Why giant beavers died out + Feathers came first, then birds

Why giant human-sized beavers died out 10,000 years ago

EXCERPT: Giant beavers the size of black bears once roamed the lakes and wetlands of North America. Fortunately for cottage-goers, these mega-rodents died out at the end of the last ice age. Now extinct, the giant beaver was once a highly successful species. Scientists have found its fossil remains at sites from Florida to Alaska and the Yukon. A super-sized version of the modern beaver in appearance, the giant beaver tipped the scales at 100 kilograms. But it had two crucial differences. The giant beaver lacked the iconic paddle-shaped tail we see on today’s modern beavers. Instead it had a long skinny tail like a muskrat. The teeth also looked different...

[...] But no one knew if the giant beaver behaved like the modern beaver. Did it also cut down trees? Or did it eat something completely different? [...] We discovered that the giant beaver was not cutting down and eating trees. Instead, it was eating aquatic plants. This strongly suggests that the giant beaver was not an “ecosystem engineer” like the modern beaver. It was not cutting down trees for food or building giant lodges and dams across the ice age landscape.

[...] We need to understand how the giant beaver lived in order to explain how and why it died out. For example, did it run out of food? Did it get too cold or too hot for it to survive? [...] Towards the end of the last ice age 10,000 years ago, the climate became increasingly warm and dry and wetland habitats began to dry up. Although the modern beavers and the giant beaver co-existed on the landscape for tens of thousands of years, only one species survived. The ability to build dams and lodges may have given the modern beaver a competitive advantage over the giant beaver. [...] Studying the ecological vulnerabilities of long-extinct animals certainly poses its own unique challenges, but it is important to understand the impact of climate change on all species, past or present. (MORE - details)

Feathers came first, then birds

EXCERPT: New research, led by the University of Bristol, suggests that feathers arose 100 million years before birds - changing how we look at dinosaurs, birds, and pterosaurs, the flying reptiles. It also changes our understanding of feathers themselves, their functions and their role in some of the largest events in evolution. The new work, published today in the journal Trends in Ecology & Evolution combines new information from palaeontology and molecular developmental biology. The key discovery came earlier in 2019, when feathers were reported in pterosaurs - if the pterosaurs really carried feathers, then it means these structures arose deep in the evolutionary tree, much deeper than at the point when birds originated. (MORE)

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