African Eve
Dr. Guy Hoelzer
(Patrick H. Adkins) wrote:
>
>
> From: pr...@helix.nih.gov (dmitry pruss)
> Subject: Re: African Eve
>
> DP> The problem with mit DNA analysis in H.sapiens was that it produced
> too counterituitive results - and wasn't paralleled by anything
> similar on other modern (recently evolved) species.
>
> [interesting material (thanks!) deleted]
>
> One of the things I don't understand about this approach is _whose_ mit DNA
> are we tracing back to? For instance, if we have an "Eve" (individual with a
> mutation that makes her the first of what will become H. sapiens), why should
> we presume that the mit DNA originated with her--instead of with her non-
> mutated mother, grandmother, or some still more distant ancestor, perhaps
> even an earlier species. Why should be presume that mit DNA leads back to
> the beginning of H. sapiens, instead of H. erecti, H habilis, etc?
>
> Sorry if this is an uninformed question.
> ---
> SLMR 2.1a Just say no to Big Government.
>
We don't trace back to Eve's mother because we are interesting in the "most
recent" common ancestor. Any other point would be arbitrary. We could
trace mtDNA ancestors back to the original event of endosymbiosis from
which mitochondria originated. To answer your second question, the most
recent mtDNA common ancestor was not necessarily H. sapiens. She could
theoretically have belonged to any of the taxa you mentioned.
******************************************************************************
Guy Hoelzer
hoe...@unr.edu
Dept. of Biology
University of Nevada Reno
Reno, NV 89557
******************************************************************************
dmitry pruss
>
>From: pr...@helix.nih.gov (dmitry pruss)
>Subject: Re: African Eve
>
>DP> The problem with mit DNA analysis in H.sapiens was that it produced
> too counterituitive results - and wasn't paralleled by anything
> similar on other modern (recently evolved) species.
>
>[interesting material (thanks!) deleted]
>
>One of the things I don't understand about this approach is _whose_ mit DNA
>are we tracing back to? For instance, if we have an "Eve" (individual with a
>mutation that makes her the first of what will become H. sapiens), why should
>we presume that the mit DNA originated with her--instead of with her non-
>mutated mother, grandmother, or some still more distant ancestor, perhaps
>even an earlier species.
It definitely originated from the earlier ancestors and before that, from
the earlier species.
The answer is, with earlier species/ population had widely diversified mit
DNAs themselves. Only the tiniest portion of this past genetic diversity
ended up inherited by our human ancestors - and the diversity was then
gradually restored in the course of hundereds of generations, just by
slow naturally occuring accumulation of mutations.
The task (one of) of the mit DNA mapping was tp get a quantitative measure
of our mitochondrial DNA iversity - and to estimate how much time would it
take to create this level of divercity from a genetically
homogenous ancestral population.
Could the answer (200 Kyr) be different from the actual age of H.sapiens?
Yes, in two ways :
-if we underestimate our genetic diversity because many genotypes are
unaccounted for, or just lost to extinction. In fact recent extinction can
hardly change the estimate: to affect the figure, we should loose the most
divergent branches of human evolution, i.e. either eliminate whole ancient
races (which unlikely took place) or eliminate the precusors of races-to-be
(i.e. to have massive human extinctions early on).
The latter possibility is described in other words as 'bottlenecking'. If
there was (were) bottlenecks in human evolution, then the species is older
than its mitochondrial age predicts - but all the present-day races evolved
from a common roots recently in human history. More precisely, their common
root was about 200Kyr ago...
-if the first human populations already had a good deal of diversity. Then,
the species is younger than predicted - with an important limitation: its
pre-sapiens ancestors were already closely related to on another - i.e. the
modern humans evolved from an evolutionarily isolated subspecies of their
ancestral species (with the 200Kyr bottleneck attributed to a predecessor
species rather than to H.sapiens).
Neither complication is compatible with a multicentric hypothesis...
BTW, there was a separate study not long ago - reported in Science - about
mapping somatic DNA divesity in humans. (This is inherited from both
parents). There's no clock rate estimate for such things, so the datings
are relative. Yet the results that emerge are very interesting.
Skipping the details (read Science!), the study detects two past
bottlenecks in our intraspecies evolution: the earlier one, which excluded
Ethiopians from the rest of Africans, and more recent one, on the way from
Ethiopians to *all other* humans outside Africa.
D
Dave Oldridge
dmitry pruss <pr...@helix.nih.gov> wrote:
>divergent branches of human evolution, i.e. either eliminate whole ancient
>races (which unlikely took place) or eliminate the precusors of races-to-be
>(i.e. to have massive human extinctions early on).
Uh, seen any Neanderthal people lately? They were a "race" of humans and
clearly existed in the time period of interest and may well represent a
major extinct branch.
>from a common roots recently in human history. More precisely, their common
>root was about 200Kyr ago...
Which is well before the extinction of Neandertalis. Of course we'd
probably need a few proteins or some DNA from a Neanderthal to really
assess the nature of this possibility...
But mitochondrial DNA is somewhat subject to extinctions, even in diverse
and growing populations lines tend to disappear. As long as those
disappearances are at a reasonably constant rate, there is no problem, but
when selection of *any* kind skews the rates, it makes the estimates less
accurate, does it not?
>Neither complication is compatible with a multicentric hypothesis...
Agreed.
>Skipping the details (read Science!), the study detects two past
>bottlenecks in our intraspecies evolution: the earlier one, which excluded
>Ethiopians from the rest of Africans, and more recent one, on the way from
>Ethiopians to *all other* humans outside Africa.
Very interesting...
--
Dave Oldridge
dold...@fox.nstn.ns.ca
Patrick H. Adkins
DP> The problem with mit DNA analysis in H.sapiens was that it produced
too counterituitive results - and wasn't paralleled by anything
similar on other modern (recently evolved) species.
[interesting material (thanks!) deleted]
One of the things I don't understand about this approach is _whose_ mit DNA
are we tracing back to? For instance, if we have an "Eve" (individual with a
mutation that makes her the first of what will become H. sapiens), why should
we presume that the mit DNA originated with her--instead of with her non-
mutated mother, grandmother, or some still more distant ancestor, perhaps
even an earlier species. Why should be presume that mit DNA leads back to
the beginning of H. sapiens, instead of H. erecti, H habilis, etc?
Sorry if this is an uninformed question.
---
ş SLMR 2.1a ş Just say no to Big Government.
Jim Bowery
>
> Uh, seen any Neanderthal people lately? They were a "race" of humans and
> clearly existed in the time period of interest and may well represent a
> major extinct branch.
Quite seriously, some of my best friends are Neanderthals -- or at least
are of Neanderthal lineage.
Just look around -- you'll see them every now and then.
--
The promotion of politics exterminates apolitical genes in the population.
The promotion of frontiers gives apolitical genes a route to survival.
Richard Hodges
pr...@helix.nih.gov writes:
>BTW, there was a separate study not long ago - reported in Science - about
>mapping somatic DNA divesity in humans. (This is inherited from both
>parents). There's no clock rate estimate for such things, so the datings
>are relative. Yet the results that emerge are very interesting.
>
>bottlenecks in our intraspecies evolution: the earlier one, which excluded
>Ethiopians from the rest of Africans, and more recent one, on the way from
>Ethiopians to *all other* humans outside Africa.
It would appear to me that it would be possible for somatic DNA to give
rise to very different results than maternal, i.e. mitochondrial,DNA. Suppose
males has very
different migration and mating patterns than females. Let's say that
females always stay close to the area they are born. Lets say males have a
persistent pattern of migration from the center of population A to the
center of population B, where they like to mate with the local females. If
eventually population A gets destroyed, then the situation will be this:
the maternal DNA will reflect the history of the females in population B.
The Somatic DNA will reflect mainly the history of population A which might
be quite different; in particular, the last common ancestor could
conceivable be of significantly different age.
An extension of this argument shows that because of possible large scale
sexual exchanges, somatic DNA can potentially be the result of a complex
mixture of populations, which is not the case with maternal DNA. Which one
however do we regard as the real picture? In terms of the percentage of the
genome, somatic DNA is dominant by far. It could easily make the
difference between whether we perceive a monophyletic or a polyphyletic
origin based on DNA analysis of current populations. In any case, it should
give us pause to question the meaningfulness of any such analysis of somatic
DNA.
Richard Hodges
writes:
>Quite seriously, some of my best friends are Neanderthals -- or at least
>are of Neanderthal lineage.
>
>Just look around -- you'll see them every now and then.
How do you recognize them? What are the signs?
Tracy Monaghan
They can often be found on most American universities' football teams. :)
Jim Bowery
The robust frame, heavy but a generally low fat to muscle ratio, for males
an exceptionally hairy body. Sometimes you'll see the prominent brows.
I think it would be very interesting to study people classicaly
termed "european peasantry" to see if there are some genetic
correlates for neanderthal-like features. There may be some remnants
of relatively pure neanderthal lineages around and if so, it would be
good to let those people know how valuable they are.
Jim Bowery
Only the linebackers and coaches. :)
R.Downing
Good one tracy!!!
dMMMMb dMP dMP dMP
dMP.dMP amr dMP.dMP
dMMMMK dMP dMMMMK"
dMP"AMF dMP dMP"AMF
dMP dMP dMP dMP dMP
*my opinions are my own, if you share them then you must be as
mad as I!*