Re: Infant carrying in apes and hominins

"Paul Crowley" <slkwuoiutiuytciuyik@xxxxxxxxxxxxxxxxx> wrote:

"Mechanical analysis of infant carrying in hominoids"
http://springerlink.com/content/q77m6056jm25230h/fulltext.html

An interesting study of a little-known subject and with consequences
for both hairy and naked bipeds.

At last -- and for the first time since Darwin --
some glimmers of elementary common sense
in this 'discipline'. I was saying this ten
years ago.

Credit where credit's due.
And that was one of the reasons I posted it here, expecting that you
would be the first one to jump on it. ;-)

" . . . It should be stressed that in a scenario with bipedalism emerging
for safe infant carrying, the selective pressure would act particularly
on females. . . . . The many scenarios invoked previously for bipedalism
evolution . . . neither take into account the problem of infant carrying
. . . . The difficulties in locomotion and food gathering for biped females
carrying infants may well be at the origin of the necessity of group
cooperation, which could initially have been among females, with males
in their usual role of primate group protection. . . "

One of the first steps in the road to bipedalism
was the putting down of the infant by the
mother.

Unless you assume that the infant was still able to cling to the
mother in an orthograde posture, carried over the hip as in gibbons
and orangutans. But that would require longer and thicker hair than in
Pan and Gorilla, and this would not be parsimonious in light of hair
reduction and larger body size in Homo.

Infant altriciality evolved at the same
time as bipedalism, some 5 to 6 mya. It had
nothing to do with brain size, and was merely
a selected adaptation. All these behaviours
started when an isolated group of 'chimps'
began to sleep in the ground, and got away
from sleeping trees. This could only have
happened in a habitat free from nocturnal
predators.

But the problem with your and other scenario's is that
australopithecines are already a widely distributed taxon, from Bahr
el Ghazal to Sterkfontein, at the time they would still have been a
vulnerable group, presumably without the advanced culture of Homo, and
part of a fauna that included large-bodied predators.

Gerrit
.