Re: Hominid Diet Examined

Thank you very much, Travsky. This again beautifully confirms our views on
apith diets.

>From a paper with prof.Puech (one of the very first to investigate afarensis
enamel electromicroscopically, see refs below):

"Hominid Lifestyle and Diet Reconsidered: Paleo-Environmental and
Comparative Data"
Marc Verhaegen & Pierre-François Puech 2000
Musée de l'Homme à Paris, BP 191, 30012 Nîmes 4, France
Human Evolution 15: 151-162
(the whole paper can be found at
http://allserv.rug.ac.be/~mvaneech/Verhaegen.html )
.... Dental studies suggest that whereas gracile australopithecines preferred
softer fruits and vegetables, the robusts' diet included harder food items
(e.g. Robinson, 1954; Du Brul, 1977; Walker, 1981; Puech, 1992; Lee-Thorp et
al., 1994). Estimates of robust australopithecine bite force suggest
'low-energy food that had to be processed in great quantities' and food
objects 'hard and round in shape' (Demes & Creel, 1988). Du Brul (1977)
noticed dental isms between the robust australopithecines and the
bamboo-eating giant panda Ailuropoda melanoleuca (broad, high and heavy
cheekbones, reduced prognathism and front teeth, broad back teeth, premolar
molarisation), as opposed to gracile australopithecines, respectively
non-panda bears.
Papyrus and reed were present in the paleo-environment of the later
australopithecines (e.g. Olduvai, Chesowanja, Kromdraai), and Cyperaceae and
Gramineae are part of the diet of living African hominoids. Gorillas eat
sedges and bamboo shoots and stalks, gorillas and chimpanzees eat cane,
chimps and humans eat water lilies, and rice and other cereals are staple
food for humans. Supplementing their diet with parts of grasslike plants
might have been enabled the robusts to bridge the dry season, when fruits
and soft vegetables were scarce.
Studies of dental enamel microwear provide other details. In the early
australopithecines of Garusi-Laetoli and Hadar (A. afarensis 4-3 Myr BP),
the cheekteeth enamel has a polished surface and the microwear looks like
that of the capybara Hydrochoerus hydrochaeris and that of the mountain
beaver Aplodontia rufa (Puech et al., 1986). These animals are semi-aquatic
rodents that feed mainly on sappy marsh and riverside herbs, grasses and
bark of young trees. It has recently become clear that Western lowland
gorillas G. g. gorilla spend some time eating aquatic herbaceous vegetation
(AHV) like Hydrocharitaceae herbs and Cyperaceae sedges (Doran & McNeilage,
1997).
Comparisons of molar enamel in South African fossils show that A. robustus
ate substantially more hard food items than A. africanus (Grine & Kay,
1988). Incisal microwear suggests that A. robustus may have ingested foods
that required less extensive incisal preparation than the foods consumed by
A. africanus, such as fruits (Ungar & Grine, 1991), and 'incisors need not
be employed in the manipulation of hard objects' (Ungar & Grine, 1989).
The enamel of the East African robusts (Olduvai and Peninj) displays more
pits, wide parallel striations and deep recessed dentine, resembling that of
the beaver Castor fiber, that eats riverine and riverside herbs, roots of
water lilies, bark and woody plants in a temperate climate. 'Many food
plants growing in marsh land and indeed many grasses, have high
concentrations of siliceous particles known as opal phytoliths. The
consumption of such foods produces a great deal of wear, and the enamel and
dentine have a blunted appearance. Ancient Egyptians ate papyrus shoots
(Puech et al., 1983b) and we suppose that [O.H.16] did the same with swamp
margin plants' (Puech, 1992). Whereas the East African robusts seem to have
had aquatic plants and papyrus shoots in their diet and ate more woody
plants than the earlier australopithecines, habilis O.H.16 apparently
supplemented the AHV of the earlier australopithecines with acid fruits
(Puech, 1984). In the habilis cheekteeth, the margins of the striae have
been polished and slightly etched, resembling the microwear of the coypu
Myocastor coypus. This rodent feeds on reed, sedges, marsh plants, fruits
and molluscs in river and lake margins. It thus seems that an early
australopithecine diet of fruits (larger front teeth) and AHV (polishing)
was supplemented with unripe fruits (acid etching) in habilis, and with
woody plants in the robusts (more wear).
The suggestion of Walker (1981) that A. boisei KNM-ER 406 and 729 were
bulk-eaters of whole fruits, 'small, hard fruits with casings, pulp, seeds
and all', could explain the deep recessed occlusal dentine, but not the
glossy appearance of heavily polished enamel, which is more typical for
marsh plant feeders. In terrestrial grazers such as sheep, tooth wear is
faster, with a different gradient and fabric-like grooves.
These microwear data are consistent with the strontium/calcium ratios in
Swartkrans fossils (Sillen, 1992). Apart from partial carnivory (rather
unlikely with the robusts' dentition, see Du Brul, 1977; Walker, 1981),
Sillen provides two possible explanations for the low Sr/Ca of A. robustus:
eating leaves and shoots of forbs and woody plants (kudu diet), and eating
food derived from a wet microhabitat, for instance, from well-drained
streamside soils.
In our opinion, the coincidence of several independent lines of evidence
(paleo-milieu, dental morphology, enamel microwear, Sr/Ca ratios) leaves
little doubt that some or all australopithecines fed regularly on AHV
growing in shallow waters, much more than Western gorillas do today
(Chadwik, 1995; Doran & McNeilage, 1997). It is conceivable that hominid
bipedality first arose in the shallow waters of gallery or mangrove or swamp
forests. 'One of the strong points about the aquatic theory is in explaining
the origin of bipedality. If our ancestors did go into the water, that would
forced them to walk upright' (Stringer, 1997). That a gradual evolutionary
transition from forest to marshland is possible is illustrated by the
Western lowland gorillas that spend some time feeding on AHV, wading
bipedally, sitting and playing in marshy forest clearings (Chadwik, 1995;
Doran & McNeilage, 1997; NDR TV film, 1997).

:-)

Marc Verhaegen

http://www.onelist.com/community/AAT

_______





"Rich Travsky" <traRvEsky@xxxxxxxxxxxxxxx> wrote in message
news:42F39C78.2AFB1864@xxxxxxxxxxxxxxxxxx
> Sez it's supposed to be in the Aug 4th Nature, but nothing on line yet...
>
>
> http://live.psu.edu/story/12922
>
> University Park, Pa. -- A Penn State researcher is part of the team that
> developed techniques that have generated insights into dietary
divergences
> between some of our human ancestors, allowing scientists to better
> understand the evolutionary path that led to the modern-day diets that
> humans consume.
>
> "Our new techniques are allowing us to get beyond simple dichotomies and
> helping us understand the processes by which dietary evolution is
> working," said Peter Ungar, professor of anthropology at the University
> of Arkansas.
>
> Ungar and Robert Scott, postdoctoral fellow at the University of
Arkansas,
> with colleagues at the Worcester Polytechnic Institute, State University
> of New York at Stony Brook, Johns Hopkins University School of Medicine
> and Penn State, report their findings in the August 4 issue of the
journal
> Nature.
>
> The researchers, including Alan Walker, Evan Pugh professor of biological
> anthropology and biology at Penn State, investigated microscopic wear on
> the teeth of two species of ancient hominims -- Australopithecus
africanus,
> which lived between 3.3 million and 2.3 million years ago, and
Paranthropus
> robustus, which lived between 2 million and 1.5 million years ago. The
pits
> and scratches found on the teeth offer a visual history of the type of
food
> consumed by the tooth's owner. Pits indicate a diet of hard, brittle
foods,
> like nuts and seeds, while scratches imply a diet of tough foods, like
> leaves and possibly meat.
>
> Traditional examinations of these ancient teeth -- counting pits and
lines
> on a black and white electron micrograph image -- suggested that A.
> africanus ate tough foods and P. robustus dined on hard, brittle fare.
> However, the researchers used a new technique developed by Ungar and his
> colleagues that combines engineering software, scale-sensitive fractal
> analysis and a scanning confocal microscope to create a reproducible
texture
> analysis for teeth -- and the analysis tells a more complete story. The
> researchers looked at both roughness, or complexity, and directionality
in
> the teeth they examined.
>
> "Since food objects interact with teeth, we have different kinds of
> complexity in different diets. Directionality also correlates with diet,"
> Scott said. Hard foods like nuts and seeds tend to lead to more complex
tooth
> profiles, while tough foods like leaves lead to more scratches, which
> corresponds with directionality.
> ...
> The analysis showed that the two species had significant amounts of
overlap in
> their diets and that while P. robustus had more complexity in its tooth
wear,
> indicating that it ate more hard and brittle foods than A. africanus, it
ate
> tough foods as well.
>
> The researchers believe that this indicates that the species frequently
ate the
> same types of foods, but that in times of scarcity or seasonal changes,
P.
> robustus changed its diet to include foods that differed from those of A.
> africanus.
>
> "The difference in their evolution in terms of diet is not driven by
their
> preferences, but by scarcity," Ungar said. "It gives you a whole new way
of
> thinking about dietary adaptation."
> ...
>
>
> scarcity...


.

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