Around 74,000 years ago, the super-volcano Toba erupted in Sumatra. This “mega-colossal” blast has been accused of nearly causing our extinction as a species: Its ash filled the skies and, the theory goes, caused a deadly global volcanic winter lasting as long as 10 years and ushering in a 1,000-year cold spell. But while the category-8 eruption definitely happened and Toba did spew out gargantuan amounts of ash that spread around the world, it didn’t cause mass extinctions far and wide, and certainly didn’t nearly stymie our Maker, argues an international team in a new study in Nature.
Their study is based on the span in time of stone tool manufacture in prehistoric India, which seems to have been unaffected by the purported super-eruption.
Today, all we see is the vast but happily quiescent caldera that holds Lake Toba, which is a stunning 100 kilometers (62 miles) long and about 30 kilometers wide. That is a big caldera. The theory of Toba causing a nearly-fatal bottleneck for humankind arose and gained popularity in 1993, claiming that extinctions encompassed much of the globe and hominin populations were reduced to unsustainably small levels. But a handful of nifty Homo sapiens with their superior adaptability grimly hung on in pockets in central and southern Africa, the theory says. Then when climatic conditions improved, they re-expanded out of Africa.
Volcanic ashes to ashes
Volcanic winter is a thing, and from eruptions much smaller than Toba’s. In the year 1816, Mount Tambora in today’s Indonesia erupted and is believed to have caused the “Year Without a Summer,” badly hurting global agriculture.
But angles of attack on the Toba theory are myriad, including estimates of how cold the volcanic winter actually was: did it lower global average temperatures by 1 degree Celsius or nearly 4? Did the volcanic winter last just a year, like after Tambora and Krakatoa’s 1883 eruption, or much longer? Why does evidence in Malawi in eastern Africa and also in South Africa show almost no effect? (Or as The Atlantic memorably put it – “Supervolcano Goes Boom. Humans Go Meh?”) If anything, the human population in Africa seems to have been thriving before and after.
The new paper in Nature further debunks the theory of the Toba-induced near-extinction of our species by reporting on continuous hominin activity in Dhaba, on the banks of the River Son in central-northern India from 80,000 until 25,000 years ago.
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No human remains have been found. But there are stone tools in layers from before to after the Toba super-eruption, with no interruption.
One school of tool the archaeologists found in Dhaba show Levallois-type technology (a distinctive form of stone knapping), which somebody there was making from 80,000 to 65,000 years ago. About 48,000 years ago, a finer “microlithic” technology appeared.
We can’t say for sure that the makers of the Dhaba tools were Homo sapiens as opposed to, say, Denisovans or even somebody else. No hominin fossils from the time of the postulated dispersal from Africa have been found in India so far, and sites featuring stone tools or any artifacts from 80,000 to 50,000 years ago are very sparse. Also, other human species, including Neanderthals, used Levallois technologies, Prof. Michael Petraglia of the Max Planck Institute confirms to Haaretz.
So: the team deduces that the manufacturers in India were Homo sapiens. How? They compared the Indian stone tools with those made by Neanderthals and to tools made by Homo sapiens in sub-Saharan Africa, Arabia and Australia, and found them most similar to the other human tools.
Ergo, the Dhaban tools were likely fashioned by anatomically modern humans as they spread eastward out of Africa. In any case, whoever made them, these tools were made before and after Toba – which in and of itself argues against the Toba devastation theory.
“The fact that these toolkits did not disappear at the time of the Toba super-eruption or change dramatically soon after indicates that human populations survived the so-called catastrophe and continued to create tools to modify their environments,” stated the study’s lead author, Prof. Chris Clarkson of the University of Queensland.
Before and after Toba
When anatomically modern humans spread out of Africa is one of the great conundrums. Some still adhere to the theory that it happened about 50,000 years ago, arguing that earlier dates postulated for the occupation of Australia are not proven. Others are satisfied that the ancestors of today’s aboriginal Australians reached there around 65,000 years ago. That would mean that anatomically modern ancestors (our forefathers) had to have left Africa a lot earlier than that, given that they had to walk the whole way – and as they did, they would have passed through India.
Recent genetic analyses have strengthened the theory that all non-Africans stem from a wave of migration by modern humans exiting Africa between 70,000 to 52,000 years ago, the paper notes. That absolutely does not mean that Homo sapiens didn’t leave Africa earlier too: the archaeological record indicates that Homo sapiens did just that, Petraglia points out.
Evidence from China about early human presence is hotly debated. This paper accepts that some modern humans reached Southeast Asia by 73,000 to 63,000 years ago, in no small measure based on the work in Madjedbebe, northern Australia, suggesting modern occupation by 65,000 years ago.
In short, India and Dhaba were en route as early modern humans spread east of Arabia from about 100,000 years ago, survived Toba’s fury (some ash did fall on Dhaba) and forged onward.
Any anatomically modern human migrations preceding the one that fathered us went extinct, as did every other hominin in the world that we know of. But it seems that Homo sapiens was thronging Asia earlier than has been assumed, and that the Toba super-volcano wasn’t quite as apocalyptic as had been assumed. Anybody near the caldera surely died, but life on Earth, including in Europe, soldiered on.
“The Toba super-eruption was a very large volcanic event. We do not dispute that,” Petraglia says. “What we dispute is that it had a major effect on human evolution. It does not seem to have wiped out hominin populations. And though there are some ecological changes in India after this event, the ecosystem changes are not at all catastrophic.”