How did birds survive the dinosaur mass-extinction?

14 February 2017

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Question

Fay - I heard that due to an asteroid a giant crater was formed 66 million years ago and the debris wiped out the dinosaurs. I have also been told that birds are dinosaurs. So, how did the birds survive?

Answer

Tom O'Hanlon put Fay's question to David Norman from the University of Cambridge. David - The overwhelming evidence suggests that there was a massive meteorite impacted at around about 66 million years ago. And the explosion created a huge set of environmental problems, in a sense: lots of water vapour, lots of chemicals introduced into the atmosphere, completely messing up our ecosystems. The equivalent, I suppose, in terms of modern theorising is the nuclear winter. It’s as though there was a nuclear holocaust, almost destroying life on earth, but not quite. Tom - Given that we’re still around today, some things clearly made it through. So was there a pattern to who lived and who died? David - Certainly on land, anything over a metre in body length probably went extinct. It maybe something to do with the biological nature of small organisms. Most of the big ones are, you could say, top of the food chain and, perhaps, more specialist and most susceptible to environmental disturbance. That’s certainly the pattern we see in ecology today. The things that have most chance to survive are the scavengers, the small fast reproducing sorts of organisms. And, in a way, the lizards, the snakes, the small crocodiles, small mammals that were our ancestors, and various other little organisms seem to have got through because they were the most resilient to environmental disturbance. The little, insulated, feathered bird-like dinosaurs also got through and, therefore the dinosaurs did survive the extinction, but they survived because they were small bird-like creatures rather than big scary dinosaurs. Tom - I suppose we’re really grateful for today? David - I guess so, yeah. Although some of us would actually quite like to see a dinosaur in the flesh at full size. The nearest we’ll ever get to it is something like an Emu, or an Ostrich, or a Rea. They’re feet, especially with something like a Rea have those three classic taloned toes which look very, very reptilian and wouldn’t be so ; different, except in scale, from something like the feet of a dinosaur like T. Rex. Tom - There you go Fay. I hope that managed to meteor your expectations.

 

Next week we’ll be looking at David’s question. David - If we put a mirror half a million light years away and reflected Earth, could we see what Earth looked like a million years ago.<

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