Re: [asa] Two questions... (biological bottlenecking with Adam and Eve)

Bernie -- as I understand it, not being an expert, from the perspective of
evolutionary biology, it is indeed nonsensical to speak of a "first human."
This point is made in a really fascinating book ironically titled "The Last
Human" (
http://www.amazon.com/Last-Human-Twenty-Two-Species-Extinct/dp/0300100477/ref=pd_bbs_2?ie=UTF8&s=books&qid=1234561177&sr=8-2)
This is one reason why, as I see it, trying to find "Adam" in our genes
isn't likely to be fruitful. It must be more of a spiritual thing, I think.

David W. Opderbeck
Associate Professor of Law
Seton Hall University Law School
Gibbons Institute of Law, Science & Technology

On Fri, Feb 13, 2009 at 3:46 PM, Dehler, Bernie <bernie.dehler@intel.com>wrote:

> Hi Dr. Campbell-
>
> I having a hard time understanding why this argument seems to be going in
> circles.
>
> Again I ask, because I don't see a clear answer (the problem may be on the
> sender or receiver side), how can anyone trace something back to "the first
> human?" For example, if someone says everyone today can be traced back to a
> mitochondrial eve, tell me how mitochondrial eve's mom is different, in that
> someone could say mitochondrial eve is the first human female but her mom
> isn't? I really don't get it, but I want to. (And I'm talking only
> biologically- not spiritually- this is a purely scientific question related
> to the human genome.) To me it seems like someone is proposing that an
> apelike creature gave birth to a human, and I don't understand that- given
> the ring species phenomenon.
>
> Here's a modern example of ring species, since you said you weren't aware
> of modern living examples (with the seagull):
> http://en.wikipedia.org/wiki/Ring_species
>
> Dr. Zack Moore talked about this on his evolution 101 podcast:
> http://www.drzach.net/podcast.htm
> (Free download at Apple iTunes; Apple iTunes is also free and you can
> listen on your PC)
>
> Again, I'm talking only biologically- not spiritually- this is a purely
> scientific question related to the human genome. It seems like the
> confusion comes in when talking about the spiritual element of humans, which
> has nothing to do (at all) with my question (which is purely biological).
>
> You say below:
> "They key problem is what all are humans?"
>
> Exactly my point. When someone claims there is a mitochondrial eve, they
> are saying that it is the first human- how is that defined such that
> mitochondrial eve's mom is not human? Obviously, mitochondrial eve is
> related to her mom!
>
> I have a hard time accepting your hypothetical analogy with Noah, because
> we both know it isn't true- there was no worldwide flood in our opinion. It
> is like using the old analogy of a frog in a pot that is brought to boil-
> bad illustration because it isn't true. I don't see how a goofy story can
> be used to illustrate something scientifically. It could be like if I
> believe that people could fly if they knew the secret- giving an analogy of
> santa's flying reindeer to illustrate the point.
>
> Maybe the big mistake here is in thinking that mitochondrial eve is the
> first human- which science says is not the case. Rather than defending how
> one person can be the parent of all humanity, maybe the thing you should be
> doing is explaining how, instead, evolution happens in populations and not
> through a single founder?
>
> ...Bernie
>
> -----Original Message-----
> From: David Campbell [mailto:pleuronaia@gmail.com]
> Sent: Thursday, February 12, 2009 3:04 PM
> To: Dehler, Bernie
> Cc: asa@calvin.edu
> Subject: Re: [asa] Two questions... (bottlenecking)
>
> <<<Bernie: Snipped- just the questions I'm interested in are captured below
> for context.>>>
>
>
> > Everything comes from something else. If you say there is a single
> ancestral pair from which all humans came from, what would that entail? The
> change of 1 gene? The change of 100's of genes? What could be the
> biological change where you say the parent is nonhuman but the child is
> human?<
>
> It might not entail anything unique genetically. They might have had
> identical twins, but they just happen to be the ones to which all
> modern lineages trace back.
>
> Where to recognize the first humans (meaning spritually accountable)
> is not necessarily the same as where the single ancestral pair is. If
> the first humans included more than a single pair (seems likely but
> not absolutely provable, given the problem of identifying the first
> humans). Under an "insert the soul"-type model, there might be no
> physical or genetic difference. If having spirituality reflects the
> arrival at a threshold level of mental capacity, then presumably there
> is some degree of genetics underlying it, although environment plays a
> role as well. The genetic difference might be quite subtle, however.
> The only case in which a line can easily be drawn between parent
> species and new species is when there is an instantaneous barrier to
> interbreeding. For example, in Glenn Morton's scenario, the
> chromosome fusion that distinguishes humans from apes plays a key
> role. Chromosome fusion (or other chromosome rearrangement) makes
> interbreeding difficult. Not directly applicable to the human case,
> but hybridization in which the hybrid can reproduce (asexually and/or
> sexually with other hybrids) but not with either parent is the easiest
> way to clearly make new species abruptly. It's common in the wild and
> in lab. However, only in hindsight can you tell that a given change
> is key to something new rather than an individual aberration. (This
> is also a problem with all the "how come we don't see new stuff
> evolving today?" type arguments. We probably are, but we can't know
> until we wait millions of years or so to see what happens next.)
>
> > In addition, I'm thinking of a presentation I heard on "ring species." A
> animal (such as a seagull) can have many changes as you follow the
> geography, with the head of the line being so different from the tail that
> they are called different species because they can't interbreed. However,
> all the in-between varieties are interbreeding along the way. If you look
> at just the head and tail, you'd say they are different species, but if you
> look at the line you can't tell where one species begins and another ends.
> Apply that to human biological evolution.<
>
> I don't know of evidence for a geographic ring, but there is something
> similar going through time in humans. Homo habilis is fairly
> different from modern humans, but when you put in a full set of
> intermediate fossils, it's hard to draw firm lines.
>
> > All this makes it impossible for me to accept a single biological pair
> for all humans. <
>
> They key problem is what all are humans?
>
>
> > Also the thing I don't understand about mitochondrial eve- what about her
> mom? What was so different about her mom... didn't she have mitochondria or
> how was it so different that there's some sort of break in which you can
> call her daughter the eve but not the mom?<
>
> Here's an example. Suppose, for purpose of the example, that all
> modern humans descend from Noah. Noah would be the Y-chromosome Adam
> in this scenario-some male descendants of each of the sons have sons,
> and so forth. Noah's Y chromosome might not be any different from his
> father's, but Noah is the most recent common ancestor. Automatically,
> there is a single Y chromosome ancestor in every generation before
> that. Noah's sons' wives would provide three mitochondrial
> lineages-Mrs. Noah's mitochondria die out with the death of her sons.
> The three wives share a common maternal ancestor at some point, if you
> go back far enough. If they were sisters, their mother would be
> mitochondrial Eve. On the other hand, if Shem had sons but no
> daughters, then one of the three mitochondrial lineages would be lost.
> If only one of the three couples had daughters, then that wife would
> be the mitochondrial Eve.
>
> Thus, being the mitochondrial Eve or Y chromosome Adam does not
> guarentee being the spouse of the other, nor does it guarentee that no
> other individuals lived at the time. It does tend to suggest a
> relatively small population (either at the time when they lived or in
> some sort of later bottleneck-i.e., only the descendants of a certain
> individual happen to make it through).
>
>
>
> --
> 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 Fri Feb 13 16:41:49 2009