“Your boyfriend is a caveman,” may have been a compliment to some ancient humans.

Interbreeding between humans and Neanderthals may have given Europeans and Asians resistance to northern diseases that their African ancestors didn't have.

BLOG: Neanderthals, Humans Interbred, DNA Proves

Peter Parham, professor of microbiology and immunology at Stanford, recently presented evidence to the Royal Society in London that Europeans gained many of the genes for human leukocyte antigens (HLAs) from neanderthals.

The antigens helped them adapt to diseases in the north much more quickly than would have otherwise occurred.

BLOG: Neanderthals' Last Stand Possibly Found

Comparisons of the human and Neanderthal genomes were conducted by Parham to locate similarities and differences in the DNA of modern human populations and Neanderthals.

Parham found that modern Europeans and Asians have some genes identical to those of Neanderthals. One form, or allele, of the HLA gene, named HLA-C*0702, was found in the Neanderthal DNA. An identical allele is quite common in modern European and Asian populations, but is absent in modern Africans.

BLOG: Hybrid Mammoth DNA Found

A recently discovered species of hominid, or human-like species, from Siberia, called the Denisovans has not yet had its genes sequenced, but Parham believes the peoples of Asia may have gained some of their DNA from them. The allele HLA-A*11 also appears in modern Asians, but not in Africans.

BLOG: Neanderthal Relative Bred With Humans

Though the contribution to European DNA from Neanderthals is only about 6 percent, that small percentage accounts for half the observed human leukocyte antigen alleles.

It seems keeping an open mind about love may have granted survival advantages to humans in the north.

This research makes me wonder…If humans and other hominid species could interbreed and their offspring were fertile, what does that mean for the distinction between humans and Neanderthals? Were we really separate species?