5 Most Incredible Discoveries of the Week Including the answer to an old question about the moon By Newser Editors, Newser Staff Posted Jun 14, 2014 5:20 AM CDT 1 comment Comments This undated artist rendering provided by the journal Nature shows a depiction of the Metaspriggina. (AP Photo/Nature, Conway Morris, Jean-Bernard Caron, Marianne Collins) (Newser) – A common ancestor for vertebrates and the discovery of a massive underground ocean make the list: Your Jaw May Come From This Little Fish: Introducing Metaspriggina, a minnow-sized fish that lived about 500 million years ago and appears to occupy a crucial branch of your family tree. Scientists say the creature might just be the ancestor of nearly all vertebrates. Specifically, we might have to thank the tiny creature for our jaws. Water Found 400 Miles Beneath Earth's Surface: Four hundred miles beneath the United States, there appears to be enough water to fill all our oceans—almost three times. Researchers have for the first time discovered direct evidence of the water, though it exists in an unusual form. Nagging Dark Side of Moon Question Answered: A lunar mystery that has persisted since 1959 has been solved, according to Penn State astrophysicists. That was the year in which a Soviet spacecraft captured the first images of the dark side of the moon—the side that always faces away from Earth. Now scientists think they now why it doesn't have the dark, flat areas that we see on the more familiar side, and the answer goes way, way back in time. Male Face Evolved to Take Punches: The faces of today's men would be different if our ancestors hadn't spent countless thousands of years slugging it out with their newly evolved fists, scientists say. Researchers studying human predecessors who lived 4 million to 5 million years ago found that male faces evolved to become stronger in areas most likely to be hit during a fistfight. Bachelor Party Unearths Ancient Remains: Members of a bachelor party at Elephant Butte Lake State Park in New Mexico spotted a tusk sticking out of the earth, stopped partying, and started digging. They ended up finding what may be the most intact skull of a prehistoric creature called a stegomastodon ever discovered. Click to read about more discoveries.