Re: Australopithecus afarensis vs. chimps

From: Andrew Nowicki (andrew_at_nospam.com)
Date: 07/30/04 

Date: Fri, 30 Jul 2004 15:15:37 +0200

Marc Verhaegen wrote:

Andrew Nowicki wrote:

> its (Australopithecus afarensis) hands were very weak...

Marc Verhaegen wrote:

> Ah??

Andrew Nowicki wrote:
 
> ...and its legs were very powerful.

Marc Verhaegen wrote:

> Ah?

O.K. I exaggerated, but it is fair to say that it
had relatively weak hands and relatively strong
legs. I looked at a painting of the Australopithecus
afarensis by John Gurche (http://www.gurche.com).
It looks almost like Arnold Schwarzenegger below
the neck. Male chimps weigh about as much as modern
humans, but their hands are *much* stronger than
human hands.

Andrew Nowicki wrote:

> Both species could use sticks and stones as tools.

Marc Verhaegen wrote:

> Chimps, yes. Apiths probably, but no direct information.

The material from Turkwel includes several wrist
bones (WT 22944), which Carol Ward describes as very
humanlike, specifically lacking any knucklewalking
adaptation. It seems natural that such a dexterous
hand could use sticks and stones.

Andrew Nowicki wrote:

> The Australopithecus afarensis fossils were found in open habitats: dry
> bushland, riparian woodland, and riverine forest habitats.

Marc Verhaegen wrote:

> open? dry??

K.E. Reed, "Early hominid evolution and ecological
change through the African Plio-Pleistocene," J. Hum.
Evol. 32 (1997) 289-322.

...claims well-watered, wooded paleoenvironments, but
a good review:

J. Anat. (2000) 196, pp. 19±60, "Human evolution:
taxonomy and paleobiology," by Bernard Wood and
Brian G. Richmond claims the opposite on page 30:
"Paleohabitat. Paleoenvironmental reconstructions
suggest that A. afarensis inhabited a mosaic environment.
Evidence from Hadar suggests a mixture
of dry bushland, riparian woodland, probably with
seasonal floodplains, and riverine forest habitats
(Johanson et al. 1982; Reed & Eck, 1997). One
reconstruction of Laetoli suggests open grassland,
with closed-woodland nearby (Harris, 1987), but
others interpret the same evidence as indicating a
much more wooded environment (Andrews, 1989)."

Marc Verhaegen wrote:

> - Stern & Susman: the small spms had curved phalanges as in apes:
> they often climbed trees arms overhead.

It does not surprise me. I believe that most of their
food grew on trees.

Marc Verhaegen wrote:

> - Radosevich cs.1992: Hadar AL.333: "The bones were found in swale-like
> features ... it is very likely that they died and partially rotted at or
> very near this site ... this group of hominids was buried in streamside
> gallery woodland."

My time machine is out of order, so I cannot check it
out, but the "gallery woodland" looks like a reasonable
compromise. I doubt that the bipedal Australopithecus
afarensis could compete with chimps in a dense rainforest.
They were more likely to live in a place that was marginal
habitat for the chimps.

Andrew Nowicki wrote:

> Chimps had much stronger hands and were better tree climbers,
> so they could easily shoo the Australopithecus afarensis
> interlopers who attempted to feed in a forest occupied by
> the chimps. The big question is why the Australopithecus
> afarensis survived

Marc Verhaegen wrote:
 
> Ah? Where do you see their descendants? gorillas?

Immediate descendants: Australopithecus africanus
Final descendants: humans

> - Ryan & Johanson 1989: "Incisal dental microwear in A.afarensis is most
> similar to that observed in Gorilla."
> - Johanson & Edey 1981: The composite skull reconstructed mostly from
> A.L.333 specimens "looked very much like a small female gorilla."
> - Schoenemann 1989 :"A.afarensis is much more similar cranially to the
> modern African apes than to modern humans."
> - Ferguson 1987: the type spm A.afarensis: "the lower third premolar of LH-4
> is completely apelike."
> - Kimbel cs.1984: "assertion that the lateral inflation of the A.L.333-45
> mastoids is greater than in any extant ape is incorrect if the fossil is
> compared to P.troglodytes males or some Gorilla mates and females. Moreover,
> the pattern of pneumatization in A.afarensis is also found only in the
> extant apes among other hominoids." ... "Prior to the identification of
> A.afarensis the asterionic notch was thought to characterize only the apes
> among hominoids. Kimbel and Rak relate this asterionic sutural figuration to
> the pattern of cranial cresting and temporal bone pneumatization shared by
> A.afarensis and the extant apes."

What is your point? Are you saying that at that
same time (3MYA) another, more advanced hominid
lived in Africa and it became our ancestor?

Marc Verhaegen wrote:

> Andrew, you're making up stories...

I do. I improve my stories as I learn more facts.
We do not know which story is true, so the best
approach is to elaborate all stories until they
are mature enough to be confirmed or disproved by
evidence. An intelligent paleontologist is the one
who publishes two mutually exclusive stories of
human evolution at the same time.

My main point is that Australopithecus afarensis
could not compete with antelopes and chimps unless
it did something that neither antelopes nor chimps
could do. Ground nest making is the most obvious
explanation. When making the nest, Australopithecus
afarensis probably tossed smaller sticks on top of
the nest. After many generations it must have become
proficient stick tosser and it probably used this
skill to harass predators, chimps, and other
competitors. The nest was a safe hiding place, so a
lone apith could forage in the vicinity of the nest
and exploit its low density food sources, such as
the gallery forest. When a lion prowled the gallery
forest, the apiths screamed "danger" and retreated
into the nests. There was nothing for the lion to
eat. No apiths, no antelopes, no chimps. A gallery
forest surrounded by a desert was a perfect habitat
because there were no competitors and no predators.