An artist's impression of Neanderthal man from an exhibition at Dusseldorf Museum, Germany. Photo / Creative Commons
An artist's impression of Neanderthal man from an exhibition at Dusseldorf Museum, Germany. Photo / Creative Commons
Climate change wiped out early humans, a study has found, as scientists warn that global warming could have a greater impact than previously thought.
Cousins of Homo sapiens failed to adapt to the cold tens of thousands of years ago, a new paper argues, leaving them vulnerable to extinction when temperatures dropped below the levels they were used to.
The reasons behind the disappearance of several species leaving only Homo sapiens to survive has been a point of debate among scientists, who hypothesised that Earth's changing climate played a role, alongside competition between species.
But a new study published in the journal One Earth claims that a failure to adapt to a shifting climate was the main cause in the loss of three species, because they were unable to cope with colder conditions.
Shortly before they disappeared, Homo erectus, Homo heidelbergensis and Homo neanderthalensis, more commonly known as Neanderthals, all experienced sudden changes in their environment.
Shortly before they disappeared, Homo erectus, Homo heidelbergensis and Homo neanderthalensis all experienced sudden changes in their environment. Photo / Ted Scambos
The team used climate modelling technology to emulate the shifts in climate going back five million years and compare it to fossil records, finding that for all three, conditions existed that would have been particularly hard for them to survive during their last known period of existence.
Climate change was the "most likely candidate" for the loss of the first two, and it combined with competition from Homo sapiens to wipe out the Neanderthal, the paper concluded.
Homo erectus, which is believed to have been adapted to warm and humid climates in southeast Asia, became extinct around the start of the last glacial period, which spanned the period from 115,000 to 11,700 years ago and made the Earth significantly colder than it is now.
This would have been the coldest period the species had ever experienced, the paper said.
Neanderthals, which died out later during the same period, disappeared from northerly latitudes first, adding evidence to the theory that they struggled to adapt to colder climates.
Earlier, Homo heidelbergensis, often thought to be an ancestor both of modern humans and of Neanderthals, had died out when they experienced similar struggles in a cold climate they were unused to.
Lead author Pasquale Raia of Universita di Napoli Federico II in Napoli, Italy, said that Neanderthals died out even despite their use of clothing, fire and tools.
"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."
He said he believed the most likely direct cause was a failure to change the plants and animals they relied on for food.
While advances in technology make us more resilient now, the paper concludes that "the threat posed by the current, anthropogenic climate change for global wildlife and, by extension, ourselves, is possibly even more powerful than is generally appreciated".
Scant fossil records make the findings for the earlier time periods less reliable, Professor Chris Stringer of the Natural History Museum, who wasn't involved in the research, told Scientist magazine, but climate change "probably was a significant factor in some of those extinctions".
Raia said the findings were "worrisome" for modern humans, especially given our reliance on other species for survival.
"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."
