Wednesday, December 16, 2009

Skull density in hominids

Gauld SC 1996 AJPA 100:411-426
Allometric patterns of cranial bone thickness in fossil hominids

Skull thickness in He is more than twice that of other primates of
comparable body size, Hn is intermediate, Hs is still above most other
primates, and A.africanus is somewhat above other equally-sized primates,
but I need more figures of other apiths, esp. robust ones.

Extraordinarily thick skull vaults are typically (AFAIK exclusively) seen in
shallow slow parttime diving animals. Slow divers in sea water (density c
1.024) are expected to have much thicker skulls than those in freshwater.
Alan Shabel found that in dentitions & enamel thickness apiths resembled
mungoes & other carnivores that fed (partly) on hard-shelled invertebrates.
Might africanus (& other apiths??) have parttime dived (or ducked) for
bottom shell+crayfish in the wetlands & swamp forests where they lived??
We need a lot more measurements of skull thicknesses esp. of fossil
hominids, but also of other animals.

I made a graph (somebody did it for me) with
- x-axis = the cubic root of the body weight of different primate spp,
- y-axis = their skull thickness.
It was almost a straight line, with small spp a bit below that line,
medium-sized a bit above (esp.orang & chimp), and very large ones (gorilla)
a bit lower.
But there were 3 obvious exceptions:
- He was far above that line (but it might have been heavier than the usual
estimation of c 50 kg),
- Hs was clearly above it,
- A.africanus was also clearly above it (depending on its body weight, which
might be a bit higher IMO than usu.estimated).
Other data suggest Hn was intermediate between He & Hn, but I still lack
enough comparable data on apiths, Ardipith etc.

Does anybody know where to find more data? MV @ AAT

This fits the pattern -

early hominoid, foraging on pond surface AHV aquatic herbs, congo lowland gorillas raking high-protein hydrocharis and yanking up sedges for their rhyzomes, not dunking their faces nor seeking benthic foods, with large inflatable laryngeal air sacs for partial flotation, with lightweight skulls. Apith afarensis similar, but in Rift valley, less fruit trees, more sedges.

Apith africanus ate more water lily rhyzomes, reaching below water so smaller air sacs and denser skull, more invertebrate foods crayfish/snails and small vertebrates, more high fruit trees. Rift - So. Africa shallow lakes?

Human ancestors similar, but more tidal saltwater, lost air sacs and gained dense skull, ate tidal mangrove oysters at lagoons, more shrub berries, less high fruit trees, Medit. zone?

Myrica gale is a flowering plant native to Europe, with sweet resinous scent, and is a traditional insect repellent, used by campers to keep biting insects out of tents. Sweet Gale can grow in a narrow band in the intertidal zone, especially if it has some logs, washed down into the estuary on which to establish itself. It is a favorite food of beavers and low beaver dams can be found in the intertidal zone if sufficient sweet gale is present. The ponds thus formed are often completely submerged at high tide but retain water at low tide and provide deep enough water to provide a refuge for fish, including juvenile salmon where the water is too deep for predation by wading birds. wiki

Ear wax & Scent: Difference of appocrine sweat glands in Europeans, Africans and Asians
scent, ear wax

rice, milk, alcohol in ancient Eurasians


Gorilla hybrids, Ardi party @ Lawnchair anthropology

Molars in hominoids
Gorilla and chimp molars evert earlier than orang and human due to more forest ground foraging (parallel with knucklewalking), orang probably has primitive hominoid condition, human also but even more so do to beaver lodge - hut/cave nesting & aquatic foraging & mainly food processing & cooking.

Speaking of dense bones and waterside herbivores, article on neolithic dugong & fishing rituals:

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