Evolution: when and where did the last pregnancy between the chimpanzee branch and the human branch occurred?

Your question is based on a misunderstanding of how evolution occurs.





It is a bit like asking when the last couple in Rome who spoke Latin got pregnant and gave birth to the first Italian-speaker.





Or (more to your branching question), when was the last child educated in Latin, and the branch occurred between the Italian branch and the French branch.








In other words, the process of evolution and branching occurs in *POPULATIONS*, not in *individuals*.





Consider a *POPULATION* of some primate species living in the mountain forests of Eastern Africa, consisting of (say) 10,000 individuals. If climate change causes the valleys between the mountain ranges to dry up, then if one population of 4,000 of them are in one mountain range that is separated from the other 6,000 in the remaining mountain ranges, then the two *POPULATIONS* will be unable to exchange genetics. So both populations will continue to have babies, and mutations, and experience natural selection, but in a way that new adaptations in one population have no way to spread to the other population. Until eventually the two populations will have lost the ability to interbreed. They are now two *species*. The ancestors of one could go on to become the chimpanzee branch, and the other the human branch.





But at NO POINT is there ever a "last pregnancy."








But to answer your question about *when* this branching occurred ... based on DNA evidence (the molecular clock, which counts mutations in certain key chromosomes where the mutations are known to occur at a certain rate per thousand years), this branching occurred between 4.5 and 6 million years ago.|||you mean the last time the ancestor of a human and theancestor of a chimp were able to interbreed?





because that's a very different question from what you asked...


you asked 'when's the last time a human and a chimp made a baby', that answer is NEVER (by definition of the word species)





if you meant 'the last time the ancestor of a human and theancestor of a chimp were able to interbreed' the answer is somewhere around 5 to 7 million years ago (the line's a little blurry)|||Molecular evidence places the branching at something like 6 to 7 million years ago. The present geographical range of chimps and the geographical limitations of fossils of human ancestors (not shared in common with chimps), such as /Australopithecus/, both indicate Africa. East Africa (in or around Ethiopia) is presently the best backed candidate.|||No one can tell you that, exactly.


It occurred some time between 7.5 million years ago and 4.5 million years ago, somewhere in Africa.





I usually say that it occurred about 5 million years ago, and that after that time there was no significant hybridization.|||Never. By the time chimpanzees and humans had evolved from their common ancestor, they had already become different species, so pregnancy could not have occurred.


.|||The final occurrence may have been as recently as 5.4 million years ago, but the divergence of the lines had already been underway.|||Never. Chimpanzee and Humans are from the same ancestor. Humans didn't come from chimpanzee.|||Creationism: Did god spit on his hand first before he jerked off a rib to start the whole female race?