Re: [asa] Out of Africa? (DNA studies to find the first humans)

Bernie asks: How can DNA studies find a "first human" if we don't even know
what that looks like?

I respond: My understanding, and others more expert can correct me if I'm
wrong: they can't. DNA studies can trace the genealogies of genes. It is
more accurate to state that the history of the human genome can be traced to
Africa through genetic studies. What constitutes "human" in terms of
physical anthropology depends on various, often disputed, physical
characteristics. Some very ancient extinct species that physical
anthropologists consider "human" would probably looked and acted much like
contemporary apes, though some ancient extinct species, like Homo
Rhodensiensis, which dates to probably 650 kya, possibly looked much like
us.

A really fascinating book the illustrates this vividly is "The Last Human:
A Guide to Twenty-Two Species of Extinct Humans." It's an expensive book,
but it includes stunning color recreations of extinct human species based on
forensic techniques that apply muscle structure to the fossil bones. (Just
a warning -- only pick this up if your applecart about finding an easy place
for "Adam" has already been upset! You can't stare into the eyes of Homo
Rhodensiensis and conclude that it was just an ape -- at least I can't!)

Whether "human" is properly reducible to physical anthropology is hotly
debated, particularly by those of us who assert a spiritual component to
human nature. Even many "secular" physical anthropologists see something
very different happening in human culture and capacities about 40 kya (see
Ian Tattersall, "The Fossil Trail: How We Know What We Think We Know About
Human Evolution" -- again, not for those who aren't ready to confront some
tricky issues).

Wentzel Van Huyssteen's Gifford Lectures, "Alone in the World: Human
Uniqueness in Science and Theology" discusses this from a Christian
theological perspective (though not an "evangelical" perspective).

On Thu, Jun 19, 2008 at 4:27 PM, Dehler, Bernie <bernie.dehler@intel.com>
wrote:

> Hi all- a question for something I don't understand. I hear of DNA
> studies to determine where humans originated (out of Africa, etc.). But how
> could that be determined since we don't even know what a 'human' is? Seems
> like the quest assumes there is some sort of DNA line where you have a
> non-human, then a human. Seems to me like evolution says change is gradual-
> no dividing line.
>
>
>
> For example, apes have one more pair of chromosomes than human. Two ape
> chromosomes fused to make 1 human chromosome (human chromosome number 2, I
> believe). Therefore, at some point an animal existed that had these
> chromosomes fused. Is that a human at that point? What does it take to be
> human? How can DNA studies find a "first human" if we don't even know what
> that looks like?
>
>
>
> A short answer would be fine. I won't be able to read any references to
> books- already have a backlog of books to read.
>
>
>

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