Re: So we're all related!

All this shows how meaningless maths can be unless related to the real
world.
There are lies damned lies and statistics.

Michael
----- Original Message -----
From: "Glenn Morton" <glennmorton@entouch.net>
To: "Vernon Jenkins" <vernon.jenkins@virgin.net>; <asa@calvin.edu>
Sent: Saturday, October 02, 2004 5:46 PM
Subject: RE: So we're all related!

>
> Vernon writes:
>
> -----Original Message-----
> From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu]On
> Behalf Of Vernon Jenkins
> Sent: Saturday, October 02, 2004 9:49 PM
>
>
> To the Forum
>
> An interesting article appeared in last Thursday's Daily Telegraph which
may
> be found at
>
http://news.telegraph.co.uk/news/main.jhtml?xml=/news/2004/09/30/wdesc30.xml
> It briefly describes the outcome of a programme of research carried out at
> MIT by a team led by Dr Steve Olson - this suggesting that all people
alive
> today share a single common ancestor who lived in Asia in 1,415 BC. [Dr
> Olson was keen to stress however that this date was an estimate.]
> If indeed true, then this finding suggests that - apart from a handful of
> fortunate individuals - mankind was completely snuffed out not that long
> ago. Had Dr Olson's estimate been 880 or so years earlier then, clearly,
the
> Genesis Flood - provided it were accepted as a _global_ cataclysm - would
> have provided the necessary mechanism for such mass extinction. But if not
a
> universal flood, then what? Perhaps the estimate is wrong; perhaps the
> procedure which has led Dr Olson to conclude that all - since 1,415 BC -
are
> descended from a single ancestor, is wrong. It is all highly intriguing. I
> invite informed comment from the list.
> ********
>
> The original article is in Nature. I have put together a couple of
> articles I posted on another site about this article.
>
> This article has nothing to say about a single ancestor from that time
> period. There are 150 generations between us and those alive 3000 years
ago.
> With each generation back there are twice as many ancestors. We have 2
> parents, 4 grandparents, 8 great grandparents, etc. Since 3000/20 =150, we
> have 2^150 = 1.45 x 10^45 slots in our ancestry. What this means, is that
> the same person occupies billions of these slots in our ancestry.
>
> The article was merely a statistical study on how likely it is that one
> person occupies at least one slot in all the genealogies of the 6 billion
> people alive today. Given that there were around 100 million people alive
> 3000 years ago (this estimate can be extrapolated from L. Luca
> Cavalli-Sforza, Paoli Menozzi and Alberto Piazzi, The History and
Geography
> of Human Genes, (Princeton: Princeton University Press, 1994), p. 68)
>
> this means that each person 3000 years ago occupies an average of 1.45 x
> 10^37 slots out of our 1.45 x 10^45 slots.
>
> Now, one should know, that just because we are all descended from some
> individual 3000 years ago it doesn't mean that we all inherited genes from
> that person. There is only a 10^-37 probability that all of us have any
> genes from this guy or gal.
>
> So in short, this person is neither Adam nor Eve, nor Noah and his wife.
>
> This is the problem with the article. They explicitly say that they
>
> Quote Taken From:
> Rohde et al, "Modeling the recent common ancestry of all living humans,"
> Nature, Sept 30, 2004, p. 562
>
> >For a population of size n, assuming random mating (and so
> >ignoring population substructure), probabilistic analysis has
> >proved that the number of generations back to the MRCA, Tn,
> >has a distribution that is sharply concentrated around log2n.
>
>
>
> Now, a guy on that other list pointed out that population substructure
> actually falsifies the common ancestor applying to the Tasmanians. It
> probably also doesn't apply to the Native Americans since they too were
> isolated from the Old World from around 12,000 years ago until 1492 AD. So
> the guys in the article calculated a simplistic model (which raises the
> question of what is so earthshattering about this model as to warrent
> publication in Nature). They say:
>
> Quote Taken From:
> Rohde et al, "Modeling the recent common ancestry of all living humans,"
> Nature, Sept 30, 2004, p. 565
> >With 5% of individuals migrating out of their home town, 0.05%
> >migrating out of their home country, and 95% of port users born in
> >the country fromwhich the port emanates, the simulations produce
> >a mean MRCA date of 1,415 BC and a mean IA date of 5,353 BC.
> >places. Studies of hunter-gatherer groups and subsistence agricultural
> >communities have found that anywhere from 1% (ref. 19) to as
> >much as 30% (ref. 20) of mates are from outside the group.
>
>
>
> But that can't apply very well to Tasmania or even Keppel Island off of
> Australia's coast as well. Thus the model really doesn't match real world
> realities.
>
>
>
Received on Sun Oct 3 08:26:58 2004