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Impact That Killed Dinosaurs Wiped Out Kangaroo Cousins (And Almost Us, Too)

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The most likely cause of the demise of dinosaurs was a huge asteroid that smacked what became Mexico's Yucatan peninsula, causing massive destruction, disrupting normal weather patterns and the food chain. The huge animals died out as food became scarce, opening a window for more scrappy mammals to take over the planet, but new research suggests that our mammalian ancestors were nearly wiped out too.

"The classic tale is that dinosaurs died out and mammals, which had been waiting in the wings for over 100 million years, then finally had their chance," said Dr. Steve Brusatte from the University of Edinburgh, one of the authors of a report published in the journal ZooKeys, in a release. "But our study shows that many mammals came perilously close to extinction. If a few lucky species didn't make it through, then mammals may have gone the way of the dinosaurs and we wouldn't be here."

Obviously, the species from which primates like humans evolved are among those that made it, but others, like those related to modern day kangaroos weren't quite as lucky. Extinct metatherian mammals who are related to today's marsupials might not have dominated in the days of the dinosaurs, but they did quite well for themselves in the shadow of the ancient giants.

"It wasn't only that dinosaurs died out, providing an opportunity for mammals to reign, but that many types of mammals, such as most metatherians, died out too - this allowed advanced placental mammals to rise to dominance," said lead author Dr. Thomas Williamson of the New Mexico Museum of Natural History and Science.

Score one for the placenta and for humanity.

The study says that metatherians never recovered to their previous level of diversity after the event that drove the dinosaurs to complete extinction, which is why their marsupial descendants are found today only in relatively unusual environments in Australia and South America.

To be clear, the report does not take a comprehensive look at how all species were affected by the extinction-level event that did the dinosaurs in, rather it focuses specifically on the Cretaceous evolutionary history of metatherians, providing an opportunity to study extinction patterns in detail along the way. 

So keep in mind, if humanity and other species should be faced with a nuclear winter or other extinction-level global catastrophe, the kangaroos may need a little extra help to make it through.

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