molecular clock hypothesis

Tandy Warnow tandy at
Sat Sep 27 00:41:56 EST 1997

In a paper I was reading today, I saw a sentence that amounted
to asserting that DNA evolves at more or less a constant rate
across different lineages. I think this amounts to asserting
that a relaxed form of the molecular clock hypothesis holds.

I'd like to know what is known about this.  To what extent,
and on what datasets, is some kind of relaxed form of the
molecular clock hypothesis going to hold?

More specifically, if we set a constant C to be the maximum
over all nodes in a tree of the ratio of the fastest to
slowest rates of evolution on the paths between that node to
the leaves in the subtree below that node, then how large
is C generally? If C=1, then the molecular clock  holds.
How large a value of C is typical, and what's the largest
that has been seen? Are there any conjectures?

Any pointers to the literature about this subject would
be greatly appreciated, too.

Tandy Warnow
Department of Computer and Information Science
University of Pennsylvania

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