According to Professor Svante Paabo, director of genetics at the Max Planck Institute for Evolutionary Anthropology, Neanderthals and modern humans had sex across the species barrier. The professor has been using DNA retrieved from fossils to piece together the entire Neanderthal genome, and plans on publishing his findings soon. He recently told a conference that he was sure the two species had had sex, but still had questions as to how "productive" the relations had been. "What I'm really interested in is, did we have children back then and did those children contribute to our variation today?" he said. "I'm sure that they had sex, but did it give offspring that contributed to us? We will be able to answer quite rigorously with the new [Neanderthal genome] sequence." What remains a mystery is what Paleolithic brewery provided the catalyst for these stone age hook-ups.