Survivors Of Dinosaur-Killing Asteroid Are Ground-Dwelling Birds: Study

Millions of years ago, an asteroid hit Earth, setting into motion the Cretaceous-Paleogene fifth mass extinction event that wiped out 75 percent of life.

Ground-dwelling birds survived, eventually going on to be the ancestors of all existing birds in the planet today.

Researchers shared these groundbreaking new findings in a study published in the journal Current Biology. The team analyzed fossil samples in hopes of piecing together what the world was like in the aftermath of the asteroid crash.

The Survival Of The Ground-Dwellers

Part of the devastation of the mass extinction event was the heat decimating entire forests and igniting forest fires throughout the planet, according to CNN. With soot completely blanketing the atmosphere, plants were unable to grow back.

Their habitats completely gone, the birds that lived among the trees faded into extinction.

Most of the bird species that survived, the researchers say, live on the ground. Smaller species reportedly lived off seeds, grains, and insects that were left post-impact. It's very similar to the diet of modern birds with a small stature.

Fossils also provided details on the legs of the surviving birds, which are long and strong, like the ones found on flightless birds that walk the ground today: emus and kiwis.

"Today, birds are the most diverse and globally widespread group of terrestrial vertebrate animals — there are nearly 11,000 living species," Daniel Field, lead study author and evolutionary paleontologist at the University of Bath's Milner Centre for Evolution, says in a statement in CNN. "Only a handful of ancestral bird lineages succeeded in surviving the mass extinction event 66 million years ago, and all of today's amazing living bird diversity can be traced to these ancient survivors."

What Critics Say

"It's a great idea, but we need to get over this one-answer-for-everything way of thinking," Jingmai O'Connor, from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, says. "No one factor caused the end-Cretaceous extinction and similarly no one factor caused the extinctions within [the birds]."

IVPP colleague Zhonghe Zhou agrees, saying more fossil evidence is necessary to support Field's hypothesis.

Even Field acknowledges that the destruction of their forest habitat isn't the only factor that killed off birds in trees. One other factor is the tendency of smaller species to survive because their dietary requirements are easier to fulfill. An efficient digestive system may also be one reason as well as certain reproductive properties.