By studying fossilized Neanderthal bones, scientists have determined that this species was extremely promiscuous. If they were having this much fun, why did they die out? Researchers have formed an image of sexy Neanderthals from the fact that the length of their second finger bones (the finger next to the index finger) show evidence of exposure to prenatal androgens, which produce high levels of testosterone and are important in the development of male characteristics such as aggression and promiscuity. In contrast, early homo erectus (our ancestors)–dating from approximately 3 to 4 million years ago–were likely to be monogamous. It just goes to show that sowing your seed over a wide area does not necessarily mean that you’ll achieve posterity. PhysOrg.com quotes researcher Emma Nelson as saying, "This method could prove to be an exciting new way of understanding how our social behavior has evolved."