Re: [asa] Two questions... (bottlenecking)

I have a question.

> If you go back far enough, you should have a single ancestral pair for
> all modern humans.

1. Would that be true of all phyla that require sexual reproduction?

Another question:

2. Why is a pair of biological human bodies related to the origin of
a pair of human minds (souls)? I mean, don't some people believe that
the human physiology was a sufficient substrate to support the mind
(and/or soul) but that the actual infusion of the soul was a separate
event in history? I mean, could not there have been a large
pre-existent population of homo sapiens into which God breathed life
(where life here means not bio but zoe)?

I'm not saying I subscribe to the idea. But I vaguely remember
reading about it. On this list there has been discussion of the idea
that the human mind itself is actually supernatural, not of natural
origin at all. The idea that when you look at a human and it's
ability to recognize design - that you are looking at something that
originates not from nature or physics but from outside the universe -
well, I'm not saying I subscribe to this idea - in fact I object to
it. But it seems some ASA members believe this and if thats true then
I fail to see why they would not also accept the idea that human
evolution prepared a repository. A repository into which was at some
point in history deposited an intelligence from outside nature. And
this intelligence does not originate from the genes. It's sort of
like like pre-Adamic humans are analogous to a computer with no
operating system. If you download an O/S into them then you have a
computer system (or a pc). Until then you just have what it takes to
support a computer system. Humans as a pre-Adamic species could have
been like that. The idea seems consistent with thinking of humans as
 being supernatural beings.

> I think Adam and Eve as representatives out of an existing human
> population is the easiest way to reconcile Genesis and genetics, but
> it is not absolutely impossible to have a single pair ancestral to all
> humans if you go far enough back in time.

Ah, perhaps that answers my question. If one believes that humans
minds are a supernatural phenomena then one can certainly believe that
Adam and Eve are the pair that "got the download" and the rest of the
existing population did not.

But I am not sure this is what you meant. It's also possible you meant
that Adam and Eve both had mutations that set them apart as the first
truly modern humans. But along with this goes the idea that they were
special and their mental capabilities were distinct from the
pre-existing population. This theory would be congruent with a view
that human minds are of natural origin, and not supernatural at all.

On Wed, Feb 11, 2009 at 12:47 PM, David Campbell <pleuronaia@gmail.com> wrote:
> If you go back far enough, you should have a single ancestral pair for
> all modern humans. However, "far enough" might involve millions of
> years, considerably more fur and less brain, living in trees, having
> tails, etc. On the other hand, it's conceivable that a scenario like
> Glenn Morton's, with Adam and Eve ancestral to all modern humans about
> 5 million years ago, would work genetically.
>
> On p. 126 of The Language of God, Collins cites population genetics as
> evidence that modern humans descend from a group of about 10,000
> people about 100 to 150kyr ago. RTB favors a separate creation of
> modern humans from Neanderthals, etc., and would want a population
> size of about 2 at the same time period. What I'm saying is that you
> probably had more than a single pair at that point, but might
> conceivably be able to get to a single pair at some earlier time, if
> you are comfortable with pushing Adam and Eve back that far.
>
> Collins knows a lot more than me about human genetics; I have more
> academic training in evolution than he does. As a paleontologist who
> does DNA work because it a) answers questions I'm interested in and b)
> seems to provide slightly more prospect of eventually getting a
> regular income, I tend to be rather more skeptical of some of the
> claims based solely on DNA evidence than the average person with a
> strictly molecular biology background. Take those into consideration
> in evaluating the comments.
>
> Assumptions that go into the estimate of 10k people at 100k years:
>
> Proportion of males and of females who contribute to the next
> generation. If only a few individuals (at least of one sex) are the
> parents of most of the kids, then the effective population size will
> be a lot smaller.
>
> Average genetic diversity of the starting population.
>
> Any unusual events, such as a population crash and rapid rebound.
>
> Mutation rate. Calibration of this (i.e., assigning dates to a
> particular level of divergence) is often very poor. After all, what
> you need is a very precise date for when two individuals last shared a
> common ancestor.
>
> Selection pressure on the changes under consideration. For example,
> the point of the MHC locus genes is to keep changing to stay one jump
> ahead of the pathogens. This favors lots of rapid change. The 18S
> gene is an essential part of making proteins. Many parts of it show
> very little change. Other parts of the genome are apparently fairly
> free to change without having much effect, but there may be structural
> reasons why some of those regions change more than others.
>
> Change the details of the assumptions, and you can get different
> results. In fact, it often seems as though you can get just about any
> possible result if you try enough population genetics models.
>
>
> One last complication, related to the mitochondrial Eve thing, etc.,
> is that you don't have to go back too far in time (rather less than
> 100 kyear) to have one pair who is _an_ ancestor of all modern humans.
>
> I think Adam and Eve as representatives out of an existing human
> population is the easiest way to reconcile Genesis and genetics, but
> it is not absolutely impossible to have a single pair ancestral to all
> humans if you go far enough back in time.
>
> --
> Dr. David Campbell
> 425 Scientific Collections
> University of Alabama
> "I think of my happy condition, surrounded by acres of clams"
>
> To unsubscribe, send a message to majordomo@calvin.edu with
> "unsubscribe asa" (no quotes) as the body of the message.
>

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Tue Feb 10 23:23:20 2009