1.18 the Toba-explosion

But there was a sudden end to this AMH population explosion. On Sumatra exploded the mega-volcano Toba, somewhere between 74-73,000 years ago.

At least 2,800 square kilometers of tephra (Greek word for ‘ash’ but it is a much more dangerous stuff than ash from wood or even coal!) rose to the stratosphere, causing ash plumes to cover a large part of the world, from the south China Sea to the Arabian Sea. It left behind what still is the world’s largest caldera: Lake Toba.

For comparison: the largest volcano event in historical times was the Tambora eruption on the Indonesian island Sumbawa in 1815. It produced the ‘year without summer’ in 1816. But Toba ejected about 300 times more volcanic ash than the eruption of Tambora and caused maybe six years of climatic deterioration (‘volcanic winter’), which in turn caused the decimation of animal and human life over very large areas.

That most paleo authors do not mention the Toba bottleneck – in the discussion between Richard Klein and his critics Hensilwood and d’Errico e.a. we don’t find any reference to the Toba event – can perhaps be ascribed to the fact that thorough research on this catastrophe is fairly recent.[1]

So far, the effect on many species of life has been demonstrated in DNA research on the history of a growing number of species, such as bonobos and chimpanzees. Geneticists Jore and Harpending[2] propose that all humans alive today are descendants from a very small part of the earlier population: perhaps some 8000 breeding pairs about 70.000 years ago[3].
The impact on the northern hemisphere was more severe than in the south; nevertheless also Neanderthals survived the supposed six years of volcanic winter. The AMHs had even better chances, not only because they lived farther south, but also because of their broader subsistence strategy based on hunting and gathering coastal resources (shellfish, fish, sea lions and rodents, as well as bovids and antelope).

Afbeeldingsresultaat voor jwalapuram The ash plume drifted obliquely to the north and covered the peninsular India with a decimetres thick layer of tephra.

At Jwalapuram in India, archaeologists dug through a meter thick Toba ash layer (see photos). First, above the Toba tuff, they found many stone artefacts from about 74,000 years ago, made from limestone, chert, chalcedony and quartzite, with blades and bladelets representing a Late Pleistocene assemblage also assigned to the Middle Paleolithic. Digging deeper, below the thick Toba tuff layer (the white one[4]), they found many more stone tools that could be dated at about 77,000 years ago, of limestone, quartzite, and chert: scrapers, blades and a burin also identifiable as Indian Middle Paleolithic. This lithic assemblage clusters together with the lithic technology of sub-Saharan Africa, and indicates that the AMHs belonged to the first migration wave out of Africa. We will talk about this in the next paragraph.

According to the excavators, before the explosion this place was a ‘paradise’ on the shore of a lake. Then it got buried under two-to-five decimeters of volcanic ash. The next six years, with the atmosphere still full of ash particles, were a volcanic winter. During the next thousand years, the climate still was extreme cold: a glacial maximum[5]. But perhaps after some decennia of annual monsoons already, big parts of the area became sufficiently overgrown to harbor grass eaters again. So archaic AMHs of the same population must have lived in this area, and after the Toba explosion survivors reappeared as soon as grass vegetation and grazing animals reappeared.

The Jwalapuran excavation is not the only site showing evidence of the Out of Africa (OoA)-migration of the AMHs, both before and after the Toba explosion. Another recent excavation pre-Toba site is Jebel Faya[6], where 125,000 year old hand axes are found, showing a pattern of flaking seen only in early Africa. Indicating an out-of-Africa migration 20.000 earlier than thought before. Indeed, 130,000 years ago, there was a window of climate change. The Sahara and the Arabian Peninsula was more habitable than today.

  1. In an article in October 1993 Ann Gibbons, a staff journalist for Science, was the first one to suggest that a bottleneck in human evolution about 50,000 years ago could be linked to the Toba eruption. Rampino and Self backed up this idea in a letter to the journal later that year. The bottleneck theory was further developed by Ambrose in 1998 and Rampino & Ambrose in 2000, who invoked the Toba eruption to explain a severe culling of the human population. (Wikipedia)
  2. Population Bottleneck from Macmillan Science Library: Genetics. Copyright © 2001-2006
  3. Wikipedia “Toba catastrophe theory”
  4. these layers, together a meter thick, originate from aeolian transport and slope-wash during annual monsoons into this low location. The location is an important one
  5. OIS 5 – 130,000 to 74,000 years ago (warm)OIS 4 – 73,000 to 63,000 years ago (cold)OIS 3 – 63,000 to 45,000 years ago (warm)
  6. Anthropology Net 27 Jan 2011: Hans-Peter Uerpmann of the University of Tubingen and his team excavating the Jebel Faya site in the United Arab Emirates.


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Used abbreviations

GHs: gatherers/hunters (the phase from 2 million years ago to 10.000 years ago)

AGRs: agriculturers (the phase from 10.000 years ago till now)

NT(s)Neanderthal people

MSA(s): Middle Stone Age people (African NTs)

AMH(s): Anatomical Modern Humans (H sapiens people), like we are

(m)ya: (million) years ago

ANBOs: Ancestor Bonobos (ape-men), our earliest human ancestors

Paleos: all scientists that are important for our story.