New Theory Emerges to Explain our Genetic Similarity

A recent article discussed the possible reasoning for why two humans from the most distant parts of the globe are more genetically similar than two chimps from the same tribe.  The explanation featured in the article is that a bottleneck event occurred around 75,000 years ago due to the Toba volcanic eruption in Indonesia.  This volcano was equivalent to 1 billion tons of dynamite or about 3000 times more devastating than the Mount Saint Helens eruption of 1980.  The severity of the blast might have reduced the average global temperature by 5° C, created a new Ice Age, and darkened the sky for 5 to 6 years.  This event clearly had a huge effect on all the species of the Earth, including our own which may have been left with only 1000 breeding pairs to spread genetic variation.  This bottleneck-type event most likely led to the small level of variation between all living humans.  Although we  barely escaped extinction during this global event, many species have come even closer to the brink of destruction and still live and reproduce successfully today.  There were between 20 to 100 elephant seals remaining in the world in the late 1890's due to hunting, but now there are at least 150,000 living in the west coast.  This just goes to show that compared to some species we have more than enough genetic variation to survive for many more thousands of years.