Hi, Glenn
This is my response to your last post of 19 Feb
[<glenn.morton@btinternet.com> Sun, Mon, 19 Feb 2001 22:13:18 -0000, ASA
list V1#2004], in which you answered my post of the same day
[<pruest@pop.dplanet.ch> Mon, 19 Feb 2001 21:32:00 +0100, ASA list
V1#2004]. Due to a bout of flu I'm somewhat late.
It seems that you misunderstood what I intended to say. Apparently, I
didn't express myself clearly enough in my rather concise comments. Let
me try once more.
Underlying my comments of 19 Feb is the following model of human origins
(and it is just a tentative model, subject to revision, cf. my earlier
contributions to the ASA list and PSCF): The human species descended
from a prehuman (hominid) species by evolution. In this evolutionary
descent are included the bodily, as well as the psychological or soulish
aspects (cf. the expression "living souls" used in Genesis 1:20 for
animals). At a certain time point "S" (for "spiritual dimension",
corresponding to the "image of God", Gen.1:27), the Creator endowed a
group of hominids with the spiritual dimension (or image of God), which
previously did not exist in any earthly creatures, creating them into
humans. The group comprised an unspecified number of males and females
(Gen.1:27, Hebrew original), possibly a few thousand, who within the
same sixth "day" filled the earth (Gen.1:28 and 31). Of course, this
definition of what it means to be human is a theological one, not an
anthropological one; it may not be easily recognizable in the scientific
evidence.
At a later time point "A" (for "Adam", Gen.2:7), the Lord God entered
into a particular personal relationship with one individual, Adam,
calling him for a specific purpose. He was one of a preexisting
population of pre-Adamite humans, just as Abraham was one of a
preexisting Chaldean population. This implies that Adam and Eve were not
the first humans, and that the doctrine of a biological inheritance of
"original sin" is incorrect. Sin is not a biological condition, but a
spiritual one. It is a fact of life that every human being voluntarily
commits his/her own "original sin" or fall, thus becoming lost and in
need of Christ's redemption. Paul very clearly specifies that "death
spread to all men, because all men sinned" (Rom.5:12), not because all
men descended biologically from Adam. By his failing in his response to
God's challenge, Adam became the representative of all of fallen mankind
- before, during, and after his time -, just as Jesus Christ is the
representative of redeemed mankind (Rom.5) - before and after his time
on earth and crucifixion.
Science has defined a time "H" (for "Homo") for the origin of our genus,
approximately 2 million years ago. It is more difficult to date time
points "S" and "A". On the basis of an apparently significant
"acceleration of cultural evolution" possibly interpretable in a
spiritual context around 100,000 years ago, I very tentatively date "S"
to about 100,000 years ago. On the basis of the few cultural indicators
in the first few chapters of Genesis, I tentatively date "A" to about
10,000 years ago, just after the last glaciation. But of course I am
ready to accept better arguments for other dates. Does either of the
time points "H", "S", or "A" necessarily imply a population bottleneck?
Maybe. We don't know. As I indicated in my last post, a thorough review
of the newest relevant genetic data seem to indicate that there was (at
least) one real bottleneck in the late Pleistocene, much later than 1
million years ago.
What do gene trees tell us about the origin of the human species? If
this origin is given by a population bottleneck, this bottleneck might
be datable approximately. If the bottleneck comprised one couple only,
there can be, for genes occurring singly in the genome, at most two
different allelic gene lineages beyond this time. I believe the
bottleneck was larger (see above). But even with a bottleneck population
of 10,000 breeding individuals, followed by a population expansion, most
allelic gene lineages would coalesce to about the time of the
bottleneck, but some will not! We must clearly distinguish between gene
lineages and (non-interbreeding) population lineages. A very ancient
coalescence time of allelic genes occurring in modern humans does not
imply the splitting of the population at that ancient time, followed by
recombining into an interbreeding population later on. Two anciently
coalescing alleles may just happen to have survived each only in one of
two different branches of a population originating in a much later
population split. It does not prove the multiregionality model of human
origins. Nor does it necessarily imply that the population at the time
of coalescence was the same species (biologically defined by
interbreeding potential) as the modern one.
And now just a few more comments to your specific objections (given as
<<...>>):
<< Of course coalescence times are very imprecise. Wo said they
weren't???
Certainly not I. In fact, the Alonso and Armour coalescence times are
very,
very broad...
Table 5. The age (T, 10^3 years) of the MRCA of human sequences
Sequences Ne Tmode Tmean 95% Interval
All samples 10,000 1,288 1,356 712~2,112 ...
But it certainly isn't 6000, 10,000 or even 120,000 years. >>
You are right, I could have left out my first point about the
impreciseness of coalescence times. On my second point, a coalescence
date is basically insecure, because it depends on the assumption of a
molecular clock, which in many cases has been shown to be incorrect.
Furthermore, Alonso and Armour are talking of the age of the most recent
common ancestor of gene sequences, not of separate human populations.
These ages don't tell us much (if anything) about the age of the human
species.
<< This is false logic. You are equivocating origination with expansion.
Everyone agrees that the population expanded in the Upper Pleistocene.
That
doesn't mean that the population ORIGINATED in the Upper Pleistocene. >>
Of course, origination is not the same as expansion. I never said the
human species originated, as an evolving population, in the late
Pleistocene. What I was thinking of was the possible transitions, during
this evolution, through the time points "H", "S", and "A" defined above,
and how these points might possibly show up in the population dynamics.
As "S" represents the origin of the human species, theologically
defined, I expect it (according to Gen.1:28) to have coincided with a
population expansion. "A" presumably was the origin of a particular
divine economy with mankind, but it is more difficult to say what this
might imply for human population dynamics.
<< If they have separate genetic lineages older than 120,000 years, then
my
point is made. If you aren't implying that mankind is very recent, then
exactly what are you implying? >>
Old separate gene lineages can happily coexist in an undivided
population evolving through a speciation process happening later.
<< Why does expansion mean a dividing line? >>
I agree that in saying time point "A" might correspond to the start of a
population expansion, I am on insecure grounds. Such a reference to time
point "A" was derived from the scientific indicators for an expansion
after the last glaciation. A similar reference to the earlier time point
"S" would be more appropriately derived from the biblical reference in
Gen.1:28.
<< And God creating their spiritual dimension made them engage in more
procreation than the animal ancestors, thus causing the expansion? >>
There are other factors to expansion than just procreation! Following
the divine command, intelligence, language, social structures, refined
tools, agriculture, opportunity, climate, etc.
<< You are claiming that mankind couldn't interbreed with H. erectus
even if he had a time machine. >>
No, I wrote: "It doesn't follow, however, that it was the same species
throughout the 2 million years: H. sapiens might well have been unable
to mate with H.erectus, even if he could have used a time machine." We
just have no way of telling whether the two (morphological) species
would be the same (biological) species. And with much less assurance can
we tell whether H.erectus was theologically human. From scientific
evidence, we cannot conclude that time point "S" occurred more than 1
million years ago.
<< Yet we know from observation that wolves and coyotes successfully
interbreed
all the time... So exactly why is the biology of man so different from
that of the coyotes and wolves? Is it as I suspect, because your
theology requires it to be different? Dogs and Jackals successfully
interbreed and they split apart 3.5 million years ago. If this can
happen with them, then why can't humans of today
interbreed with H. erectus of 2 million years ago?... But of course you
wouldn't want this type of ability in mankind and H.erectus would we?
Thus you exclude it on theological grounds. But if we apply what we see
in other species, we would have to conclude that we and the
Australopithecines would have been able to interbreed. >>
The point of the argument is the question of dating time point "S". I
did not claim the two Homo species could not be interfertile, but just
that we cannot know, and therefore cannot claim for certain that they
would have been. The whole argument from canine species is beside the
point, even if it were possible to conclude from the interfertility of
two given species to the interfertility of two other species elsewhere
in the tree of life.
<< This contradicts what you said above. If multiregionality is wrong,
then it isn't possible to have multiple genetic lineages older than the
origin of our species. Yet you acknowledge that the genetic lineages are
probably older than the origin of humanity. You can't have it both
ways. >>
There is no contradiction if you distinguish between gene lineages and
population lineages. They are not collinear. Gene coalescence can
predate a population split (or speciation) by far.
<< Secondly, it seems apparent to me that most of the support for the
recent origin of humanity is depended upon non-recombining types of DNA.
Mitochondria don't recombine, the Y chromosome doesn't. I don't know
about the autosomal regions they studied, whether they recombine or not,
but it does seem like an awful lot depends upon this to the exclusion
of any and all nuclear (recombining) data.
And as I said, all it takes is for one gene to have multiple lineages
prior
to 120,000 years ago for the recent origin of humanity to be false. We
have
passed that hurdle now. >>
No. Takahata et al. used all reasonably usable data available to reach
their conclusion. So, the present state of affairs is quite strongly
against multiregionality and for a recent expansion of humanity. Of
course, you may always expect future results to reverse the situation.
Glenn, I am challenged by your intensive criticism, but I invite you to
continue with it. It might improve my model...
I would also appreciate the comments of others on this list!
Peter Ruest <pruest@dplanet.ch>
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