system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any human populations without any Neanderthal DNA? Are there measurable differences from that absence?
gpt
Native African tribes. Neanderthals lived in Europe and Western Asia, and only encountered humans after we migrated out of Africa. From there, we interbred with Neanderthals, and moved across the globe, first to East Asia, then the Pacific Islands and Australia, and finally North and South America. Since no human groups (that we know of) went back to Africa, most Southern African tribes and their descendants have next to no Neanderthal DNA. 

However, there isn't much of a measurable difference in our DNA because of this. Most Europeans and Asians only have about 2% Neanderthal DNA in their genome.
Although, some studies have found that a higher concentration of Neanderthal DNA can possibly lead to a minor increase in risk for genetic diseases, like Crohn's Disease and lupus. Also, because Neanderthals and humans are nearly separate species (genetically), those with higher concentrations of Neanderthal DNA can have a higher risk of issues with their X chromosomes, which leads to a lower rate of fertility. But again, these changes have been part of us for tens of thousands of years, and are as much a part of us as any other human ancestor.

Daven Presgraves has even postulated that breeding with Neanderthals made it easier for our species to adapt to northern climates, since Neanderthals carried traits for lighter skin, hair, and eyes, as well as being shorter and heavier-set than us.