During 2.4 million years of existence on Earth, a total of 2.5 billion Tyrannosaurus rex ever lived, and 20,000 individual animals would have been alive at any moment, according to a new calculation method we described in a paper published on April 15, 2021 in the journal Science.
To estimate population, our team of paleontologists and scientists had to combine the extraordinarily comprehensive existing research on T. rex with an ecological principle that connects population density to body size.
From microscopic growth patterns in bones, researchers inferred that T. rex first mated at around 15 years old. With growth records, scientists can also generate survivorship curves – an estimate of a T. rex‘s chances of living to a given age. Using these two numbers, our team estimated that T. rex generations took 19 years. Finally, T. rex existed as a species for 1.2 to 3.6 million years. With all of this information, we calculate that T. rex existed for 66,000 to 188,000 generations.
上溯 50,000 年前至2019年，地球上一共生存过
100,800,000,000 / 1,008 亿 Homo sapiens 现代智人；
时光荏苒到了 2050 年呢？地球上生存过的人类
将会累积到 113,000,000,000 / 1,130 亿。
“Modern” Homo sapiens (that is, people who were roughly like we are now) first walked the Earth about 50,000 years ago. Since then, more than 108 billion members of our species have ever been born, according to estimates by Population Reference Bureau (PRB). Given the current global population of about 7.5 billion (based on our most recent estimate as of 2019), that means those of us currently alive represent about 7 percent of the total number of humans who have ever lived.
PRB estimates that by 2050 about 113 billion people will have ever lived on Earth.
