How many T. rexes were there? Billions

 Holden D’Avico

Mr. Ippolito

AP Bio

4/16/21

“How Many T. Rexes Were There? Billions.” ScienceDaily, ScienceDaily, 15 Apr. 2021, www.sciencedaily.com/releases/2021/04/210415142623.htm.  

It is very difficult to estimate the size of extinct populations because it is a miracle to even find any fossils. Despite this, paleontologist Charles Marshall teamed up with his students at UC Berkeley in order to estimate how many T. rexes were roaming around North America during the Cretaceous period. His findings are summarized in “How many T. rexes were there? Billions”. The article begins by presenting Marshall and his colleagues’ findings: “about 20,000 adult T. rexes probably lived at any one time, give or take a factor of 10” (UC Berkeley 1). This means that “some 2.5 billion lived and died over the approximately 2 1/2 million years the dinosaur walked the earth” (UC Berkeley 1). Before this study was conducted, no one had been able to estimate the population size of long-extinct animals. The article goes on to reveal what sparked Marshall’s curiosity and motivation in order to calculate the population size of T. rexes. Marshall was astonished by the fact that he was holding a fossil in his hand and thought that it was very improbable; he wanted to calculate exactly how improbable it was depending on the number of dinosaurs that have lived and died. Marshall was able to conduct a very difficult study, however, he admits that the 95% confidence interval of the calculated population size is very wide. 20,000 isn’t exact and could be off by a factor of 10. Marshall and his colleagues dealt with a lot of uncertainty in the data which resulted in uncertainty in the results. In order to estimate a population size, information about the species such as population density, ecological niche, and body mass need to be known. However, these facts are also just estimates based on fossil records. Finally, the article goes on to describe the biological characteristics such as mass and age of sexual maturity that the research team was able to determine from the fossils. Using this information, they determined the ecological niche of the T. rex, the energy consumption, etc. This helped them make an estimate on how many T. rexes could roam the continent at once. 

I chose this article because the title hooked me in. I was surprised by the fact that there were billions of T. rexes. I always thought that T. rexes were very rare and it was weird to think that at one time they were very common and just roamed the earth. This article is important because the technique that Marshall and his team used in order to estimate a long-extinct species's population size has never been done before. This new technique can be used for other species in order to create a more accurate record of what the world looked like many years ago. 

The article was very interesting and I was able to learn a lot. The article was written in a way that allowed me to understand it fully without any confusion. However, one thing I was dissatisfied with was the order that the information was presented. The article begins by presenting the findings of the research and then outlining how the research was conducted. This may be the norm for scientific articles, however, it would’ve been more interesting if the findings were presented last.