Saturday, June 18, 2011

The Math of Heredity

Today, I read an article entitled: We're All Mutants: The Average Human Has 60 Genetic Mutations.  Now, if 60 mutations sounds like a lot realize that scientists were actually expecting to see 100-200 genetic mutations in each generation. The article went on to say that this has forced scientists to revise their estimations on human evolution.

That article got me thinking about the math behind evolution, and whether or not math really supports the theory of human evolution at all. Then I wondered just how many people would it take, based on every ancestor of mine having two different parents, to come up with one me.  I used a generation gap of roughly 21 years to make my prediction which gives me an estimate of 96 generations from the year 1975 until the year 1 AD. In order to make one me, there would need to have been 19,807,040,628,566,100,000,000,000,000 people living on planet earth (hint - that's way more than a trillion so anyone who is worried about overpopulation just contemplate that for a moment).  We know that there were not that many people living on planet earth during the year 1 a.d.  In fact, it is estimated that the world population in 1 AD was roughly 300 million people. 300 million is 19,342,813,113,834,100,000,000,000 less people than would be necessary to make one me IF every ancestor had a unique set of parents.  This ignores, of course, natural population reduction that occurs with famines, floods, or plagues. What's interesting is that in 1250 AD, it is estimated there were 400 million people living on planet earth. Math tells me there should have been no fewer than 34.36 billion people as that is the number of ancestors I should have had.  In fact, the only year in which there is an estimate of more people on planet earth than I should have had ancestors wandering about is in the year 1500, where there was an estimated population of 500 million people, and I had 4.19 million ancestors walking about.

If every generation inherits 60 mutations, then in that 96 generations from me to my ancestor living in 1 AD there I should be carrying approximately 5,760 genetic mutations from the original ancestor. Given that there are only 20-25,000 genes in the human genome that means that my genes would need to vary by 20-25% from a person living in 1 ad. That's a shocking amount of variation, and just isn't supported in the science. In fact, most humans vary by only about 1 or 2% of genes from one another.

I do not have a degree in science or in math. I have had three classes in biology and six in higher mathematics. This does not make me an expert. I'm sure there are people more qualified than I to explore this topic, but if someone as simple as I can poke such a very large hole in the theory of evolution using a simple mathematical calculation, one has to wonder why it is a theory at all? Why is it being pushed as fact when the "facts" very literally don't add up?

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