October 27, 2020

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Past tropical forest changes drove megafauna and hominin extinctions

Impression: Artist’s reconstruction of a savannah in Middle Pleistocene Southeast Asia. In the foreground Homo erectus, stegodon, hyenas, and Asian rhinos are depicted. Water buffalo can be viewed at the edge…
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Credit: Peter Schouten

In a paper revealed today in the journal Nature, experts from the Office of Archaeology at MPI-SHH in Germany and Griffith University’s Australian Investigation Centre for Human Evolution have observed that the reduction of these grasslands was instrumental in the extinction of lots of of the region’s megafauna, and in all probability of ancient individuals much too.

“Southeast Asia is usually forgotten in world wide discussions of megafauna extinctions,” claims Affiliate Professor Julien Louys who led the research, “but in fact it when had a significantly richer mammal neighborhood comprehensive of giants that are now all extinct.”

By seeking at stable isotope data in modern and fossil mammal enamel, the researchers have been capable to reconstruct no matter if earlier animals predominately ate tropical grasses or leaves, as properly as the climatic problems at the time they have been alive. “These forms of analyses provide us with exceptional and unparalleled snapshots into the diet programs of these species and the environments in which they roamed,” claims Dr. Patrick Roberts of the MPI-SHH, the other corresponding author of this research.

The researchers compiled these isotope data for fossil web pages spanning the Pleistocene, the previous two.six million decades, as properly as adding in excess of 250 new measurements of modern Southeast Asian mammals symbolizing species that had by no means right before been researched in this way.

They showed that rainforests dominated the space from existing-working day Myanmar to Indonesia all through the early aspect of the Pleistocene but began to give way to far more grassland environments. These peaked all-around a million decades ago, supporting prosperous communities of grazing megafauna this sort of as the elephant-like stegodon that, in switch, allowed our closest hominin kinfolk to prosper. But whilst this drastic transform in ecosystems was a boon to some species, it also lead to the extinction of other animals, this sort of as the greatest ape at any time to roam the planet: Gigantopithecus.

However, as we know today, this transform was not everlasting. The tropical canopies began to return all-around 100,000 decades ago, along with the basic rainforest fauna that are the ecological stars of the area today.

The reduction of lots of ancient Southeast Asian megafauna was observed to be correlated with the reduction of these savannah environments. Furthermore, ancient human species that have been when observed in the area, this sort of as Homo erectus, have been not able to adapt to the re-growth of forests.

“It is only our species, Homo sapiens, that seems to have had the needed capabilities to properly exploit and prosper in rainforest environments,” claims Roberts. “All other hominin species have been evidently not able to adapt to these dynamic, extraordinary environments.”

Ironically, it is now rainforest megafauna that are most at threat of extinction, with lots of of the previous remaining species critically endangered all over the area as a result of the pursuits of the a person surviving hominin in this tropical aspect of the environment.

“Alternatively than benefitting from the growth of rainforests in excess of the previous couple of thousand decades, Southeast Asian mammals are underneath unprecedented threat from the steps of individuals,” claims Louys. “By getting in excess of wide tracts of rainforest by way of urban growth, deforestation and overhunting, we’re at threat of dropping some of the previous megafauna continue to strolling the Earth.”

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