Is the number of men in a female's life written in her genes?
Nelke
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Posted: Friday, June 2, 2000 | 9:11 a.m.
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GEORGE JOHNSON ON SCIENCE : Is the number of men in a female's life
written
in her genes?
By George Johnson
Not all scientific questions are boring. As an example of the interesting
kind, imagine asking "Why are some animals monogamous, and others not?"
That's the sort of question you would expect a novelist to ask, not a
scientist, and perhaps because of this I find it irresistibly interesting.
A particularly vivid exploration of this question is being carried out by
Professor Patricia Parker, a new member of the world-class tropical
ecology
group at University of Missouri at St. Louis.
Patty Parker studies hawks. For several years she has been carrying out
detailed ecological, genetic and behavioral studies of the hawks that
inhabit the Galapagos Islands about 600 miles west of Ecuador.
Famous for Charles Darwin's investigations over a century earlier, this
cluster of volcanic islands is so isolated that animals only rarely reach
it
from the mainland. Hawks are a recent arrival, carried in on high air
currents from South America about 33,000 years ago.
Now imagine you are a member of that intrepid group of birds, arriving
exhausted on a group of islands with no other hawks or indeed any other
predators there. Like Robinson Crusoe, you are free to assume whatever
lifestyle you choose. There is no one supervising your behavior, no one to
say you should be monogamous. Would you be?
The beauty of studying this problem with Parker's hawks is that on some of
the islands, like Espanola, all the hawks are monogamous, while on other
islands, like Pinta, none are.
The hawks on Pinta are polyandrous: One female is shared by as many as
eight
males, all of whom mate with her and all of whom help in rearing the
young.
Is the choice by a female of one mate or many dictated by the genes of the
birds that settled her island? Or does the ecological nature of the island
dictate the choice?
To investigate this question, Parker and co-workers studied the DNA of the
birds. Like all vertebrates, these hawks contain within their chromosomes
certain variable bits of DNA called minisatellite sequences.
Minisatellite sequences vary a lot among individuals. In humans,
minisatellite "fingerprints" are used to establish the identity of
suspects
in criminal trials.
Parker used minisatellite fingerprints to establish that each of the nine
islands on which hawks are found was settled only once. Hawks don't like
to
fly over water, and seem to have passed from one island to another only
rarely.
On each of the smaller islands, like Pinta and Espanola, the minisatellite
fingerprints of the hawks are identical, as if all the hawks on a
particular
island were clones of a single individual. Each island's hawk population
has
its own unique minisatellite fingerprint, so you would know without a
doubt
that a hawk came from Pinta and no other island by looking at its
minisatellite profile.
A hint that genes determine the choice between monogamy and polyandry came
when Parker discovered that the hawks that are genetically uniform are
also
behaviorally uniform.
The hawks on Espanola are entirely monogamous; the ones on Pinta are
entirely polyandrous. This is just what you would expect if the preference
for multiple mates is determined by genes. Monogamy would occur on
Espanola
simply because its original founder was monogamous; polyandry on Pinta
because its founder carried genes promoting polyandry.
But might environmental differences between Espanola and Pinta be
responsible instead? One can sort this out by looking at bigger islands.
The large islands Isabela and Santiago support much larger populations of
hawks, which exhibit far more genetic variation than hawks found on the
small islands. These large islands are ecologically diverse, and so could
be
expected to exert different ecological influences on the hawks.
On Santiago, one end of the island is dominated by old lava flows, with
little vegetation, while the other end of the island is richly vegetated.
The pickings are slim for hungry hawks living on the lava end of the
island.
Are the hawks living on that end more monogamous? Less monogamous?
Parker found that the ecological contrast had little or no effect. The
hawks
were polyandrous on both ends of the island, and the number of males in a
family group was almost identical (2.1 males at the lava end vs. 2.5 at
the
vegetated end).
Comparing the ecology of different islands, Parker found far larger
differences in the size of polyandrous groups (from two to seven males)
among islands whose ecology was no more different than the two ends of
Santiago.
Thus, it looks like genes do tell the tale, at least among Galapagos
hawks.
Parker's work is still preliminary, and there are four more islands to be
looked at, but the number of males a female admits into her "marriage"
seems
to reflect the genes she carries, rather than the life she lives.
George Johnson is a biology professor at Washington
University.\onsc...@txtwrtier.com\http://txtwriter.com
Garrison Hilliard
On Fri, 2 Jun 2000 13:33:45 -0500, you wrote:
>http://www.stlnet.com
>http://www.stlnet.com/postnet/stories.nsf/ByDocID/766B9435C2C538D6862568F200
>3C6B46
>
>COPIED FROM: ST. LOUIS POST-DISPATCH
>Posted: Friday, June 2, 2000 | 9:11 a.m.
SIGN OF A CRAP NEWS STORY BELOW
|
>E-mail this Story to a friend
>GEORGE JOHNSON ON SCIENCE : Is the number of men in a female's life
written
>in her genes?
>By George Johnson
Ol' George seems to not understand the term "false analogy", as in "A
comparison study between isolated island dwelling raptors and human beings
makes many a false analogy."
"BAD BIOLOGIST, BAD BIOLOGIST! DOWN, BOY!"
Nelke
------------------
Here is how you can reach him - give him your views and let us know what
he
said
Scott Campbell
>On Fri, 2 Jun 2000 13:33:45 -0500, you wrote:
>
>>http://www.stlnet.com
>>http://www.stlnet.com/postnet/stories.nsf/ByDocID/766B9435C2C538D6862568F200
>>3C6B46
>>
>>COPIED FROM: ST. LOUIS POST-DISPATCH
>>Posted: Friday, June 2, 2000 | 9:11 a.m.
>
>SIGN OF A CRAP NEWS STORY BELOW
> |
>>E-mail this Story to a friend
>
>>GEORGE JOHNSON ON SCIENCE : Is the number of men in a female's life
>written
>>in her genes?
>>By George Johnson
>
>Ol' George seems to not understand the term "false analogy", as in "A
>comparison study between isolated island dwelling raptors and human
beings
>makes many a false analogy."
>
>"BAD BIOLOGIST, BAD BIOLOGIST! DOWN, BOY!"
To be fair to George, the stupidity here is mainly confined to the idiotic
headline, and there's no way in the world that he would have written that
himself; some careless sub-editor would have. There's nothing in the story
itself that approaches that level of badness.
____________________________________
Dr. Scott Campbell,
School of Philosophy,
University of New South Wales,
Sydney, NSW, 2052, Australia.
(61 + 2) 9385 2329 (Uni)
(61 + 2) 9547 3497 (Home)
(61 + 2) 9385 1029 (Uni fax)
<s.cam...@unsw.edu.au>
____________________________________