PRESIDENT’S ADDRESS. 31 
of what the world would be like if the majority of these infants 
were to survive. The decline in the birth-rate in countries already 
over-populated is often deplored, and we are told that a nation in 
which population is not rapidly increasing must be in a decline. The 
slightest acquaintance with biology, or even school-boy natural history, 
shows that this inference may be entirely wrong, and that before such 
a question can be decided in one way or the other, hosts of considera- 
tions must be taken into account. In normal stable conditions 
population is stationary. The laity never appreciates, what is so clear 
to a biologist, that the last century and a quarter, corresponding with 
the great rise in population, has been an altogether exceptional period: 
To our species this period has been what its early years in Australia 
were to the rabbit. The exploitation of energy-capital of the earth in 
coal, development of the new countries, and the consequent pouring 
of food into Europe, the application of antiseptics, these are the things 
that have enabled the human population to increase. I do not doubt 
that if population were more evenly spread over the earth it might 
increase very much more; but the essential fact is that under any 
stable conditions a limit must be reached. A pair of wrens will bring 
off a dozen young every year, but each year you will find the same 
number of pears in your garden. In England the limit beyond which 
under present conditions of distribution increase of population is a 
source of suffering rather than of happiness has been reached already. 
Younger communities living in territories largely vacant are very 
probably right in desiring and encouraging more population. Increase 
may, for some temporary reason, be essential to their prosperity. But 
those who live, as I do, among thousands of creatures in a state of 
semi-starvation will realise that too few is better than too many, and 
will acknowledge the wisdom of Ecclesiasticus who said ‘ Desire not a 
multitude of unprofitable children.’ 
But at least it is often urged that the decline in the birth-rate of 
the intelligent and successful sections of the population—I am speaking 
of the older communities—is to be regretted. Even this cannot be 
granted without qualification. As the biologist knows, differentiation 
is indispensable to progress. If population were homogeneous civilisa- 
tion would stop. In every army the officers must be comparatively 
few. Consequently, if the upper strata of the community produce 
more children than will recruit their numbers some must fall into the 
lower strata and increase the pressure there. Statisticians tell us that 
an average of four children under present conditions is sufficient to 
keep the number constant, and as the expectation of life is steadily 
improving we may perhaps contemplate some diminution of that number 
without alarm. 
