evidence: The first humans were mega-carnivores who took down prey with savvy hunting skills, a controversial new study suggests. [...] The ancient human species Homo habilis was eating meat at least 2.6 million years ago, Ben-Dor said. Another early human species, Homo erectus, seems to have been a particularly enthusiastic meat eater by 1.8 million years ago; its teeth and gut shrank compared with earlier ancestors — adaptations for digesting meat instead of plants — and it used stone tools capable of butchering meat. [...] Despite the limited evidence from humanity's early evolution, the researchers said there is more work to be done to show whether these human ancestors truly were specialized carnivores. This might include more work on the abundance of animals of different sizes throughout the Pleistocene, explorations of genetic changes over time that would have altered humans' ability to digest different foods and comparisons of trends in prey size over time.