A Mars colony is necessarily a technological society, as it is incapable of surviving without technology due to the hostility of the environment. A technological society requires a high level of education in its individual members. High levels of education are correlated with low birth rates. It is therefore likely that a Mars colony or settlement will have a low birth rate, and may have no birth rate at all if there are serious problems with gestation in low gravity.
So population growth is likely to be done mainly through immigration. And the colony will need to limit emigration to retain the skill set required for an autonomous colony. Population growth is limited by the availability of resources, in particular the availability of energy on Mars. It is also limited by the transportation system available from Earth to Mars.
Population growth rate is a variable that is highly dependent on conditions on both Earth and Mars.
There are many different tasks for the colonists to carry out. Mars is an alien world and bears imponderable conditions. People will need to improvise. The following skills are vital:
- Profound knowledge and experience in technical matters and engineering
- Scientific expertise in Geology, Biology, Medicine and Radiology
- Agricultural knowledge
- Capabilities for Education, Health, Nursery and Psychology
- Production skills in both low and high complexity fabrication, from glass blowing to 3D printing.
The size of the human population must not be too big due to the risk of overpopulation, causing lack of food and resources. It must also be high enough to maintain the required skill set necessary for maintenance and expansion. As colony growth is likely to be mainly through immigration it should be possible to regulate immigration in order to control population. Illegal immigration to Mars is unlikely to be a significant problem due to the difficulty of procuring adequate transportation. At least for the first century or so.
The size of the human population must not be too small due to the risk of inbreeding depression. However Mars is not isolated from Earth, baring catastrophe, and immigration should solve this issue. Eventually, as one of the aims of the colony is self sufficiency, the size of the population will need to be significant, both for genetic diversity but also for skill diversity. A martian culture cannot allow itself to loose too many technical skills or it will collapse through technological failure.
A group of male individuals tend to be more aggressive than a mixed group of males and females. The mix in age of the individuals has an effect, too. An entirely male colony is hardly a colony, in the sense that it has no possibility of self perpetuation, unless significant progress is made in artificial gestation. The same could be said for an entirely female population, although in that case there already are technological solutions to the absence of males.
While the first Martian settlers, who grew up on Earth, will be full of enthusiasm, the next generation might have a different attitude. This has to be taken into account. An initial population of mixed age can reduce the effect of division into groups with different interests.
Living on Earth will always be an alternative to living on Mars. So a martian society will need to provide sufficient opportunities to its members, in particular to younger individuals, to keep them interested in living on Mars.
Criminality in a highly technological society. When an action against the technological support system of the colony can imperil the entire population, what is the proper response to criminality?
A Martian Society is likely to be a high energy society, with high individual productivity. What can be done with less productive individuals, including the young, the elderly and the physically limited individuals? This question relates to what is the fundamental purpose of a society. Although a martian settlement may start out as a group of exceptional individuals, it will necessarily average out over time. Children need to be educated, and therefore require time. The elderly have heavily invested in the society, and expect returns. And in many cases, own a large part of the production facilities, possibly in indirect ways (pensions and private funds, for example), and will get services from their revenue from these facilities.
Diversity is a fundamental need of a group, society or ecosystem. Robustness comes through diversity. And diversity, due to statistical requirements, includes both very able individuals and less capable individuals. It is statistically impossible to have a 'normal' population composed entirely of healthy and performing individuals. So any society needs to value this diversity, as this mechanism and spread in capabilities is part of what makes it capable of surviving different experiences and hardships.
As a group, individuals have ties with all other types of individuals, be they equal, more able or less abled. So individuals will require from the society that houses them that it takes care of its less able members, are they will have personal ties with them. Perceptive individuals should also realize that circumstances change, and that when they, as able individuals become disabled, through age or accident, would certainly like and expect to receive proper and adequate care.
Minimum population size
Minimum population sizes have been explored extensively, through the aspects of historical perspectives, biological requirements and social requirements. The cultural inheritance of skills in the case of an isolated society would require a large number of individuals, However, one should hope than in most future cases, Earth will remain as a reservoir of both genetic diversity and cultural skills.
Isolated cultures. Pitcairn islanders. Greenland.
What is the minimum size of a human population to avoid inbreeding effects? Studies have established the minimum population at a few hundred individuals. Se of frozen sperm, eggs or embryos might supply additional genetic diversity.
A study for Interstellar Exploration by Cameron Smith proposed a minimum population at about 40 000 individuals to allow the possibility of survival in case of catastrophe.
The needs of diverse skills in a technological society require a much large group than the basic biological diversity. The need for above average individuals and their influence on society also requires a larger population base to provide the statistical possibility of exception.