Main trends of research in the social and human ... - unesdoc - Unesco

356 Jean Bourgeois-Pichat
adjectives that are frequently used to qualify the word ‘demography’, such as:
economic, historical, social - or better still - psycho-social demography; math-
ematical demography (one also speaks of pure demography), population
genetics demography, i.e. statistics, etc.
13. Despite demography’s close links with the other sciences, little interchange
takes place betweeen demographers and other science specialists. The result is
that the latter are unaware of the full scope of their own particular branch in
which their researches would prove useful to demographers. It is to be hoped
that this situation will change and that demographers and other scientists will
be led to cooperate fully together. The present work might well serve to start such
collaboration. The questions that have hitherto been left unanswered by the
other sciences, because actually they had never really been put to them, will
then be the ones that demographic research will take up during the coming
years. We now propose to examine some of these questions.
n. DEMOGRAPHIC RESEARCH AND BIOLOGY
Population genetics
14. We pointed out just now how each human being, at his conception, was
chosen haphazardly from among the multitude of genetic combinations possi-
ble, and how the sum total of possibilities formed the genetic heritage of the
human race. But it is only a potential heritage; every moment we see how
it is incompletely realized. All configurations are possible, each stands a
virtual chance of being realized, but of course there is only one which is, in
fact, realized.. . The individual can, by his behaviour, exert an influence on the
materialization of this collective heritage: in the first place, by the way in which
he and society regulate the choice of the marriage partner. Speaking broadly,
there are two categories of genes: the dominant and the recessive. The character
of each individual is determined by two genes (or two groups of genes), one
proceeding from the mother, the other from the father. A gene is said to be
dominant when it can display its character in one single dose, whether it be
from the father’s or mother’s side. The recessive gene can only display its
character if it exists in double doses, that is, if it proceeds from both father
and mother at the same time. This explains the influence exerted by matri-
monial customs. Consanguineous marriages, for instance, encourage the appear-
ance of recessive characteristics, because the couple then stand a greater chance
of transmitting to their offspring the identical recessive genes they themselves
inherited from their common ancestors.
However, the individual can also bring his influence to bear on the materializa-
tion of the collective heritage through his own fertility. According to whether he
chooses to have, or puts up with having, few or many children, the genetic in-
formation which he carries within him will be transmitted in a greater or lesser
degree to the following generation. The differential mortality rate has a similar
effect in so far as it concerns groups that are genetically different. We shall