Guns, Germs & Steel on PBS

August 12, 2005

PBS just aired a three-part documentary based on Jared Diamond's best-selling book Guns, Germs, and Steel, which outlines the role geography has played in shaping human history. You should try to catch it in reruns because it's very thought-provoking. But if you can't, there's a lot of information available at the show's website, including detailed summaries, full transcripts and a neat section called "The World" that analyzes global climates and resources by continent.

Episode One: Out of Eden

Diamond believes the blueprint for global inequality lies within the land itself, its crops and animals. [...] [He] realized that the development of successful and productive farming, starting nearly 12,000 years ago in the Fertile Crescent, was the critical turning point in the origins of global inequality. From this point on, one group of people — the natives of Eurasia — would have a head start on the path to civilization.

Successful farming provides a food surplus, and allows some people to leave the farm behind and develop specialized skills — such as metal-working, writing, trade, politics, and war-making. Plus, the simple geography of the continent of Eurasia — one coherent landmass spread on an east-west axis, with universal latitudes and climates — allowed these technologies and ideas to spread beyond the Middle East with ease.


Episode Two: Conquest

So, when presented with a copy of the Bible on November 16th, 1532, Atahuallpa throws the alien object to the floor, prompting a furious and surprise attack from the conquistadors. The combined impact of mounted troops, gunpowder and sharpened steel lead to a massacre, and Atahuallpa is personally seized by Pizarro himself.

In a matter of hours, the Inca Empire lies in ruins. But the story of Eurasian triumph isn't over. [...] Native Americans fell victim to European germs — infections which they had never encountered before. And Diamond realizes that European diseases like smallpox were a fatal inheritance of thousands of years of mammal domestication — the lethal gift of livestock.


Episode Three: Into the Tropics

As the settlers traveled further north, life suddenly became a lot harder. The foundations of their success, their crops and animals, refused to grow. They were forced to barter for food from their neighbours. And they started to fall ill with a mysterious and terrifying fever. It was a complete reversal of the usual pattern of European conquest.

Jared realizes that, unlike elsewhere in the world — where Europeans had landed in a temperate zone and traveled from east to west, maintaining similar climates — here in Africa, Europeans landed in the south and migrated north, moving through latitude zones and experiencing radically different climates. [...] Temperate crops such as wheat simply can't survive in a tropical climate. Nor can European animals — plagued by the diseases which thrive in the Tropics.


Uselessness of Blood Groups

August 5, 2005

Certain people continue to draw conclusions about ancestry from frequencies of blood groups and other blood-related genes, a common practice decades ago when the field of population genetics was still in its infancy. However, David Goldstein, Professor of Genetics at Duke University, stated in a recent interview that "blood groups are not now considered a good marker for population relationships, and they provide very little information about individual ancestry."

Here are four blood markers once used to measure African admixture in Southern Europeans, and the specific reasons why they aren't reliable for this purpose:

HbS (sickle cell)

African admixture in Sicily has been long suspected because of the presence of the sickle gene. Nevertheless, the degree of African admixture cannot be derived from the study of HbS frequency, since this gene was most likely expanded by the selective pressure of malaria, for a long time endemic to the region. We have examined 142 individuals from the Sicilian town of Butera (12% sickle trait) to search for other markers of the globin gene cluster less likely to be selected for by malaria. The TaqI polymorphism in the intervening sequences between the two gamma genes is informative. We have found only two instances of this African marker (TaqI(-)) among 267 normal chromosomes, demonstrating that the admixture occurred at a much lower level than previously thought. [Ragusa et al. 1992]

Fy(a-b-) (Duffy-null)

The Duffy system is also a single locus with two antigens, Fy a and Fy b. The only rare phenotype is Fy(a-b-), which has a higher frequency in countries where there is a high incidence of Plasmodium falciparium malaria. This phenotype gives a degree of immunity to the disease because the malarial parasite requires Duffy antigens to enter the red cells. Duffy antibodies are almost exclusively IgG. This system is named after the family of the antibody producer, Duffy. []

GM and KM allotypes

Fulani and Masaleit, sympatric tribes in eastern Sudan, are characterized by marked differences in susceptibility to Plasmodium falciparum malaria. To determine whether the two tribes differ in the frequency of immunoglobulin GM/KM allotypes, which are associated with immunity to several pathogens, serum samples from 50 Fulani and 50 age- and sex-matched Masaleit subjects were allotyped for several GM/KM determinants. The distribution of GM phenotypes as a whole, as well as a particular combination of KM and GM phenotypes, differed significantly between the two tribes (P = 0.03). These data suggest that GM allotypes may contribute to the genetic aetiology of malaria. [Pandey et al. 2007]

cDe (Rhesus)

But note that the cDe gene is nevertheless present in a fraction of the gene pool almost everywhere in the world. [...] Does it follow that once upon a time everybody in sub-Saharan Africa was homozygous for cDe, and in the rest of the world nobody had this gene? Should Europeans, Asiatics, and Americans who carry the cDe gene be presumed to have some Negro ancestry? There is no basis whatsoever to think so. The gene cDe is almost cosmopolitan in distribution, though for some unknown reason it reaches its highest frequency in Africa. [Dobzhansky, 1962]

Frequencies of the cDe gene in various populations (after Mourant 1954):


Spaniards ..... 3.7%
English ....... 2.8%
Germans ....... 2.6%
Danes ......... 1.8%
Italians ...... 1.6%
Basques ....... 0.5%


Bushmen ...... 89.0%
Hutu ......... 62.9%
Shona ........ 62.7%
S.A. Bantu ... 59.6%
Kikuyu ....... 59.5%
Egyptians .... 17.3%


S. Chinese .... 4.1%
E. Pakistan ... 3.9%


Aborigines .... 8.5%
Javanese ...... 6.5%
Papuans ....... 2.0%
Marshallese ... 0.5%


Navajo ....... 28.0%
Eskimos ....... 2.1%

Updated 11/03/2009