The Evolutionary Relationship of Chimpanzees and Humans

In a strict Linnaean taxonomy, humans do appear to have split from the great apes somewhere in their evolutionary relationship. However, it is important to bear in mind that a phenetic taxonomy only analyzes modern traits. It does not take into account the time when a trait might have diverged. A cladistical tree, on the other hand, will often show humans not branching off from the ape line and, with the exception of the orangutan, in the same family as the bonobo, gorilla, and chimpanzee. We only begin to truly diverge at the subfamily and tribe level. In this light, it is crucial to realize that humans are not evolved from chimpanzees. We simply share a common ancestor. It is misleading to state that humans evolved from chimpanzees or, to be fair about this, that chimps evolved from humans.

There are obvious, phenotypical differences between chimps and humans, but the reason for this may only result from a few, select genes. For example:

One potential candidate is the gene FOXP2, whose protein plays an important role in language development. The FOXP2 protein differs by two amino acids in humans, compared to chimps and other apes (Raven, 2005).

Still, for sake of argument, it should be remembered that there have been mutations and selective pressures imposed on our ancestral line that have resulted in numerous differences between humans and great apes. These are more than enough to account for the phenotypical differences, despite the apparent genetic similarity. For example, comparative, genetic studies often state a great deal about evolutionary relationships, but they can be misleading in many regards. It is haphazard to simply state that chimps/bonobos and humans are genetically similar without examining "which genes differ between humans and chimps, how those genes differ, and what those genes do" (Park, 2008).

The reasoning for this, according to Park (2008), is:

1) Since there are only four bases in the genetic code, any two long sequences of DNA from any two species are likely to be at least 25 percent identical.

2) Different sections of DNA evolve at different rates, so some portions of our two species' DNA might be completely identical while others are very different (p. 209).

We also might want to consider which genetic sequences chimpanzees, gorillas, and orangutans have in common and which are missing (gaps) from our shared lineage:

Most of the gaps are less than 30 nucleotides long. The longer ones, typically 300 nucleotides, usually involve the transposable element ALU, a DNA sequence that has multiplied and inserted new copies of itself throughout the human genome far more frequently than in the chimp genome (Raven, 2005).

At any rate, comparative analysis involving phenotypical traits, derived characteristics, and genes continues to make headway as the years pass. Luckily, we are no longer stuck within the confines of a phenetic taxonomy. We do share a unique relationship with all the great apes that is much closer (and more complex) than Linnaeus realized.

References

Park, M. (2008). Biological Anthropology. New York: McGraw-Hill.

Raven, P. (2005). Biology. New York: McGraw-Hill.