Prehistoric mammals grew fast and died young

A new study led by the University of Edinburgh has found that some prehistoric mammals were born almost independent from their parents and grew up twice as fast as most of today’s mammals, features which gave them a significant edge over other animals after the dinosaurs went extinct. 

The scientists used dental analysis to uncover the life history of Pantolambda bathmodon, a member of the earliest known group of herbivores from the post-dinosaur era which grew to approximately the size of a sheep. By examining razor-thin sections of this animal’s teeth, and using laser to vaporize the teeth to expose their chemical constitution, the experts identified the mammal’s daily growth lines, known as “bands.”

The analyses revealed major transitions in P. bathmodon’s early life, such as high levels of zinc deposited at birth, and enrichment with barium during the suckling period, providing evidence that these animals’ mothers were pregnant for under seven months and gave birth to single, well-developed infants, sporting a mouthful of teeth. They were most likely mobile from the first day after birth, and suckled for less than two months before becoming fully independent.

Although the gestation period is similar to that of today’s mammals, P. bathmodon has probably lived and died more rapidly. According to the researchers, they were ready to mate before their first birthday, and lived only three to four years on average – a rather short lifespan compared to the roughly 20 years lifespan of modern mammals of similar size.

“When the asteroid knocked off the dinosaurs 66 million years ago, some mammals survived, and they ballooned in size really quickly to fill the ecological niches vacated by T. rex and Triceratops and other giant dinosaurs,” said study senior author Steve Brusatte, a professor of Paleontology and Evolution at the University of Edinburgh.

“Being able to produce large babies, which matured for several months in the womb before being born, helped mammals transform from the humble mouse-sized ancestors that lived with dinosaurs to the vast array of species, from humans to elephants to whales, that are around today.”

“Our research opens the most detailed window to date into the daily lives of extinct mammals. This unprecedented level of detail shows the kinds of lifestyles that make placental mammals special evolved early in their evolutionary history,” added study lead author Gregory Funston, a paleontologist at the same university.

“We think that their babies’ longer gestation period could have nurtured large body sizes faster than other mammals, which may be why they became the dominant mammals of today,” he concluded.

The study is published in the journal Nature.

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By Andrei Ionescu, Earth.com Staff Writer