Re: ASPM allele origin dated to Adam's time

Dick Fischer wrote:
> Peter Wrote:
>
> Lahn's new study suggests the allele of the ASPM gene prevalent today "arose
> 5800 years ago (with a possible range of 500 to 14,100 years), just before
> cities arose in the Near East." This sounds suspiciously close to the
> time for
> Adam, as deduced from the cultural indications of the early Genesis
> chapters.
>
>
> Is this found in the general population or only in a certain group?

Acording to Balter, the 90 cell lines from which Lahn's group sequenced the
microcephalin and ASPM genes were from the "Coriell Institute for Medical
Research in Cambden, NJ, whose cell collection is broadly representative of
global human diversity." I don't think Lahn's group (or Nature's peer reviewers)
would have settled for less.

> At 5800 years ago it should not be found in all humans as these are modern
> humans who covered the globe by that late date. The Americas have been
> populated for at least 12,000 years, so it would be unlikely that the
> ASPM gene would be found on both sides of the Atlantic in Africa, China,
> etc. If it is then the date is suspect.

> ~Dick Fischer~ Genesis Proclaimed Association
> Finding Harmony in Bible, Science, and History
> www.genesisproclaimed.org

Yes, the early distribution of humans is a fact, and we would assume that there
was hardly any more recent gene transfer between early Americans or Australians
and the "old world". Yet, there are some problems.

We have to distinguish between a most recent common ancestor, in a genealogical
sense, and the coalescence time of DNA sequences [cf. A.M. Shedlock et al.,
"SINEs of speciation: tracking lineages with retroposons", Trends Ecol.Evol. 19
(2004), 545-53]. Furthermore, genes passing only through one sex (e.g.
"mitochondrial Eve" or "Y-chromosome Adam") have much longer coalescence times
than the others, which are subject to genetic recombination between different
lines of descent.

Another recent paper may perhaps shed light on this problem: D.L.T. Rohde et
al., "Modelling the recent common ancestry of all living humans", Nature 431
(2004), 562-566. The abstract says:

"If a common ancestor of all living humans is defined as an individual who is a
genealogical ancestor of all present-day people, the most recent common ancestor
(MRCA) for a randomly mating population would have lived in the very recent past
(1-3). However, the random mating model ignores essential aspects of population
substructure, such as the tendency of individuals to choose mates from the same
social group, and the relative isolation of geographically separated groups.
Here we show that recent common ancestors also emerge from two models
incorporating substantial population substructure. One model, designed for
simplicity and theoretical insight, yields explicit mathematical results through
a probabilistic analysis. A more elaborate second model, designed to capture
historical population dynamics in a more realistic way, is analysed
computationally through Monte Carlo simulations. These analyses suggest that the
genealogies of all living humans overlap in remarkable ways in the recent past.
In particular, the MRCA of all present-day humans lived just a few thousand
years ago in these models. Moreover, among all individuals living more than just
a few thousand years earlier than the MRCA, each present-day human has exactly
the same set of genealogical ancestors."

Some snippets of their further text:
"As genealogical ancestry is traced back beyond the MRCA, a growing percentage
of people in earlier generations are revealed to be common ancestors of the
present-day population. Tracing further back in time, there was a threshold, say
Un generations ago, before which ancestry of present-day population was an all
or nothing affair. That is, each individual living at least Un generations ago
was either a common ancestor of all of today's humans or an ancestor of no human
living today. Thus, among all individuals living at least Un generations ago,
each present-day human has exactly the same set of ancestors. We refer to this
point in time as the identical ancestors (IA) point." ...

"With 5% of individuals migrating out of their home towns, 0.05% migrating out
of their home country, and 95% of port users born in the country from which the
port emanates, the simulations produce a mean MRCA date of 1,415 BC and a mean
IA date of 5,353 BC." (Ports are archeologically documented overseas connection
points. More migration produces more recent dates.) ...

"If a group of humans were completely isolated, then no mixing could occur
between that group and others, and the MRCA would have to have lived before the
start of the isolation. A more recent MRCA would not arise until the groups were
once again well integrated. In the case of Tasmania, which may have been
completely isolated from mainland Australia between the flooding of the Bass
Strait, 9,000-12,000 years ago, and the European colonization of the island,
starting in 1803 (13), the IA date for all living humans must fall before the
start of isolation. However, the MRCA date would be unaffected, because today
there are no remaining native Tasmanians without some European or mainland
Australian ancestry.
No large group is known to have maintained complete reproductive isolation for
extended periods. The populations on either side of the Bering Strait appear to
have exchanged mates throughout the period documented in the archaeological
record (14)... For example, with a migration rate across the Bering Strait of
just one person in each direction every ten generations, rather than the ten per
generation in the more conservative simulations described earlier, Tn [the time
back to the MRCA for a population of size n] only increases from 3,415 years to
3,668 years.
Conversely, other factors could reduce the time to the MRCA from that predicted
by the model. Examples of such factors include the existence of more diverse
intercontinental migration routes, the large-scale movement and mixing of
populations documented in the historical record (17), marked individual
differences in fertility (18), and the population increase of the past two
millennia, which would result in more migrants."

Dating Adam is constrained quite strictly to a few thousand years BC. But what
are the conclusions we have to draw as to the placing in time of the creation of
humans in God's image? All living humans must be counted as such.

Peter

-- 
Dr. Peter Ruest, CH-3148 Lanzenhaeusern, Switzerland
<pruest@dplanet.ch> - Biochemistry - Creation and evolution
"..the work which God created to evolve it" (Genesis 2:3)