Re: Becoming altricial/bipedal

Paul Crowley (
Fri, 06 Oct 95 02:29:33 GMT

In article <451pp8$> "Alex Duncan" writes:

> writes:

> >a) A species of ape became fully bipedal sometime between 7mya and 2mya.
> Your entire argument rests on this incorrect premise. If, by "fully
> bipedal" you mean "bipedal in the same manner as modern humans", then you
> are incorrect. Your statement is not supported by the fossil record.
> The fossil record suggests that the hominid species that were extant
> between ~4.5 and 2.0 Myr WERE NOT bipedal in the same manner as modern
> humans, and that they retained significant tree-climbing abilities.

Please state what you mean by "significant tree-climbing ability"

If you mean that the hominid was probably able to grasp branches with
its foot, please quote references.

> >e) It is not a viable lifestyle for a bipedal maternal ape to spend
> > every night in the trees (which she cannot grasp with her feet)
> > while looking after a bipedal infant which cannot grasp her
> > with its feet.
> I would really have to say that this depends on a lot of other factors
> that you haven't addressed. But, for the sake of this particular
> argument I'll agree with it.

I'd like to know the "other factors".

> f) Such creatures would suffer devasting predation if they were to
> > regularly spend nights on the ground in the forest, or in the
> > savannah, or in the mosaic/savannah.
> This is incorrect. "Fully bipedal" hominids are large, tool-using,
> group-living primates. For a carnivore to a attack a GROUP of healthy
> humans is foolhardy.

At night? Lions, leopards and hyenas are nocturnal. Hominids are
diurnal and effectively blind at night. They would only injure each
other, and their females and young, if they were to use clubs and
stones whenever they heard a rustle and thought a big cat was near.
This must be one of the craziest ideas of all time. How much sleep
would any of them get each night? What's the life expectation?
Can you imagine the stress levels with the screams of the hyenas and
the lions' growls?

> >g) They did not suffer devastating predation, so they must have had
> > some other form of safe refuge during the night.
> What are you suggesting -- they lived behind locked doors?

I'm sure you know what I'm suggesting - they waded or swam to an island
on the rocky foreshore, and snored contentedly in the warm breeze from
the sea to the sound of lapping water. Which way would you and your
family prefer to spend the night - and every night?

> My anatomy (and yours) is not similar to that of the earliest hominids in
> all significant aspects. In fact, it is very different in many
> significant aspects. You still have not provided any support for your
> basic assertion.

All standard accounts of human evolution have all hominids, from the
CA to civilisation, sleeping either in trees or on the ground.

As I argued above, the ground is not sensible.

It's easier to see what a bad idea trees are, if you think about more
recent hominids (say <1.6 mya) because their post-cranial anatomy is
near enough identical with yours. Once you accept that you and your
family, with infants and children, could not possibly sleep naked in
the trees, you can see that the same would apply to hominids at
1.6 mya (e.g. KNH-WT 15000).

So where was he sleeping?

When you have the answer to that, you can readily work back to the CA.
Any differences in anatomy will be seen to have no significance to the
problem and its answer.

I'm sorry that the problem is so stupid and the answer is so simple.
All I can say is that the sooner you academics get off your high horse
and admit it, the better. The longer you stay up there, the more
foolish you are going to look. From a personal point of view, I don't
think you have much to worry about. This change is going to be rapid
and all your colleagues will shortly be saying: "That was my belief
all along - ask my wife". You might as well be a bit ahead of the
pack. It won't do you any harm, and you might get some credit. You
haven't got any real choice anyway: your students will shortly be
giving you hell. For the moment, you just need a little balls.