Re: Is Oreopithicus the Aquatic Ape Link?

From: JAE (jae_at_ucdavis.edu)
Date: 02/23/05 

Date: 23 Feb 2005 11:46:19 -0800

Pauline M Ross wrote:
> On 22 Feb 2005 15:02:30 -0800, "JAE" <jae@ucdavis.edu> wrote:
>
> >How does energetic efficiency matter
> >for a female with infant? Same way it matters for anyone else.
Move
> >farther with less energetic cost means as food stuff gets more
> >disperse, the more efficient movers do better.
>
> This answer doesn't address the question. The issue is not *how*
> energy efficiency matters for females with infants, but whether there
> is in fact any energy efficiency benefit at all. Research has
> indicated a small benefit in the (male) samples tested, but it isn't
> obvious that this would automatically apply to females carrying
> infants. Do you think it would, and if so, why?

I'm not sure that the benefit is necessarily small. The efficiency
measured by Taylor and Roundtree was, if I recall correctly, about 50%
higher in the biped than in the knucklewalker. Is there a reason to
suspect that the situation with a mother carrying child would be
different than an adult male? Sure. It's more difficult to move while
carrying someone than while walking by one's self. This doesn't
however mean that mom walking bipedally is less efficient

I've said it before. I think that the data here is very shallow
[though I do know individuals who are trying to rectify this
currently]. It indicates that there's a possible advantage and, given
other variables like more patchily distributed resource--something
there is some paleo-ecological support for--a difference in efficiency
would translate into differential survival or reproductive success as
moving longer distances to obtain food became a bigger component of the
animal's energy budget. This would be true for all members of the
species, or at least all members of the species who want to eat, though
it's not clear that bipedalism would give all the same benefit.
Walking with babe-in-arms is harder than walking hands-free, but if
it's better than knuckle-walking while infant-laden, then it's still
favorable. This calls for more data, but I'm unaware of any data that
actually contradicts this currently.

> There is also the matter of whether the measured benefit is
> significant. The number quoted on the BBC's 'Walking With Cavemen'
> program was said to be equivalent to a packet of biscuits (cookies) a
> year, which I estimate to be around 3 calories a day. This seems a
> very marginal advantage in energy efficiency, when set against the
> mechanical disadvantages of bipedalism (poorer stability,
> load-distribution and speed, relative to quadrupedalism - all
> especially significant for females with infants to carry).

I am not sure where "Walking with Cavemen" got their cookie figure.
It's at odds with what I've seen in the literature, which translates to
much more than 3 calories a day and I tend not to use the Discovery
Channel as my primary source for comparative data. The 3 calories a
day would, in my opinion, be rather limited to expect that it would
compensate for the apparent lack of footspeed that bipedalism incurs
relative to terrestrial quadrupedalism.

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  • Re: On low gears
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    (rec.bicycles.tech)
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