At about 74,000 years ago, Mount Toba on the island of Sumatra erupted in a massive explosion that supposedly rocked the Middle Palaeolithic world to its very foundations, bringing contemporary human populations to their knees, reducing the global population level to around 15,000 individuals, thereby precipitating a so-called bottle-neck of human evolution, as proposed by Stanley Ambrose, from the University of Illinois at Urbana-Champaign, discussed in this BBC News article from 1998, and in an essay at the Bradshaw Foundation, in the same year. However, recent discoveries made by Michael Petraglia, from the University of Cambridge, have now cast doubt on this theory…

(the team)…found the stone tools at a site called Jwalapuram, in Andhra Pradesh, southern India, above and below a thick layer of ash from the eruption of the Toba volcano in Indonesia — an event known as the Youngest Toba Tuff eruption.

The tools from each layer were remarkably similar, and Petraglia says that this shows that the huge dust clouds from the eruption didn’t wipe out the population of tool-using people. “Whoever was there seems to have persisted through the eruption,” he says.

This is the first archaeological evidence associated with the Toba super eruption, says Petraglia, and it contradicts theories that the eruption had a catastrophic effect on the area that its ash blanketed.

Following this eruption, a phase of dramatic global cooling ensued, evidenced by a 6-year global winter, which in turn was followed by the onset of the Würm glaciation event. Petraglia proposes that only modern humans could have survived such an event, giving as his evidence the supposed similarity of the lithic assemblage, and purported others, which he claims correspond with those found in Africa dating to around 100,000 bp, by which time modern anatomically modern humans had been extant there for some 100,000 years.

Petraglia thinks that modern humans — rather than Neanderthals or other hominins — are the only species that would have been able to persist through an event as dramatic as the Toba eruption. This theory will spur much debate, he admits, because modern humans were not thought to have reached India, from Africa, so long ago. “It’s controversial,” says Petraglia, “but it makes a lot of sense.”

Petraglia and his team compared the tools they found to others from Africa from different periods in this week’s edition of Science1. The Indian tools look a lot like those from the African Middle Stone Age about 100,000 years ago, when modern humans were thought to have lived, he says. “Whoever was living in India was doing things identical to modern humans living in Africa.” Neanderthal toolkits found in Europe are very different, he says. This is more evidence, he says, that the plucky ash-covered inhabitants of Jwalapuram were modern humans.

However, we know that modern humans weren’t the only individuals capable of withstanding sudden and extreme climate change, as Eurasian Neanderthals lived through the Riss glaciation which occurred from 180,000 bp – 130,000 bp, and they also survived the Mount Toba event, regardless of its supposed global impact. It’s possible too that Homo erectus lived on as late as 50,000 bp in Asia, and if Homo floresiensis turns out to be a genuine new species, they too survived this event (n.b. – but see this latest update from John Hawks, which I’ll attempt to address later)

Moreover, lithic assemblages, whether in India, Africa or Europe don’t always indicate exactly which species of Homo may or may not have been responsible for their manufacture, as pointed out by Stanley Ambrose…

(who) disagrees with Petraglia’s conclusions. “It is highly speculative to say the eruption had no impact,” he says. Ambrose argues that Petraglia’s sample size is too small to make proper comparisons with other tools. And, he adds, “stone artifacts cannot be used to differentiate Neanderthals from African moderns.”

…which raises the question of exactly which species of Homo would have been living in India at the time of the Toba event. At 74,000 years bp, it is generally assumed that anatomically modern humans were still resident only in Africa, from where they would emerge at around 50,000 bp to commence their purported total replacement of all other species across the globe, culminating in the extinction of the Neanderthals at around 24,500 bp.

However, we know this can’t be true, because as John Hawks points out in his post on this topic, Australia was populated by moderns by at least 50,000 bp, and quite possibly even earlier still, at around 60,000 bp, depending on one’s interpretation of the widely different/wildly conflicting dates given for Mungo Man. And if Homo erectus managed to navigate the open seas to Flores at 840,000 bp, it would appear that modern human behaviour is a great deal more ancient than in its comparatively youthful Middle and Upper Palaeolithic claimed origin, meaning that theoretically any species of human from Homo erectus up to and including early Homo sapiens could have prevailed in a post-Toba environment.

But even more crucially, there is evidence of modern and symbolic behaviours coming out of India at dates far earlier than these Middle Palaeolithic dates, as indicated by Robert Bednarik’s paper from here, in which he details what may be evidence of Indian palaeoart dating back to around 300,000 bp, making it roughly contemporary with ostrich shell disc beads from Lake Fezzan in Libya.

On a very generalised basis, it could be argued that there were constant pulses of emigration from Africa to Asia, dating back from the Acheulean, through the African Middle Stone Age, as indicated by the purported modern survivors of Mount Toba, followed by others at around the Middle/Upper Palaeolithic boundary of Eurasia, and especially western Europe, plus many other African exodus which have so far remained undetected.

On the other hand, others might argue that what we are seeing here is evidence for various multi-regional events, in which local populations in Asia and Africa evolved in some kind of parallel, possibly mediated by more or less frequent encounters and genetic exchange between the two populations over the course of hundreds of thousands of years.

But until fossil evidence is retrieved from sites like Jwalapuram, we will have no clue as to the true identity of the makers of the stone tools and other sites alluded to by Petraglia – even if, and when fossil remains are recovered, further clarification as to the geographical origin of those specimens may be in need of yet further clarification. (TJ)

see also: Early Indian Petroglyphs project