In 1980, the Alvarez hypothesis suggested that an asteroid impact killed off the dinosaurs and many other species in one of the six largest mass extinctions in Earth’s history. That went from crazy idea to mainstream science fairly quickly (because once scientists knew what to look for, the data were overwhelming) and the details are still being studied.
It was such a spectacular, world-wide disaster that I understand why three-quarters of animal and plant species on Earth died out. Evidence supporting a vast loss of forests includes “a thin rock layer formed during the first thousand or so years after the impact, [where] 70 to 90 percent of the spores found come from just two species of fern… pioneer species rapidly recolonizing open ground, such as seen today when ferns recolonize lava flows in Hawaii.”
I’ve always wondered how anything survived. I’ve read that, on land, small burrowing animals were doom-dayers surviving in their Cretaceous bunkers. That seems plausible.
But how did birds survive? Sure, birds had relatively large brains, but I’m not sure my enormous ape-brain will help me if another 9-mile wide asteroid hits.
The only birds that survived were ground-dwellers, including ancient relatives of ducks, chickens, and ostriches. Following the cataclysm, these survivors rapidly evolved into most of the lineages of modern birds we are familiar with today, according to paleontologists led by Daniel Field at the University of Bath in the U.K., as argued in the journal Current Biology.
Climates changed catastrophically, temperatures were depressed for years, and the food chain left tattered. I have mental images of chicken ancestors peeking out from scrubby reeds in deep valleys or along the wet edges of streams and lakes, staring in slack-beaked awe at a dark, ash-filled sky. Modern kiwis nest in burrows, so perhaps this is plausible too. It’s an amazing thought.
However they did it, birds did survive and prospered. But now I have a lot of new questions. Where on the globe were the survivors? Did they migrate? What path led the ground dwellers back into trees to nest? And while we’re at it, how did tree seeds survive? Maybe in the burrows of those doom-dayers? Many more studies will fill in the gaps and support or falsify Field et al. Can’t wait!
Note: The evolutionary link between dinosaurs and birds was originally hypothesized in the 1860s when fossils of feathered dinosaurs were first described by scientists. It took decades to assemble enough evidence to turn this speculation into mainstream science.
Thanks to nationalgeographic.com for their article and the quotes above.