Re: beach & brain (was Re: DHA ... savannah and bipedalism.

From: Andrew Nowicki (andrew_at_nospam.com)
Date: 07/24/04 

Date: Sat, 24 Jul 2004 17:50:04 +0200

Marc Verhaegen wrote:

> I don't know when fire use evolved (earlier than 1.5 Ma?) & how important it
> was, but it might well have been very important (for Homo, not for apiths of
> course: enamel micro-wear suggests most apiths ate predom.wetland plants).

"Grasses have large quantities of silica crystals in their
cells which scratch tooth enamel. Browsing animals feed on
the leaves, branches and fruits of trees and bushes. These
plant materials have fewer silica crystals in their cells,
and a more finely polished tooth surface results. Omnivorous
animals, eating meats as well as plant material, scratch their
teeth heavily when biting into bone."
http://www.yale.edu/ynhti/curriculum/units/1979/6/79.06.02.x.html

"Little is known about the diets of hominids that predate the
Homo genus, because these hominids did not leave archeological
traces such as 'kitchen middens' and stone tools. Consequently,
researchers have made inferences concerning hominid diet on the
basis of craniodental morphology, gross dental wear, and dental
microwear. The current consensus is that the 3-million-year-old
Australopithecus africanus hominid subsisted on fruits and
leaves, similar to the modern chimpanzee. Early hominid diets
are of some theoretical significance, since one current view is
that the emergence of the more intelligent Homo genus depended
on the consumption of high-quality animal foods that made
possible biological changes resulting in the evolution of a
larger brain.
        M. Sponheimer and J.A. Lee-Thorp (1999) now report a
stable carbon isotope analysis of A. africanus fossils from
Makapansgat Limeworks, South Africa. The authors sampled 4 of
the 14 Australopithecus africanus individuals that have been
unearthed at that location, and also analyzed the dental enamel
of associated 3-million year old animals (65 individual animals
from 19 mammalian taxa) in order to place A. africanus within a
broader ecological context. The authors report their results
demonstrate that A. africanus ate not only fruits and leaves,
but they also ate large quantities of carbon-13 enriched foods
such as grasses and sedges, or they ate animals that ate these
plants, or both. The authors suggest their results indicate
that early hominids such as A. africanus regularly exploited
relatively open environments such as woodlands or grasslands
for food, and that early hominids may have consumed high-quality
animal foods before the development of stone tools and the
origin of the genus Homo. (Science Week April 1999)"
http://cogweb.ucla.edu/ep/Paleoanthropology.html
http://aeroman.de/html/paleoanthropology.html

"Marc Verhaegen & Stephen Munro – 23 July 1999 (excerpt)
        Sponheimer & Lee-Thorp (1999) say that A. africanus
‘ate not only fruits and leaves but also large quantities of
carbon-13-enriched foods such as grasses and sedges or
animals that ate these plants, or both’. Since terrestrial
grasses are incompatible with the polished microwear (e.g.
Sponheimer & Lee-Thorp 1999, Puech et al. 1986), and regular
meat-eating is incompatible with the small front teeth and
the huge and broad cheekteeth (e.g. Wood & Aiello 1998,
DuBrul 1977, Walker 1981), their diet more probably included
marshland plants such as Cyperaceae, as is shown by the very
different studies by Puech (1992), Sillen (1992) and
Sponheimer & Lee-Thorp (1999)."
http://allserv.rug.ac.be/~mvaneech/Verhaegen.html

"Diet and the evolution of the earliest human ancestors,
Mark F. Teaford*† and Peter S. Ungar‡
Proc Natl Acad Sci U S A. 2000 December 5; 97 (25):
13506–13511 Anthropology (Biological Sciences) (excerpt)
        As for the early hominids, A. africanus had more
occlusal relief than did Paranthropus robustus, suggesting
a dietary difference between these species (30). Additional
preliminary shearing quotient studies support this idea
while reaffirming that the australopithecines, as a group,
had relatively flat, blunt molar teeth and lacked the long
shearing crests seen in some extant hominoids (28). By
itself, this indicates that the earliest hominids would
have had difficulty breaking down tough, pliant foods, such
as soft seed coats and the veins and stems of leaves—
although they probably were capable of processing buds,
flowers, and shoots.
        Interestingly, as suggested by Lucas and Peters
(46), another tough pliant food they would have had
difficulty processing is meat. In other words, the early
hominids were not dentally preadapted to eat meat—they
simply did not have the sharp, reciprocally concave
shearing blades necessary to retain and cut such foods.
In contrast, given their flat, blunt teeth, they were
admirably equipped to process hard brittle objects. What
about soft fruits? It really depends on the toughness of
those fruits. If they were tough, then they would also
need to be precisely retained and sliced between the
teeth. Again, early hominids would be very inefficient
at it. If they were not tough, then the hominids could
certainly process soft fruits."
http://www.cast.uark.edu/local/icaes/conferences/wburg/posters/pungar/satalk.htm
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=17605

"A. afarensis were eating fibrous material. This type of
tooth wear is indicative stripping leaves. Broken enamel
also indicates that they were eating hard foods such as
nuts as well. Microwear on anterior teeth in the form of
microstriations suggests they were using their front
teeth to strip vegetation."
http://anthroclass.com/lectures/anlec/class12.html

The majority view is that A. afarensis inhabited a mosaic
environment, a mixture of dry bushland, riparian woodland,
probably with seasonal floodplains, and riverine forest
habitats. A. africanus lived in dry woodland, with grassland
beyond.

____________________________________________________________

My comment:

A. afarensis may have eaten buds, flowers, and shoots of
marsh plants, but A. africanus did not. A. africanus ate
meat but its teeth do not look like teeth of an animal
which ate raw meat.

Homo have smaller masticatory apparatus than Apiths. This
may be explained as Apiths eating smaller, fried animals
(snakes, lizards, and insects) along with their bones. It
would take too much time to remove the bones and skin, so
the Apiths ate these small animals whole.

I am not a professional paleontologist, so I may be wrong,

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