Re: Holloway/Morgan

Elaine Morgan (
Mon, 24 Jul 1995 11:24:01 GMT

You say I tend to use different standards in assessing the validity if
facts that fit into my scenario as opposed to facts which do not. Yes,
of course. This tendency is universal. All we can do is try to curb it.
and point out to one another blatant specific examples

If you don't mind I would like to postpone discussion of specific
topics like hair loss and skin glands, I am noting and filing what
is being said, but I'd like to deal first with the more basic premises,
like the processes of evolution.

I am often told that according to modern evolutionary thinking, natural
selection is not the only cause of evolutionary change. It may be
attributable for example to genetic drift. And then some of the genetic
differences are in regulatory genes which control the operation of a
lot of others, or the order in which they are switched on, and so on.

These items are described as "things we now know", as if they were
significant new revelations of which I had strangely remained
unaware. I was aware all right. I just don't buy it. I've taken time
out to check whether some new data have been unveiled in recent months
which I had missed. Apparently not.

It is fuzzy thinking to suppose that a major evolutionary change may be
caused either by natural selection or by genetic drift. They are not
alternatives. It is like a detective saying: "That woman may be dead
because her husband had a fit of jealous rage. Or she may be dead
because a blunt object smashed her head in. One or other of these
things must be true, and the big question is which?"

Natural selection cannot initiate any change. All it can do is monitor
it. Edit it. So someone, I am told, has worked out that genetic drift
can account for brain growth. Big deal. That does not absolve us from
enquiring why it was allowed to. Brain growth was on balance, most
people would agree, conducive to inclusive fitness. If it had decreased
inclusive fitness natural selection would have vetoed that drift and
it would not have occurred. Okay, regulatory genes by means of
e.g.heterochrony can produce a lot of change in a short time, but they
are neither more nor less subject to editing by natural selection than
other genes.

So am I saying that there has to be a reason and a Just So Story for
everything? No, I'm not. Random mutation or genetic drift can produce
small changes which are neither adaptive or maladaptive and natural
selection ignores them. For example chows have black tongues. A measure
of unnatural selection ( the Kennel Club) may be involved here, but it
is quite conceivable that in the wild among a small population of
wolves a black-tongue mutation in one powerful sexy male could have got
a toehold in the gene pool and spread.

But that does not justify the alarming growth of the prevalence of the
"may be no reason" shrug-off. and specifically it does not justify the
use of it against AAT. All the enigmatic features discussed in "The Scars
of Evolution" were chosen because they were not, repeat not, adaptively
neutral. They were inconvenient, they had arguably deleterious
consequences for a land animal. You may disgree with the arguments, but
you cannot pretend it is not legitimate to ask why they got a foothold
in the first place.

The other instance where "we'll never know" may be pardonable is in the
case of extremely ancient adaptations. Phil Nicholls gave the exmple of
why we have five fingers and not four or six. Again this is irrelevant
to AAT. It does not concern itself with features shared by all primates
or all mammals. It does not ask "Why a spine, why a four-chambered
heart?"It focusses on the items in which we differ from
other apes and often from all other primates, The question "Why?" is
not only legitimate but central to our understanding.

To say "We may never know" is not an answer. If you have A saying "I
believe we will never know the answer", and B saying "I believe I know
the answer", then the onus is on A to listen to B and disprove his
hypothesis. He may be able to do it. But he cannot do it by simply
asserting his agnosticism and representing it as the great new tenet of
modern evolutionary thinking.

Daniel Dennet's new book "Darwin's Dangerous Idea" recounts the history
of this anti-national- selection trend in a more scholarly fashion than
I can, and he also lucidly explains why he does not go along with it. It
is a very important contribution to evolutionary thinking and is going to
stir up a lot of controversy. Essential reading.