The Toba Catastrophe

Lets just say you wanted to prove that, in fact, Noah did save all the animals. How would you do it? Probably the most certifiable way to do this would be to analyze the mitochondrial DNA of each species (or a only a few if you’re lazy), and see whether or not the variations suggest a population bottleneck at a certain point in time. Why use mitochondrial DNA? I’m glad you asked. Consider the normal DNA in our bodies. When you are created, your DNA is a gooey mixture of the genetics of your father and your mother (a notable exception is made for the male Y chromosome). However, the DNA in your mitochondria (the energy producing organelle in your cells) are received only from your mother, meaning they remain intact. It also turns out that mitochondrial DNA mutates significantly faster than normal DNA. So, by comparing the minute changes, you can trace your lineage back to a very certain point. You can also, by sampling a population, see if they have a common female ancestor. So, one would expect that if Noah did put all those animals onto an ark, that we could not only tell that it happened, but also pinpoint, with in a certain degree of accuracy, what year it happened.

If, for example, you started with the Great Panda, things would be looking in your favor. Genetic evidence has it that the Giant Panda almost went extinct about 43,000 years ago. That’s a bit old for Noah, but its a good start. It would be even more exciting if you tried the Golden Snub Nosed Monkey, as they almost went extinct at around the same time period. Unfortunately, your luck runs out there, animals worldwide show a remarkable amount of mitichondrial genetic diversity. Well, then if Noah and his kin were the the ones to survive the flood, then we should be able to see it in the genetic register. In fact, Stanley Ambrose at the University of Illinois Champaign-Urbana investigated this in 1998, and found something remarkable. Genetic evidence suggests that modern humans are descended from a group of 1,000 – 10,000 individuals, dating back to 70,000 – 75,000 years ago. Yes you read that right. There is a distinct possibility that the human race was limited to a population 1/3 of Green Bay. Humans were known to be around at least 140,000 years ago, so what caused them all to die off to such a small group?

It turns out that 70 – 75,000 years ago there was a massive volcanic explosion in what is now the Toba caldera. This eruption was a category – 8 (which classifies it as being “mega – colossal”). It was 3,000 times as big as the Mt St Helens eruption, an energy release greater than a giga ton of TNT. The earth was going through an ice age at the

Uh oh.

Uh oh.

time, and this made it way, way worse. Not bad enough to kill off the human race though.

At this point in time there is an excavation in India which suggests that another pocket of humans survived through the volcanic fallout. So the Toba disaster may not be as catacolysmic as many would have you believe. In fact, evolution takes its course much faster in smaller pockets, so this bottleneck may have been crucial for the development of the modern human.  Its scary to think about, but it is a good reminder of how risky it is to be living on this planet.

Published in: on July 23, 2009 at 10:05 pm  Leave a Comment  
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