Re: Multi-age Broods. Ignorance or Apathy?

Wallace Neslund (
Tue, 06 Aug 1996 23:18:45 -0700

John Waters wrote:
> In fact, the human
> specie is the only mammal to rear multi-age broods to maturity. Apes by
> contrast, have single age broods.

This is not so. Pan females have non-adult children of different ages, both
breast feeding infants and adolescents.

> A multi-age brood is defined as a brood of mammal young, of different
> ages, all of whom are in their preweaning stage of development. The age
> difference must be at least one gestation period.

Pre-weaning by definition means they are still living on breast milk and have
not switched to solid food

> Apes generally rear one infant at a time. They can give birth to twins,
> but these do not generally survive in the wild, due to feeding and
> transportation problems. As a 'norm', apes wean off their previous born
> infant at least three months before the next infant is born. The average
> birth interval for chimpanzee infants born in the wild is five and a
> half years.

The Pan female does not breast feed her young for five and a half years!

> By contrast, in modern industrial societies, human mothers may give
> birth every year. As the age of weaning for a human infant is about
> seven years of age, a human mother can concurrently rear six infants at
> once.

The average age for weaning is not seven years in Hss. Most Hss infants can
eat pre-chewed food at a year. They can, and most do, live entirely on solid
food by age three. The average age for weaning in Hss is one to three years,
depending more on culture and society than on physical need. Weaning is also
further modified by the use of bottle fed babies. Breast feeding has some
amount of inhibitor effect on the mother's getting pregnant again. If a Hss
baby is bottle fed instead of breast fed, the mother can get pregnant
relativly soon after giving birth. This inhibitor effect is not an absolute
constant, though, and a breast feeding mother can sometimes still get
pregnant. I do not know if any studies have been done on Pan mothers with
bottle fed babies, but this same inhibitor trend may apply to Pan as well as

> It is curious that this multi-age brood characteristic is not mentioned
> in any encyclopedia, or any reference work on primates. Is this due to
> ignorance or apathy?
> John Waters

The fact is that your definition of multi-age brood is not consistant.
Neither Hss nor Pan usually have a second birth while still breast feeding
the first infant. Both Hss and Pan, though, do have multi-age brood that are
still sub-adult and to some extent dependant on their mother for support and
protection, but only the youngest is still breast feeding. The older children
in Pan, are, to the most extent, self feeding. In Hss, the older children,
with a much more drawn out childhood, are being fed pre-chewed or soft food,
but are no longer breast feeding. If a Hss mother had a child every year for
three years, or even a theoretical five children in three years (ages 0, 9
months, 18 months, 27 months, 36 months) she would have trouble keeping all
of them fed with breast milk alone. By necessity, the older child would be
weaned when the next one is born. The inhibitor effect of nursing tends to
postpone prgenancy until the first child is weaned. There is also the
question of estrus to consider. Most mammals will not enter estrus while
still nursing infants. This is true of Pan and other primates. Hss, though,
has no seasonal estrus cycle, replaced instead by a monthly cycle of
fertility. If the only normal prohibitor of pregnancy in Hss is due to
nursing, then the use of bottle fed babies will disturb this cycle and allow
for multi-age broods by your definition. This must be viewed as a social
abberation to an organic cycle, though, rather than as a normal state. There
are other natural prohibitors of pregnancy, such as starvation and very
extreme physical labor, but those are survival trends for extreme situations
and are not pertinent to this post.


God knows, I don't. - Thomas Aquinas