非典型（Ea1）和耐氟（Ef1）胆碱酯酶基因：在美洲印第安原住民群体中不存在。

Hum Hered. 1977;27(6):433-6. doi: 10.1159/000152905.

A population of 358 Navajo Indian children screened for serum cholinesterase variants failed to show the presence of either atypical or fluoride-resistant genes. This is the first significant anthropological observation of the absence of both variants in a native North American population.

对358名纳瓦霍印第安儿童进行血清胆碱酯酶变异体筛查，结果未发现非典型或氟抗性基因的存在。这是首次在北美原住民群体中对两种变异体均不存在的重要人类学观察。