with recent positive selection related to the emergence of cattle domestication and milk consumption ~10 kya in the Middle East (Edwards et al., 2007; Enattah et al., 2008).
In African populations, the lactase persistence phenotype is generally highest in pastoral populations (Swallow, 2003; Mulcare et al., 2004; Ingram et al., 2007, 2009; Tishkoff et al., 2007b). However, with the exception of the Fulani and Hausa populations (Mulcare et al., 2004), other African pastoralist populations do not have the T-13910 mutation associated with the lactase persistence trait (Ingram et al., 2007; Tishkoff et al., 2007b). Recent studies have identified at least three additional and independent mutations that are associated with lactase persistence in East African pastoralist populations: C-14010, which is most common in Kenya and Tanzania (Tishkoff et al., 2007b); G-13907, which is present at low to moderate frequency in northeast Africa (Ingram et al., 2007; Tishkoff et al., 2007b); and G-13915, which is most common in the Middle East (Enattah et al., 2008) and northeastern Africa (Ingram et al., 2007; Tishkoff et al., 2007b) and may be associated with camel domestication in the Middle East ~6 kya (Enattah et al., 2008). Tishkoff et al. (2007b) demonstrated that all three variants result in significant increases in gene expression levels driven by the lactase promoter.
The most common variant within Africa associated with lactase persistence (C-14010) is also located within an extremely large linkage disequilibrium block (2 Mb) and is thought to have arisen ~6.8–2.7 kya in either the agropastoralist Afroasiatic populations that migrated into Kenya and Tanzania from Ethiopia within the past 5,000 years or the Nilo-Saharan pastoralist populations that migrated into the region from southern Sudan within the past 3,000 years, and the variant then subsequently spread throughout pastoral populations in eastern Africa relatively rapidly, con-