Isotopic evidence of early hominin diets

[Gerrit Hanenburg]

Isotopic evidence of early hominin diets.
http://www.pnas.org/content/early/2013/05/31/1222579110

Abstract:
Carbon isotope studies of early hominins from southern Africa showed
that their diets differed markedly from the diets of extant apes. Only
recently, however, has a major influx of isotopic data from eastern
Africa allowed for broad taxonomic, temporal, and regional comparisons
among hominins. Before 4 Ma, hominins had diets that were dominated by
C3 resources and were, in that sense, similar to extant chimpanzees.
By about 3.5 Ma, multiple hominin taxa began incorporating
13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their
diets and had highly variable carbon isotope compositions which are
atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern
Africa diverged toward C4/CAM specialization and occupied an isotopic
niche unknown in catarrhine primates, except in the fossil relations
of grass-eating geladas (Theropithecus gelada). At the same time,
other taxa (e.g., Australopithecus africanus) continued to have highly
mixed and varied C3/C4 diets. Overall, there is a trend toward greater
consumption of 13C-enriched foods in early hominins over time,
although this trend varies by region. Hominin carbon isotope ratios
also increase with postcanine tooth area and mandibular
cross-sectional area, which could indicate that these foods played a
role in the evolution of australopith masticatory robusticity. The
13C-enriched resources that hominins ate remain unknown and must await
additional integration of existing paleodietary proxy data and new
research on the distribution, abundance, nutrition, and mechanical
properties of C4 (and CAM) plants.

Diet of Australopithecus afarensis from the Pliocene Hadar Formation,
Ethiopia.
http://www.pnas.org/content/early/2013/05/31/1222559110

Abstract:
The enhanced dietary flexibility of early hominins to include
consumption of C4/crassulacean acid metabolism (CAM) foods (i.e.,
foods derived from grasses, sedges, and succulents common in tropical
savannas and deserts) likely represents a significant ecological and
behavioral distinction from both extant great apes and the last common
ancestor that we shared with great apes. Here, we use stable carbon
isotopic data from 20 samples of Australopithecus afarensis from Hadar
and Dikika, Ethiopia (>3.4�2.9 Ma) to show that this species consumed
a diet with significant C4/CAM foods, differing from its putative
ancestor Au. anamensis. Furthermore, there is no temporal trend in the
amount of C4/CAM food consumption over the age of the samples
analyzed, and the amount of C4/CAM food intake was highly variable,
even within a single narrow stratigraphic interval. As such, Au.
afarensis was a key participant in the C4/CAM dietary expansion by
early australopiths of the middle Pliocene. The middle Pliocene
expansion of the eastern African australopith diet to include
savanna-based foods represents a shift to use of plant food resources
that were already abundant in hominin environments for at least 1
million y and sets the stage for dietary differentiation and niche
specialization by subsequent hominin taxa.

Stable isotope-based diet reconstructions of Turkana Basin hominins.
http://www.pnas.org/content/early/2013/05/31/1222568110

Abstract:
Hominin fossil evidence in the Turkana Basin in Kenya from ca. 4.1 to
1.4 Ma samples two archaic early hominin genera and records some of
the early evolutionary history of Paranthropus and Homo. Stable carbon
isotopes in fossil tooth enamel are used to estimate the fraction of
diet derived from C3 or C4 resources in these hominin taxa. The
earliest hominin species in the Turkana Basin, Australopithecus
anamensis, derived nearly all of its diet from C3 resources.
Subsequently, by ca. 3.3 Ma, the later Kenyanthropus platyops had a
very wide dietary range�from virtually a purely C3 resource-based diet
to one dominated by C4 resources. By ca. 2 Ma, hominins in the Turkana
Basin had split into two distinct groups: specimens attributable to
the genus Homo provide evidence for a diet with a ca. 35/65 ratio of
C3- to C4-based resources, whereas P. boisei had a higher fraction of
C4-based diet (ca. 25/75 ratio). Homo sp. increased the fraction of
C4-based resources in the diet through ca. 1.5 Ma, whereas P. boisei
maintained its high dependency on C4-derived resources.

"savanna-based foods"?
Now, that wouldn't be shellfish, would it?

[RichTravsky]

And on a related note

http://www.pnas.org/content/early/2013/05/31/1222571110
Diet of Theropithecus from 4 to 1 Ma in Kenya

[Claudius Denk]

> Overall, there is a trend toward greater
> consumption of 13C-enriched foods in early hominins over time,
> although this trend varies by region. Hominin carbon isotope ratios
> also increase with postcanine tooth area and mandibular
> cross-sectional area, which could indicate that these foods played a
> role in the evolution of australopith masticatory robusticity.

This evidence proves, as predicted by my Ecological Gatekeeper
Hypothesis, that hominids were, originally, limited to the lushest
garden habitat. This strategy, locating themselves in the lushest
habitat of the greater savanna, was their method of surviving the dry
season (and it's dramatic food-competitor and predatory factors).
This proves that the savanna notion that bipedalism arose as as a
means of travelling from one location to the next is nonsense.
Bipedalism is more directly related to the necessity of them
maintaining a perimeter between themselves and the encroaching food
competitor species by way of rock throwing and threat displays.
Masticatory robusticity is itself a strategy to survive the dry season
as they began to expand their territory into the less lush parts of
their communal locality and, therefore, have to deal with dryer and
harder foods.

The evidence is clear. Conventional theory is convoluted and,
otherwise, just wrong.

[RichTravsky]

The middle Pliocene expansion of the eastern African australopith diet
to include savanna-based foods represents a shift to use of plant food
resources that were already abundant in hominin environments for at

least 1 million y ...

"already abundant"

[Claudius Denk]

Yeah so?

[RichTravsky]

That means they were already there - duh - and so independent of the
conditions your "scenario" requires.

[Claudius Denk]

LOL. The conditions of my scenario go back to the beginning of the late Miocene, about 8.1 mya--with the beginnings of the Monsoon climate that underlies the origins of savanna habitat. If I remember, the Pliocene began about 4 or 5 mya (look it up). Species (any species) generally won't adopt new foods/resources unless these food/resources are, uh, "already abundant."

[RichTravsky]

Then you admit your "hypothesis" has nothing to do with this paper.

[Claudius Denk]

LOL. Once again, your desperation is showing.

[RichTravsky]

LOL, your stupidity is showing.