Travel Reference
In-Depth Information
Ambrose of the University of Illinois has proposed that the ef ects of Toba
were so devastating that our own species nearly went extinct.
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Violent as the event was, most scientists are pretty doubtful that Toba
had as severe an impact on our species as Ambrose suggests. To begin with,
its ef ects were not planet-wide. Arctic ice cores show a trace of the Toba
eruption in the form of a distinct pulse of sulfate. But a similar spike of sulfate
has not been found in the Antarctic.
A few large southeast Asian mammal species might have disappeared
after Toba, but they also might have disappeared because of general climate
changes, human hunting, or simply the incompleteness of the fossil record.
As for human activity, there is only one piece of evidence with a direct bear-
ing on the question. Michael Petraglia of the University of Cambridge has
shown that the stone tools made by early modern humans living in southern
India at that time were the same before and after the eruption, even though
these peoples were directly in the path of the ash fall.
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Intriguingly, there is genetic evidence that human populations outside
Africa may have become reduced in size around the time of the Toba erup-
tion, and Ambrose has suggested that the eruption was the cause. But there
are large uncertainties about exactly when this reduction in population size
took place, and much of the evidence has more than one interpretation.
We simply do not have enough data to measure the ef ect of Toba on our
population in the past. Did the eruption nearly kill us of ? Possibly, but if it
was so disastrous then it seems strange that the eruption did not do more
detectable damage to other animal and plant populations. In particular, it did
not kill of the orangutans of Sumatra, even though they lived at the epicen-
ter of the explosion.
The true evolutionary role of the Earth's upheavals
Though I did not enjoy my little earthquake at the time it happened, in ret-
rospect I am pleased to have re-lived, in some small way, Darwin's experi-
ence with the Chilean earthquake. We both had the same kind of encounter
with the massive forces that have shaped our Earth. My encounter with the
