Danevan

Hello, just joined the site because have been watching the new Brian Cox series and it reignited a problem that I have had understanding an anthropological concept for some time. Some background; I am a veterinary scientist, I remember doing some work at uni on speciation in orang-utans. It was fascinating and what I remember from it was the discussion of the point at which speciation occurs. People have done research into the number of genetic differences between the two major subtypes. Even though when kept together the two still seem perfectly able to breed and produce viable off spring, their differences on a genetic level are greater than between some different species of apes. The upshot was that my understanding has always been that if individuals can mate and produce viable offspring then they are, by the most popularly accepted definition of the same species. So, even though lions and tigers, horses and donkeys can reproduce, as the off spring are nearly always sterile, they are not of the same species. I love watching documentaries on human evolution and I have trouble understanding how the same principle is applied to hominids. Recently I have seen several programs talking about the fact that it is now accepted that early homo sapiens interbred with Neanderthals, to the extent that perhaps between 10-15% of some human genomes could be 'neanderthal'. So, if that's right and homo-sapiens and Neanderthals were breeding and those off-spring were going on to contribute significantly to the human genome, surely they were the same species? However most authors insist they were a different species. I also saw a commentator recently discussing the recent allocation of what had been previously thought of as the same species into different species based on phenotypic variations such as dental variations or mandible shape. Yet I look at dogs and the variety of phenotypic examples, all from the same 'species' who are perfectly able to reproduce effectively. So, is there a broadly used definition of species amongst the early hominids that explains why different s, which existed alongside homo-sapiens could have contributed to our dna? Obviously there are any number of different species further up the tree that have contributed their dna to what eventually became modern humans but would not have been able to inter-breed with them. But isn't anyone who could breed with homo-sapiens, by definition homosapien? I'd be happy to follow up any useful links if you have them, Cheers in advance