Bruce Sherrod writes:

>However, regardless of which phase of the ice ages is seen as boom time and
>which is seen as the time of stress, so long as we believe that there
>were alternating times of relaxation and constriction of environmental
>pressures then the "boom-time/neoteny/enlargement" theory of human
>encephalization is still reasonable.
>
>I still very much would like to hear the counterarguments both
>to this theory and to the Expensive Tissue Hypothesis.

I'm not versed in what counterarguments there may be to the "boom-time/
neoteny/ enlargement" theory. However, this thesis doesn't oppose the
expensive tissue hypothesis (ETH), or really even compete with it. Rather,
it's _complementary_ to the ETH.

What Calvin's discussion addresses are the proposed _external_
evolutionary/ environmental selection pressures that might have driven the
evolutionary process of encephalization, plus the idea of neotenization as
an evolutionary strategy leading to encephalization. However, neotenization
as an explanation for brain enlargement essentially only addresses
macro-level events, which still have to be explained by the principles
governing the body's underlying metabolic-energy equation (the micro level
here).

The ETH deals with this other side of the coin, namely the _internal_
nutritional and metabolic/ energetic constraints, or bottlenecks, to
encephalization that have to be dealt with by primate mammalian physiology
(as well as any other theory addressing nutritional/ metabolic issues) in
building a bigger brain.

As Aiello and Wheeler reiterate several times in their paper, the ETH's
viability as an explanation does not depend on what the actual selection
pressures for intelligence/ brain enlargement might have been (or we can
add, whether it was accomplished via neoteny or not). Its concern is how
the hominid organism managed to accomplish the metabolic feat of a larger
brain while still adhering to the constraints of Kleiber's law. That is,
how exactly is it that the body managed the task of "robbing Peter (the
metabolic budget of other parts of the body) to pay Paul" (supply the
energy/ nutrition needed for an expanded and very energy-intensive brain)?
And what does that imply or require nutritionally, digestively, etc.?

Out of curiosity, I pulled up my (as yet mostly unread) copy of William
Calvin's "The Ascent of Mind" from cold storage in the basement ("cold
storage" at this time of year, at least :-) ). It turns out Calvin's book
was written/ copyrighted in 1990, published in 1991, which predates by 4-5
years the Expensive Tissue Hypothesis, which didn't see print in Current
Anthropology until 1995. I took some time to check the book's extensive
index for key terms related to the ETH, and also scanned page by page
through the book, but unless I overlooked something in the time I had
available, could not find the ETH or similar concepts mentioned anywhere.

Could be your memory is just playing tricks on you here, Bruce. (You
certainly wouldn't be the first--experience has shown [luckily mostly in
private] that distinction to be ALL MINE, which over time has ended up
making me chary of sticking my neck out too far on anything too technical
like this without sources at hand. :-\ ...And how entirely uncooperative
for a book to go out of print on you like that. :-\ )

As far as relevant counterarguments to the ETH, I'd be interested in
hearing if anyone knows of any too. (Or ones regarding Calvin's thesis for
that matter.) So far, I haven't heard of anything that deals with the key
issues head on without sidestepping one or more inconvenient facts, such as
the recent Wrangham tuber hypothesis.

--Ward Nicholson <[log in to unmask]>