Re: Multi-age Broods. Ignorance or Apathy?
John Waters (jdwaters@dircon.co.uk)
Tue, 13 Aug 1996 20:16:44 +0100
Paul Crowley wrote:
>
> In article <32046496.7C29@dircon.co.uk>
> jdwaters@dircon.co.uk "John Waters" writes:
>
> > It is curious that this multi-age brood characteristic is not
> > mentioned in any encyclopedia, or any reference work on primates.
>
> No, it's not curious. It applies to only one primate and most
> thinking about that one is inevitably distorted -- if not purblind.
>
> I agree wholeheartedly with your identification of its importance.
> The multi-age brood gave enormous advantages to the hominids that
> first adopted it. If they found a new resource they could expand
> at a fantastic rate (e.g. when they found a whole new continent
> occupied by a techologically inferior people). This would have
> given them such an enormous edge that they would have very rapidly
> predominated. From then on, the rate of hominid evolution would
> have escalated. A hominid population that was wiped out by disease,
> famine or war would have been replaced in no time by its (superior?)
> neighbours/conquerors.
>
> But when was it? I'd say this capacity undoubtedly dated from the
> time the hominid mother put down the child. (Does this latter event
> have a name?) This was a break with a 65+ Myr primate behaviour
> pattern and requires a lot of justification. The multi-age brood
> would explain its success -- so long as we get a reasonable account
> of the new resources (or new niche) that this step made exploitable.
>
> This "putting-down-of-the-child" is conventionally dated to some
> vague time when there was a descent from the trees and an expansion
> of the brain. My own, very strong, opinion is that such a radical
> change would only have been adopted by a small population and for
> very special reasons. In other words, it was a speciation event.
> So I date it to the hominid split from the apes, and firmly believe
> that it was a requirement for bipedalism itself.
>
> Thanks for the insight.
>
> Paul.
JW: 1. For what it is worth, I estimate the first kind of multi-age
brood to have evolved sometime between one million and two millions
years B.P. I generally average this to 1.5 Myrs.
2. It is important to understand that there are two kinds of multi-age
broods, namely: long birth interval (L.B.I.) and short birth interval
(S.B.I.) multi-age broods. The type with we are familiar today is the
S.B.I. brood, which in prehistoric times was the product of sedentary
agriculture and wetnursing. Nowadays, structured breastfeeding or bottle
feeding of infants allows the nursing female to come into estrus within
a few months of the birth of each baby.
3. More important from an evolutionary point of view is the L.B.I.
multi-age brood. This is the kind of brood found in hunter-gatherer
tribes. Generally there is a birth interval of four years in this type
of brood. As Apes are gatherer-hunters, it is generally thought that
hominid ancestors were either gatherer-hunters or hunter-gatherers.
4. It can be shown that as a result of normal mainstream evolution, the
L.B.I. multi-age brood would lead to the evolution of speech and
language, social sharing and unified teamwork.
5. It should be noted that the multi-age brood characteristic could only
be maintained by a specie with pre-adapted advanced infant rearing
characteristics. These pre-adaptions were caused by long term biological
selection of improved infant rearing characteristics due originally to
changes in the head-to-body ratio of the specie. Such changes increased
the period of infant helplessness after birth. This created the
evolutionary pressure for more advanced maternal responses, including
(as you have surmised) bipedalism.
Thank you for your intelligent response Paul.
John Waters
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