To: All Dec-08-93 11:11AM
Subject: Something for Creationists to chew on...
Organization: The University of North Carolina at Chapel Hill
From: KG Anderson
Well, it's been pretty clearly documented on this newsgroup that
most Creationists aren't going to be swayed by the evidence.
Nevertheless, I though the following factoid might be interesting;
perhaps it could even go into a FAQ somewhere.
Creationists assert that that humanity began as two individuals
around six thousand years ago. It's been pointed out on t.o. before
that this cannot account for the current genetic diversity we see in
humans, since two people can carry four alleles (at most) between them
for any given locus. Furthermore, Creationists assert that humanity
was again narrowed down to a handful of people (Noah, his wife, their
sons and their sons' wives) after the Great Flood .tm.. Again, this
runs counter to everything we see in the current genetic diversity of
human beings. (Never mind every other organism on the planet.)
I've always liked this counter-argument to Creationism; it's succinct
and easy to remember. (Let's face it, most of us don't leave home
with the entire t.o. FAQs in our briefcase.) But I've also wanted
a good reference to back it up, so that when the inevitable reply,
"Oh yeah? *Prove* that humans have that much genetic diversity" comes
along, I'll have something to show 'em.
Well, I just found what I was looking for: "MHC Polymorphism and Human
Origins," by Jay Klein, Naoyuki Takahata and Francisco J. Ayala, in
the December 1993 issue of Scientific American (pp. 78-83). Yes, I
know SciAm doesn't count as a hard-core scientific reference, but that's
all the better: it's available to people who don't have access to
research libraries, and it's written in plain English (unlike most
papers in genetics journals), so pretty much any C'ist should be able to
look it up if they won't take your word for it.
In a nutshell, the major histocompatibility complex (MHC) is a bunch of
loci located on chromosome 6. They are the genes responsible for
labeling your own cells as your own, so that the immune system can
recognize foreign cells (including those from transplanted organs)
as "invaders," ripe for attack. (That's a gross simplification, but
gets the point across.)
One gene in particular is of interest to us: HLA-DRB1. Remember how
the Creationist "Theory" "predicts" that there should be, at most, just
a handful of alleles for any particular gene. On page 78 of that
article, they list FIFTY-NINE alleles for HLA-DRB1. (Those are
identified as "known alleles," so I guess there could be more out
there, as yet unsequenced.)
At this point, your shrewd creationist who's had a decent high school
biology course (which rules most of them out) may point out that a
single point mutation can create a new allele, as in the case of
normal hemoglobin converted to the sickled form. I'll quote from p. 79
to answer that point:
"The high number of alleles is, however, only one of two extraordinary
features of the MHC polymorphism. The other is the large nucleotide
diversity among the MHC alleles. In other genetic systems, alleles
at a given locus usually differ by a few nucleotide substitutions at
most. In the MHC, some alleles differ by 100 or more substitutions."
The unescapable conclusion, of course, is that the major
histocompatibility complex is far older than creationists would allow.
(Another possible explanation is that humans were recently created, but
did not begin with just two individuals. Instead, over fifty were
created, and they were created with a large degree of genetic diversity.
But I don't think anyone is advocating this view--it certainly runs
counter to what Genesis says.)
If any Creationists out there can think of any flaws in the above logic,
I'd love to hear them. If not, we can just add this one to the FAQs--
I think it makes a pretty good "60 second" disproof of Biblical