Re: Brain size, IQ

Gerold Firl (
10 Sep 1996 19:48:59 GMT

In article <>, (Richard Foy) writes:

|> In article <50nadd$>,
|> Gerold Firl <> wrote:

|> >I have tried to estimate human genetic diffusion time, using very
|> >crude assumptions and modelling, and I get very short periods of time;
|> >something on the order of 10,000 years for genes to diffuse from one
|> >end of the old world ecumene to the other (say, zimbabwe to java).

|> Could you please post the assumptions and model you used? Did you do
|> any work to establish the senstivity of your resuls to variations if
|> the different assumptions?

Heh - when I say very crude, I mean so crude that no perturbation
analysis is necessary. I assumed that human generation times were
around 20 years, and that the average birthplace separation between
mates was 20 miles. With a hunter-gatherer small-band population
densities and exogamy, this seems reasonable.

That then implies that genes will diffuse throughout connected
breeding populations at a rate of about one mile per year. During
interglacials the sahara becomes a desert, and may well have acted as
a true genetic barrier (or at least as a serious restiction) for h.
erectus, but there does not appear to be ant indication that the
widely scattered erectus sub-populations scattered throughout the old
world diverged sufficiently to form new species.

I'm not sure how many cycles of glaciation took place during the out-
of-africa tenure of h. erectus; I would guess something between 5 and
10. During those successive cycles of isolation and re-connection new
mutations and adaptations were developing in the various erectus sub-
populations, but the species did not branch. Even if no large-scale
migrations took place, genetic diffusion would suffice to spread novel
genes and gene combinations among the old world hominids.

Disclaimer claims dat de claims claimed in dis are de claims of meself,
me, and me alone, so sue us god. I won't tell Bill & Dave if you won't.
=-=-=-=-=-=-=-=-=-=-=-=-=-=---- Gerold Firl @ ..hplabs!hp-sdd!geroldf