[ExI] Fwd: mutations

Rafal Smigrodzki rafal.smigrodzki at gmail.com
Thu Jan 6 04:09:00 UTC 2022

On Wed, Jan 5, 2022 at 6:04 PM William Flynn Wallace via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> ---------- Forwarded message ---------
> From: William Flynn Wallace <foozler83 at gmail.com>
> Date: Wed, Jan 5, 2022 at 12:13 PM
> Subject: mutations
> To: spike <spike at rainier66.com>
> In the last 3 to 10 thousand years, adaptive mutations have independently
> occurred in Africa, Europe, and Central Asia, in the LCT gene, which
> codes for lactase.  Curiously, the mutations occur only in the people who
> are herders of animals, and not in the foraging tribes nearby.
> We are taught that mutations are random.  This seems anything but random.
> It seems that the ability to digest milk genetically develops among the
> people who need it and not otherwise.
> What is going on here?  Epigenetics?

### No. Natural selection. Mutations that enable lactose digestion occur
randomly in all populations but they are fitness-enhancing only in
populations where adults have access to plentiful milk. This mutation then
increases in frequency over time only in such populations and is easy to
find in a genetic screen. In other populations the same mutations are
fitness-decreasing, since they lead to the production of an enzyme (which
costs energy) that has nothing to do in an adult without access to milk. A
one-in-a-million new lactase mutation in a forager therefore stays at that
very low frequency or disappears, so you never find it in a genetic screen
that looks at a few hundred individuals.

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