Coevolution of Arranged Marriage Culture, Hepatitis B Virus Infection, and Acetaldehyde Dehydrogenase Allele Selection

媒妁婚姻文化、B型肝炎盛行率、與乙醛脫氫酶基因的共同演化

與大多數歐美國家相比較，漢人社會顯現較少的飲酒過量問題，許多研究指出亞洲一些族群的乙醛脫氫酶基因多屬於缺陷型（ALDH2*2），較無法正常代謝酒精，因此能夠預防飲酒過量。東亞是高B型肝炎盛行率區域，與乙醛脫氫酶缺陷基因（ALDH2*2）的分佈區域互相呼應。感染B型肝炎者若進一步過量飲酒將造成更高的死亡率，合理推斷帶有ALDH2*2基因者因不善飲酒而有較高的生存優勢。但即使有生存優勢，並不擔保ALDH2*2基因者有較高生育後代的機率，也就是生殖優勢。實際檢視流行病學數據，一些低B型肝炎盛行率的東亞國家，ALDH2*2基因頻率也很高。因此，除了B型肝炎感染之外，應該有其他因素造成ALDH2*2基因頻率升高。本文提出媒妁婚姻造成ALDH2*2基因頻率升高的假設。帶有ALDH2*2基因者因酒精不易代謝，即使極少量飲用亦容易臉部潮紅，此反應極可能成為媒人在傳統漢人社會推銷未婚男女的重要條件：易臉紅者較容易在婚姻市場中被選擇而生育後代，增加ALDH2*2基因被留存的機會，提升生殖優勢；並間接減低B型肝炎帶原者因飲酒過量造成的死亡增加，提升生存優勢。

Asians seem to have only minor drinking problems compared to Westerners. Some research proposed that many Asians inherit an inactive alcohol metabolic enzyme allele, Acetaldehyde Dehydrogenase 2*2 (ALDH2*2), which can help suppress excess drinking. In this paper, biological and cultural selective forces are introduced and synthesized into a coevolution model to explain the selection of ALDH alleles. The liver disease caused by hepatitis B virus (HBV) infection as a biological selective force gave nondrinkers with the ALDH2*2 allele a better adaptation for survival, but late onset of liver disease could not stop transmission of the active ALDH2 enzyme allele. Chinese drinking norms and arranged marriages enhanced the selective advantage of reproduction toward ALDH2*2 allele carriers. Even after only a small amount of alcohol, the face of an ALDH2*2 allele carrier will be flushed. In ancient Chinese Han culture, drinking norms molded the idea that nondrinkers with the flushing reaction were good subjects for an arranged marriage, which ensured that ALDH2*2 allele carriers had higher selective advantages in the marriage market and transmitted the AlDH2*2 allele to their offspring.