Evidences of Evolution

What Are the Evidences of Evolution?

The Darwinian theory of evolution eventually became accepted when scientists were able to supply the proofs Darwin had been unable to provide during his time. There are two kinds of evidence for Darwin's theory of evolution: direct and indirect. However, these evidences (whether direct or indirect) support the theory of evolution. What are some evidences or signs that organisms change through time?

Fossil Evidence

Most of what is known about life in the past comes from the study of fossils. Fossils are the remains or traces of ancient organisms. Many kinds of fossils have been found in various places in t he world.

Fossils formed from remains of organisms which were buried in layers of sediments. Over millions of years, these remains were replaced by minerals forming rock-like materials called fossils. Through time, the fossil-bearing rocks were exposed by movement of the Earth's surface by weathering; or dug out by fossil collectors, and paleontologists. Paleontologists are scientists who study fossils.

Many fossils have no living representatives today. By comparing the fossils in the different rock layers, scientists were able to infer the changes that occurred in the characteristics of various organisms and to reconstruct the order of changes that these generations of organisms have undergone.

The period at which the various fossilized organisms existed on Earth can be estimated. This is done by analyzing the age of rocks where fossils are found using radioactive elements or radioisotopes to determine the rate of decay of certain radioactive isotopes. This is called absolute dating position with respect to one another, rocks in deeper strata are generally older. This is called relative dating.

Biochemical Evidence

Another evidence of evolution is provided by the biochemical analysis of the organism's DNA and of the proteins they control. This activity will show you that DNA of organisms are important in determining evolutionary relationships.

In humans, the beta chain of hemoglobin is 147 amino acids long, which form the basic structure of the polypeptide chain. Some human proteins were found at the same positions with other mammals suggest that the protein had a common ancestor. In can be inferred then that organisms probably arose from some common ancestors. Thus, it is worth mentioning that the less amount of amino acid differences there are, the closer species are in evolutionary terms.

Embryological Evidence

Embryological development and similarities in DNA and protein composition provide additional evidence of evolutionary relationship. Indirect evidences of evolution include similarities in structure and embryonic development, vestigial organs and structures, and biochemical similarities.

Homologous structures are body structures of different organisms that have the same basic arrangement and pattern of embryonic development. Analogous structures have similar function but differ in appearance.

Vestigial Structures

Vestigial structures are parts of the body without a particular function. Examples are the flightless birds such as the kiwi in Australia, toes of pigs, "blind" eyes of salamanders, bats whose eyes are useless in the dark caves, the hind limb and hip bones of a python (Python sebae), and the pelvic bones of a baleen whale.

Vestigial organs are body structures that do not serve any apparent function of some organism but resemble structures their presumed ancestors had. They were most probably once functional in the ancestral form. In humans, some vestigial structures are the vermiform appendix, third molars (wisdom teeth), fused tail vertebrae (coccyx), and a complete set of muscles that wiggle the ears, just as the coyote does.

Share this