Absence of the lactase-persistence-associated allele in early Neolithic Europeans
Absence of the lactase-persistence-associated allele in early Neolithic Europeans
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DOI：
10.1073/pnas.0607187104
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发表时间：
2007-03-06
影响因子：
11.1
通讯作者：
Thomas, M. G.
中科院分区：
文献类型：
--
作者：
Burger, J.;Kirchner, M.;Thomas, M. G.
乳糖酶持久性(LP)是孟德尔人的主要特征，赋予成年人消化牛奶糖乳糖的能力，在过去的20,000年里，在中欧和北欧人中出现的频率很高。这一特征很可能赋予了食用相当数量的未发酵牛奶的人一种选择性优势。有些人主张“文化历史假说”，即在新石器时代早期奶牛业出现之前，Lp等位基因很少见，但在自然选择的作用下，Lp等位基因的频率迅速上升。其他人倾向于“反向原因假说”，即在具有适应前高LP等位基因频率的人群中采用挤奶。基于乳糖酶基因单倍型保守性的分析表明，LP的起源是最近的，选择系数很高，尽管还不能说新石器时代早期的欧洲种群是否以可察觉的频率持续存在乳糖酶。我们开发了一种从古代骨骼中获得可靠的核古代DNA的逐步策略，其基础是(I)从考古遗址中选择具有良好生物分子保存性的骨骼，(Ii)获得高度可重复性的人类线粒体DNA序列，以及(Iii)从相同的标本中获得可靠的短串联重复序列(STR)基因型。通过应用这一实验策略，我们使用一系列严格的古代DNA工作标准，从8个新石器时代和1个中石器时代的人类遗骸中获得了高置信度的LP相关基因类型。我们没有观察到欧洲人中最常见的与LP相关的等位基因，从而为文化历史假说提供了证据，并表明LIP在早期欧洲农民中是罕见的。
Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern Europeans in the last 20,000 years. This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Some have argued for the "culture-historical hypothesis," whereby LP alleles were rare until the advent of dairying early in the Neolithic but then rose rapidly in frequency under natural selection. Others favor the "reverse cause hypothesis," whereby dairying was adopted in populations with preadaptive high LP allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for LP, although it has not been possible to say whether early Neolithic European populations were lactase persistent at appreciable frequencies. We developed a stepwise strategy for obtaining reliable nuclear ancient DNA from ancient skeletons, based on (i) the selection of skeletons from archaeological sites that showed excellent biomolecular preservation, (ii) obtaining highly reproducible human mitochondrial DNA sequences, and (iii) reliable short tandem repeat (STR) genotypes from the same specimens. By applying this experimental strategy, we have obtained high-confidence LP-associated genotypes from eight Neolithic and one Mesolithic human remains, using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with LP in Europeans, thus providing evidence for the culture-historical hypothesis, and indicating that LIP was rare in early European farmers.