Re: erectus (or their immediate ancestors) were parttime divers? (Re: A critique of the BBC aquatic ape programme and the transcript.

"Rick Wagler" <taxidea3@xxxxxxx> wrote:

>> Algis, H.erectus had unexpectedly dense bones *for his size*!
>> The traditional PA "explanations" are clearly ridiculous: bee-brood
>> eating, vitamin intoxication (a whole species intoxicated :-D),
>> head-banging & other nonsense.
>> IOW, there's no alternative explanation as the one we see in other
>> thick-boned mammals. Why on earth can't something that is true for other
>> mammals not be true for our ancestors??
>> We know Homo 1.8 Ma had dispersed to Java in the East & to Ain-Hanech in
>> the West. Why do you believe they had not followed the coasts?? If they
>> did follow the coasts, why should they not have collected sea foods??
>> including through diving? If they dived parttime, why would they not have
>> acquired to some extent some typical features of slow diving species,
>> incl.somewhat thicker bones?

>You appear to be usung the words "dense" and
>"thick" interchangeably. 'Thick" is an expression
>of linear dimension. Dense is an expression of
>mass per unit volume. What evidence do you
>have that erectus bone was denser than the bone
>of other hominids?

H. erectus obviously had relatively thicker bones than modern humans.
When quantified as percent cortical area (%CA = relative cortical
thickness around the entire cross section) of the femur then H.
erectus with an mean value of 83.7 (n=9) is significantly different
from modern H. sapiens (71.3, n=322). but there is almost complete
overlap with regard to range (71-91 and 47-88 respectively).

>As for thick the dimensions of
>the WT-17000 skeleton (Nariokotome Boy) would
>appear to belie this.

Indeed, femoral %CA of WT 15000 with a value of 69.6 is close to
average modern human. But mind its juvenile status.
On the other hand, if Homo erectus juveniles were gracile relative to
adults then a biomechanical reason for increased robusticity in adults
is a viable explanation.

>So what exactly are you
>trying to argue? And how is the desnsity - properly
>defined - of fossil bone determined?

It can possibly be determined at the microscopic level as the number
of cells per unit area (less cell space relative to matrix would mean
denser bone).
Bone of Homo erectus has been studied at the microscopic level in
KNM-ER 1808 and the non-pathological section of this individual does
not suggest significant differences in cell density between H. erectus
and modern H. sapiens.

Gerrit

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