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The clarification of the mechanism of action of biological evolution was only concretely obtained from the works of two scientists, the French Jean Baptiste Lamarck (1744 - 1829) and the English Charles Darwin (1809 - 1882).
The evolutionary discussion, however, raises great controversy. For this reason it is necessary to describe initially the main evidence of evolution used by evolutionists in defense of their thesis. Among the most used are:
- the fossils;
- the embryological and anatomical similarity between the components of some animal groups (notably vertebrates),
- the existence of trace structures and
- the biochemical evidence related to certain molecules common to many living things.
A fossil (from Latin fossilis, taken from the earth) is any trace of a living being that inhabited our planet in ancient times, as a body part, a footprint and a body impression. The study of fossils allows us to deduce the size and shape of the organisms that left them, enabling the reconstruction of a possibly similar image of animals when they were alive.
Fossil of a dinosaur and a plant.
A fossil forms when the remains of an organism are safe from the action of decomposing agents as well as natural weather (wind, direct sun, rain, etc.). The most favorable conditions for fossilization occur when the body of an animal or plant is buried at the bottom of a lake and quickly covered with sediment.
Depending on the acidity and minerals present in the sediment, different fossilization processes may occur. THE permineralizationFor example, it is the filling of the microscopic pores of a being's body with minerals. The replacement consists in the slow exchange of the organic substances of the corpse for minerals, turning it into stone.
Gastropod preserved by permineralization
Radioactive Dating of Fossils
The age of a fossil can be estimated by measuring certain radioactive elements present in it or in the rock where it is located.
If a fossil still contains organic substances in its constitution, its age can be calculated with reasonable precision by the carbon-14 method. O carbon-14 (14Ç) is a radioactive isotope of carbon (12Ç).
Scientists have determined that the half-life of carbon-14 is 5,740 years. This means that in this period half of the carbon-14 in a sample disintegrates. At the time of death, a fossilizing organism contains a certain amount of 14C, which scientists estimate to be the same as that found in beings today. After 5,740 years, only half of the amount of 14C present at the time of death will remain in the fossil. After another 5,740 years, it will have disintegrated half of what remains, and so on, until there is virtually no more radioactive isotope in the remaining organic matter.
Thus, by measuring the residual amount of carbon-14 in a fossil, it is possible to calculate how much time has passed since the death of the living creature that originated it. For example, if a fossil has 1/8 of the estimated radioactive carbon for a living organism, it means that its death must have occurred between approximately 22 and 23,000 years.
Because the carbon-14 half-life is relatively short, dating for this isotope only serves fossils under 50,000 years old. To date older fossils, “paleobiologists” use longer half-life isotopes that can be found in fossil rocks. For example, rocks that formed a few million years ago may be dated via the isotope. Uranium-235 (235U), whose half-life is 700 million years. For even older rocks hundreds of millions of years old, you can use the potassium-40, which has a half life of 1.3 billion years.