I read that the chimps share 99% of the genome with the humans and this is given as one of the strong evidence that humans and chimps share the common ancestry. Also I read that we share 95% genome with potato and high percentage with other animals like pigs. If this is true, how could we conclude that we are one of the apes based on genetic matching.
ANSWER: Dear Amtry,
The more genetic information shared between two taxonomic groups, the more recent their common ancestor. This is a basic rule of biology.
We classify organisms on the basis of recency of descent from a common ancestor. In the cladistic system, specialization and differentiation after splitting from a "sister" taxon (e.g., humans and chimpanzees share a recent common ancestor), one does not assign a group to its own classification just because it seems more "special" than its relatives. For this reason, humans are included in Family Hominidae along with Chimpanzees and Gorillas. We are all considered great apes, along with orangutans, simply because we are descended from a common ancestor. We could just as easily consider all great apes to be "humanoids", but because the great ape taxonomic grouping was created earlier, it has precedence and we are all classified in it because of our common ancestry.
I hope this helps.
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QUESTION: Thanks for your reply. I wanted to know how could 99% genetic matching with chimpanzees can be cited as evidence for common ancestry with chimps when we have high genetic matching with other animals too.
But we have *greater* genetic similarity to chimps than to any other organisms. That is how we base classification: recency of common descent. By definition, the more shared, derived characters two species share, the more recently they shared a common ancestor.
Species derived from a common ancestor are classified in the same taxonomic group. Hence, humans, chimps and other great apes are all now classified in Family Hominidae. It is clear from our shared morphology, as well, that we are great apes. Some of us greater than others. :)