最新研究表明:小行星撞擊地球之前恐龍就已開始走向滅亡!

The dinosaurs were already in decline 50 million years before the asteroid strike that finally wiped them out, a new study suggests.

近日，一項最新研究顯示，在小行星撞擊地球、最終導致恐龍滅絕的五千萬年前，恐龍數量已經在逐步減少。

The new assessment adds further fuel to a debate on how dinosaurs were doing when a 10km-wide space rock slammed into Earth 66 million years ago.

在人們爭論恐龍究竟在6600萬年前那個10km寬的太空隕石撞擊地球時做什麼的時候，這項新的評估無疑爲這場爭論火上澆油。

A team suggests the creatures were in long-term decline because they could not cope with the ways Earth was changing. The study appears in PNAS journal.

一個研究小組表示，由於不能適應地球的變化，恐龍在很長一段時間內數量有所下降。這項研究刊登在美國科學院院刊。

Researchers analysed the fossil remains of dinosaurs from the point they emerged 231 million years ago up to the point they went extinct. To begin with, new species evolved at an explosive rate. But things started to slow about 160 million years ago, leading to a decline in the number of species which commences at about 120 million years ago.

研究者對恐龍於2.31億年前出現直至滅絕期間的恐龍化石進行了分析。最開始，新物種以爆炸性的速度出現，但1.6億年前這個過程開始放緩，導致在1.2億年前恐龍數量開始減少。

Dr Manabu Sakamoto, a palaeontologist from the University of Reading, who led the research, said: "We were not expecting this result. Even though they were wiped out ultimately by the impact of the asteroid, they were actually already on their way out around 50 million years before the asteroid hit."

英國雷丁大學古生物學家Manabu Sakamoto博士主導這項研究，他說：“我們沒料到是這樣的結果。儘管恐龍是由於小行星撞地球而滅絕，但在這之前，即距今約5000萬年前，恐龍已經開始走向衰落。”

Dr Sakamoto's analysis shows that the long-necked giant sauropod dinosaurs were declining the fastest, whereas theropods, the group of dinosaurs that included the iconic Tyrannosaurus rex, were in a more gradual decline.

Skamoto博士的分析表明，長頸巨型蜥腳類恐龍衰亡速度最快，而以雷克斯霸王龍爲代表的獸角類恐龍數量下降則較爲緩慢。

Co-author Dr Chris Venditti, an evolutionary biologist from the University of Reading, told BBC News:

來自雷丁大學的演化生物學家、論文聯合作者Chris Venditti博士告訴BBC：

"The current widespread view is that dinosaurs were reigning strong right up to the impact that hit the Earth - and it's the impact that drove their final extinction," he said. "And while that's certainly true, what we found was that they were on the decline long before that."

“目前普遍認爲恐龍在小行星撞地球前統治着地球。而小行星撞擊也是導致它們最終滅絕的原因。”他說。“這當然是事實，但我們發現它們早在那之前就已經走向衰亡。”

Dr Venditti believes that the dinosaurs' 50 million year decline rendered them even more susceptible to the environmental catastrophe that followed the asteroid impact. "If they were reigning strong perhaps they would have fared much better than they did," he said.

Venditti博士認爲，恐龍在5000萬年前數量的減少導致它們更易受到小行星撞地球過後的環境大災難影響。他說：“如果它們數量再多些，可能會更好地適應這種情況。”

The asteroid impact is commonly thought to have paved the way for mammals to take over. But the new study suggests that mammalian supremacy might have occurred eventually, without a space impact.

人們普遍認爲，小行星撞地球爲哺乳動物的翻身鋪平了道路。但新的研究表明，即使小行星沒有撞擊地球，哺乳動物最終也會統治地球。

Co-author Prof Mike Benton of Bristol University, told BBC News: "World climates were getting cooler all the time. Dinosaurs rely on quite warm climates and mammals are better adapted to the cold. So there might have been a switch over in any case without the asteroid impact."

論文的聯合作者、布里斯托大學德Mike Benton教授告訴BBC：“全球氣候一直在變冷，恐龍適合在溫暖的氣候條件下生存，而哺乳動物更好地適應了寒冷的氣候。因此，無論是否有小行星撞地球，最終哺乳動物都會取代恐龍。”