Archiver > GENEALOGY-DNA > 2010-03 > 1268627488

From: Steven Bird <>
Subject: Re: [DNA] Clades, Definitions, Discoveries, FTDNA
Date: Mon, 15 Mar 2010 00:31:28 -0400
References: <>,<SNT115-W100A5F4E30C0231B9E890ACC2E0@phx.gbl>,<016301cac3e3$fe0b33e0$5e82af48@Ken1>
In-Reply-To: <016301cac3e3$fe0b33e0$5e82af48@Ken1>

Let's do the numbers:

There were 134 million births last year, according to the U.N. estimates. Half of these were boys, so about 67 million boys. The odds of a SNP occurring, according to Hartwell 2008, are 1 in a billion. That means that there is just a 6.7% chance of a Y-SNP occurring within ONE birth among those 67 million boys last year. Following your logic, on average, ONE new SNP occurs among all births every 15 years or so. However, since the new SNP is always de novo and can occur anywhere, and there are 3 billion base pairs in the human genome, the odds of any one SNP being duplicated are 3.0 * 10 to the -17 power.

This is ignoring the fact that some SNPs (not so much on the Y chromosome) result in a deleterious mutation that is fatal to the offspring and so it is not passed on.

> But let's just use your 1 in a billion claimed rate. There are 3 billion
> males today. In one generation of them producing male sons there would be
> about one occurrence of each and every snp in the y. Every snp has happened
> many times in the y tree. But most occurrences have been in the most recent
> generations, so are therefore so private-like they will be among the hardest
> to be discovered. ]]
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