Modern amphibians never would have gotten their start if it weren’t for a mass extinction long ago. A new study analysing the DNA of hundreds of frog species shows that nine out of 10 modern-day frog species descended from three lineages that survived the mass extinction that killed off dinosaurs some 66 million years ago.
The very asteroid disaster that wiped out so much life on Earth made room for the survivors to flourish, filling in newly open niches in ecosystems and diversifying. While some 10 lineages survived, only Hyloidea, Microhylidae, and Natatanura really found footing and launched an array of thousands of new species.
“The results, to be published this week in the journal Proceedings of the National Academy of Sciences, are a surprise, because previous studies of frog evolution pinpointed the blossoming of the main frog lineages today to about 35 million years earlier, in the middle of the Mesozoic era," according to a press release. "The new analysis of 95 genes from frogs within 44 of 55 living families shows that these three lineages started to take off precisely at the boundary between the Cretaceous and Paleogene periods — the K-Pg boundary, formerly called the KT boundary — when the last mass extinction occurred, and not 100 million years ago."
The researchers note that the success of frogs is due to two key changes. First, the evolution of producing young on land, rather than having a tadpole stage. Second was the simultaneous evolution of tree species that sprouted up after the KT event, which provided safety and food sources and allowed frogs to become arboreal. These two things — in addition, of course, to the asteroid plowing into Earth — were critical to creating the roughly 6,700 species of frog we know today.
Unfortunately, modern frogs are facing threats they can’t adapt to and are rapidly going extinct. Climate change, habitat loss, pollutants, and the infamous chytrid fungus are all causing amphibian numbers to decline dramatically worldwide.