A growing number of species in the modern world (nearly 200 in fact!) go extinct every day due to factors such as climate change and habitat destruction. During the earth's history, there also have been a number of mass extinctions, like the one that killed off the dinosaurs. Increasingly, scientists are turning to past mass extinctions to gain new insight into what is happening today.
Not all life vanished in past mass extinctions. Some living things survived, making it through an “evolutionary bottleneck”. Picture an hourglass – only a few species are able to squeeze through while the others die off.
So, how do species that survive recover from such a crisis? Often, they evolve new anatomical features and lifestyles as they adapt to a dramatically changed environment. But is that always the case?
Recently Field Museum scientists, along with collaborators from the UK and Germany, tried to answer those questions. They looked at an ancient group of mammal relatives called anomodonts -- plant eaters with turtle-like beaks and walrus-like tusks. Anomodonts were a dominant group of land animals at the time of a mass extinction about 252 million years ago. They made it through the bottleneck and survived the extinction but they did not evolve any dramatically new features or ways of life. In fact, it appears that anomodonts (and there were a large number of different species of these animals) evolved few new features over their entire evolutionary history. What worked for anomodonts prior to the extinction, worked for them afterwards, although this may have limited their ability to take advantage of new opportunities during the recovery.
This discovery demonstrates that evolution can be unpredictable and sometimes change is minimal, even after a major mass extinction. The implications of the finding are important -- we don't know how the recovery from modern extinctions will proceed; animals and plants that were successful before a die-off may or may not be the ones that thrive during the recovery.