JISHOU, HUNAN — If you feel as if your dog or cat is a member of the family, you’re right. You and your pet are very distant cousins. Very, very distant cousins.
The Timetree of Life allows you to find out how long ago any two organisms had a common ancestor, also known as the Most Recent Common Ancestor (MRCA).
You and your dog, Fido, have a common ancestor, a mammal that lived about 95 million years ago in the Cretaceous period. Fido and his feline pal, Fluffy, have an MRCA, a carnivore that was alive 55 million years ago.
Humans’ closest cousin in the animal kingdom is the chimpanzee (Pan troglodytes). Our MRCA lived about 6.3 million years ago. Its descendants also included other members, now extinct, of the genus Homo and the genus Australopithecus.
When he first proposed the theory of evolution, Charles Darwin surmised that every organism on Earth was descended from a common ancestor. Time, isolation and environmental pressures led different populations to diverge into new species. Until the development of genetic analysis, biologists relied on anatomical and behavioral similarities, as well as the fossil record, to judge how closely related two organisms are.
Genetic research has changed all that. Now we can determine how closely different organisms are related, and when approximately their most recent common ancestor lived.
Every organism has its own DNA, but since they are all related, portions of more ancient DNA molecules are embedded in it. We know, for example, that humans and chimps are more closely related than humans and gorillas, because humans and chimps have more DNA in common than humans and gorillas. Or, to say it another way, the MRCA of humans and gorillas is older than the MRCA of humans and chimps.
The Timetree of Life website puts this information at your fingertips, but you have to use the taxonomic (scientific) name of the organisms you want to trace. For help with that, you can visit a webpage at the National Center for Biotechnology Information, where you can enter the common name for a critter (“cat”) and get the taxonomic name (Felis catus) for it.