Lisa's anthro paper -Reply to Adrien

Lisa Rogers eqwq.lrogers at
Mon Dec 4 11:53:19 MST 1995

{2 and 1/2 weeks ago, Adrien asked me a question about my
anthropology paper...}

Dear Adrien,
Your biologist is correct to point out some of the bad, old nonsense
about looking for correlations between brain size and other things.

However, Aiello and Wheeler 1995 are explicitly trying to do
something different from that.  Although it is a bit over-grandiose
to treat the "expensive tissue hypothesis" as an entirely new thing,
I believe that it is a new contribution, a new way to put some older
observations together in a new way, that makes a lot of sense.  

It is not so much a matter of looking for correlations, rather, it is
the application of rigorous thinking about natural selection, and the
[ultimately reproductive] costs and benefits of diet change and gut
and brain size.

Among primates [and probably within some other groups] it is clear
that there is a correlation between gut size [relative to body
weight] and diet quality.  This is simple to understand, as the
digestion of leaves takes a longer time and more processing, in order
to get enough nutrition to make it worthwhile eating and digesting
them at all, due to the nature of cellulosic fibers and such.

Primates that eat fruit, insects, eggs, etc. have much smaller
relative gut size.  These foods are more easily digestible, and are a
more concentrated source of nutrition, in terms of high energy and
other stuff per mass ingested, compared to foliage.

It is true that brain tissue is highly metabolically expensive to
grow, operate and maintain, so this is linked to issues of diet and
the energetic expense of obtaining calories, as part of any
evolutionary scenario for increasing brain size, in carnivores as
well as primates, I believe.

Aiello and Wheeler's point is that operating and maintaining tissues
such as the gut itself is just as expensive as the brain.  This was a
new fact to me.  I know the brain's use of calories is usually
compared to the "rest of the body" in aggregate, and the difference
is huge.  But all the tissues vary in the amount of energy required
to run them.  One of the major implications is that in the analysis
of the evolution of diet change, one of the factors that has been
previously ignored is the energy savings one gets by the reduction of
the gut size itself.  

This is assuming the framework of an ecol/evol/econ method, wherein
one keeps accounts of an energy budget.  

I am trying to explain why I see A+W as doing something important and
new, not just the same ol' same ol', [that means 'same old stuff'].

I'm interested, if your biologist would like to look at the A+W
paper, if hse may agree that they are doing something newer and

That is exactly the focus of my draft review paper, to summarize the
*recent* and on-going developments in the field of evolutionary
ecology of humans.  

Sorry to be so slow to answer,
Thanks for asking,
anthropology grad stu UU

>>> Adrien Verlee <Adrien.Verlee at>  11/14/95, 03:15pm >>>
You say:
One newer development regarding encephalization is its relation to
the size of the gastrointestinal tract, etc. ....

My 'biologist' say:
...I doubt that this is a good trail. ...
But there are herbivores with relativ big brains (horses) and
allied/related/congeniality herbivores with verry small brains
Carnivors have relativ big brains but that's fore hunting, or because
their wealthy food...
Take care,

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