Toba bottleneck illuminated

[Rokcet Scientist]

The nuclear winter scenario is that there is sufficient ash to block out the sun EVERYWHERE.

Not necessarily Min!
The northern hemisphere is enough to create a strangling evolutionary bottleneck for a gazillion species. Which some species succumbed to, while others survived.

[Minimalist]

You'll have to take it up with Wiki.

The nuclear winter scenario predicts that the huge fires caused by nuclear explosions (particularly from burning urban areas) would loft massive amounts of dark smoke and aerosol particles from the fires into the upper troposphere / stratosphere. At 10-15 kilometers (6–9 miles) above the Earth's surface, the absorption of sunlight would further heat the smoke, lifting it into the stratosphere where the smoke would persist for years, with no rain to wash it out. This would block out much of the sun's light from reaching the surface, causing surface temperatures to drop drastically.

[Rokcet Scientist]

Whatever causes it, no 2 events in that 'class' - in any class - will be the same. One will cause more havoc than the other. The consequences of one will be more serious and longer lasting than those of another.

Hence, I'm guessing, the moniker 'bottleneck', a concept with no fixed absolute dimensions, but rather describing a relative perspective. I.o.w. NOT a total wipe-out, but a close shave.
Like the 5 now recognised mass extinctions. And thousands of less spectacular events. At least less advertised.

But that could just be me of course.

[Cognito]

The Toba eruption apparently caused a nuclear winter for six years. Many probably died due to the initial deep freeze, but there weren't the extinctions that the authors claim.

Due to prevailing wind patterns, most of the eruption's ash fell on India and its environs. Sapiens in Africa survived along with Neanderthals in Eurasia, some Erectus in Indonesia as well as Hobbits on Flores. And then there is the newly discovered species near the Altai that made it. I count five which brings me to the conclusion that the authors didn't do their homework. For a decent analysis of Toba see: http://www.andaman.org/BOOK/originals/W ... /textr.htm.

[Digit]

Unfortunately Cog professionals can be as bad as amateurs at promoting pet ideas even beyond logic or common sense.

Roy.

[Rokcet Scientist]

The Toba eruption apparently caused a nuclear winter for six years.

...in the northern hemisphere!

[Cognito]

...in the northern hemisphere!

RS, I am really not certain why you would make such a statement when the Toba cauldera sits at 2.5 North Latitude. See:

http://www.solcomhouse.com/laketoba.htm

Atmospheric circulation could take Toba's 74kya ejecta in either direction, north or south, and likely did so.

http://en.wikipedia.org/wiki/Atmospheric_circulation

[Digit]

Generalisations can of course be tricky but everything i've read about a Toba induced NW states 'global' or 'worldwide'. Not exactly a scientific piece of terminology unfortunately is it Cog?

Roy.

[Cognito]

Here is what I was looking for from Rutgers, Roy. See page 6 of 9 for the "Toba Zonal Mean Visible Optical Depth", ie airborne particulate from the eruption. The affect was a six year nuclear winter which was probably more severe in the north, but also included the south. Then, the most severe 1,000 years of cold during the last Pleistocene age followed, affecting both north and south (ie the entire planet).

http://climate.envsci.rutgers.edu/pdf/T ... 011652.pdf

The initial ash cloud covered India, but the stratosphere eventually picked up enough sulfates from the eruption to make everyone on the planet miserable for a very long time.

[Rokcet Scientist]

So it looks like the Toba event came close to the status of "mass extinction", doesn't it? But as "mass extinctions" are defined by them not being total, not 100%, a scenario whereby 70% of hominids, which could translate into 5 of 7 'separate' hominid species, disappeared is entirely acceptable for debate, imo.

That would be HSS and HN populations surviving Toba, albeit severely affected and decimated, while HH, HA, HE, and a couple other variants perished altogether.

It would really be a standard "mass extinction" scenario. Fitting a standard pattern.

[Rokcet Scientist]

But surely Toba is being sold as causing a bottleneck in HSS, who is supposed to be still in Africa at this time, or did I miss something?

The 'classic' OOA concept from the sixties – as I remember it – held that HS(S) left Africa in 2 waves: one a little over 100,000 YBP, and the other around 70,000 YBP.

The recognition of Toba as a giant eruption 73,000 YBP dates from the early eighties, as far as I remember. By then the 2 OOA waves theory was starting to lose steam – HS(S) as a species was recognized as having evolved around 196,000 YBP.
So any way you cut it HS(S) would have been affected by Toba. How hard? Who knows.
MtDNA Research seems to indicate that all of us, all 6 billion (supposedly) HS(S), descend from just 11 individual HS(S) "Eve's", 11 maternal lineages. 7 of which are around 70,000 years old, and 4 are a little over 100,000 years old. That's two bottlenecks for ya right there!
Haven't a clue, though, what the 100,000 YBP bottleneck event would have been.