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Path: utzoo!utcs!mnetor!toram!chris
From: chris@toram.UUCP (Chris Robertson)
Newsgroups: net.bio
Subject: Re: Bipedalism
Message-ID: <147@toram.UUCP>
Date: Thu, 24-Apr-86 12:15:20 EST
Article-I.D.: toram.147
Posted: Thu Apr 24 12:15:20 1986
Date-Received: Thu, 24-Apr-86 17:47:40 EST
References: <1287@ihuxe.UUCP>
Reply-To: chris@toram.UUCP (Chris Robertson)
Distribution: net
Organization: Toram/Globe-Tek Systems Ltd., Toronto, Canada
Lines: 32
Summary: 

In article <1287@ihuxe.UUCP> krista@ihuxe.UUCP (K.J.Anderson) writes:
>
> ...The strain on the biped's back while pregnant is
>significant ...
>   These factors are irrelevant to reptiles and birds since they lay
>eggs.  So now I'm wondering about marsupials, particularly the
>kangaroo.  Her joey is born while still an embryo and completes its
>development in the pouch.  This would alleviate the miscarriage
>problem, but it seems that the mother would still have the leg and
>back problems.

Although kangaroos are bipedal, they actually spend a lot of time
on all fours while grazing,* or lying on their sides resting.  Upright
stance is normally taken during running (hopping, actually), and when
sitting up on their haunches looking about.  Otherwise, 'roos are
pretty laid-back creatures (pun intended).  Hence, the joey is
mostly carried slung under the mother's body, and when she sits up,
the pouch is actually resting on the ground.  So they don't have the
same sort of strain on the lower back that people do.

A baby 'roo is so tiny at birth (less than 1") that its weight is
negligible.  Joeys, however, still like to cram into the pouch when
all they can fit inside is their behind, with head and legs hanging
out in a tangle!

* back legs are taking the weight, front ones used mainly for balance,
but body posture is essentially horizontzal.
-- 

	Christine Robertson  {ihnp4,linus,decvax}!utzoo!toram!chris

	An apple a day keeps the doctor away, especially if aimed well.