[ti:Scientists Estimate All-time T. Rex Population Was 2.5 Billion] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]A new study suggests [00:02.56]that up to 2.5 billion Tyrannosaurus Rex dinosaurs [00:10.28]lived on Earth over a period of a few million years. [00:15.52]However, the research shows [00:19.84]that not many of these powerful creatures [00:23.84]lived in the same place at the same time. [00:29.48]Tyrannosaurus Rex, commonly known as T. rex, [00:33.32]existed on Earth for millions of years. [00:39.04]Scientists involved in the study estimate about 2.5 billion of them [00:48.08]lived over a period of 2.4 million years. [00:54.36]The dinosaurs mostly lived in the area of the world [00:59.56]now known as North America. [01:04.44]A team at the University of California at Berkeley [01:10.56]came up with a method to estimate how many T. rex, [01:16.68]called "the dinosaur king," had ever lived. [01:22.16]The findings were recently published in the journal Science. [01:29.44]The method aimed to establish a relationship [01:34.40]between body size and population density. [01:41.48]The scientists based their research [01:45.24]on the theory that the larger an animal is, [01:50.28]the smaller its population will be. [01:55.44]To come up with an overall number, [01:58.16]the team considered the dinosaur's body size, [02:03.48]sexual maturity and energy needs. [02:08.20]Experts say it is the first time [02:11.96]that such an estimate has been made. [02:16.32]Some scientists who study dinosaurs [02:20.84]said they are very interested in the new findings. [02:27.08]Kristi Curry Rogers is a paleobiologist at Macalester College. [02:35.84]She said she "did a double-take" when she saw the number. [02:44.60]Charles Marshall was the main writer of the study. [02:49.88]He is the director of the University of California Museum of Paleontology. [02:58.12]"That's a lot of jaws," he said. [03:03.00]"That's a lot of teeth. That's a lot of claws." [03:08.92]The researchers said a city the size of Washington D.C. [03:15.08]would likely have had only two T. rex living in the area. [03:22.36]They estimated that around 4,000 [03:26.16]would have lived on a piece of land the size of a large state, like California. [03:35.36]The estimates are useful for scientists who study dinosaurs [03:40.00]because it helps them understand the percentage of T. rex bones, [03:46.00]or fossils, that have survived. [03:51.08]Marshall said there have only been [03:54.00]about 100 identifiable T. rex fossils ever found. [04:01.92]That means that if there had only been 2.5 million of the dinosaurs, [04:09.52]humans might never have learned about them. [04:14.16]The scientists considered that a T. rex lived about 28 years [04:21.20]and that it had food needs somewhere between a large lizard and a lion. [04:29.04]Since all the numbers are just estimates, [04:33.84]the scientists say the results are not perfect. [04:39.28]They think it is possible the actual number of T. rex [04:44.56]was somewhere between 140 million and 42 billion. [04:52.08]The middle number is about 2.4 billion. [04:56.96]Some people may question why scientists [05:00.24]choose to research animals that lived so long ago. [05:04.92]James Farlow, a geology professor [05:08.88]from Purdue University offered his opinion. [05:13.96]He said he believes the study is important, [05:17.72]but also, "this kind of thing is very cool." [05:24.32]I'm Dan Friedell. 更多听力请访问51VOA.COM