The Cancer Journal - Volume 6, Number 5 (September-October 1993)
Can human biology reduce the historical guilt of Europeans with respect to the American Indians?
In December 1992, Francis Black, an epidemiologist from Yale, published an article about the restricted genetic diversity of the American Indians and their high suspectibility to infection (I). We feel that this article merits reconsideration since its consequences call for widespread reflection and debate.
Black collated data from 36 publications concerning the serological, analysis of 127 different populations and pointed out that although about 40 different alleles have been identified at the A and B loci of the class I major histocompatibility complex genes in European and Black African populations, only 10 different alleles have been detected among South American Indians and Papuans from New Guinea. Genetic polymorphism is considered to be one of the major factors in the adaptability of a population to adverse changes in the environment. This is one of the strong points of the neo-Darwinian theory of evolution. Genetic polymorphism in the major histocompatibility complex, which the article reports as being reduced in American Indians, is one of the best known systems, with its relationship to the immune response and a number of syndromes and diseases, including cancer and leukemia.
The invasion of America by the Europeans was a singular catastrophe in the history of mankind which reduced the Indian population to 10 to 20% of its former level. The usual explanation is the combination of the violence of the conquering Europeans and the virulence of the infectious agents which they brought with them. In his article, Black stresses the contribution of imported infections, rendered particularly serious by the limited genetic pool of the Indians. The situation was very different during the later colonization of Africa by the same European forces. At the moment of the quincentenary of Christopher Columbus' voyage this point of view highlights the responsibility of the conquistadors and those who followed them, but reduces their culpability since it was not until the 19th century that the existence and rôle of infectious agents were discovered. Those who carried the microbes across the Atlantic were responsible, but not guilty.
Before lifting the burden of guilt from the invaders, certain questions should be pondered. The genetic status which the author describes is the present-day situation. He assumes that this not very different from the one prevailing five hundred years ago. That is to say, the limited genetic pool of the American Indians existed before the Europeans arrived. In this case, the biological and anthropological problem is to understand how this immense continent populated by tens of millions of humans for thirty or forty thousand years could be such an exceptional case. America, although certainly isolated from the Old World, was not a far-flung island; and what we know of Pre-Columbian civilisations suggests that they were not made up of a patchwork of separated groups of people. Moreover, genetic diversity is not given once and for all: it seems to be a dynamic system. Diversity in human populations is generated by intermixing and also by continuous mutation. Do American Indians have a lower mutation rate than the rest of the world?
Or, was the reduced genetic pool observed by Black in this meta-analysis the result of a decline in the number of American indians, whatever the mechanism ? A vicious circle of massive, prolonged elimination, in which populations were regularly pushed back, reduced and weakened, with perhaps a progressive reduction in genetic polymorphism gradually becoming irreversible.
Recent history alone will not allow us to decide and it is unlikely that we will be able to retrace the biological evolution of the Pre- and Post-Columbian Indians*. This lack of knowledge cannot be used to justify reducing the blame on the conquerors; nor can it support the opposite view. What can be done is to compare the epidemiology of Indian and half-caste populations in South America where they share the same environment and living conditions, if such a situation exists. As to deciding whether intermarriages between populations had the undesirable result of destroying indigenous culture, as Francis Black writes at the end of his article, this statement reminds us of other, similar, ones and we suggest that our readers do not take it as a hard and fast truth. Far from it.
(CNRS, BP 8, 94801 Villejuif cedex, France)
*Even by analysing DNA from mummies, it seems unlikely that enough data could be obtained to give a representative view of polymorphism in Pre-Columbian times.
1. Black FL. Why did they die. Science, 258, 1739-1740, 1992.