Re: tree-climbing hominids

H. M. Hubey (hubey@pegasus.montclair.edu)
28 Oct 1995 20:05:33 -0400

pnich@globalone.net (Phil Nicholls) writes:

>>>Nope, nope, nope. A full rebuttal goes beyond the scope of
>>>sci.anthro.paleo, but perhaps I should ask: How do you define "higher up
>>>the evolutionary scale?"

>>Brain mass divided by body mass. On this scale bacteria and
>>viruses are zero. That puts us at the top.

>Therefore, we are "higher up" based on a criteria that has been
>specifically selected to put us on top. Does the phrase "begging the
>question" mean anything to you?

Of course. The fact is that almost the same thing can be said
about everything else too. For example let's look at F=ma.

Well, guess what? Do you think Force and Mass were defined to
make it come out to be true? Yep. For mechanics the fundamental
dimensions are F,L,T or M,L,T. Yep, if you use F,L,T then M is
defined in terms of F=ma, and vice versa.

That's the beauty of the whole thing. Newton recognized all this
and saw that using it would be a very parsimonious way of producing
what we now call Newtonian mechanics.

The trick is that we are looking to quantify something which
we all know to be true. We are last and we are the smartest,
and we are top dogs. Someone asked what I'd use to judge the
intelligence of animals instead of IQ tests, so I suggested
brain/body mass ratio.

But there's more. There's info from Briten and Davidson (1969)
Science, vol 165 that plots 'genetic information' (in DNA
nucleotide pairs per haploid cell) against 'time of origin'.

A similar plot can be found in Sagan, Dragons of Eden, p. 26
and also plottted is "brain information". Same kind of exponential
curves. Yep, we are it. No question about it.

And even the conditions (and probability) for this happening on
some generic planet and solar system have already been
computed, decades ago. See the book 'We Are Not Alone'.

>Your criteria is rather simplistic for a quantitative guy like
>yourself. Don't you think that there is a component of brain size
>that is simply a scaling effect of body size? Don't you think that a
>better approach might be to run a regression on brain size and body
>size data and then look at the residuals?

It's simplistic. It's a good start. It was only meant to
counter PC arguments for bacteria and insects :-)..

Yes, the approach of looking at residuals is a better idea. But so what
some of this has been done already. I don't know where the original
work got done. I see the one in Sagan. It seems that the equation
is b=c*(B^s) where b=brain size, B=Body size. The plot shown in
Sagan is log-log and it looks like a nice straight line so it's
log(b) = log(c) + s*log(B). Yep. We top out again!

>Since you place such a premium on quantitative analysis you will be
>pleased to know that the relationship between brain size and body size
>in evolution has a rather extensive literature.

I didn't know that. Anyway, I had suggested that the plots would
look even better if we subtract some constant to account for the
minimum housekeeping functions, etc.

>But why the emphasis on size? Why not look at the organization of
>the brain which is at least as important as the increase in size?

That's where we should look naturally but that's also difficult.

>Vision is much less important to aquatic animals than hearing. None
>of the endocranial casts of fossil hominids shows any evidence of an
>expansion of those parts of the brain that are enlarged in aquatic
>mammals.

This is taking it too far. In order for that to happen they'd
have to be completely aquatic; their heads would have to be
submerged all the time. I'd guess not even hippos show this
kind of adaptation.

>>The first appearance on earth, if we could ascertain it, would
>>be a reasonably good choice.

Of course it would. It correlates with brain/body mass, and
also the DNA information.

-- 





				Regards, Mark

				http://www.smns.montclair.edu/~hubey