Re: Bone density in mustelids

Rich Travsky <traRvEsky@xxxxxxxxxxxxxxx> wrote in
news:475599BF.6A59F7E5@xxxxxxxxxxxxxxx:

Mujin wrote:
Marc Verhaegen <m_verhaegen@xxxxxxxxx> wrote in
Op 03-12-2007 03:34, in artikel
65242200-57e1-4fcc-91a0-e740aa97b3ff@xxxxxxxxxxxxxxxxxxxxxxxxxxxx,
Lee Olsen <paleocity@xxxxxxxxxxx> schreef:

On Dec 2, 4:36 pm, Marc Verhaegen <m_verhae...@xxxxxxxxx> wrote:
FE Fish & BR Stein 1991 Zoomorphol.110:339-345
Functional correlates of differences in bone density among
terrestrial and aquatic genera in the family Mustelidae
(Mammalia)

"the costs of maintaining an increased skeletal mass increases
according to locomotor function as follows : swimmers, sedentary
forms, slow runners, fast runners, and flyers"
No reason why erectus must be an exception, IOW, the H.erectus
endurance running hypothesis is pure nonsense.

Of course the fallacy in wet ape thinking is that Homo e has to
run as fast as a today's
marathon runners to catch a kudu, when in fact one does not. Nor
does
one have to
run fast to catch a tortoise.

So?? And??

My little boy, H.erectus has pachyostosis,

"In some specimens [of tapinocephalian] this boss is of only moderate
thickness, while in others it has become greatly thickened into a
huge mass of bone (pachyostosis). It has been suggested that these
animals engaged in intra-specific head-butting behaviour (left),
presumably for territory or mates. A similar thickening of the skull
occurs in pachycephalosaur ("boneheaded") dinosaurs, and it is
speculated that all these animals practised head-butting behaviour
like modern goats and bighorn sheep, and late Eocene Titanotheres."
http://www.kheper.net/evolution/therapsida/Tapinocephalidae.htm

In regards to pachys:

http://www.berkeley.edu/news/media/releases/2004/06/07_pachy.shtml
...
And in a paper appearing in the spring 2004 issue of the journal
Paleobiology, they conclude that the radiating structures associated
with the spongy interior of the domes, which some have argued allowed
the dinosaur to absorb the power of a head-***, are actually typical
of fast-growing bone and are found only in young pachycephalosaurs,
not adults.

"The porous areas of the dome are associated with vascular tissue,
and some have argued that these radiating structures gave a
biomechanical advantage for head butting, or perhaps were used in
temperature regulation," said Goodwin, a UC Berkeley vertebrate
paleontologist. "But this tissue disappears in adults, who are the
ones who would have head-butted. The truth is, these structures were
involved in the development of the dome and were not built for
head-butting." ...

This link

http://www.trieboldpaleontology.com/casts/pachycephalosaur.htm

mentions in passing

The strong "U" curve of the rather dainty cervical vertebrae suggest
that head-butting may not have been possible.

Interesting stuff - and stuff I didn't know, not being up on the dinosaur
literature. So it seems my example was a poor one, since clearly the
pachycephalosaur skulls aren't strictly pachyostosis but rather
representative of rapid bone growth in juveniles. No matter, there are
plenty of other examples to draw from:

Svrba, Elizabeth and George Schaller
2000 _Antelopes, Deer and Relatives: Fossil Record, Behavioral Ecology,
Systematics and Conservation_ Yale University Press.

Chapter 2 discusses the ruminant radiation, and notes the phenomenon of
pachyostosis in a variety of fossil species.

Megaloceros species are also well known to have pachyostosis of the skull
and mandibular ramus.
http://www.lincei.it/pubblicazioni/rendicontiFMN/rol/pdf/S2004-02-07.pdf

Likewise, Dinocephalians exhibit significant pachyostosis in the cranium
and vertebrae:
http://www.jstor.org/view/00948373/di995885/99p0033t/0

The point, which of course certain posters in SAP will not get, is that
pachyostosis is not invariably associated with diving. There are, in fact,
at least two other causes: weight bearing strain (as I noted below) and
intraspecific fighting.



osteosclerosis

"Most of the sabertoothed cat vertebral specimens we studied
exhibited diffuse osteosclerosis on both conventional radiographs and
CT images." www.ajronline.org/cgi/reprint/148/4/779.pdf

Obviously, sabertooths were aqautic ;)

No, not completely aquatic. They were just beach dwelling slow divers who
fed on sessile prey like abalone. That's what the sabre-teeth were for you
know.


, medullary
stenosis

As medullary stenosis is properly a pathological condition compared
to the general population, I presume that what you mean is that
H.erectus *as a population* has greater cortical thickness and
reduced medullary cavity. Two problems:

1. To which other population are you comparing H.erectus?

2. Increased cortical thickness and decreased medullary volume don't
seem to mean what you think they mean:

"Conclusions: Running, a weight-bearing exercise, is associated with
more favorable geometric and biomechanical characteristics in
relation to bone strength, compared with the weight supported
activities of swimming and cycling. Differences may reflect skeletal
adaptations to the specific mechanical-loading patterns inherent in
these sports"
http://www.acsm-msse.org/pt/re/msse/abstract.00005768-200204000-
00018.htm;jsessionid=HJxhg51XTP76vm2Q2tjGNy9JTQCZFcv3xHG8Qh2XL470Kzjk7
kPB!- 1601909834!181195629!8091!-1

Thanks for the link.

No problem. Here's another good one:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4Y-47W67DF-
8&_user=1068138&_coverDate=01%2F31%2F1996&_rdoc=1&_fmt=&_orig=search&_sort=
d&view=c&_acct=C000051258&_version=1&_urlVersion=0&_userid=1068138&md5=94fd
eca997dee8316ed0adae90ce3d35

A subscription is required for the full article, but the main points are in
the references, esp 4, 13, and 19. The link above is a summary of various
research into the effect of stress on bone density and strength, but
references 4, 13 and 19 in the bibliography are specifically research into
the effect of certain types of exercise on human bones. Basically the
point gleaned from these is that among human athletes femur and spine bone
density is greatest in weight lifters and runners, and least in swimmers.

This is obviously contrary to what AATers (well, one anyway) are trying to
claim.


Clearly weight bearing, high impact activity increases cortical
thickness and decreases medullary cavity sizes. More importantly:

"SWIM[swimmers] and CYC[cyclists] had significantly larger (P < 0.05)
size- adjusted medullary cavity CSA than RUN[runners] and
TRI[triathletes]" (ibid)

So while you may be correct that H.erectus medullar cavity size is
smaller (than what?) the pattern appears to show that this would mean
H.erectus spent *more* time walking and running, not less.

- all these are *only* found in slow divers.

Apparently you are incorrect.

Unless you can explain these, keep your big mouth shut.

Unless you can explain why counterexamples to your "absolute"
evidence don't count, perhaps you should take your own advice?

See also


http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_ui
ds=10949001&dopt=AbstractPlus
Med Sci Sports Exerc. 2000 Aug;32(8):1373-7.
Total and regional bone density in male runners, cyclists, and
controls. ...
Conclusion: Running is associated with increased bone density,
particularly in the leg, whereas cycling is associated with a mild
decrease in bone density in the spine. In athletes who do both,
running exerts a stronger influence than cycling.

Thanks for this link, Rich. I also recall a similar study on weight
training vs cardio wrt bone density and medullary volume, but can't seem
to find it now. The conclusion was similar: weight stress on human bones
results in a thickening of the cortex and a reduction of the medullary
cavity. It's interesting that the actual mineral density doesn't seem to
change very much - just the volume of dense material.

--
Bon nou mujin sei gan dan
.

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