Microsatellite variation and evolution of human lactase persistence.

Area of Science:

• Human evolutionary genetics
• Population genetics
• Molecular anthropology

Background:

• Human lactase persistence (LP) is a key adaptation to milk consumption.
• Two single-nucleotide polymorphisms (SNPs), -13910 C/T and -22018 G/A, are strongly associated with LP.
• Understanding the evolutionary history of LP requires detailed population genetic analyses.

Purpose of the Study:

• To investigate the evolutionary origins and selective pressures of lactase persistence.
• To assess haplotype diversity and reconstruct the demographic history of LP-associated alleles.
• To evaluate the utility of microsatellite loci for studying the evolution of complex traits.

Main Methods:

• Analysis of microsatellite variation in 794 chromosomes from diverse populations (Portugal, Italy, Cameroon, São Tomé, Mozambique).
• Age estimation of the -13910*T allele using intraallelic microsatellite variation.
• Application of neutrality tests to detect selection on LP-associated variants.

Main Results:

• The -13910*T allele, linked to lactase persistence, originated in Eurasia before the Neolithic period.
• Significant evidence of selection was found for the -13910*T variant in European and African populations.
• Microsatellite data suggest independent origins of lactase persistence in Europe and Africa, driven by convergent selection.

Conclusions:

• Natural selection played a crucial role in the evolution of lactase persistence.
• Convergent evolution likely explains the widespread occurrence of lactase persistence despite potentially different causal mutations.
• Microsatellite loci offer a cost-effective and high-resolution approach for reconstructing evolutionary histories of genetic traits.