Re: AAT
Alex Duncan (aduncan@mail.utexas.edu)
9 Jul 1995 17:15:21 GMT
In article <736355424wnr@desco.demon.co.uk> Elaine Morgan,
Elaine@desco.demon.co.uk writes:
>Yes, okay, I'm familiar with the term. So tell me what you think the
>other purpose was that produced the adaptation later co-opted to serve
>bipedal locomotion. Then we'll be in business.
Everything has to have a purpose, doesn't it. That's why we still have
appendices, and why embyological humans develop pharyngeal pouches in
exactly the same places fish have gills -- right? A feature does not
have to be an adaptation to exist. Is there a functional or adaptive
reason why gibbons or spider monkeys are largely bipedal when they're on
the ground? I've never heard one suggested. As far as I or anyone else
knows, the reason these creatures are bipedal when they're on the ground
is because they're so specialized for arboreal suspension that bipedalism
is the only option left to them when moving terrestrially (yes, I know
they sometimes put a hand to the ground).
Gibbons and spider monkeys rarely come to the ground, because
they're not terribly good at moving there, and because their food sources
are all arboreal. But, what would happen if there were a climate change
and the environments these creatures live in were to become a little less
lushly tropical? What if the patches of trees were separated by short
distances of open space. Would these creatures suddenly adopt
quadrupedalism to move from one patch of trees to the next, or would the
efficiency of their already existing mode of terrestrial locomotion
increase?
>About the energy used in running, I've got Rodman and McHenry, thanks. My
>reference was Carrier. I've given the details and quotes under "reply to
>Moore". Sorry about the "four times" reference.I did have a cutting
>giving that ratio but can't track it. So scrub it - I can't be certain
>what two units were being compared.
I wasn't talking about energy used when running, but about energy used
when walking. Human walking is no less efficient than quadrupedal
walking (and is actually more efficient than chimp quadrupedal walking).
I don't recall anyone ever suggesting that human running capability was
all that important. Most models of human bipedal adaptation talk about
the efficiency of WALKING for covering a large daily territory. Yes, I
am aware that human running is not efficient compared to the running of
"normal" quadrupeds. How important would running be for a terrestrially
adapted biped with a complex social organization? I don't know. I do
know that modern accounts of groups like the !Kung rarely mention them
running to escape predators or to capture prey (since the majority of
their calorie intake is from vegetable matter -- running isn't that
important). When they do actually capture animal prey, my understanding
is that they try to injure it from ambush, and then basically WALK it to
death.
>I could give you (and Moore) a raft of other references confirming that
>human running - which involves a stage of both feet off the ground- is
>quite different from and more energetically expensive that anything a
>chimp does in the way of bipedal locomotion. But it is the only way a
>biped can attain a speed comparable to that of an ape running on all
>fours.
>
> Elaine MorganAlex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086
512-471-4206
aduncan@mail.utexas.edu
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