Elevation May Drastically Impact Mammal Evolution and Survival

How does elevation impact evolution? That's exactly what scientists have asked themselves as they've examined the mammals of the ancient past. Now, they've taken a closer look at mass extinctions and have found that evolution at elevation may affect whether or not a species survives.

"Regional tectonically driven surface uplift resulted in large-scale reorganization of precipitation patterns, and our data show that the mammalian faunas adapted to these changes," write the study authors in a news release. "We suggest that the late Eocene mammalian faunas of North America were already 'pre-adapted' to the colder and drier global conditions that followed the EO climatic cooling."

In this latest study, the researchers analyzed the fossil record of two continents and combined previous oxygen isotope data that revealed precipitation patterns. The researchers found that the rise of the Rocky Mountain range spread south in three phases from Canada, starting more than 50 million years ago, down through Idaho, and finally into Nevada by 23 million years ago.

While this occurred, precipitation in the interior regions dropped, and major shifts in mammal populations, such as a complete loss of primates, took place. Estimated rainfall total based on plant fossils in Wyoming shows that it dropped from about 1,200 millimeters per year about 56 million years ago to only 75- millimeters a year about 49 million years ago.

In Europe, though, tectonic developments weren't a major factor driving local climate. When the global climate change occurred, that continent's mammals were, essentially, sitting ducks. It's likely that Europe's mammals were largely overrun and outcompeted by Asian mammals that were already living in colder, drier conditions.

The findings reveal the importance of regional tectonic and surface uplift processes-essentially, elevation-that spurs the evolution of mammals. This, in turn, may make them more adaptable or elss adaptable to environmental change.

The findings are published in the journal Proceedings of the Royal Society B.

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