Re: Bipedalism and the Terrestrial Sifaka Theory

Gerrit Hanenburg (
Fri, 7 Jul 1995 19:51:43 GMT

Dave B. wrote:

>While watching sifakas on a David Attenborough program, a few thoughts
>occurred to me. First, sifakas seem to have proportionally longer legs than
>most primates. Second, sifakas always travel bipedally on the ground. Is it
>possible that the development of sifaka bipedalism could be similar to that
>of the first hominids? Has this ever been considered? I'm not exactly sure of
>the estimated size of the first hominids, so perhaps this idea is not very
>realistic. How big are those hominids thought to be? And how big were the
>most recent apes before the gap in the fossil record? In my semi-ignorant
>state, it seems to me that sifaka bipedalism could potentially lead to some
>reasonable speculations about our own bipedalism.

The manner of bipedalism in sifakas (family:Indriidae) is different
from that in humans.Sifakas move by jumping with their arms spread to
the sides on the level of the shoulder or higher and the upper part of
the body slightly tipping backwards.They don't move with a humanlike
alternating stridepattern.The mechanics of jumping is very different
from "real" bipedalism as in humans,so I don't think it is likely that
jumping ,as in sifakas, could have been the onset for "genuine"
Despite this I do think the TST deserves more credit than the AAT. :-)