遺伝子・文化共進化の立場から見た成人乳糖吸収能と乳使用〔英文〕
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概要
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Two major hypotheses proposed to explain the observed association between prevalence of adult lactose absorption and milk use in human populations are the "culture historical hypothesis" and the "calcium absorption hypothesis". A rigorous formulation of the evolutionary problem calls for an approach based on gene-culture theory. This paper selectively reviews data bearing on the coevolutionary approach. First, a reinterpretation of the data on Finnish school children suggests that lactose malabsorption is fully expressed by age 12 rather than after age 15. This result is consistent with a one-locus two-allele determination of the trait, and also suggests that lactose is not an inducible enzyme. Second, a comparison of milk preference in lactase absorbers and malabsorbers suggests that a difference in preference may manifest itself when malabsorbers are in the majority, as was presumably he case in ancestral human populations. Third, calcium absorption in the presence of lactose is more efficient in lactose absorbers than malabsorbers. This result supports the contention that malabsorbers were more susceptible to bone diseases and hence at a selective disadvantage in northern Europe. Fourth, a simple model of gene-culture coevolution is presented to show how the reviewed data pertain. The time required for genetic change is computed as a function of the intensity of selection. Strong selection pressures must be invoked if the genetic change is to have occurred by natural selection during the 6000 years since adoption of milk use. Finally, the incompleteness of the association between prevalence of adult lactose absorption and milk use among the populations surveyed is discussed.
- 日本遺伝学会の論文