Evidence Supporting Evolution

By Matt Baker   Updated 8 Jan 2013

When you hear the term Theory of Evolution, it is important to understand that the word theory does not mean that evolution is just an idea. In science, the word theory is used to mean a well-established model of how things work based on massive amounts of data and observation. That all life on earth evolved from a single common ancestor is a fact and this chart outlines the evidence supporting that fact.

	Fossils	Fossils provide a snapshot of what life on earth looked like at various stages in the past. These can be dated using methods such as Carbon-14 dating. What the fossil record shows is that, as you look deeper and deeper back in time, species become much less complex and fewer different types of species can be found. This suggests that life started off simple and then gradually evolved into the various different forms we see today. If a fossil of a modern species were ever found in a very ancient layer of the earth, this would disprove the theory of evolution. However, over 250,000 different types of fossils have been found and this has never happened.
	Comparative anatomy	Although animals are very different from one another, there are a lot of similarities as well. For example, all mammals have a similar bone structure in their limbs, even though the bones are different sizes. This indicates that there was once an original animal with that structure and that that structure eventually evolved into many different forms. Other similarities in anatomy structure can be seen in insects and plants.
	Vestigial structures	Vestigial structures are body parts that are no longer used. For example, dolphins and whales have bones for legs inside their body even though they no longer use them. This indicates that as animals evolve, they sometimes stop using certain body parts or end up using them in different ways. Examples of vestigial organs in humans include the appendix, the bump on the ear, wisdom teeth and goose bumps.
	Fetal development	Generally speaking, traits that developed earlier in evolutionary history (such as the backbone) appear first in the fetuses of all animals possessing that trait whereas traits that developed later, occur last (such as the cerebrum in humans). Watching a fetus grow therefore gives us a small glimpse of how that particular animal evolved. The fetus shown here is that of a dolphin.
	Geographical diversity	Species in the old world (Europe, Asia, and Africa) are often quite different than species in the new world (North & South America). Species in Australia and other remote islands (e.g. - kangaroos) are especially unique. This indicates that as animals spread out over the earth, they evolved differently in different locations.
	Chromosome No. 2	Chimpanzees have 24 pairs of chromosomes whereas humans have only 23. However, our extra long chromosome no. 2 matches almost perfectly with two of the chimpanzee's smaller chromosomes, indicating that our two species share a common ancestor and that at some point along our ancestral line, the two chromosomes became fused together to create our chromosome no. 2.
	Endogenous Retroviruses (ERV's)	ERV's are a special type of virus that infects DNA. They continue to get copied from generation to generation even when they no longer cause damage and are thus a type of fossil in our DNA. When you compare the DNA of humans and chimpanzees, you will find the exact same ERV's in the exact same locations, something that simply could not have happened by chance. Again, this indicates that humans and chimpanzees share a common ancestor.

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