yes exactly... and if evolutionists really believe that the Australian Aboriginals are 40,000 years old, then they were isolated for all that time and yet they were able to reproduce offspring with europeans only a few hundred years ago.
So if 40,000 years is not enough time for an isolated human population to 'speciate' then perhaps they need to re think what sepciation actually is and how it works.
Sounds like an interesting thread proposal (as for population size: we're up there with the best of them - but I think some of our domesticated species (esp sheep) probably outnumber us as well as small non insect animals such as plankton and maybe even some rodents outnumber us).