Re: AAH update (was: Bipedalism and other factors and AAT)

Pat Dooley (
26 Jun 1995 23:12:36 -0400

>I can't help but chime in here.
> The fact that hominids are capable of maintaining a constant
>temperature in a heat-stressing environment is evidence that we are well
>adapted to that environment. There is often more than a single solution
>to a given problem, and simply because we don't use the same mechanisms
>that bovids and equids do to deal with a hot open ecosystem doesn't mean
>we're not well-adapted to it.
> In fact, it might be suggested that the hominid adaptation to
>living in a heat-stressing environment is superior to that of other
>critters that are out there. We can travel much longer distances in a
>given time than most other savannah-dwelling critters, and there are many
>accounts of humans "walking their prey to exhaustion" in the hot sun. A
>bovid may be able to run fast for a short distance on a hot day, but it
>can't run long. Ambush predation is one way to deal with this, and
>"exhaustion predation" is another. Yes, there is a cost -- we can't
>stray too far from the water hole (unless we use tools: canteen, gourd,
>skin water-bag).

The pack hunters, such as the wild dog and hyena, fill the "exhaustion
predation" niche. Lions fill the ambush niche, to an extent. Was there
room for a 10 mph weaponless bipedal ape to go pack hunting on the
savannah? Doesn't compute for me.

The problem is that the range depends on the ability to carry water. That
requires a level of tool building sophistication that was not available
H. Erectus arrived on the scene; an event post dating the evolution of

> Another point -- there really isn't a lot of evidence that early
>hominids were living strictly in a savannah environment. The faunal
>remains associated w/ A. ramidus are definitely suggestive of a more
>closed habitat, and much of the evidence for A. afarensis and A.
>africanus also point to life in a mosaic habitat in which a number of
>different microhabitats were available. A. boisei is found in
>depositional environments that are indicative of wetter habitats than the
>co-eval H. erectus. In fact, its not until the appearance of H. erectus
>that we see good evidence for "good" adaptation to open habitats
>(human-like intermembral index, 1.8 m stature, thin "equatorial" body

Which leads back to the $64k question. If bipedalism wasn't a savannah
adaptation, what was it?

Arboreal? The arms would be more orang like, and the legs much shorter.

Display? No sign of sexual dimorphism.

Temperature Regulation? But bipedalism didn't evolve on the savannah.

Speed? A new-born Gnu can out-run a mature human. You need a great 800m
time to survive on the savannah.

Tool carrying? Bipedalism predates tools.

Food gathering? Lots of problems with disadvantageous intermediate forms.

Wading & Swimming? Crazy notion, but it fits with some other oddities.

> And finally, a comment on leopards -- yes, they climb trees, but
>they don't hunt in trees (their prey are almost exclusively terrestrial

But they often hunt from trees. The Tatung boy was, apparently, an early

Pat Dooley