LBI Broods and Social Sharing

John Waters (
29 Sep 1996 21:43:47 GMT

Can anybody help me to determine the time and place where the
hominid LBI Brood and Social Sharing first developed?

Let me put these concepts into their physiological and
behavioural perspective. Social Sharing is a behavioural trait
whereby adults of a mammal specie voluntarily share food with
other adults. This is a characteristic which is unique to the
human specie. Apes will share food under duress, but not
voluntarily. Wolves and related species of social carnivores can
be stimulated into sharing food, but this is an
instinctive behaviour and not voluntary.

As this characteristic is unique to the human specie, the
question arises as to how and why it evolved in just this one
mammal specie. I believe that it is possible to show that the
behaviour is the result of another unique human characteristic,
namely: the human LBI (Long Birth Interval) multi-age brood.

Multi-age broods can be defined as any brood of mammal young of
different ages all of whom are in their infantile stage of
development. (My thanks to Paul Crowley and Walter Neslund for
helping me to improve on the previous definition.) The age
difference must be at least one gestation period. The brood
stage is the period of when an adult is directly responsible for
rearing the young. At the very least, the adult will supply food
to the infants during their infantile period.

Humans rear multi-age broods of young. That means they supply
food to differently aged infants at the same time. Apes rear
single age broods. They only feed one single age group at a
time. They will not feed any previous born infants, unless the
present born infant dies. Humans may rear and feed several
differently aged infants at the same time.

Where the age difference of surviving infants is one to two
years, the multi-age brood is called an SBI (Short Birth
Interval) brood. This is typical of the broods reared in
agricultural and industrial communities. The LBI brood is
defined as any multi-age brood where the age difference of
surviving infants is four to six years. This sort of multi-age
brood is typical of the broods reared by hunter gatherer tribes.

The multi-age brood characteristic developed as a result of the
increasing period of hominid infantile helplessness after birth.
In this regard, it should be noted that Ape infants are helpless
for the first 12 to 24 hours after birth. Thereafter, they can
crawl and clamber up their mother to suckle. In addition, they
can attach themselves to
their mother€s body, so that the Ape mother can knuckle walk on
the ground, (Gorillas and Chimpanzees), and/or climb trees (all

A human baby only reaches a similar level of behavioural
competence, about six to seven months after birth. The human
baby undergoes a number of neurophysiological and physiological
changes in this time period, which are typical of changes which
occur in other species€ foetal periods of development. In this
context, it is generally held that the human baby€s foetal stage
of development extends beyond its gestation period.

The foetal stage of development of a Chimpanzee baby (Pan
Troglodytes) lasts for eight months. This is its gestation
period. By contrast, the foetal stage of a human baby lasts
sixteen months. This comprises its gestation period of nine
months, plus seven months of post birth foetal development. All
the stages of human development
increase by the same percentage as the increase in the foetal
stage of development.

It was the increase in the hominid infantile stage which led to
the development of the LBI brood characteristic. At some point
in time, the hominid mother gave birth to a new baby, while her
previous born infant was still in its infantile stage. The
mother concerned may have been overindulgent, perhaps even
abnormal. But if there was a
super abundance of food, she would be able to feed the previous
born infant on adult foods, while breastfeeding her new-born

The new-born baby would witness its mother feeding the elder
sibling. It would observe its mothers behaviour every day. In
this regard, it should be noted that infants of many species
learn to fend for themselves by copying their mothers'
behaviour. In addition, the early learning tends to become a
stereotyped behaviour, due to a process known as imprinting.
This stereotyped behaviour is continued
throughout adulthood.

In this early LBI multi-age brood situation, the new-born baby
would learn by copying its mother€s behaviour in the usual way.
As such, it would learn to feed its elder sibling; and continue
to feed the sibling in adulthood. If the sibling was a female,
who later had a multi-age brood, she would be able to rear this
brood even when food was not super abundant. Furthermore, as the
female would continue to receive food from its younger brother
or sister, it could afford to site its nest some distance from
the main feeding sites. This would reduce the predation risk to
the young.

In this way, the advent of social sharing would create a
positive biological and behavioural feedback loop which would
maintain the LBI multi-age brood characteristic. But the
question is, when and where did this happen? The LBI multi-age
brood is a fact. Social sharing is a fact. But neither exist in
any Ape specie. So when and where did they develop?

If it is any help, it can be shown that the advent of social
sharing would lead to a substantial increase in the rate of
evolution. Furthermore, it can be demonstrated that the LBI
multi-age brood would lead directly to the evolution of human
speech and language. Any ideas anyone?

John Waters

John Waters is the author of "Helpless as a Baby",
a book concerned with general and human
evolution. It may be accessed at URL