In Southeast Asia, rainforests have continued to turn into savannah and back in the last 2.6 million years. These fluctuations have led to the extinction of many large animals, which probably included Homo erectus, the most successful member of the human family, according to new research.

Over 100,000 years ago, every continent except Antarctica was home to many large animals, known as megafauna. Whether their disappearance was triggered by humanity or the climate is one of the most heated debates in science.

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Curiously, however, too little attention has been paid to extinct species in Southeast Asia, despite the presence of at least five members of the genus Homo in the region, said Dr. Julien Louys of Griffith University.

Unique snapshots of the diets of these species and the environments through which they roamed

Louys and Dr. Patrick Roberts of the Max Planck Institute addressed this issue in a study published in Nature , which reworked the diets of various extinct animals in Southeast Asia from the isotopes found in their teeth. "These types of analyzes give us unique snapshots of the diets of these species and the environments in which they roamed," Roberts said.

These isotopes show that tropical forests were dominant in the early Pleistocene, but were largely replaced by grasslands a million years ago. Grazing animals, such as Stegodon, the elephant's relative, thrived in the new environment. Many forest dwellers, such as Gigantopithecus blacki, the largest monkey to ever live, have died.

Global temperatures and geological changes have led to an increase in precipitation

Homo erectus, the first member of the human family to leave Africa and survive the longest, thrived in this new environment. Other early human species , including H. floresiensis and H. luzonensis, established subgroups on the islands from which they derive their name. For most of this period, the land mass was much larger than it is today, the sunken region now known as Sundaland, along with Borneo, Java and Sumatra.

However, a combination of global temperatures and regional geological changes has led to increased rainfall, Louys and Roberts explained, causing rainforests to expand again, eventually becoming dominant until recent industrial-scale deforestation. During this process, many species died, including some of our closest relatives.

Only Homo sapiens had the skills needed to live in tropical forest environments

"Only our species, Homo sapiens, seems to have had the skills to exploit and thrive in tropical forest environments. All other Hominini species have been apparently unable to adapt to these extreme and dynamic environments, ”Roberts explained, according to IFL Science .

Modern humans arrived in the area 72,000 to 45,000 years ago, even as rainforests expanded.

But now deforestation, especially for palm oil plantations, means that the species in the region are most at risk, trying hard to cope with changes that are often faster than those that have survived previously.