The Evidence Behind Evolution
The origin of life has been a mystery that has puzzled many great minds throughout the history of civilization. Theories to explain this phenomena have ranged from divine creation to spontaneous generation, however neither have the evidence to reach a universally accepted conclusion. Instead, they’re based merely on circumstance and speculation. On the contrary, the theory of evolution is backed with commanding evidence.
One of the most compelling pieces of evidence in support of evolution is the record of fossils. The fossil record, in simple terms, is the chronological placement of fossils in their respective time periods. This chronological placement of fossils clearly shows organisms have been incrementally changing over time, becoming more biologically sophisticated and advanced.
At the beginning of the fossil record, furthest back in time, you find very simple, basic organisms such as the Cooksonia plants. These plants were very primitive, vascular plants. There was no differentiation between the root, stem or leaves. Clearly, plants no longer look like that. They have evolved and changed, but still contain some of the basic characteristics of their ancestors. The fossil record shows this progression to modern plants. The same can be applied to any group of fossils.
“The fossil record is fundamental to an understanding of evolution,” says renowned paleontologist Michael Benton. “Repeated, and tough, regimes of testing have confirmed the broad accuracy of the fossils and their dating, so we can read the history of life from the rocks with confidence.”
With all that being said, there is still an incredible amount of evidence to support evolution without even examining a single fossil. Another piece of evidence are the homologous structures, or shared features, between organisms. One of the best examples of homology can be seen in the forelimbs of mammals. While on the outside the forelimbs of say, a human, a bat and a whale, look very different, they’re structurally quite similar. All three contain the ulna, radius, and humerus bone. Each of these organisms also has carpels, and a total of five digits extending from their limb. The similarity in build indicates that although these organisms look very different now, they shared a common ancestor.
Branching off from homologous structures, another type of shared characteristic exists between many organisms; vestigial structures. A vestigial structure is a structure that serves no purpose to an organism. For example, the wings of flightless birds such as ostriches and emus are vestigial. The eyes of many cave dwelling species of salamanders are vestigial because the amphibians are actually blind. Because other organisms have these same organs, only in a functional form, its evident that both evolved from a common ancestor.
In addition to homologies, many organisms share characteristics during embryonic development. In fact in the case of vertebrates, the early stages of development are nearly identical. As the image shows, they're virtually indistinguishable. They all have:
- a notochord (developing backbone)
- a dorsal hollow nerve cord
- a post-anal tail
- a series of paired branchial grooves
Some of those characteristics, such as the tail, do not develop fully in all organisms- yet oddly they appear in early development. These similarities indicate that these traits and embryonic developmental processes were inherited from a common ancestor.
The key component that ties all the pieces of the evolution puzzle together is the science of genetics. The science of genetics shows us how traits are passed between generations, and how they evolve. There are naturally occurring genetic variations in nature. Some of these variations are advantages, while others are not. As common sense would indicate, survival of the fittest takes over. The organisms with disadvantages die off, while the organisms with the advantages are more likely to survive and pass on their genes. Over thousands of years, this continuous reproduction and passing on genes results in changes in organisms, making them more suited to their environment, a process known as natural selection.
The science of genetics is important to natural selection because it rules out the possibility of spontaneous adaption. An organism can not change to meet the needs of its environment instantly, but a species can change overtime as the gene pool is modified. For example, fossils indicate that thirty to fifty million years ago, giraffes were significantly shorter than they are now, which prevented them from feeding on high vegetation like they do now. When the competition for food became fierce, a giraffe’s neck could not grow longer simply because it needed to- its genes would not allow that. However, organisms with natural variations, genetic mutations for longer necks, had an advantage. They were able to survive the competition for food, and pass on their genes for longer necks to their offspring who would then also develop the trait.
The evidence to support evolution is strong, valid and undeniable. Such a brilliant idea should not ignorantly be dismissed as nothing but a thoughtless theory, when it is clearly much more.
