Outside the property development and population growth lobby, very few people who are worried about population growth and high immigration appreciate the effect of endogamy (marrying within your people) and exogamy (marrying outside your people) on population size and fertility. They also don’t recognize its effect on the private amassing of wealthy estates and political power. Anyone who wants to understand modern day problems with overpopulation, poverty, and loss of democracy would do well to study this article. This article is intended to stimulate debate about democracy, wealth distribution, and overpopulation. The author invites critical comments and argument.
Article based on S.M. Newman Demography, Territory and Law: Land-tenure and the origins of capitalism in Britain, Countershock Press, 2014. and S.M. Newman Demography, Territory and Law: The Rules of Animal and Human Populations, Countershock Press, 2013.
How to read the diagrams: White squares in the diagrams below indicate permitted marriages and black squares indicate forbidden marriages. White squares become black squares when someone is already married, although polygamy varies this factor. The symetrical rules for marriage to "in-laws" are indicated by mirror images, creating an overall pyramid form in the diagram of an extended family or clan.
"Endogamy" refers to marrying within one’s clan, tribe or similar social unit. "Exogamy" refers to marrying outside those units. The most extreme kinds of endogamy tend to be practiced by ancient royal clans, such as the Egyptians and the Incas, where there were sibling, father-daughter and grandfather-granddaughter marriages. Less extreme, but more common, are first and other cousin marriages, frequently practiced by nobility and other established clans and tribes. The wealthy, whether they are noble or not, tend to marry other wealthy people for similar reasons.
High Endogamy, Low Exogamy, Low Fertility
If you look at the white squares, you will see that the pharaohs of Ancient Egypt could marry their children and their grandchildren and other close relatives. The rigidity of this practice varied from pharaoh to pharaoh, and lesser relatives might also be married, however marriage within close blood relatives was encouraged.
The purpose of highly endogamous marriages is to preserve land and power within a small group of people (known as a caste). To this day, dynasties can only preserve themselves by intermarrying. Although sibling marriage and parent or grandparent marriage is widely prohibited, first cousin marriage practiced over several generations can bring about similarly close genetic inheritance.
Although this system promotes fertility, it only does so within a very limited pool of candidates. This means that dynasties are powerful but small populations, able to concentrate, conserve and control their material assets through numerous social, legal and genetic bonds.
Outside the easily recognized institutions of tribe and nobility, people in countries where tradition holds them close to the land and preserves their extended families, still tend to live near and to marry within their own class, region and culture. This is the case with most continental European countries. It has a moderating effect on fertility opportunities and a strengthening effect on local self-government and democratic organization.
Low Endogamy, High Exogamy, Low Fertility
There are very few white squares, so very few permitted marriages. With incest avoidance to the 8th degree fertility opportunities within a clan are very low. This is the opposite system to the Ancient Egyptian one.
In cultures, such as those of desert indigenous populations and South Korea, fertility is kept low by restricting marriage opportunities within the family and clan and relying on external opportunity where external opportunity is limited – for instance by distance. If you are a very small clan, with only your feet for transport and your activities take place many kilometers from the next clan’s location, your opportunities to meet suitable partners will be limited. Infertile environments - typically with low rainfall - make for low density populations and big spaces between clans. The difficulty of finding a mate in such circumstances is well shown in the film Ten Canoes. (Although admittedly there were canoes, their use in the film was local rather than inter-clan.)
High Endogamy, High Exogamy, High Fertility
High exogamy is well represented by the biblical laws of Leviticus 18, very influential on Western societies. See the diagram below.
Lots of white squares here mean that you can marry a lot of people in your clan. Brothers are encouraged to marry their deceased brother's wife and niece marriage is legal. The rules differ according to whether you are male or female. This was the system that accompanied the exhortation to "Go forth and multiply."
Western societies tend to follow the Leviticus pattern, although you do get legal restrictions on cousin marriage in some places (such as Illinois, in the United States) where first cousins are not allowed to marry until they are over 55 years old) and there are age restrictions and social restrictions on marriage between uncles/aunts and nieces and nephews.
Multiculturalism as high fertility exogamy and its effect on self-government and citizen capacity to organize
Extreme exogamy applies in the English speaking ‘settler states’ of the United States, Australia and Canada. The populations in these ‘settler states’ are in continual motion due to constant reorganization of suburbs and infrastructure to accommodate high rates of immigration. This people movement occurs at international, national, regional and inter-suburban and intercity level, rather reminiscent of the increased movement of molecules in a heated substance.
Because families and clans tend to be split and disorganized in these societies, the level of endogamy is reduced, despite lack of legal restrictions. Exogamy is strongly encouraged by policies of ‘multiculturalism’. People move far away from their parents and divorce, remarriage and serial families are frequent impoverishing factors. In continental Europe there just isn’t the same amount of structural turmoil. Although the first and second world wars in those areas did cause significant disturbance, the arrangement of clans and their geographic position in villages and towns persisted.
The most important thing to understand about endogamy and exogamy, however, is their role in promoting or limiting population growth. The diagrams in this article should help the reader to see what is meant by this.
Transport factors in creating the Post War Baby Boom
Another important factor already alluded to that affects these patterns in most cases is the introduction of new transport because it permits individuals to travel greater distances. Horses, camels and elephants will take people a lot further and afford them significantly more fertility opportunities than travel on foot will. Trains, cars, boats and planes multiply opportunity exponentially. Trains are associated with massive population growth, but they impose a geometrically restricted pattern. Those restrictions disappeared with the advent of cheap oil and the automobile. Without these there would not have been a post war baby boom without precedent in size.
In general high endogamy plus high incest prohibition means low fertility. It is difficult to find people who are not married already and who are not forbidden to you in marriage but who are also members of your tribe. A person in this situation might have to go quite a long way in search of a partner and it is likely that a fairly high proportion of the clans-people would die without marrying or having children.
High endogamy but low incest prohibition, where cousin marriage is frequent means high fertility. In these kinds of situations it is considered important to lock all the land up in the tribe but to have a large tribe with many workers and potential soldiers. Nonetheless there are strict boundaries. Marriage outside the tribe is rare, although usually some immigrants will be accepted into the tribe. Living examples of such tribes are the Karen, the Hutterites and some orthodox Jewish peoples.
High exogamy and high incest prohibition will tend to disperse a people so that they ultimately become unidentifiable as clan or tribe, so you won’t find many intact tribes like this. It is a major factor in the dispersal and disintegration of many previously discrete peoples after they become affected by colonization and lose their contact with their land. Examples include Australian aborigines and possibly the Dutch of the 16th and 17th century during the minor industrial revolution that occurred in the Netherlands and which entailed major population drift from country to city. The capturing of African slaves and their transport to the Americas and Pacific Islands like Haiti is another example where the transported survivors of peoples who probably had low fertility in their original tribes encountered significantly increased fertility opportunities.
Low incest prohibition and low endogamy mean that where a clan is not isolated, it has more fertility opportunities than one with stricter rules. Such patterns characterize the settler states of Canada, Australia, the United States and Britain. Usually even first cousin marriage is permitted, but families and clans are so dispersed and fragmented that marriage to members of unidentified and equally dispersed descendants of clans are common. With the very high immigration in these countries, this potentially results in huge population growth. These are synthetically structured societies. Such countries lack the capacity to organize from the bottom up that is possible in countries where several generations are embodied in clans and historically settled and networked in a particular locality within a larger polity. An example of this strong capacity to organize based on relatively natural distribution would be France or Japan. Some examples of this capacity to organize are the French Revolution, which was able to persist over several generations until a lasting republic was formed, and the German and Japanese manufacturing sectors.
There is good reason to think that variations in endogamy and exogamy are instinctive social responses to environmental fertility signals because these rules also occur in most other animals and plants, as The Rules of Animal and Human Populations explains in chapters 3 and 4 which are also published by themselves as The Urge to Disperse. In a globalized society these signals are diffuse, remote and confusing. Media and government interpretation of signals can influence false perceptions of real environments.
Polygamy helps to make such populations larger. An exceptional case was King Abdul Aziz, who began the current Saudi kingdom in 1932 and had 44 legitimate sons by 17 wives. The Saudi royal family had more than 4000 princes and 30,000 noble relatives in 2002 and is considered the largest royal dynasty. Without the commercial industrialization of petroleum the kingdom and dynasty could never have been so powerful. Without this kind of intermarriage the Saudi clans would not have been able to maintain control over Saudi assets. Corporations and international interference would have eroded their power, as they do among ‘common people’ by keeping them disorganised.
“Ibn Saud fathered dozens of sons and daughters by his many wives. He had at most only four wives at one time. He divorced and married many times. He made sure to marry into many of the noble clans and tribes within his territory, including the chiefs of the Bani Khalid, Ajman, and Shammar tribes, as well as the Al ash-Sheikh (descendants of Muhammad ibn Abd al-Wahhab). He also arranged for his sons and relatives to enter into similar marriages. He appointed his eldest surviving son, Saud as heir apparent, to be succeeded by the next eldest son, Faisal. The Saudi family became known as the "royal family," and each member, male and female, was accorded the title amir or amira ("prince" or "princess"), respectively.
Ibn Saud died in 1953, after having cemented an alliance with the United States in 1945. He is still celebrated officially as the "Founder," and only his direct descendents may take on the title of "his or her Royal Highness." The date of his recapture of Riyadh in 1902 was chosen to mark Saudi Arabia's centennial in 1999 (according to the Islamic lunar calendar).” Wikipedia, http://en.wikipedia.org/wiki/House_of_Saud (Accessed 26 February 2013.)
 "Fertility Opportunity" is a phrase borrowed from anthropologist Virginia Abernethy's theory of that name.
 Without intergenerational organization in the form of locally organized clans, the French Revolution probably would not have occurred. It had to persist over several generations.