Do most caucasian homo sapiens have some Neanderthal DNA?

[bluemoonKY]

I just received the results from the DNA tests that I ordered at 23andme.com. According to 23andme, I have 298 Neanderthal variants in my DNA. 23andme says that I have more Neanderthal DNA in my genes than 80% of 23andme customers. This has really gotten me thinking about Neanderthal DNA, and it has raised some questions in my mind.

The Neanderthals lived in Europe. Therefore, people of European descent are far more likely to have Neanderthal DNA in their genes than people not of European descent. I believe that if all of a person's ancestors were from, say, Africa, then such a person would have no Neanderthal DNA in their genes at all. I don't think that the Neanderthals lived in Africa, Asia, Australia, or the Americas.

Do most Caucasian homo sapiens have some Neanderthal DNA in their genes?

 

[Ygggdrasil]

Essentially all populations, except those native to sub-Saharan Africa, have some small fraction of Neanderthal DNA in their genome:

An X-Linked Haplotype of Neandertal Origin Is Present Among All Non-African Populations

Recent work on the Neandertal genome has raised the possibility of admixture between Neandertals and the expanding population of Homo sapiens who left Africa between 80 and 50 Kya (thousand years ago) to colonize the rest of the world. Here, we provide evidence of a notable presence (9% overall) of a Neandertal-derived X chromosome segment among all contemporary human populations outside Africa. Our analysis of 6,092 X-chromosomes from all inhabited continents supports earlier contentions that a mosaic of lineages of different time depths and different geographic provenance could have contributed to the genetic constitution of modern humans. It indicates a very early admixture between expanding African migrants and Neandertals prior to or very early on the route of the out-of-Africa expansion that led to the successful colonization of the planet.

https://academic.oup.com/mbe/article/28/7/1957/1048596

See also: http://blogs.nature.com/news/2011/12/the-age-of-neanderthal-personal-genomics-begins.html

All non-Africans tested so far owe some of their genetic diversity to interbreeding between Homo sapiens and Neanderthals. This conclusion comes from comparing the draft genome of Neanderthals to the genomes of contemporary humans from around the world.

A team led by Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reported in 2010 that European and Asian populations owe about 1–4% of their genomes to Neanderthals (see ‘European and Asian genomes have traces of Neanderthal‘). Sub-Saharan African genomes, meanwhile, do not contain these traces of Neanderthal DNA.

 

[BillTre]

The story goes that people (Homo Sapiens) migrating out of Africa in countered Neanderthals (H. neanderthalansis) in the Mid-East area, as well as Europe and Asia. Interbreeding occurred and some of Neanderthal DNA still remains in the genomes of the descendants of these people.
Similarly, some of these migrating people also encountered Denisovans (H. sapiens ssp. denisova), interbred with them and some of their DNA was acquired and passed on to their descendants. The Denisovans were more to the east, and interacted with different but overlapping groups of people.
Some people carry DNA from both groups.