Global warming could make humans shorter, warn scientists who claim to have found evidence that it caused the world's first horses to shrunk nearly 50 million years ago.

　　In fact, a team from the universities of Florida and Nebraska says it has found a link between the Earth heating up and the size of mammals -- horses, in this case, the last time the world heated up.

　　The scientists used fossils to follow the evolution of horses from their earliest appearance 56 million years ago.

　　As temperatures went up their size went down, and vice versa; at one point they were as small as a house cat, said Dr Jonathan Bloch, curator of the Florida Museum of Natural History, was quoted by the "Daily Mail" as saying.

　　The scientists say that the current warming could have the same effect on mammals -- and could even make humans smaller.

　　"Horses started out small, about the size of a small dog like a miniature schnauzer. What's surprising is that after they first appeared, they then became even smaller and then dramatically increased in size, and that exactly corresponds to the global warming event, followed by cooling.

　　"It had been known that mammals were small during that time and that it was warm, but we hadn't understood that temperature specifically was driving the evolution of body size," Dr Bloch said in the "Science" journal.

　　科学家警告说，全球变暖可能会使人类变矮。科学家宣称已经找到证据：近5000万年前全球变暖就曾让世界上最早的马个头变小。

　　事实上，来自佛罗里达州和内布拉斯加州的大学的一支研究团队称，他们已经找到地球变暖和哺乳动物个头之间的联系。这一案例中马变矮的现象是上一次全球变暖时发生的。

　　科学家用化石来追溯马从5600万年前诞生至今的进化历程。

　　随着气温的上升，马的个头变小，反之马的个头就变大。《每日邮报》援引佛罗里达自然历史博物馆馆长乔纳森?布洛赫博士的话说，它们曾一度像家猫那么小。

　　科学家称，当前的全球变暖可能也会对哺乳动物产生同样的影响，甚至可能会让人类的个子也变小。

　　布洛赫博士在《科学》杂志中写道：“马最初的个头很小，和一只小狗的个头差不多，大约也就像一只迷你型雪纳瑞犬那么大。令人惊讶的是，在马诞生后过了一段时间，它们的个子变得更小，之后个头又显著变大，而这些变化与全球变暖和变冷正好是相对应的。

　　“我们已经知道哺乳动物在那个时期个头较小，而那个时期气候也较暖，但我们还未意识到正是温度驱动着身体大小的进化。”

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