"human brains are like peacock tails."

Joe Barrera (joebar@MICROSOFT.com)
Fri, 17 Jul 1998 08:05:53 -0700

-----Original Message-----
From: <mailto:nev@bostic.com> nev@bostic.com
<mailto:[mailto:nev@bostic.com]> [mailto:nev@bostic.com]
Sent: Friday, July 17, 1998 7:05 AM
To: /dev/null
Subject: The Red Queen.
From: <mailto:hitz@netapp.com> hitz@netapp.com (Dave Hitz)

Speaking of which, I just read the most interesting theory on why human
intelligence evolved. I wrote up a summary for my brother, but I think it
applies to your conjecture. The basic premise is that human brains are like
peacock tails. They are not there for any fundamental survival reason,
except that humans prefer to mate with people who have big brains.

I just finished a book on evolution called the Red Queen. The title is
based on the story in Alice and Wonderland about the land where you had to
keep running as fast as you can just to stay in the same place. The analogy
applies to evolution: if you've got two species in competition (e.g. hunter
and hunted) then both need to keep evolving as fast as they can, just to
stay even with each other. The same thing can apply within a species too,
in competition for food or mates. One common way is sexual selection, such
as the preference that peahen's have for larger tails leading to the amazing
tails that peacocks have. Since peacocks are competing with each other,
they have to run as fast as they can just to stay even in the competition
for peahens' favor.
So he argues that when you've got an absolute runaway characteristic, like
the tail, that's so far outside the norm, that it's unlikely to have evolved
in response to the physical environment. The environment just isn't
changing that fast. Such an outlandish characteristic strongly implies a
selective pressure that is also evolving, thus leading to the Red Queen
phenomenon. For truly bizarre characteristics, you always need to look for
a Red Queen.
Given this setup, he then argues that the human brain is similarly
outlandish, and could not have evolved in response to simple environmental
requirements. He points out that wolves have wonderfully coordinated
hunting packs, without massive brains or language, and baboons do
wonderfully at digging up tubers and remembering where they are from year to
year, again without language.
The author discusses Richard Alexander who originated this theory:
It was logic like this that led Alexander to propose that the key
feature of the human environment that rewarded intelligence was the presence
of other human beings. Generation after generation, if your lineage is
getting more intelligent, so is theirs. However fast you run, you stay in
the same place relative to them. Humans became ecologically dominant by
virtue of their technical skills, and that made humans the only enemy of
humans (apart from parasites). "Only humans themselves could provide the
necessary challenge to explain their own evolution," wrote Alexander.
He argues two potential mechanisms. One is for humans to outsmart each
other, in their competition for status and resources. The second he
describes with a quote from Geoffrey Miller:
I suggest that the neocortex is not primarily or exclusively a
device for toolmaking, bipedal walking, fire-using, warfare, hunting,
gathering, or avoiding savanna predators. None of these postulated
functions alone can explain its explosive development in our lineage and not
in other closely related species.... The neocortex is largely a courtship
device to attract and retain sexual mates: Its specific evolutionary
function is to stimulate and entertain other people, and to assess the
stimulation attempts of others.
Just as the peahen is satisfied with nothing less than a visually
brilliant display of peacock plumage, I postulate that hominid males and
females became satisfied with nothing less than psychologically brilliant,
fascinating, articulate, entertaining companions.
I found this theory absolutely fascinating.
I don't know if I buy the "courtship device" part (not enough evidence one
way or the other), but the argument that "Only humans themselves could
provide the necessary challenge to explain their own evolution" seems very
compelling. It makes much, much more sense than all the theories that the
brain is for this or that particular thing which so many other animals do
just fine (sometimes better than us) without such a giant brain.