The Toba Extinction Theory Takes A Gut Punch

[Minimalist]

https://www.nature.com/articles/s41467-020-14668-4

Human occupation of northern India spans the Toba super-eruption ~74,000 years ago

The Dhaba localities together provide evidence of long-term human occupation spanning the last ~80 thousand years. Occupation spans the Toba eruption and the stone tool industry shows no significant change in technology until the introduction of microlithic technology ~48 ka. The lithic industry from Dhaba strongly resembles Middle Stone Age stone tool assemblages from Africa, Arabia and Australia, here interpreted as the product of Homo sapiens as they dispersed eastward out of Africa.

[circumspice]

Wasn't the Toba eruption considered a bottleneck event? A near miss? Signs of human presence & their diversity seem to have taken a nosedive after the eruption & there was a considerable time lapse before the population rebounded and/or recovered. At least that's what I remember the various articles stating.

[Minimalist]

That was the initial claim by geneticists, Circ. The blast and the following "nuclear winter" blasted humanity all the way back to East Africa.

The problem was that the Neanderthals and the megafauna didn't seem to know they had been wiped out. And now we find that humans much closer to Toba kept right on making tools throughout the whole period of their "extinction."

[circumspice]

I'm not sure where you're going with this Min... Geneticists discovered a bottleneck that showed reduced diversity indicating a possible near extinction event. Then anthropologists & geologists began looking for the source of the proposed event. They settled on the Toba eruption as the most likely cause. Nowhere was it said that all the mega fauna & hominins were obliterated in the area affected by the eruption. They just indicated that it was a possible source for the unexplained reduction in human diversity.

[Minimalist]

How can you have an impact so severe that it kills all the humans east of the Rift Valley but misses the Neanderthals and mega fauna? That seems like a highly selective volcano to me. And now they have found that humans far closer to Toba were merrily making tools right through the whole period when they were supposedly dead. Something does not compute. My guess is that there was some flaw in that earlier genetic finding.

Sort of reminds me of this:

[circumspice]

Hey Min... I don't recall any articles that were citing die offs in east Africa. From what I do recall, the geneticists found a genetic bottleneck causing a drastic reduction of genetic diversity in the the early modern human genome. They estimated how long ago that the bottleneck occurred then geologists & anthropologists ran with the ball, looking for a likely candidate for a disaster that could have reduced the early modern human population to such an extent that it would reduce the diversity. I recall reading that the estimate of the breeding population was extremely low, perhaps as few as 1000-1500 individuals. (Remember... we're talking about the genetic lines of people who had successful descendant lines. Any other lines that went extinct wouldn't be represented in the current genome) In my personal opinion, the cause of the bottleneck could have been anything, such as warfare or an epidemic... It didn't necessarily need to be a natural disaster.

[Minimalist]

This recap sort of agrees with your conclusion.

https://www.businessinsider.com/genetic ... ans-2016-3

The Toba catastrophe theory offers a convenient answer to the near doom written in our DNA.

The hypothesis says an enormous supervolcano eruption occurred around the same time as humanity's biggest bottleneck. Research from the late 1990s and early 2000s suggested that this eruption, on Sumatra in Indonesia, blocked the sun across much of Asia, causing a harsh volcanic winter and a 1,000-year-long cooling period on earth.

But archaeological evidence shows that human hunter-gatherer settlements in India weren't too affected by the eruption and quickly recovered. Temperature data embedded in the geology of Lake Malawi, in East Africa, also suggests that the region didn't cool off that drastically.

So what did cause that major bottleneck 70,000 years ago, if not a giant volcano and an ice age?

Scientists aren't sure, but they have some new ideas. A catastrophic spread of disease, for example, may have played a role. Or perhaps the way we currently think humans dispersed out of Africa needs some adjustment.

That last line is probably the one that comes closest. I'm having a hard time imagining a pre-historic World War!

[circumspice]

Perhaps a set of multiple causes? I can imagine warfare caused by severely limited resources, famine & epidemics all striking in a near simultaneous time frame. People fight over more trivial issues. Imagine what it would be like after such a scenario. But the point is that SOMETHING caused a genetic bottleneck that we barely survived. We may never really know the exact cause.

[Minimalist]

I wonder if anyone ever tried to do a population density guesstimate on that time period?

[circumspice]

I wonder if anyone ever tried to do a population density guesstimate on that time period?

I would wonder how they could possibly estimate the population density of an extinct population from the scanty remains that survive to the present day... I read somewhere that ALL the remains of ALL extinct hominins would fit into the bed of a short wheelbase pickup with tons of room to spare. Some species are represented by remains that can fit into a shoebox & not fill it up.

[Minimalist]

Sometimes they do things just on the basis of mathematical models. We are free to wonder about how accurate those are.

[circumspice]

Sometimes they do things just on the basis of mathematical models. We are free to wonder about how accurate those are.

I do wonder. Since they are using the fossil record to do any estimates, how accurate can any estimate be? From what I understand, fossilization requires a certain set of circumstances in order to happen. Ideally, the organism gets fossilized because those specific requirements are met... Such as being covered by some type of soil or sediment shortly after the organism dies. If it's covered quickly, the fossil could be articulated and/or nearly complete. Then the process of mineralization can start. But if the soil or sediment covering the dead organism is acidic the organism will probably decompose entirely before the slow process of mineralization can take place... There are varying degrees of fossilization, too. Some fossils are nearly perfectly preserved & most are way less than well preserved. I love it when they find fossils that exhibit amazing detail due to being optimally preserved. It's a crap shoot. Like fossils preserved in lithic shales. Finds that preserve details like skin texture or feathers on dinosaur fossils... fossils that show preservation of internal organs or abdominal contents... *big gusty sigh*

[Minimalist]

Certainly. What is found tends to be overvalued merely because we have found it. While it cannot be overlooked one should resist the urge to make too many conclusions from them.

We do not know what we don't know.

[circumspice]

Certainly. What is found tends to be overvalued merely because we have found it. While it cannot be overlooked one should resist the urge to make too many conclusions from them.

We do not know what we don't know.

Words to live by...

[Greatly]

We are free to wonder about how accurate those are.