Lactase persistence, 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 lactase persistence 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 pre-adaptive high lactase persistence allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for lactase persistence although it has not been possible to say if early Neolithic
European populations were lactase persistent at appreciable frequencies. We developed a stepwise strategy for obtaining reliable nuclear ancient DNA from ancient skeletons. This is based on 1. selecting skeletons from archaeological sites that showed excellent biomolecular preservation 2. the obtaining of highly reproducible human mitochondrial DNA sequences, and 3. reliable STR-genotypes from the same specimens. By applying this experimental strategy, we have obtained high-confidence lactase persistence-associated genotypes from 8 Neolithic and 1 Mesolithic human remains using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with lactase persistence in Europeans, thus providing evidence for the “culture-historical hypothesis” and indicating that lactase persistence was rare in early European farmers.
Johannes Gutenberg University
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Joachim Burger,