Population density and disease

The Neuropolitics website has an interesting article on the difference between European and Asian people in regard to living space, which has got me thinking about cultural and evolutionary differences and diseases.

Historically, the population densities of Asian civilizations have been much greater than their European counterparts, and this pattern is also found in countries where Asian and Western immigrants live side by side.

While population densities in some European countries like Holland and Denmark rival those found in densely populated Asian states like Vietnam and Japan, most European countries, and countries colonised by Europeans, have relatively low population densities.

On one level the ability of people to live in densely populated areas, can be seen as an evolutionary advancement, since those who live in densely populated areas make better use of land, and tend to use less resources than those who live in lightly-populated areas. Cold, sparsely populated Canada for example has the world's highest per capita level of energy use, and warm, densely populated India one of the lowest.

From an evolutionary perspective the downside of high population densities is disease.

Modern history books tend to be full of stories about western oppression of indigenous people, but it's often forgotten that the main cause of death among indigenous people have been introduced diseases that were largely Asiatic in origin.

Influenza, bubonic plague, smallpox, and cholera for example, first came to Europe via trade with more densely populated Asian cultures, and were then passed on to indigenous people in America and Australasia during colonisation.

Cholera, which originated in India, is still continuing to spread around the world, with Peru being hit for the first time in the early 1990s.

Some historians now think that smallpox actually arrived in Australia before Europeans through Aboriginal contact with Indonesian traders.

Although most diseases of Asian origin were caused by close contact with domesticated animals, it seems population density must also have played a significant part since, although Europeans and Africans also lived in close proximity to livestock, few diseases have spread in the opposite direction - from Europe and Africa to Asia.

The native Indian population of the Americas are an interesting case because while they are of Asian origin, they had little or no resistance to modern Asian-derived diseases bought in by Western immigrants. Before European contact, the population densities of most Indian settlements were also relatively low, reflecting a predominantly hunter-gatherer way of life, although a few densely-populated civilisations did emerge in areas like Southern Mexico. In the Americas there were also fewer domesticated animals to pass on diseases.

When Eurasian diseases arrived in the 16th Century, the Native Americans living in the most densely populated areas, such as the Mississipi Valley and Cuba, also suffered the highest mortality rates.

In the modern era population densities in some Latin American cities are now rivaling those found in Asia, and Eurasian livestock is now widely dispersed throughout the Americas. Not surprising, Latin America is now changing from somewhere that suffers from introduced diseases, to a potential source of infectious diseases that may threaten other parts of the globe.

With increasing population densities, the same pattern in also emerging in Africa, with AIDS being one of the first instances of an African-sourced disease going on to kill significant numbers of people in other parts of the world.