PBS Becoming Human (3 of 3) Spencer Wells, geneticist, says all modern humans share 99.9% genetic diversity at the DNA level.  https://en.wikipedia.org/wiki/Neanderth … me_project says neanderthals share 99.7% genetic features with modern humans (chimps are at 94%). 

Is it possible for an isolated community of modern humans today to have something less than 99.9% shared dna diversity compared to another group?  Though this is not going to be a popular research area for social reasons, has anyone documented the genetic diversity among modern humans?

My questions:

how is "species" defined regarding archaic Homo examples when we now have access to their genetic data? neanderthal, denovisians and (according to the same PBS program) neanderthals had larger brains and had the genetic markers indicative of human speech ability.

Why are H. neanderthals not H. sapien?  Whatever is that answer, why will that not apply to modern human groups based on the same criteria?  Thank you.

great questions! the whole issue of separate species/subspecies is a subject of much debate, some polarisation of views and very little consensus! largely that is because there is no one solid accepted definition of a species. Many of the comments in the url below are I think helpful.
https://www.quora.com/In-what-sense-wer … mo-Sapiens

so extending that to isolated modern humans is equally difficult - my own view would be that given we all originated from African ancestors within the last 80-100,000 year ago the chances of any remote group of modern humans having less than 99.9% similarity seems very remote (pun intended) to me.

I'll be interested to see what others on the site think.

also an intersting and somewhat relevant article just published in Nature:
http://www.nature.com/nature/journal/v5 … 16544.html