GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2006-11 > 1162588468


From: (John Chandler)
Subject: Re: [DNA] Molecular clocks: when times are a-changin'
Date: Fri, 3 Nov 2006 16:14:28 -0500 (EST)
References: <042401c6fe97$5ce8b830$6401a8c0@Precision360><011001c6fed3$2c9fe9f0$0300a8c0@belinda>
In-Reply-To: <011001c6fed3$2c9fe9f0$0300a8c0@belinda>(belindadettmann@optusnet.com.au)


There was some discussion here of the article when it first appeared.
Note that the article proposes a general "law" but admits that the
underlying mechanism or mechanisms are unknown. In fact, we *know*
the underlying mechanisms for the discrepancy between rate
calculations based on direct observation and those based on
millennium-scale population studies -- random extinction and
population expansion. There is no way to invoke natural selection on
junk DNA in the first place and certainly no way to invoke selection
based on correlations between the vastly different time-scale
behaviors of STR's and coding mutations on the tiny handful of genes
on the Y chromosome. Indeed, we know that random extinction depends
critically on the (unknown) details of population history, and
therefore is not subject to a general law that can make specific
predictions. To the extent that we can guess at the population
history, we can make corresponding guesses at the so-called
"effective mutation rate" for a given population, but we must
remember that there are large uncertainties in such guesses.

John Chandler

This thread: