Aoki K, Feldman M W
Department of Anthropology, University of Tokyo, Japan.
Theor Popul Biol. 1994 Feb;45(1):101-20. doi: 10.1006/tpbi.1994.1006.
Two unlinked autosomal loci are assumed to affect the ability to hear in such a way that homozygosity for the recessive allele at either locus causes deafness. The five deaf genotypes are subject to the same negative selection due to a lower likelihood of marriage, but unmarried deaf persons remain socially active and participate in the cultural transmission of sign languages. Marriages are assortative for deafness or for hearing, and mutation occurs irreversibly from the dominant to recessive allele at each locus at the same rate. At mutation-selection balance, the fully polymorphic equilibrium is symmetrical. Based on this genetic model, we consider the relative importance of various forms of cultural transmission as they affect the persistence of sign languages. Horizontal transmission is shown to be effective when deaf children are able to interact with many peers. This observation is especially pertinent if assortative meeting of deaf children occurs, for example, at schools for the deaf. Oblique transmission can also be effective, but the literature suggests that this kind of transmission plays only a minor role. It is necessary, however, that some form of cultural transmission occur between generations. Thus, vertical transmission is a critical factor, despite the fact that parent-child transmission is often interrupted due to the recessive inheritance of deafness. In particular, the contribution of vertical transmission is enhanced by assortative mating for deafness.
任一基因座上隐性等位基因的纯合性都会导致耳聋。由于结婚可能性较低，这五种耳聋基因型受到相同的负选择，但未婚的耳聋者仍保持社交活跃，并参与手语的文化传播。婚姻在耳聋或听力方面是选型婚配，且每个基因座上的显性等位基因以相同速率不可逆地突变为隐性等位基因。在突变 - 选择平衡时，完全多态平衡是对称的。基于这个遗传模型，我们考虑各种形式的文化传播在影响手语存续方面的相对重要性。当耳聋儿童能够与许多同龄人互动时，水平传播被证明是有效的。如果耳聋儿童的选型相遇发生，例如在聋校，这一观察结果就尤为相关。间接传播也可能有效，但文献表明这种传播只起次要作用。然而，某种形式的文化传播在代际之间发生是必要的。因此，垂直传播是一个关键因素，尽管由于耳聋的隐性遗传，亲子传播常常被打断。特别是，耳聋的选型交配增强了垂直传播的作用。
