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What is the Fossil Evidence for Evolution?

written by: Emma Lloyd • edited by: Donna Cosmato • updated: 4/5/2012

Evolution is still a subject under contention due to the religious controversy surrounding the subject. One argument is that there is a lack of fossil evidence for evolution, but is this claim true?

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    The Creation of Fossils

    There is, in fact, a relative lack of fossil evidence for evolution, but this isn’t because evolution didn’t happen. Fossils are rare for two reasons—first, that living things decompose relatively quickly after death. Second, the conditions which allow fossilization to occur are relatively rare.

    For fossilization to occur, the remains of an organism must be covered by layers of sediment soon after death. There are few exceptions to this requirement. For example, if an organism becomes frozen, dries out, or is located in an environment which is free of oxygen, it can be well-preserved even if there is no sediment layer.

    These strict conditional requirements mean that it is rare to find transitional species in the fossil record. As noted by Charles Darwin, transitional species—which exhibit traits of both their ancestors and descendants—are often in existence for a relatively short period of time, in a fairly restricted geographical location. This makes it much less likely that a member of a transitional species will die in just the right circumstances to make fossilization possible.

    Despite these important requirements, large numbers of fossils have been found. However, rather then entire large animals, what is often found are much smaller pieces—teeth, bone fragments, or tiny organisms. Larger fossils are more likely to be displayed in museums and other locations, but these types of fossils are rarer than this tendency suggests.

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    Evidence for Evolution

    Given all of this, it does not seem that a lack of fossil evidence should lead to the conclusion that evolution did not occur. However, there is in fact a great deal of fossil evidence for evolution—but it’s not of a kind that is immediately recognizable by the layperson. This means that to the average person trying to argue against evolution on religious grounds, the fossil argument actually seem to work in their favor.

    But does it really? In fact, the fossil record can tell us quite a bit about evolution, and the record is highly consistent with the way evolution is thought to work.

    Simply looking at the diversity of life—particularly the genetic diversity—is in itself evidence for evolution, and it is easily possible to find plenty of evidence for evolution with ever considering fossils. Examining fossil evidence does provide one important advantage, however, in that it allows us to actually look at the past, where the vast bulk of human (and non-human) evolution took place.

    The simplest fossil evidence for evolution is simply that the fossil record suggests that life appeared incrementally, with simple organisms appearing first, and more complex organisms evolving over time. The rock that fossils are embedded in (and the fossils themselves) can be dated, and in most cases these dates support the idea that the simpler organisms appeared much earlier than the more complex varieties.

    There are some gaps in the fossil record—most likely due to the conditional requirements as explained above—and some other anomalies, such as the Cambrian explosion, a period of time around 530 million years ago in which complex life forms appeared rapidly, whereas only very simple life forms had existed prior to that time. Overall, however, the fossil record is highly suggestive of a long series of small changes which occurred very gradually.

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    Other Scientific Evidence Backs up the Fossil Record

    Evidence obtained in other scientific disciplines—such as anatomy, biochemistry, and genetics—backs up evidence found in the fossil record. Anatomy and biochemistry analysis both back up the fossil record in showing the order in which organisms appeared in the fossil record.

    As for genetics, there are many recorded examples of human populations evolving—genetic mutation is, after all, simply evolution in action.

    In Africa, people are more likely to carry a gene called ‘sickle cell.” Two copies of the gene causes a person to develop a serious blood disease called sickle cell anemia, but a person with one copy of the gene is more resistant to malaria. There is, therefore, a survival-oriented reason for people in this part of the world to retain the gene, despite the harm it can inflict. In other parts of the world, where malaria is much less prevalent, populations evolved and lost the sickle cell gene, because it was no longer necessary.

    Between the fossil record and evidence from other scientific disciplines, there is in fact plenty of evidence for evolution—it’s just a question of knowing where to look, and in what context to view the evidence.