Warning From the Past: Climate Change Likely Drove Early Human Species to Extinction

(Gleiver Prieto/Katerina Harvati via AP)

(CN) — A new study suggests early humans may have been unable to pull through the harsh fluctuations in climate during their time and were ultimately led to extinction by climate change — a warning as we face the same threat today.

This research, published Thursday in the journal One Earth, consisted of fossil analysis and building of climate models to investigate how our ancestors met their end and how we can avoid the same fate by learning from their stories.

“Our findings show that despite technological innovations including the use of fire and refined stone tools, the formation of complex social networks, and — in the case of Neanderthals — 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 Pasquale Raia of Università di Napoli Federico II in Italy. 

“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,” Raia said in the statement accompanying the study.

There are six different main species of humans: H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, and H. sapiens. Members of the genus Homo had large craniums, an upright posture and the ability to walk on two legs, opposable thumbs capable of gripping with precision, and the intellectual capacity to create tools. The best example scientists have of an ancient hominid is an Australopithecus skeleton named Lucy, who had a humanlike hip bone and knee joints, long primate-like arms, long fingers and flexible feet.

Of the Homo genus species, all except for us are extinct. To get a closer look at the cause of their demise, the research team combined climate data with fossil data. Using a state-of-the-art climate emulator that accounts for temperature, rainfall and several other factors, they analyzed changes over the past 5 million years. They also scanned through over 2,750 archaeological records of the ancient humans in search of how they fared against the shifts in their environments over time.

They found the species H. erectus, H. heidelbergensis, and H. neanderthalensis all suffered greatly in their population following severe climate change. According to the authors, the Neanderthals may have also suffered from having to compete for resources with H. sapiens.

Homo erectus thrived for an estimated 1.5 million years before their extinction. Their population rapidly declined due to severe climate change, when their environment transformed from open woodland similar to Africa to a rainforest ecosystem. They were unable to adapt and as a result, no fossils were found after the drastic change and their long-term existence came to an end.

Modern humans have only existed for about 200,000 years and, as proven by the past, we are not invincible.

“We were surprised by the regularity of the effect of climate change,” 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.”

Raia adds that although there is room for error in their analysis, “the main insights hold true under all assumptions. The findings may serve as a kind of warning to humans today as we face unprecedented changes in the climate.”

Global climate change is already presenting us with the effects scientists have warned about for years, as glaciers melt and sea levels rise, resources rapidly diminish and temperatures continuously climb. Experts predict that the global temperature will continue to rise if solutions aren’t put in place effective immediately, forecasting a rise of 2.5 degrees to as much as 10 degrees Fahrenheit. The Intergovernmental Panel on Climate Change (IPCC) says the effects will vary from region to region and on different timetables depending on the ability to adapt.

“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,” Raia said. “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.”

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