Re: An alternative to ST and AAT

Paul Crowley (
Tue, 12 Nov 96 18:46:47 GMT

In article <> "Gerrit Hanenburg" writes:

> The ulna/humerus length index of A.afarensis of ~91% (chimpanzee
> mean=95%,r=88-101% and modern human mean=80%,r=74-88%) is indeed
> closer to the chimpanzee mean and outside the human range,but the
> estimate is based on the AL 137-50 humerus (incomplete) and the AL
> 438-1 ulna. These do not belong to the same individual.

Thanks for all the detailed information, and apologies for my
(near-)duplicate postings. My internet provider is having major
difficulties and I thought the first had got lost in cyberspace.

> I wonder how you arrived at the figure of 2.5Myr. It seems a little
> long.

2.5 Myr comes from speciation at about 5 Myr and the origin of
the homo line at about 2.5 mya. It is probably too long.

> If you can climb a vertical pole then you can climb any tree with a
> similar diameter. Side branches make it even easier because they
> provide hand and footholds.
> And once an animal like Lucy was in the tree it could build a nest and
> sleep in it.

Lucy *could* have climbed other kinds of trees, but did she?
There must have been some change in habitat. Surely it has to
be a separation from the kinds of trees in which her pre-hominid
ancestors slept? A translocation to a equatorial rain-forest
could help to justify the new morphology.

I don't believe that a female hominid with bipedal feet, holding
an infant which had bipedal feet, while looking after other
children, would sleep comfortably in a nest in the canopy.
Though male or juvenile hominids might do so, on occasion.

As you know, I also believe that females would not adopt an upright
stance unless they had stopped carrying the child in the ventral
position. So they must have become habituated to off-shore or
littoral islands for nocturnal refuges. But if they had a tropical
rain forest not too far from the littoral, they could have obtained
its food while retaining bipedal feet.

> >So why was a shorter leg maintained for 2.5 Myr?
> Because long legs get in the way when climbing trees . . .

Is this true? I can see it when trying to climb vertical pole-
like tree trunks, but not otherwise.

> and A.afarensis
> didn't have to rely on very efficient long distance travel

Efficient long distance travel is always desirable. Something
which prevents it must be important.

> Since the liver has only a limited ability
> the convert ammonia to urea a high protein intake will lead to toxic
> levels of ammonia in the blood. Second,you will need a considerable
> amount of fresh water to excrete urea.

With a high shellfish diet, you'd also need lots of fresh water to
eliminate the salt. They go together.

> You can't life for extended periods on a diet with a protein
> content that exceeds 50% of total calories. Even Alaskan
> Eskimos,who have the highest protein intake,have a diet in which
> protein contributes only 22-25% of total calories.

You are talking about H.s.s. All predators can take much more.
There is no reason why the Australopithecines could not have
adapted to a diet with a somewhat higher protein content.
(What else did traditional Eskimos eat, btw, especially in the

> Many nuts have a high protein content and are generally also rich in
> fat and carbohydrates. The protein of mongongo nuts,for
> example,accounts for ar least 10% of total calories of the !Kung. This
> is adequate to meet the minimum daily protein requirement of an adult.
> Fruits,eggs,insects and small mammals can add to that.

We're looking at about 2 Myr for the australopithenes. During all
this time they have to be at least as efficient in gathering these
resources as their competitors: baboons, monkeys, chimps. They
have to be at least as effective in avoiding nocturnal and diurnal
predators. They have to have some particular "edge" or advantage.
It can't be better speed at getting around.

Well, I have a hypothesis. What's your's?