As often happens when I stay with my mother we discussed evolution. Initially we were discussing dogs (due to a program I recorded for her) being descended from wolves, with jackals and coyotes being separate but having in their past a common ancestor. But I explained that they can interbreed.
When discussing humans, and our common ancestor with Chimpanzees I tried to explain that there would be no sudden dramatic difference from the previous generation and the immediate one. That in theory it was literally conceivable that at this departure humans and chimpanzees would still be sexually attracted enough to each other to mate. Over time, with gradual steps, natural selection would occur and today we can clearly see a difference and a genetic inability to interbreed. As well as hopefully less of an impulse to do so than our early human ancestors.
I have no problem with saying that we are descended from Apes [we are technically human apes] – but maybe discussing the sex of our early ancestors is not something you think about. A bit like thinking about your parents having sex – you just do not picture it.
So a little bit of internet searching to see if my theory had any supporting evidence I came across this article from The Washington Post:
Human Ancestors May Have Interbred With Chimpanzees
Washington Post Staff Writer
Thursday, May 18, 2006; Page A01
When the ancestors of human beings and the ancestors of chimpanzees parted ways 6.3 million years ago, it was probably a very long goodbye. Some of their descendants may even have gone back for a final tryst.
That is the conclusion a group of scientists has reached, using a comparison of the genes of humans and their closest animal relatives to sketch a picture of human origins far more detailed than what fossil bones have revealed.
According to the new theory, chimps and humans shared a common apelike ancestor much more recently than was thought. Furthermore, when the two emerging species split from each other, it was not a clean break. Some members of the two groups seem to have interbred about 1.2 million years after they first diverged — before going their separate ways for good.
If this theory proves correct, it will mean modern people are descended from something akin to
chimp-human hybrids. That is a new idea, and it challenges the prevailing view that hybrids tend to die out.
It also strongly suggests that some of the oldest bones of “proto-humans” — including the 7 million-year-old Toumai skull unearthed in Chad in 2001 — may have belonged to a line of non-hybrids that died out, and were not human ancestors at all.
This narrative, by a team of geneticists and biostatisticians from the Broad Institute of the Massachusetts Institute of Technology and Harvard, not only casts new light on the origin of humans, but also raises questions about how all new species arise.
“This is contributing to the idea that species are kind of fuzzy. They become real over time, but it takes millions of years,” said James Mallet, a geneticist at University College London who was not involved in the new research. “We probably had a bit of a messy origin.”
The research is the latest fruit of the Human Genome Initiative, the effort to transcribe and read out the entire genetic message of human chromosomes, which was completed in 2003.
The evidence of ancestral chimp and human interbreeding emerged from comparing parts of their genomes to each other and to those of gorillas, orangutans and macaques. The scientists now want to know whether similar “hybridization events” happened between other emerging species.