At a time when Earth was going through massive environmental changes and most species were wiped out by Siberian volcanic eruptions, some animals actually managed to survive the chaos.
During this extreme period, which was known as the Permo-Triassic extinction, billions of tons of carbon were spewed into the atmosphere, forever changing the climate of the planet.
One of the species that survived the aftermath of the Permo-Triassic extinction were the therapsids, the ancient animals that soon gave rise to mammals. Scientists were able to study one particular genus of the therapsids - the Lystrosaurus.
Drastic Physical Changes
Paleontologists from the Field Museum and other experts said that the therapsid Lystrosaurus had become suited to the drastic climate change by adapting shorter life expectancies.
Combining results from survivorship models, this observation allowed researchers to suggest that the Lystrosaurus changed their breeding behavior: they began to breed at a younger age than their predecessors.
Study author Ken Angielczyk said that based on the growth record preserved on bones, the Lystrosaurus had a typical life span of 13 to 14 years before the extinction event.
And yet, almost all of the Lystrosaurus bones that scientists found from after the extinction were completely young, at 2 to 3 years old, he said.
"This implies that they must have been breeding when they were still juveniles themselves," said Angielczyk.
The drastic adjustment equated to a physical change for the Lystrosaurus. Prior to the massive extinction event, the Lystrosaurus would have been about the size of a pygmy hippo, a couple of meters long and hundreds of pounds heavy.
However, after the extinction event, the creature's size dropped to that of a large dog, somehow due to its changed lifespan.
Still, scientists said the alterations actually did well for the Lystrosaurus.
Simulations revealed that by breeding much earlier, the Lystrosaurus could have upped its survival chances by 40 percent, especially in the erratic environments that existed 252 million years ago.
The limitation of the study, however, is that it does not provide physical evidence of early breeding. Rather, the findings are an inference based on size distributions and expectations of survivorship models.
Implications Of The Study
Meanwhile, this fascinating transformation in breeding behavior is not sequestered to ancient animals. Researchers found that in the past 100 years, the Atlantic cod -- a fish consumed by humans -- has went through a similar change due to human interference.
In fact, scientists said industrial fishing removed majority of the large Atlantic cods from the population, causing the average size of the fish to shrink. Likewise, the remaining Atlantic cods are forced to breed as early as possible.
The same changes has also occurred among African monitor lizards, researchers said.
With that, Angielyczyk said paleontological studies help scientists understand the world today, especially as we are facing the sixth mass extinction. He said studying how species such as the Lystrosaurus adapted in the face of disaster would aid us in predicting how looming changes in our environment may affect modern animals.
The findings of the study are featured in the journal Scientific Reports.