The theory of evolution is a shortened form of the term “theory of evolution by natural selection,” which was proposed by Charles Darwin and Alfred Russel Wallace in the 19th century.
What is the theory of evolution?
In the theory of evolution or natural selection, organisms produce more offspring than can survive in their environment. Those that are better physically equipped to survive grow to maturity and reproduce. Those that are lacking in such fitness, on the other hand, either do not reach an age when they can reproduce or produce fewer offspring than their counterparts.
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Natural selection is sometimes called “survival of the fittest” because the “fittest” organisms — those most suited to their environment — are the ones that reproduce most successfully and are most likely to pass on their traits to the next generation.
If an environment changes, the traits that enhance survival will also gradually change or evolve. Natural selection was such a powerful idea in explaining the evolution of life that it became established as a scientific theory. Biologists have since observed numerous examples of natural selection influencing evolution.
New fossil discoveries
It was in the 19th century that fossil discoveries picked up pace, and branches of science such as geology, archeology, and paleontology came to the forefront. Scientists fathomed that they could learn about the fauna and flora of various periods by analyzing sedimentary layers of rocks.
Each rock layer has different organisms, and scientists could find family resemblances and seek explanations regarding evolution. Darwin’s theory relied heavily on fossils and living organisms and tried to fit them into a pattern, but a precise mechanism was lacking.
This mechanism was established after DNA was discovered in 1869 by Swiss researcher Friedrich Miescher, who originally tried to study the composition of lymphoid cells (white blood cells). Instead, he isolated a new molecule called nuclein (DNA with associated proteins) from a cell nucleus.
The incompleteness of the fossil record
Each fossil discovery represents a snapshot of the process of evolution. Because of the specialized and rare conditions required for a biological structure to fossilize, many important species or groups may never leave fossils.
Even if they leave fossils, humans may never find them — for example, if they are buried under hundreds of feet of ice in Antarctica. The number of species known through the fossil record is less than 5 percent of the number of species alive today. Fossilized species may represent less than 1 percent of all the species that have ever lived.
The fossil record is very uneven and is mostly comprised of fossils of organisms with hard body parts, leaving most groups of soft-bodied organisms with little to no fossil record.
Groups considered to have a good fossil record, including transitional fossils between these groups, are the vertebrates, the echinoderms, the brachiopods, and some groups of arthropods. Their hard bones and shells fossilize easily, unlike the bodies of organisms like cephalopods or jellyfish.
Romer’s gap is an example of an apparent gap in the tetrapod fossil record used in the study of evolutionary biology. These gaps represent periods from which no relevant fossils have been found. Romer’s gap is named after paleontologist Alfred Romer, who first recognized it. Romer’s gap spanned approximately 360 to 345 million years ago, corresponding to the first 15 million years of the Carboniferous Period.
There has been much debate over why there are so few fossils from this period. Some scientists have suggested that the geochemistry of the period caused bad conditions for fossil formation, so few organisms were fossilized. Another theory suggests that scientists have simply not yet discovered an excavation site for these fossils due to inaccessibility or random chance.
Still, scientists can deduce how evolution took place
While there are gaps in found fossils, it is not difficult to deduce how evolution took place by analyzing the development of a species. Several examples can be mentioned in this context, including the trunks of elephants, the necks of giraffes, and the excellent nocturnal vision of predatory mammals.
Scientists also point out the whale family for explaining the theory of evolution. Whales evolved from early land mammals, adapting to life in the oceans by losing their hind limbs, growing a flat tail, developing flippers, and streamlining their bodies. The front fins resemble the same skeletal pattern of legs seen in small mammalian species.
This brings us to the favorite topic of humans evolving from apes. Evolution does not teach that humans descended from apes; it states that both have a common ancestor. The gaps in the fossil record can be justified through shreds of evidence, carbon dating, and genetics.
The ongoing debate between creationists and evolutionists
Questions about scientific integrity and rigor are at the heart of debates among creationists and evolutionists. Creationists often justify their rejection of biological evolution by claiming that the methodologies and interpretations of evolutionary scientists are flawed.
The conflict is, at its heart, one of authority and ways of knowing. Neither creationists nor evolutionists can legitimately claim all the answers to the questions that human beings ask.
Albert Einstein once commented:
“Science without religion is lame; religion without science is blind.”