At least six species of early human walked the Earth nearly three million years ago, of which Homo sapiens is the only one to have survived. Multiple theories have been put forward to explain their gradual extinction with a new study published in the journal One Earth suggesting climate change played a major role in shaping the evolutionary history of life on Earth. The study proposes the inability to adapt to a warming or cooling climate sealed the deal on their fate.
Study co-author Pasquale Raia of the University of Naples Federico II in Naples, Italy, said: “Our findings show that despite technological innovations including the use of fire and refined stone tools, the 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.
“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.”
The study combined climate models with the data from the fossil record to analyse what happened to past members of the Homo genus.
These include Homo habilis (handy man), Homo ergaster (working man), Homo erectus (upright man), Homo neanderthalensis (the Neanderthals), Homo Heidelbergensis (Heidelberg man) and Homo sapiens (wise man).
The researchers’ climate models simulated rainfall and temperature data spanning the last five million years.
The study found at least three Homo species – Homo erectus, Homo Heidelbergensis and Homo neanderthalsis – lost a portion of their “climatic niche space” just before they went extinct.
And the researchers believe this coincides with sharp changes in the global climate and an increased vulnerability to these changes.
Professor Raia said: “We were surprised by the regularity of the effect of climate change.
“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.”
I personally take this as a thunderous warning message
Pasquale Raia, University of Naples Federico II
In the case of the Neanderthal, the extinction was likely made worse through competition with Homo sapiens.
Scientists have in the past argued Neanderthals found themselves in the “wrong place at the wrong time”, leading to their demise.
But what does this mean for the future of our species on this Earth?
Since the second half of the 20th century, scientists have been sounding the alarm bells on anthropogenic global warming and climate change.
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The continued emissions of greenhouse gasses like carbon dioxide (CO2) have led to rising temperatures, rising sea levels, more extreme weather across the globe and the threat of entire ecosystems collapsing.
Some models predict our planet is on course to warm between 2C and 6C by the end of the 21st century.
And some of this warming is expected to happen even if future greenhouse emissions are curbed.
The warming will lead to increased rainfall, more frequent coastal flooding and erosion, melting polar ice caps and glaciers, and even affect the spread of infectious diseases.
As such, Professor Raia believes it is critical to learn lessons from our past.
He said: “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 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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