The secret is out: Neanderthals and modern humans had sex, geneticist Svante Pääbo declared Sunday during a conference at Cold Spring Harbor Laboratory in New York. But the jury’s still out on whether these relations resulted in offsrping and, if so, whether those offspring contributed to humans today. (The Times)

Pääbo led the three-year project to sequence the Neanderthal genome at the Max Planck Institute in Leipzig, Germany. The team completed the draft sequence in February, but the preliminary genetic analysis, announced at the American Association for the Advancement of Science annual meeting in Chicago, was little more than a tease.

It seems Pääbo is continuing to be rather tight-lipped about the findings, disclosing few details to The Times, besides announcing that he’s “sure that they had sex”. Pääbo will publish his analysis of the entire Neanderthal genome “shortly”, The Times reports.

Given some 12,000 years of coexistence and presumably compatible sex organs, it seems reasonable that the two species got it on. But the bigger question is whether these intimate relations gave rise to children — and whether such children were fertile and contributed to the modern human genome.

The idea that Neanderthals and humans interbred is supported by fossils with features from both, but so far there has been no evidence of gene flow. Human-Neanderthal hybrids, if they existed, may have been sterile, like zebroids, leopons, wolphins and male ligers and tigons.

Image: erix!/Flickr