Re: New Hominid Fossil Finds In Ethiopia, 3.5-3.8 mya




Op 12-07-2007 07:59, in artikel 4695C356.B76C3346@xxxxxxxxxxxxxxx, Rich
Travsky <traRvEsky@xxxxxxxxxxxxxxx> schreef:

claudiusdenk@xxxxxxxxxxxxx wrote:

Dr Haile-Selassie said the new dig sites yielded the bones of many
monkeys, antelopes and wild pigs, suggesting that the hominids lived
in a far greener and more wooded countryside than the bare stony Afar
desert region seen today.

What, no oyster shells?

You do you think that??

No, no, my boy: green & wooded, nicely confirming our scenario in our TREE
paper (google "aquarboreal"):

Australopithecine lifestyle
It has become increasingly clear that most, if not all, hominids dwelt in
?wet¹ rather than ?dry¹ habitats, and there is little doubt that the early
australopithecines of between four and three million years ago dwelt in
well-wooded and even forested milieus such as swampy woodlands or streamside
forests. For example, Radosevich and co-workers, in a paper on
Australopithecus afarensis from Hadar, East Africa, said: ?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 woodland¹6. In addition, Rayner and co-workers
wrote that the A. africanus fossils of Makapansgat, South Africa, were found
in ?very different conditions from those prevailing today. Higher rainfall,
fertile, alkaline soils and moderate relief supported significant patches of
sub-tropical forest and thick bush, rather than savannah ... sub-tropical
forest was the hominins¹ preferred habitat rather than grassland or
bushveld, and the adaptation of these animals was therefore fitted to a
forest habitat¹7. Tobias, on the same species, recently wrote:
?From Sterkfontein, suggestions of greater woodland cover at the time when
Australopithecus was deposited in Member 4, had emerged from studies on
fossil pollen, but these were not compelling. Then Wits team member Marian
Bamford identified fossil vines or lianas of Dichapetalum in the same Member
4: such vines hang from forest trees and would not be expected in open
savannah. The team at Makapansgat found floral and faunal evidence that the
layers containing Australopithecus reflected forest or forest margin
conditions. From Hadar, in Ethiopia, where ?Lucy¹ was found, and from Aramis
in Ethiopia, where Tim White¹s team found Ardipithecus ramidus, possibly the
oldest hominid ever discovered, well-wooded and even forested conditions
were inferred from the fauna accompanying the hominid fossils. All the
fossil evidence adds up to the small-brained, bipedal hominids of four to
2.5 million years ago having lived in a woodland or forest niche, not
savannah¹5.
The later robust australopithecines of two to one million years ago, lived
in more open, though not treeless, environments, apparently near riverbanks,
lake margins and reedbeds. For example, Kromdraai A. robustus was found near
grassveld and streamside or marsh vegetation, in the vicinity of quail,
pipits, starlings and swallows, as well as parrots, lovebirds and similar
psittacine birds19. Turkana A. aethiopicus was discovered in ?overbank
deposits of a large perennial river¹, amid water- and reedbucks20.
Chesowanja A. boisei lay in a lagoon amid exclusively aquatic species21.
?Abundant root casts ? suggest that the embayment was flanked by reeds and
the presence of calcareous algae indicates that the lagoon was warm and
shallow. Bellamya and catfish are animals tolerant of relatively stagnant
water ?¹21.
This impression of marsh vegetation ­ the early australopithecines in more
wooded and the robusts in more open milieus ­ is compatible with all other
information we have on australopithecines: postcranial skeleton, masticatory
and dentitional data, enamel microwear, strontium/calcium ratios, and
isotopic evidence.
Fossilized footprints and skeletal remains suggest that australopithecines
were bipedal, though their short-legged style of bipedalism was different
from that seen in humans22, and apparently included a somewhat
forward-leaning trunk posture23. The StW 573 foot ?had both bipedal and
climbing adaptations. This skeleton¹s foot morphology is consistent with the
bipedal Laetoli footprints, which are not those of fully human feet, but
which have very clear ape-like morphology¹ xxx. Other tree-climbing features
in early australopithecines include the apelike upward directed shoulder
joints (glenoid fossae) and curved finger and toe phalanges, whereas such
features are less obvious in the later robusts.

Dental studies suggest that whereas gracile australopithecines preferred
softer fruits and vegetables, the robusts¹ diet included harder food
items24-28,pp. Estimates of robust australopithecine bite force suggest
?low-energy food that had to be processed in great quantities¹ and food
objects ?hard and round in shape¹29. DuBrul noticed striking dental
parallelisms between the robust australopithecines and the bamboo-eating
giant panda (broad, high and heavy cheekbones, reduced prognathism and front
teeth, very broad molar teeth, premolar molarization), particularly when
compared to gracile australopithecines and non-panda bears respectively25.

Students of fossil hominid teeth agree that broad molars with thick enamel
and rounded cusps, while unsuitable for the regular processing of tough
foods like leaves or meat, are suitable for the processing of hard food
items. Papyrus and reed were abundant 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 hominoidspp. Gorillas eat
sedges and bamboo shoots and stalks, all African hominids eat cane,
chimpanzees and humans eat water lilies, and rice and other cereals are
staple food for humans. Supplementing their diet with harder parts of plants
possibly helped the robusts to bridge the dry season, when fruits and soft
vegetables were scarcer.

Studies of dental enamel microwear provide further details. In the early A.
afarensis (Garusi-Laetoli and Hadar), the cheekteeth enamel has a typical
glossy polished surface and the microwear has resemblances to that of
capybaras and mountain beavers30. These animals are semi-aquatic rodents
that feed mainly on succulent marsh and riverside herbs, as well as grasses
and the bark of young trees. It has recently become clear that Western
lowland gorillas spend some time eating what researchers call AHV (aquatic
herbaceous vegetation) such as Hydrocharitaceae herbs and Cyperaceae
sedges3.
Comparisons of molar enamel in South African fossils show that A. robustus
ate substantially more hard food items than the earlier A. africanus31.
Incisal microwear suggest that A. robustus may have ingested foods that
required less extensive incisal preparation than the foods consumed by A.
africanus32, and incisal reduction in A. robustus also suggests a less
frugivorous diet, since ?incisors need not be employed in the manipulation
of hard objects¹33.
The enamel of the East African robusts (A. boisei of Olduvai and Peninj)
displays more pits, wide parallel striations and deep recessed dentine27,pp.
This microwear pattern has some resemblances with that of beavers, which
feed on riverine and riverside herbs, the roots of water lilies, bark and
woody plants. It thus seems probable that an early australopithecine diet of
fruits (larger front teeth) and aquatic herbs (polishing) was supplemented
with woody plants in the robusts (more wear). The suggestion of Walker, that
A. boisei KNM-ER 406 and 729 were bulk-eaters of ?small, hard fruits with
casings, pulp, seeds and all¹26, could explain the deep recessed occlusal
dentine, but not the glossy appearance of the heavily polished enamel, which
is more typical of marsh plant feeders27,30. In terrestrial grazers, tooth
wear is very different34. In sheep, for instance, the occlusal wear facets
are not rounded.
These microwear data are consistent with the strontium/calcium ratios35, as
well as with the isotopic data of South African australopithecines34. Apart
from partial carnivory, Sillen provides two possible explanations for the
low Sr/Ca ratios of A. robustus: eating leaves and shoots of forbs and woody
plants, and eating food derived from a wet microhabitat, for instance, from
well-drained streamside soils35. Sillen as well as Sponheimer and Lee-Thorp,
following ?hunting hypotheses¹, prefer the regular consumption of animal
food as an explanation for the Sr/Ca ratios and the isotopic data in A.
robustus35,34, rather than considering ­ in our opinion the more logical
explanation ­ that they might have eaten invertebrates as well as
cyperaceous sedges and other marshland plants. Sponheimer and Lee-Thorp 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 both¹34. Since terrestrial grasses are incompatible with
the polished, rounded microwear30,34, and predominant meat-eating is
unlikely in view of the blunt, huge and broad cheekteeth25,26,36, their diet
more probably included marshland plants such as Cyperaceae, as is indicated
by several very different studies27,30,34,35,pp.
Several independent lines of evidence ­ paleo-milieu, postcranial skeleton,
dental morphology, enamel microwear, Sr/Ca ratios, isotopic data ­ suggest
that some or all australopithecines regularly waded bipedally in search of
plants growing in and near shallow waters. They might have waded in much the
same way as living hominid species such as bonobos and Western gorillas do
today (Figure 4), only much more frequently2,3. This does not exclude the
possibility, however, that early hominids, including some australopithecine
species, might have processed and consumed animal food when available37,38.





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