On Fri, 18 Jul 1997, Troy Gilchrist wrote:
> If you breed wolves for tameness you get dogs. Dogs are basically
> underdeveloped wolves. This process is known as neoteny. The smaller the
> dog the more neotenized it is. Chihuahuas are basically fetal wolves.
> For this reason both wolves and dogs thrive on wolf food: raw meat and
> scant amounts of vegetable matter.
I have no quarrel with the point about neoteny, as far as it
goes. Obviously, neoteny is not the *whole* story about the
difference between wolves and chihuahuas. If it were, there
would be no differences between chihuahuas and lhasa apsos and
beagles -- other neotenized wolf varieties. These varieties have
been subjected to selection pressures other than (and in addition
to) those favoring neoteny. If dogs and wolves both thrive on
wolf food (apart from my sister's Golden Retriever, who gets sick
when fed meat), that is because there has been so significant
selection pressure to cause them to adapt to a different diet.
> There is great evidence to show that
> Homo sapiens sapiens are neotenized hominids (Ray Audette can give you
> information on this). Identical diets would satisfy the nutritional
> requirements of a Cro-Magnon and a modern hominid in the absence of
> technology.
Again, the fact of neoteny may not be the whole story. The
explosion of agriculture has subjected most of the human race to
intense selection pressures. It is quite possible that this has
caused adaptations that would make the Cro-Magnon's diet less
than optimal for some populations of modern humans. Whether this
is in fact the case is an empirical question; it cannot be ruled
out a priori.
[anecdote about my grandmother deleted]
> An interesting story. But as you say it's only an anecdote. (The placebo
> effect is typically 30%.)
I'm not sure what the relevance of the placebo effect is here.
Are you suggesting that because my grandmother *thought* she was
getting adequate nutrition her body responded as if she were
(even though, on your view, she couldn't have been getting
adequate nutrition, since she ate no meat other than fish for 50
years)?
> And you admit that she consumed some animal
> protein throughout her life, meaning that she was not a strict
> vegetarian.
But she was a strict avoider of the red meat that you appear to
believe is essential for health.
> In
> nature, in the absence of technology--fire, domestic animals, pottery,
> agriculture-- a vegetarian diet will kill a human very quickly.
Perhaps so. It doesn't follow that a technology-driven diet is
necessarily harmful.
> Your
> grandmother rolled the cosmic dice and got lucky. The fact is that she
> was a hominid, and that the ideal diet for a hominid, and indeed any
> other animal, is that diet possible in its natural habitat. No matter
> what diet she consumed, a hominid diet is what she was designed to eat.
> What her immune system allowed her to get away with is another story.
Note that my grandmother's case is not unique. John Harvey
Kellogg, the vegetarian king himself, lived about as long as
Vilhjalmur Stefansson. George Bernard Shaw, a vegetarian since
his teen years I believe, lived to be almost 100. William S.
Sadler, another Adventist vegetarian health reformer
(disfellowshiped at the same time as Kellogg, and for the same
reasons) lived to be 94. These people were all hominids, and
what their immune systems allowed them to get away with is
*precisely* the measure of the extent to which they exhibited
adaptation to an agricultural diet. In fact, "what your immune
system allows you to get away with" makes an excellent
*definition* of dietary adaptation.
> If we stripped you naked of all technology and dropped you into a
> wilderness environment, you would quickly discover the nutritional
> limitations and requirements of your DNA: raw meat (herbivores, insects,
> reptiles, birds, et al), fruits, nuts, vegetables and berries. These are
> the possibilities in our ancestral environment. 20,000 years (less that
> 1% of hominid evolution) is not nearly enough time to allow for
> biolgical changes significant enough to change the dietary requirements
> of members of a common animal genus.
This point is still much controverted, as the following article
makes clear...
Lizard experiments show evolutionary change can occur
quickly
Copyright 1997 N.Y. Times News Service
(May 1, 1997 01:56 a.m. EDT) -- Darwin's theory of
evolution is the foundation of biology, yet the
process is so slow that it has seldom been witnessed
outside the laboratory.
A remarkable experiment with lizards in the Caribbean has
now shown that evolution moves in predictable ways and
can occur so rapidly that changes emerge in as little as
a decade or so.
The finding bears on debates as to whether evolution on
the time scale of millions of years is governed by the
same rules as short-term evolution. Biologists favoring
the idea of punctuated equilibrium have argued that there
are natural constraints that may keep a species unaltered
for millions of years. The new study can be interpreted
as showing that there are no such constraints, and no
difference between long-term and short-term evolution.
The experiment involved introducing a species of lizard
to 14 small, lizard-less islands near the Exumas in the
Bahamas and leaving them for 14 years.
Lizards in the Caribbean have been carefully studied by
biologists because, like Darwin's finches in the
Galapagos Islands, they have adapted to the different
conditions on various islands with changes in body shape.
For example, lizards that inhabit large trees tend to
have long legs, while those that live on twigs are
shorter limbed. The reason has to do with speed, which is
essential for success in the lizard world, both to catch
insects and elude predators.
Dr. Jonathan Losos of Washington University in St. Louis
said such adaptation enabled him and his colleagues to
forecast what would happen to the lizards exiled to the
14 islands, some of which were smaller than a football
field. The more the vegetation differed from that of
their home, Staniel Cay, the more the lizards should
evolve, and the direction of evolution should be toward
shorter legs, since Staniel Cay is wooded and most of the
islands are almost treeless.
Some 14 years after being delivered to their new homes,
the lizards have indeed evolved as predicted, Losos and
his colleagues are reporting on Thursday in the journal
Nature, with those with the stubbiest legs being found on
islands with the scrawniest vegetation.
Dr. Douglas Futuyma, an evolutionary biologist at the
State University of New York at Stony Brook, said the
study was "distinctive and exciting and one that will be
cited for many years to come." Though there are many
examples of rapid evolution in terms of an animal's
biochemistry, like the development of resistance to
pesticides, there are far fewer instances of bodily
changes like those seen in the lizard study, Futuyma
said.
A longstanding issue in biology is whether the small
evolutionary changes sometimes noticed within a species
are the same as giant shifts in the kaleidoscope of
species that take place over millions of years or, in
biologists' terms, whether microevolution is the same as
macroevolution.
The well-studied spread of lizards, which have evolved
into 150 species in the Caribbean islands, is a
macroevolutionary event. Losos and his colleagues write
that their lizard transplant experiment seems to be a
response to the same natural forces, suggesting that
"macroevolution may just be microevolution writ large."
Some biologists have suggested that a species may get
locked into genetic paralysis and stay unchanged for
millions of years until released by some event that
shakes up the gene pool. But since the lizards on all 14
islands evolved in the expected direction, Futuyma said,
"it means you don't need to invoke a complicated
hypothesis of this type."
The rate of evolutionary change in a species' wing or leg
or beak is assessed in units called darwins, which
measure the proportional change in an organ over time.
The changes typically seen over millions of years in the
fossil record usually amount to one darwin or less. But
the transplanted lizards evolved at daredevil speeds of
up to 2,000 darwins.
"Darwin thought that natural selection had to be slow and
gradual," Losos said from the Bahamas. "I think it is
clear he was mistaken. In some cases change can be very
rapid."
The lizard evolution experiment was started in 1977 with
a very different purpose in mind by Dr. Thomas Schoener
of the University of California at Davis. Schoener
installed the lizards on the islands to study extinction,
an outcome faced by many species. But nature failed to
cooperate. Instead of dying out, most of the lizard
colonies thrived.
Hearing of the experiment's misfire, Losos said he had
suggested to Schoener the idea of converting the goal of
the study from extinction to evolution.
Losos is now planning a second experiment to see whether
he can catch the arrival of a new species. One force
behind the development of new species, biologists
believe, is when a species is adapted to its surroundings
and a second, very similar species comes along. Both vie
for food in the same environment, forcing the two species
to diverge from each other so as to minimize competition.
To test the idea, he plans to stock islands with two
similar species of lizard.
Ecologists like to leave nature as they find it, but
Losos contends that there is little danger that his
experiments will leave any permanent mark on nature's
fabric. The reason the small islands have no native
lizards, it now seems, is not because they are
inhospitable but because hurricanes sweep through every
century or so and wipe the slate clean.
By NICHOLAS WADE, New York Times
The related point is that adaptations that favor a new
environment may well make the organism poorly adapted to the
previous environment. My wife has distinctly Irish
characteristics: red hair, white skin with freckles that sunburns
very easily. If you drop her into the African grasslands, the
fact that the genetic differences between her and an Ethiopian
are negligible wouldn't prevent her from quickly perishing from
exposure. The fact that hominids were originally well adapted to
the sunny grassland environment certainly doesn't mean that they
all still are adapted to it. Likewise, the fact that hominids
were originally well adapted to the diet of that environment
doesn't mean that all are still well adapted to it.
To my way of thinking, it remains very much an open question
whether all, most, many, or a few modern humans are best served
by a paleolithic diet. I have to agree with you that it is a
good bet, but I suspect it is far from a sure thing.
Todd Moody
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