GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2007-07 > 1184497692


From: "Joe Knapp" <>
Subject: Re: [DNA] Help please with marker 458
Date: Sun, 15 Jul 2007 07:08:12 -0400
References: <008701c7b415$794b0120$2401a8c0@your447023ae6b><REME20070707152459@alum.mit.edu><a81622ac0707071304x11373a0en3b0b4e52a7b2e3c@mail.gmail.com><REME20070707183721@alum.mit.edu><a81622ac0707071637o34a3421dr36660529da9f75a4@mail.gmail.com><REME20070709202718@alum.mit.edu><a81622ac0707092003u290a5dd4s96c4a87a62fe3230@mail.gmail.com><REME20070711175004@alum.mit.edu><a81622ac0707120434g62d3796bk63d9ce33299bb67c@mail.gmail.com><REME20070713160416@alum.mit.edu>
In-Reply-To: <REME20070713160416@alum.mit.edu>


On 7/13/07, John Chandler <> wrote:
> I'm not sure why there would be an initial spike in birth rate.
> Didn't you say that the population starts out at 10,000 (the same
> as the quota)?

No--it just happens that it always starts with 500 men and 500 women
and then ramps up to whatever the carrying capacity is set to.

> A growth rate of 2.8% per generation would expand from 1 pair to
> 20,000 people in about 10,000 years. Because the population is
> small at the beginning, the total number of simulated persons
> is much smaller in this type of scenario.

In this model a generation averages something like 25 years, with life
expectancy at birth around 43, more of a hunter-gatherer model. So
that's about 400 generations in 10,000 years. Starting with a
population of 1,000 and a growth rate of 1.01/gen results in an ending
population of about 45,000 and the run terminates a little early at
year 9,572 when the max number of people born (2,500,000) is reached.
Here's a file of the ending male haplotypes:

http://coolohio.com/dna/onetribe_expgrowth.tab

There are 22,392 males at the end of the run.

> As long as the growth
> rate is much larger than the mutation rate, the simulation would
> steer clear of the draconian weeding-out that characterizes a
> static population.

Is 1.01/gen as above large enough? In this model, BTW, it's less
weeding-out than strict birth control to keep the population steady.

> > 10-tribe case:
> >
> > male#/descendants
> > 36 486
> > 45 526
> > 78 867
> > 125 142
> > 324 949
> > 338 492
> > 369 489
> > 408 6
> > 450 498
> > 479 523
>
> There's something I don't understand here. If each tribe has an equal
> quota of 1,000, and there is no mixing between tribes, why don't you
> have very close to 1,000 living descendants for each of the ten men who
> end up saturating their respective tribes?

Good point--just a quirk of how the program handles creation of new
tribes. It starts with one tribe of 1,000 at year 0 and at 100 years
this tribe fissions into two tribes of 500. Each of those two tribes
then ramp up to 1,000 in pretty short order. At 200 years one of these
tribes fissions and so on every 100 years until there were ten tribes
total. After the 900 year point there were 10 tribes and they were
separate from that point until the end of the simulation. If that's a
problem, it could be changed.

> Don't you find it remarkable that the number of surviving male lineages
> is exactly the same in this case?

Just a coincidence. There are other values in other runs.

Joe

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