Do you have a friend - or spouse - who peers at you from a protruding brow? Are they thick, strong and durable, but never work out? Do they wear lion skin tunics and carry large clubs? Are they so hairy that not even ethnic insinuations fail to sufficiently explain the furriness? Are they the brunt of jokes about being evolutionary leftovers from cavemen and Neanderthals?

Well, the latter might be right on the button, for a few it seems.

Reporting in the latest issue of Science, findings of Swedish researcher Svante Pääbo, who leads the Neanderthal Genome Project at the Max Planck Institute in Germany, said that at least a small percentage of your friends (or even yourself) can have Neanderthal ancestors. The undeniable DNA in genes doesn't fib about those things.

Using bones up to 40,000 years old, he and his team examined some four billion base pairs of DNA from Neanderthals. Then they looked at our own modern DNA, and the truth was out: there was some inter-species hanky-panky going on back in those prehistoric times.

Neanderthals have left their mark
According to a statement from the institute, initial analyses of four billion base pairs of Neanderthal DNA indicate that, contrary to previous beliefs, Neanderthals left their mark in the genomes of some modern humans. The researchers identified a catalog of genetic features unique to modern humans by comparing the Neanderthal, human, and chimpanzee genomes. Genes involved in cognitive development, skull structure, energy metabolism, and skin morphology and physiology are among those highlighted in the study as likely to have undergone important changes in recent human evolution.

But the Neanderthal DNA signal shows up not only in the genomes of Europeans, but also in people from East Asia and Papua New Guinea, where Neanderthals never lived. The experts said that this indicates that the mating occurred early on, probably in the Middle East, and is shared with all descendants of the early humans who migrated out of Africa.

The line of hominid and chimpanzees separated about 6 million years ago, and research shows that original Neanderthals and our own humans, went on separate paths as long ago as 440,000 years. Nonetheless, Neanderthals are more closely related to us than to other prehistoric men.

The scientists also found that the frequency of Neanderthal matches is higher for non-Africans than for Africans. They concluded that the two hominid species started doing the wild thing on a small scale between 50,000 - 80,000 years ago. This meant that humans had their first dates with Neanderthals as soon as they left Africa and encountered their never-before-seen kinsmen for the first time.

The researchers expect new findings to emerge from ongoing investigations of the Neanderthal genome and others. Pääbo's group recently found evidence of an unknown type of hominid in Siberia after analyzing DNA from what they first considered to be a Neanderthal finger bone.

"The Neanderthal genome sequence allows us to begin to define all those features in our genome where we differ from all other organisms on the planet, including our closest evolutionary relative, the Neanderthals," noted Pääbo.