Toba catastrophe theory and genetic bottleneck

The Youngest Toba eruption occurred at the present location of Lake Toba in Indonesia, about 75,000 ± 900 years BP according to potassium argon dating.[4] This eruption was the last and largest of four eruptions of the Toba Caldera Complex during the Quaternary period, and is also recognized from its diagnostic horizon of ashfall, the Youngest Toba tuff.[5] It had an estimated volcanic explosivity index of 8 (the highest rating of any known eruption on Earth); it made a sizable contribution to the 100 × 35 km caldera complex.[6]Dense-rock equivalent (DRE) estimates of eruptive volume for the eruption vary between 2,000 km3 and 3,000 km3; the most common DRE estimate is 2,800 km3 (about 7×1015 kg) of erupted magma, of which 800 km3 was deposited as ash fall.[7]


The erupted mass was, at the very least, 12 times greater than that of the largest volcanic eruption in recent history, the 1815 eruption of Mount Tambora in Indonesia, which caused the 1816 "Year Without a Summer" in the Northern Hemisphere.[8] Toba's erupted mass deposited an ash layer of about 15 centimetres (5.9 in) thick over the whole of South Asia. A blanket of volcanic ash was also deposited over the Indian Ocean, the Arabian Sea, and the South China Sea.[9] Deep-sea cores retrieved from the South China Sea have extended the known reach of the eruption, suggesting that the 2,800 km3 calculation of the erupted mass is a minimum value or even an underestimate.[10] Based on new methods (computational ash dispersal model using a 3D time-dependent tephra dispersion model, a set of wind fields, and several tens of thickness measurements of the YTT tephra deposit), the Toba Caldera Complex possibly erupted as much as 13,200 km3 in total bulk volume.[11] This has lead to some sources labelling the Youngest Toba eruption as a "VEI-9" event.[12]

Genetic bottleneck in humans[edit]

The Youngest Toba eruption has been linked to a genetic bottleneck in human evolution about 70,000 years ago,[29][30] which may have resulted in a severe reduction in the size of the total human population due to the effects of the eruption on the global climate.[31] According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals.[32][33] It is supported by some genetic evidence suggesting that today's humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.[34][35]



Proponents of the genetic bottleneck theory (including Robock) suggest that the Youngest Toba eruption resulted in a global ecological disaster, including destruction of vegetation along with severe drought in the tropical rainforest belt and in monsoonal regions. A 10-year volcanic winter triggered by the eruption could have largely destroyed the food sources of humans and caused a severe reduction in population sizes.[18] These environmental changes may have generated population bottlenecks in many species, including hominids;[36] this in turn may have accelerated differentiation from within the smaller human population. Therefore, the genetic differences among modern humans may reflect changes within the last 70,000 years, rather than gradual differentiation over hundreds of thousands of years.[37]

Calypso Jones wrote:how do they know this.   They admit it's a theory.

JMWinPR wrote:

Calypso Jones wrote:how do they know this.   They admit it's a theory.

They discovered it on "YouToba" Duhhhh.