Evidence of Homo erectus hunting bovine ancestors and extracting bone marrow was also discovered. Related Story Ancient ‘Hobbit’ Bone Discovery Stirs DebateThese human ancestors would have had plenty to take advantage of near these ancient rivers. Trees bore fruit all year, and the ancient hominins would have been able to gather edible plants in addition to catching fish and shellfish. They may have even used mussel shells as tools—the oldest known evidence of them being used for that purpose—and engraved some of them (the most ancient human engravings have been found on shells that previously turned up in Java). Bones of river turtles and bovine ancestors showed cut marks and breakages that suggested the consumption of both meat and bone marrow.