New finding: Climate change doesn’t always impact the evolution of species 

For so long, scientists have believed that climate change through different ages vastly impact evolution of species. However, the observations of a recent study nudge us to think otherwise. It has analysed temperature data with fossil records of large-sized mammals that lived in the African continent more than 5 million years ago during the Plio-Pleistocene period (includes the last Ice Age which was 20,000 years ago). 

The study that was recently published in the journal Proceedings of the National Academy of Sciences reveals that environmental variability and periodic fluctuations in climate did not always drive evolutionary patterns and shifts in mammals. For instance, something as severe as Milankovic cycle too did not have any significant effect on the species’ evolution. Instead, it only resulted in shift in global ice volume and sea temperatures.  

For those unaware, Milankovic cycle refers to the natural phenomenon that brings about changes in the Earth’s orbit and orientation with respect to the sun. It exposes the planet to varying intensity of solar radiation in turn leading to cyclical effects on the Earth’s climate at various levels. No wonder it surprises the scientists to learn that all these didn’t really affect the origin and extinction of species, let alone their behaviours.  

The study that was led by the Department of Geosciences and the Department of Ecology and Evolutionary Biology of the University of Arizona, USA, thus sheds light on the fact that it’s not just climate change in itself but other factors, such as its direct causes (pollution for one) that affects species’ evolution, not to forget the rapid frequencies and shifting conditions associated with it. 

As part of the current study, researchers took fossil samples from various locations spread across the African continent such as lakebeds, ocean floors, terrestrial outcrops and more. Similarly, environmental data was derived from pollen, algae, dust, leaf waxes, and soil isotopes among others. Together, these revealed that what was believed so long that it was climate change alone that led to evolutionary changes in species is not true. But comparing these variable data was not easy, which is why the researchers had to develop their own cutting edge statistical methods. One such method was to divide down the time periods into sets of 20000, 100000 and 400000 years and then put species’ origin and extinction markers into the most relevant sets and then average the numbers out. For instance, fossils of a prehistoric large herbivorous mammal called bovid (similar to antelope) was put in the set of 1 million to 1.2 million years when they existed and climactic records are compared to their evolutionary status. And as it turns out, it wasn’t climate change that led to their disappearance but subsequent arrival of other dominant species.  

This study also opens a new door to determine how today’s climate change is going to affect existing species. For instance, it’s not just climate change that affects the lifespan of polar bears, but what originally leads to climate change. To understand this scheme better, researchers have come up with the technique of capture, mark and recapture. It includes catching animals, analysing the factors responsible for its evolution and releasing them back to their natural habitat once done. This can also be applied in the recent study wherein if a species is identified in fossil records during time period X, but is not seen in Y, but again reappears in Z, it means they were around during Y. They were either spread out or declined and again rose in number.  

However, what’s striking is that, the evolution of species has seen more changes since the last Ice Age than before, meaning, climate change has been adverse in the near years.