Impact of Ancient Indonesian Volcanic Eruption
The Toba super eruption occurred between 69,000 and 77,000 years ago at Lake Toba (present day Indonesia), and it is recognized as one of Earth's largest known eruptions. The related catastrophe theory holds that this super volcanic event plunged the planet into a 6 to 10 year volcanic winter, which resulted in the world's human population being reduced to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution. Some researchers argue that the Toba eruption produced not only a catastrophic volcanic winter but also an additional 1,000 year cooling episode.
Newly discovered archaeological sites in southern and northern India have revealed how people lived before and after the colossal Toba volcanic eruption 74,000 years ago.
According to the supporters of the genetic bottleneck theory, between 50,000 and 100,000 years ago human population suffered a severe population decrease (only 3,000 to 10,000 individuals survived). Genetic evidence suggests that all humans alive today, despite apparent variety, are descended from a very small population, perhaps between 1,000 to 10,000 breeding pairs about 70,000 years ago.
Ambrose and Rampino proposed in late 90s that this bottleneck could have been caused by the climate effects of the Toba eruption. The supporters of the Toba catastrophe theory suggest that the eruption resulted in a global ecological disaster with extreme phenomena, such as worldwide vegetation destruction, and severe drought in the tropical rain forest belt and in monsoonal regions. Τhis massive environmental change created population bottlenecks in species that existed at the time. Toba may have caused modern races to differentiate abruptly only 70,000 years ago, rather than gradually over one million years.
The Toba explosion instantly destroyed all life in its immediate area. The eruption was more powerful than Krakatoa in 1883 that helped lower global temperatures by about 1.2 degrees C in the next year.
It also sent hundreds of cubic kilometers of ash and gases high into the atmosphere, even as the volcano itself collapsed inwards to form a huge sunken caldera (now Lake Toba). The gases, including sulfur dioxide, circled the globe on air currents, while the ash spread out to the north and west fanned by prevailing winds. When the ash began to fall, it covered the Indian subcontinent and rained down into oceans from the Arabian Sea in the west to the South China Sea in the east.
Around this time the earth slipped into a dramatically colder portion of the ice ages, and while this was underway before Toba’s eruption, the super volcano undoubtedly had an important influence.
An international, multidisciplinary research team, led by Oxford University in collaboration with Indian institutions, recently unveiled to a conference in Oxford what it calls "Pompeii like excavations" beneath the Toba ash in India.
The seven year project examines the environment that humans lived in, their stone tools, as well as the plants and animal bones of the time. The team has concluded that many forms of life survived the super eruption, contrary to other research which has suggested significant animal extinctions and genetic bottlenecks.
According to the team, a potentially ground-breaking implication of the new work is that the species responsible for making the stone tools in India was Homo Sapiens. Stone tool analysis has revealed that the artifacts consist of cores and flakes, which are classified in India as Middle Palaeolithic and are similar to those made by modern humans in Africa. "Though we are still searching for human fossils to definitively prove the case, we are encouraged by the technological similarities. This suggests that human populations were present in India prior to 74,000 years ago, or about 15,000 years earlier than expected based on some genetic clocks," said project director Dr Michael Petraglia, Senior Research Fellow in the School of Archaeology at the University of Oxford.
This exciting new information questions the idea that the Toba super eruption caused a worldwide environmental catastrophe.
An area of widespread speculation about the Toba super eruption is that it nearly drove humanity to extinction. The fact that the Middle Palaeolithic tools of similar styles are found right before and after the Toba super eruption, suggests that the people who survived the eruption were the same populations, using the same kinds of tools, says Dr Petraglia.
Although some scholars have speculated that the Toba volcano led to severe and wholesale environmental destruction, the Oxford led research in India suggests that a mosaic of ecological settings was present in the world, and some areas experienced a relatively rapid recovery after the volcanic event.
Dr Petraglia said: "This exciting new information questions the idea that the Toba super eruption caused a worldwide environmental catastrophe. That is not to say that there were no ecological effects. We do have evidence that the ash temporarily disrupted vegetative communities and it certainly choked and polluted some fresh water sources, probably causing harm to wildlife and maybe even humans."
For further information: http://www.ox.ac.uk/media/news_stories/2010/100223.html