At least six different species of the genus Homo — H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, and H. sapiens — populated the world during the latest Pliocene to the Pleistocene. The extinction of all but one of them is currently shrouded in mystery. According to a new modeling study, climate change was the primary factor in the extinction of past Homo species.
A Homo heidelbergensis, a Neanderthal and a Cro-Magnon. Image credit: SINC / José Antonio Peñas.
“Our findings show that despite technological innovations including the use of fire and refined stone tools, the formation of complex social networks, and even the production of glued spear points, fitted clothes, and a good amount of cultural and genetic exchange with Homo sapiens, past Homo species could not survive intense climate change,” said Dr. Pasquale Raia, a researcher at the Università di Napoli Federico II.
“They tried hard; they made for the warmest places in reach as the climate got cold, but at the end of the day, that wasn’t enough.”
To shed light on past extinctions of Homo, Dr. Raia and colleagues relied on a high-resolution past climate emulator, which provides temperature, rainfall, and other data over the last 5 million years.
They also looked to an extensive fossil database spanning 2,754 archaeological records to model the evolution of Homo species’ climatic niche over time.
Their studies offer robust evidence that three species, Homo erectus, H. heidelbergensis, and H. neanderthalensis, lost a significant portion of their climatic niche just before going extinct. This reduction coincided with sharp, unfavorable changes in the global climate.
In the case of Neanderthals, things were likely made even worse by competition with Homo sapiens.
“We were surprised by the regularity of the effect of climate change,” Dr. Raia said.
“It was crystal clear, for the extinct species and for them only, that climatic conditions were just too extreme just before extinction and only in that particular moment.”
“There is uncertainty in paleoclimatic reconstruction, the identification of fossil remains at the level of species, and the aging of fossil sites. But the main insights hold true under all assumptions,” he added.
“The findings may serve as a kind of warning to humans today as we face unprecedented changes in the climate.”
“It is worrisome to discover that our ancestors, which were no less impressive in terms of mental power as compared to any other species on Earth, could not resist climate change.”
“And we found that just when our own species is sawing the branch we’re sitting on by causing climate change. I personally take this as a thunderous warning message.”
“Climate change made Homo vulnerable and hapless in the past, and this may just be happening again.”
The study appears in the journal One Earth.
_____
Pasquale Raia et al. Past Extinctions of Homo Species Coincided with Increased Vulnerability to Climatic Change. One Earth, published online October 15, 2020; doi: 10.1016/j.oneear.2020.09.007
