DOYLE RICE: ‘Throughout history, humans and their ancestors have perfected the art of killing big animals. Now, a new study finds that as humans spread around the globe, extinction of large mammals soon followed. Massive mammals such as wooly mammoths, elephant-sized ground sloths and various saber-toothed cats roamed the Earth between 2.6 million and 12,000 … Continue reading Humans have killed off most of Earth’s big mammals. In 200 years, cows could be biggest ones left.