Re: Homo amphibius and Hypothermia
Troy Kelley (tkelley@hel4.brl.mil)
Wed, 28 Dec 1994 18:10:29 GMT
Subject: Re: Homo amphibius and Hypothermia
From: Phillip Bigelow, n8010095@henson.cc.wwu.edu
Date: Wed, 28 Dec 1994 04:35:06 GMT
In article <1994Dec28.043506.21348@henson.cc.wwu.edu> Phillip Bigelow,
n8010095@henson.cc.wwu.edu 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:
>
(stuff deleted)
>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).
>
(stuff deleted)
>
>5) The least massive are the La Plata River Dolphin, the Gulf Porpoise,
and
>the Estuarine Dolphin, with a mass of 36 KG, or 80 pounds, and the
Finless
>porpoise, with a mass of 30 KG, or 66 pounds. These four species are the
>only hairless mammals in the world that are aquatic at less than 100
>pounds. They therefore comprise 5% of all cetacean species. (Watson,
>1981).
MMmmm.. So the mass of a male Lucy was 50 KG and the mass of the Gulf
Porpoise and Estuarine Dolphin is 36KG, which is 14KG less than Lucy!!!
I have no problem with that.
The big difference here is that the dolphin is FULLY AQUATIC, and AAT
claims that early man was only semi-aquatic. So if a fully aquatic
organism can stay warm with that body mass, why couldn't Lucy?
(stuff deleted)
>result of it's small mass (25-50 KG, or less), since the smallest
tropical
>dolphins have at least 20% body fat. Furthermore, female A. afarensis
Today's population has about 13% body fat for healthy individuals. Early
hominids could have had more, and quite possibly did have more,
especially any pre-savanna ancestors, because they would not have been
exposed to any fat-overheating pressures from a hot arid lifestyle. (As a
side note, It is interesting that Africans have a lower fat content than
Europeans).
So if a fully aquatic animal can get by with 20 percent body fat, I see
no problems with our current 13% body fat (an possibly more for earlier
ancestors) fitting into a semi-aquatic hypothesis.
> Another problem that Morgan and her Aquatic Ape supporters _constantly_
>ignore is the _reason_ why dolphins are hairless. It is not simply
because
>they are aquatic; rather, it is because hairlessness reduces drag in the
>water during high-speed swimming. If the ancestor of humans was
>"semi-aquatic" (as many of the proponents claim), there is no
evolutionary
>need to loose insulating hair, because "semi-aquaticness" doesn't involve
>high-speed swimming. If all these creatures did was wade around the
>shoreline, a hairless, low-drag body would be a useless evolutionary
>adaptation.
There may have been some intense selection pressures if our early
ancestors used water as an escape route from predators. Remember, many
big cats can climb trees but don't particularly care for water (except
the Bangle Tiger of India) So, if those ancestors who could not make it
to the water and swim away fast enough, where those ancestors who were
most likely to get eaten, then those ancestors who had the most hair were
the ones most likely to get eaten.
The model for the dolphin as a high speed swimmer fits if you look at it
in terms of selection pressure for high speed swimming in escaping from
predators.
>
>Yet another problem with the Aquatic Ape Hypothesis is that the young
(the
>new-borns and the children) would be even smaller than the adults. In
>whales and dolphins, calves that are newly-born are already 45% of their
>mother's length, and are over 18% of their mother's weight (Watson,
1981).
>In humans, an 8 lb. new-born is only 6% of the mass of its mother
(assuming
>a 130 lb mother, which is pretty typical). In order to compensate for
their
>small mass, cetacean babies are fed an _extremely_ rich diet of milk,
which
Didn't you just say that dolphins had a high mass? That they were born
"already 45% of their mother's length". Why do you then say "In order to
compensate for their small mass"
>In my opinion, there are absolutely _no_ similarities between humans and
>dolphins, as far as aquatic adaptation is concerned. I still think the
>small "aquatic apes" would spend all of their time trying to keep warm.
>(Remember, water takes heat away from the body more than 20 times faster
>than air does (Watson, 1981, page 22)), and the smaller an animal is, the
>worse it gets.
This "hypothermia" argument from AAT opponents is pretty weak. Anyone who
has spent a nice relaxing day at the beach; swimming, laying in the sun,
eating a nice picnic lunch, knows the real truth, the truth of personal
experience.
I would imagine that East Africa about 4 million years ago would have
been a nice place to spend a day at the beach. Sorry, but I don't have
any references to support that claim.
Troy Kelley
|