’s true that people may vary in size–and thus vary in their number of cells–adult humans don’t vary by orders of magnitude except in the movies. The scientists declare with great confidence that the common estimate of a trillion cells in the human body is wrong. But they see their estimate as an opportunity for a collaboration–perhaps through an online database assembled by many experts on many different body parts–to zero in on a better estimate.

Curiosity is justification enough to ponder how many cells the human body contains, but there can also be scientific benefits to pinning down the number too. Scientists are learning about the human body by building sophisticated computer models of lungs and hearts and other organs. If these models have ten times too many cells as real organs do, their results may veer wildly off the mark.

The number of cells in an organ also has bearing on some medical conditions. The authors of the new study find that a healthy liver has 240 billion cells in it, for example, but some studies on cirrhosis have found the disease organ have as few as 172 billion.

Perhaps most importantly, the very fact that some 34 trillion cells can cooperate for decades, giving rise to a single human body instead of a chaotic war of selfish microbes, is amazing. The evolution of even a basic level of multicellularity is remarkable enough. But our ancestors went way beyond a simple sponge-like anatomy, evolving a vast collective made of many different types. To understand that collective on a deep level, we need to know how big it really is.


Wiener (1932) was the first to examine the genetic basis of arm folding by comparing parents and offspring, with the following results:

Each of the three kinds of matings has about the same proportion of R and L offspring, so Weiner (1932) concluded that there is no genetic basis for arm folding preference. If the myth were true, two L parents could not have an R child, but close to half of the children of LxL matings are R. For some reason, people kept doing family studies of arm folding, so that Reiss and Reiss (1998) were able to summarize the numbers from 12 studies:

There is some association between parents and offspring, in that R x R parents have a higher proportion of R offspring than do L x L parents. All studies have found many R offspring of L x L parents and L offspring of R x R parents, so even if there is some genetic influence on arm folding, it is not a simple one-locus, two-allele genetic trait.


Severed Octopus Arms Have a Mind of Their Own

Octopuses are renowned for their smarts (they can open jars!), and most of their 130 million IQ-raising neurons are located not in their brains but along their eight tentacles. Researchers think this allows octopuses to become the ultimate multi-taskers, Katherine Harmon, who’s got a book on octopi coming out soon, writes at Scientific American, since each of their arms can busily work away at some pesky mollusk shell or feel around in some new corner of habitat, nearly independent of the brain.

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And these arms can continue reacting to stimuli even after they are no longer connected to the main brain in fact, they remain responsive even after the octopus has been euthanized and the arms severed.

In one experiment, researchers chopped off euthanized octopuses’ tentacles, chilled them in water for an hour, and then still managed to get a split-second response when they probed the severed limbs. Other research found that, when encountering a piece of food, a severed limb will snatch it up and try to move it in the direction of a phantom octopus mouth.

If an octopus’ arm is cut off without the poor guy being euthanized, it’s no sweat for the cephalopod. While cut-off limbs do not regrow a new octopus, à la starfish, the octopus can regenerate tentacles with a far superior quality than, say, a lizard’s oftentimes gimpy replacement tail, Harmon writes.

To do this, octopus use a protein called protein acetylcholinesterase, or AChE. Humans have this protein, too, but our store of the molecule is much less active than an octopus’. Harmon describes what happens when an octopus loses its leg:

Within three days, some cascade of chemical signals cued the formation of a “knob,” covered with undifferentiated cells, where the cut had been made. And further molecular signals were responsible for the “hook-like structure” that was visible at the end of the arm in the second week. Around that time, a mass of stem cells and a hefty amount of blood vessels have arrived at the site. Yet by day 28, these features disappeared. And for the next hundred days or so, the arm tip grew back in to resemble the original one.

AChE rose, peaked and dipped throughout this process, conducting a regrowth orchestra of tissues, nerves and structures until the arm was good as new. The ultimate hope, of course, is to harness the AChE trick for human limb regeneration, although that’s still a distant vision. On the other hand, we probably don’t want to start implanting neurons in our arms: imagine a severed human hand crawling across the floor, creating a real-life Addams Family moment.


Watch the video: Θεωρία Παιγνίων: Το Δίλημμα του Φυλακισμένου (July 2022).


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