Monthly Archives: May 2013

Annals of Comparative Advantage

In my last post I talked about two interesting things I learned from John Reader’s Africa: A Biography of a Continent. I also mentioned that the book is sometimes infuriatingly superficial or wrongheaded in its treatment of science or economics. Let’s look at an example:

During the 16th century the Portuguese expanded their empire to include territories spread around the globe from South America to the Spice Islands of the Far East. Best estimates suggest that up to 10,000 Portuguese were working abroad at any one time. Ten thousand, when the population of Portugal was only around 1 million, and large numbers were continuously leaving to replace those who died abroad. The empire imposed a drain on manpower and resources that Portugal could not sustain–and the empire collapsed. The wonder is not that it collapsed, a history concluded, “but that it flourished for exactly a century and lasted as long as it did.” (383)

First, is ten thousand out of a million (1% of the population) really so high? For comparison, today about 10% of the population of the Philippines are working overseas. But more importantly, you should do the activity with the highest return! Reader described the Portuguese Empire as largely a series of trading missions that paid taxes on their return.

Trade flourished and the merchants prospered. It has been estimated that returns were hardly ever less than 50 per cent and sometimes as high as 800 per cent….between 1450 and 1458…the traffic yielded from five to seven times the invested capital. (339)

In an economic sense you don’t need to worry about “manpower” for other activities. What exactly was Reader worried about? If 1% of Americans went to work in Silicon Valley, the result wouldn’t be a dangerous draining of “manpower and resources” (= Labor and Capital) away from other activities. When you have prices, resources tend towards their highest-valued allocations. Saying “lots of resources went to this really high-valued activity” does not explain the collapse of an empire.

Africa: Reproductive Strategies and the Value of Gold

Partway through John Reader’s Africa: A Biography of a Continent I’ve been disappointed in some superficial or misleading sections about science and economics. But the book is definitely worth a read if you have broad interests and I wanted to post about two topics that caught my interest.

Reproductive Strategies:

Evolutionary biologists have grouped the ways of life which natural selection has favoured during the course of evolution into two broad categories: r- and K-strategies.

Organisms [with] r-strategiesare opportunists, existing in minimal numbers for much of the time but able to increase rapidly and move on to colonize other regions when conditions permit…

K-strategists … occupy more predictable environments … [and] seek equilibrium and stability. (pp. 129-130)

It’s pretty easy to sort species into one group or the other, though again these are just broad groups.1 The quintessential r-strategists are most insects, rodents, and weeds. Whales and elephants on the other hand are standard K-strategists: very few offspring, late reproductive age, long lifespan. Interestingly the tsetse fly is actually a K-strategist as it only lays a few eggs in its lifetime and lays them one at a time, which makes eradication very difficult (241).

More interestingly, humans look a lot like K-strategists in terms of our physical characteristics since we are large,¬† mature slowly, invest a lot in our few children, and so forth. But “the evidence of human population growth patterns, modern as well as prehistoric, indicates that humans are supreme opportunists who survive in numbers some way below the carrying capacity of the environment for much of the time, but whose growth rate potential [and adaptability] enables them to multiply rapidly when circumstances permit.” (131) For example, only a few hundred humans left Africa and look how that turned out.

The Value of Gold

A nice reminder about the cultural determination of value, and also about the forces of supply and demand:

Though locally abundant, [gold] served no practical, ritual, or even ornamental purpose in the affairs of people in sub-Saharan Africa until demand from the north reached the region, and even then it remained solely an item of trade…a source from the early fourteenth century reports that copper was exchanged for two-thirds its weight in gold. (287)

Anyway, the book is full of these kinds of topical digressions and he’s quite good about integrating them later in the narrative as well. Pick it up next time you want to read 700 pages of interesting factoids loosely related to the history of Africa.

  1. And interestingly it looks like this paradigm fell out of favor among evolutionary biologists in the early 90’s while the book was published in ’97, which confirms my suspicions about the writer’s scientific chops. []