Re: Homo amphibius and Hypothermia

Jonathan E. Feinstein (jfeinstein@umassd.edu)
Fri, 30 Dec 1994 04:36:40 GMT

In article <1994Dec28.043506.21348@henson.cc.wwu.edu>, n8010095@henson.cc.wwu.edu (Phillip Bigelow) writes:
>Troy Kelley <tkelley@hel4.brl.mil> writes:
>
>
>>See if you can post a reference as to the weight of the average dolphin.
>>My guess is that an average dolphin weights less than 500 pounds. I would
>>guess, A LOT LESS. Probably about 250 pounds for a male. So how can a
>>dolphin weighing less than 500 pounds possibly stay warm in the water??
>
>>Troy Kelley
>
>Actually, the average mass of a dolphin is 363 pounds, which is right
>between my rough approximation and your approximation. My _point_ was:
>
>There are no low-mass, hairless aquatic mammals that weigh as little
>as a female A. afarensis. Four estuarian dolphins _may_ fall within the
>uppermost weight estimate for a _male_ A. afarensis, but, keep in mind, that
>is four species out of 76 species of whales _and_ dolphins (total).
>
> The summaries that I could gather on mass are below:
>
>1) Mass estimate of Lucy (A. afarensis): Female= 25 KG
> Male= approx. 50 KG
>
> (taken out of: Carroll, R.L. 1988. Vertebrate Paleontology and Evolution.
> Freeman Press).
>
<large interesting section deleted>

While you could be correct that mass is a determining factor in resistance
to hypothermia, I think we should also considered the differences in surface
area/mass ratios. Where cetaceans have relatively stubby limbs and compact
(if that's the right word to describe blue whales <g>), streamlined body shapes,
hominids have long thin limbs, providing for more skin (surface area) per kilo
of critter. Further, I don't have the figures at hand to back this up, but I
suspect that if you look into this you'll find that susceptibility to
hypothermia will cube as the surface area squares so that even a hominid
massing the same as a small dolphin would be more susceptible to hypothermia
while in the water.

Jon.
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JFeinstein@umassd.edu
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