How do fossils support the theory of evolution?

Expert Answers

An illustration of the letter 'A' in a speech bubbles

Fossils are remains of plants, animals, or other organisms that have been preserved in nature such as bones which are sometimes found buried in caves or other similar sites. Fossil records that are well-preserved reveal a lot of information about the past, particularly the environment of the organisms, their interaction with other organisms within their era, and even their relationship with other organisms to which they may be related - whether their ancestors or descendants.

In the study of evolution, fossil records become relevant because, by identifying fossils and using dating techniques to build a timeline of species, ancestry can be established at best, or chronology at worse. With DNA sequencing and carbon-dating, direct relationship between species with available fossil records can be established. This is the ideal case which directly supports evolution. Meanwhile, if no high quality and specific information is available, the existence of fossils, and the specific time point/era in which the organisms existed, will allow for the generation of a timeline of species, which can help a lot in validating evolutionary hypotheses, or generating new ones. 

For instance, fossil records can reveal transitional forms between related species. The ancestor of the gray whale had nostrils in front of its skull, while the modern gray whale has its on top. Fossil records have been identified where a related, potentially transitional form, has nostrils in the middle of the skull. Thus, a less coarse transition can be established, and this is made possible by fossil records. 

Homologies can also be established. Homology is the degree of similarity between similar structures in organisms. Related organisms will have more similar structures than more diverse organisms -- although the function can complicate things, and since we possibly have not encountered organisms whose fossils are being studied, it may be difficult to be conclusive with regards to function, but structure identification is more definitive. 

Fossil records have allowed for identification of similarities and relationships between mammals, birds, and other organisms in the modern world and their ancestors. Another example would be fossil records of ancestors of humans. There are available fossil records that trace evolution of humans by the development of certain features that distinguish humans from their primate cousins - like opposable thumbs and bipedalism. Fossil records also then help in creating ancestral/evolutionary trees. Gaps or missing links are usually filled in once fossil records are found that satisfy the hypotheses.

In general, fossil records support the theory of evolution because it allows us to trace the past to the present. 

Approved by eNotes Editorial
An illustration of the letter 'A' in a speech bubbles

How do transitional fossils support the theory of evolution?

Transitional fossils are fossilized remains that exhibit traits from two groups - an ancestral group and a descendant group. Because of this characteristic, they can be used to construct phylogenetic trees, and determine how one species is related to an older species. This can particularly be a lot of help when a common trait is found in a descendant/derived species and an ancestral group where the descendant species has a very different mode of living or gross anatomy from the older group. 

The relationship between the ancenstral group and the descendant group, however, is not clearly claimed to be a direct due to the fact that evolution is a branching process, and that the point of divergence cannot clearly be identified, particularly how near or how far the transitional species is from the point of divergence. 

Nonetheless, these transitional fossils serve as evidence to Darwin's Theory of Natural Selection as conserved traits are proven to survive the test of time. This also supports evolution in a way that is shows gradual change in traits of species over generations due to change in living conditions. 

An example of a transitional fossil is the Austrolaphitecus afarensis. This fossil is a hominid which has the traits of both the quadrepedal ape ancestors and modern bipedals. 

See eNotes Ad-Free

Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Get 48 Hours Free Access
Last Updated on