Global warming could make humans shorter. Scientists claim to have found evidence that it caused the world's first horses     （shrink） nearly 50 million years ago. In fact,a team from the universities of Florida and Nebreaks says      has found a link between the Earth heating up and the size of mammals-homes，during the last time the world heated up. The scientists used fossils to follow the evolution of homes from their earliest      （appear) 56 million years ago. As temperatures went up．their size went. The scientists say that the current warming could have the same effect    mammals and could even make humans  （small）．“Horses started out small，about the size of a small dog. What's  （surprise）is that after they first appeared，they then became even smaller and then dramatically increased in size, and that（exact）corresponds to the global warming event, followed by cooling.”"It had been known that mammals  small during the last warm time，  we hadn't realized that temperature specifically was driving the evolution of body size”Dr. Bloch said in the "Science”journal.