Re: LBI Broods and Social Sharing

John Waters (
10 Oct 1996 18:35:15 GMT

Paul Crowley <> wrote in article
> It's not a matter of the mother's choice; there has to be
> mechanism in which prevents a harmful number of pregnancies.
> chimp mother would not want two small infants at the same time
> both would have reduced chances of growing up strong enough to

> leave descendants.) In apes it seems that lactation inhibits

> ovulation. Conception is delayed until the infant has weaned.
> I wonder if there is an allied mechanism. Chimps appear to
> a significant proportion (10%?) of animal protein in their
> Males hunt small monkeys, and females fish for termites and
> Older infants get most of their sustenance from fruit, but
> they get their protein from mother's milk. By weaning age at
> or five, can they termite-fish? Or beg meat from adults? Or
> bird's nests?

JW: These are good points.

It is clear that the nursing hominid female would need an
improved physiological condition to meet the gestation and post
foetal demands of an LBI brood. Fortunately, the hominid nursing
female had evolved an increase in subcutaneous fat. This enabled
it to meet the demands of a growing embryo and the previous born
infant. In this context, it should be noted that there is
virtually no difference in the subcutaneous fat levels of male
and female Apes. By contrast, the human female has 12 - 15
percent more subcutaneous fat than the human male.

The increase in hominid female subcutaneous fat level was due to
the extension in the period of helplessness of the hominid
infant. This increased period of helplessness required the
hominid nursing female to carry her baby in her arms. This
encouraged and helped to maintain bipedalism as the main method
of ground level locomotion in the hominid specie.

However, when a baby is carried in its mother€s arms, its skin
comes into direct contact with the mother. This can result in a
twenty percent reduction in the amount of infant skin exposed to
the air. As infants lose most of their body heat through their
skin, this can lead to an increase in the infant€s core body
temperature. A further complicating factor is the heat created
by the nursing female as she carries her baby. This can be
conducted into the body of her baby via the points of skin
contact. This would increase the core temperature of the baby.

If the baby€s core temperature rises beyond a certain level, the
baby will die of heat-stroke. This was the evolutionary
background of the hominid helpless baby and its mother. This
long term evolutionary pressure resulted in physiological
changes in both the infant and the female.

The infantile adaptation to the thermoregulation problems of the
helpless baby was
the moulting of the foetal hair. This is a condition observed in
a proportion of present day babies. The baby is born with a full
head of hair and this is moulted soon after birth. Thereafter,
the baby gradually grows a new head of hair. This condition is
inexplicable except in the context of a previous evolutionary
requirement. The moulting of the foetal hair results in
temporary baldness. As babies can transmit up to 30 percent of
their body heat through their head, the moulting of the foetal
hair enables a substantial reduction of their core body

The maternal adaptation to the thermoregulation problems of the
helpless baby was the development of an increased level of
subcutaneous fat. This fat was concentrated in the parts of the
female anatomy which came into direct contact with the baby,
when it was carried by the mother. When the baby was very young,
it would be carried in front of the mother cradled in her arms.
Subcutaneous fat in the chest, breasts and upper arms prevented
the mothers own internal body heat from being transmitted to the
baby. As the infant grew, it became heavier and was carried on
the mothers hips. This is where most of the female subcutaneous
fat is concentrated.

However, the subcutaneous fat has other properties beside that
of insulation. It is also a store of long term chemical energy.
This extra energy resource enabled the hominid nursing female to
meet the extra physical demands of the LBI broods.

Social sharing created significant advantages for the nursing
females who reared LBI broods. One advantage would be an
increase in protein levels for the mother and her infants. In
this context, it should be noted that Chimpanzees occasionally
hunt monkeys and other small mammals. If the hunt involves a
group of Chimpanzees, the Chimpanzee who makes the final capture
shares the kill with the other Chimpanzees in the group.

But this is sharing under duress, and not social sharing. The
fact that this is not social sharing is highlighted by the
behaviour of Chimpanzees when they hunt and kill alone. When
this happens, the Chimpanzee concerned does not share the kill.
They keep very quiet, and eat the prey alone.

In a group hunt, a social sharer could be expected to behave in
the same way as
Chimpanzees. They too would share the kill. However, when social
sharers hunted and killed alone, their behaviour would be
different. The social sharing hominid would take the newly
killed prey to their elder sibling, and share the food with that
sibling. If the sibling was a nursing female with a LBI brood,
there would be nutritional gains for the nursing female and her

If the sibling was a male, this would increase the male€s
protein levels. This would improve the physique and aggression
levels of the male concerned; and enable it to improve its
social ranking. If the male became a Alpha male, there would be
social advantages conferred on its relations. These would
include any sisters who had LBI broods. This is another example
of a biological feedback loop which would enhance the survival
of the LBI brood characteristic. The Alpha male would reduce the
intraspecie competition for food for the LBI brood females,
while increasing the degree of predator protection of the LBI


The riddle of life: What regular sided solid can be divided into
two equal halves, in such a way that each half is exactly the
same shape, and exactly the same size as the original solid?