Over 65 million years North American mammal evolution has tracked with climate change

Posted By News On December 26, 2011 - 8:30pm
Over 65 million years North American mammal evolution has tracked with climate change

PROVIDENCE, R.I. -- History often seems to happen in waves – fashion and musical tastes turn over every decade and empires give way to new ones over centuries. A similar pattern characterizes the last 65 million years of natural history in North America, where a novel quantitative analysis has identified six distinct, consecutive waves of mammal species diversity, or "evolutionary faunas." What force of history determined the destiny of these groupings? The numbers say it was typically climate change.

"Although we've always known in a general way that mammals respond to climatic change over time, there has been controversy as to whether this can be demonstrated in a quantitative fashion," said Brown University evolutionary biology Professor Christine Janis. "We show that the rise and fall of these faunas is indeed correlated with climatic change – the rise or fall of global paleotemperatures – and also influenced by other more local perturbations such as immigration events."

Specifically, of the six waves of species diversity that Janis and her Spanish collaborators describe online this week in the Proceedings of the National Academy of Sciences, four show statistically significant correlations with major changes in temperature. The two transitions that show a weaker but still apparent correlation with the pattern correspond to periods when mammals from other continents happened to invade in large numbers, said Janis, who is the paper's senior and second author.

Previous studies of the potential connection between climate change and mammal species evolution have counted total species diversity in the fossil record over similar time periods. But in this analysis, led by postdoctoral scholar Borja Figueirido, the scientists asked whether there were any patterns within the species diversity that might be significant. They were guided by a similar methodology pioneered in a study of "evolutionary faunas" in marine invertebrates by Janis' late husband Jack Sepkoski, who was a paleontologist at the University of Chicago.

This painting by artist Carl Buell depcits a scene from the late Eocene of North America. The rhino‑like animals in the background are brontotheres. The pony‑sized Hyracodon, a closer relative of living rhinos, in the foreground.

(Photo Credit: Courtesy of Carl Buell)

What the authors found is six distinct and consecutive groupings of mammal species that shared a common rise, peak and decline in their numbers. For example, the "Paleocene fauna" had largely given way to the "early-middle Eocene fauna" by about 50 million years ago. Moreover, the authors found that these transfers of dominance correlated with temperature shifts, as reflected in data on past levels of atmospheric oxygen (determined from the isotopes in the fossilized remains of deep sea microorganisms).

By the numbers, the research showed correlations between species diversity and temperature change, but qualitatively, it also provided a narrative of how the traits of typical species within each wave made sense given the changes in vegetation that followed changes in climate. For example, after a warming episode about 20 million years in the early Miocene epoch, the dominant vegetation transitioned from woodland to a savannah-like grassland. It is no surprise, therefore, that many of the herbivores that comprised the accompanying "Miocene fauna" had high-crowned teeth that allowed them to eat the foods from those savannah sources.

To the extent that the study helps clarify scientists' understanding of evolution amid climate changes, it does not do so to the extent that they can make specific predictions about the future, Janis said. But it seems all the clearer that climate change has repeatedly had meaningful effect over millions of years.

"Such perturbations, related to anthropogenic climatic change, are currently challenging the fauna of the world today, emphasizing the importance of the fossil record for our understanding of how past events affected the history of faunal diversification and extinction, and hence how future climactic changes may continue to influence life on earth," the authors wrote in the paper.

Cave man see ice melt. Cave man put out fire to please angry weather gods.
Ice Ages? eons of tropical dinosaurs? Volcanoes? comet hits? solar storms? Earthquakes? polar reversals?.......and now..........SUV gas? Na.
This wasn't about climate change, it was about controlling a changing climate with corporate run and bank funded CARBON TRADING STOCK MARKETS run by politicians, taxing the very air we breathe. The majority of progressives both scientifically and politically, are former climate change believers “now” as 25 years of condemning billions of children to the greenhouse gas ovens has a shelf life. Fear is never sustainable and progressivism has moved on. Occypywallstreet makes no mention of it in their list of demands and Obama didn’t even mention the “crisis” in his state of the union address. And no, you can’t have a little catastrophic climate crisis; this was a CO2 death threat to our kids.
To suggest that this climate of the last 180 years has NEVER happened before, denies the tropical fossils under the melting ice and denies all ancient climates and evolution itself. And "no", ice cores are not some temperature dipstick like in some Harry Potter movie and beyond correlation from the last 180 years to Human Monkey gas, there does not exist any "proof" that this correlation means Humans now control climates. When scientists are studying a worst case scenario, of course they will say it's real. Why would a scientist deny climate change when paid to study and or "teach" the effects, not causes of climate change?

This was a consultant's wet dream from the world of science that used to be the enemy because they polluted the planet with their pesticides and chemicals in the first place and climatologists have done to science what abusive priests did for the Catholic Church.
Nobody is going to vote YES anymore to taxing the air to make the weather colder and real planet lovers are relieved the crisis was exaggerated, not disappointed.