Our findings show that lactase persistence evolved not through a single story of selection, but as a mosaic shaped by diverse demographic and cultural histories, each leaving a distinct mark on the genome.

We thank our collaborators and welcome any feedback!

Why then is LP under strong selection only in pastoralists like the Toda (South India) and Gujjar (Pakistan), despite their distinct environments and shared exposure to famine and disease with nearby non-pastoralists? This suggests unique selective pressures linked to pastoralism itself.

Widespread dairy use (in both pastoralist and non-pastoralist) but limited LP in South Asia raises important questions about gene–culture coevolution. Do traditional milk processing (e.g, fermentation) reduce lactose, enabling dairy consumption without genetic adaptation, as seen in Central Asia?

Only exceptions are two geographically-distant pastoralist groups- Toda & Gujjar. By performing local ancestry inference, we find significant enrichment for Steppe pastoralist ancestry around the LCT locus in these two geographically-distant pastoralist groups, indicative of strong recent selection.

Interestingly, unlike in other worldwide populations, the LP prevalence is almost entirely explained by Steppe ancestry—not selection––in most contemporary South Asians.

Ancient DNA evidence indicates that this allele was introduced into South Asia during the historical to early medieval periods (756 BCE–52 CE), through Steppe pastoralist–related gene flow.

We find that the Eurasian variant, −13.910:C>T, is widespread across South Asia, with regional heterogeneity. The frequency ranges from 10%–15%, except in two pastoralist groups: the Gujjar (Pakistan) & Toda (South India), where frequencies reach ~65%—similar to Northern Europeans.

We assembled genome-wide data from ~8,000 present-day and ancient genomes from India, Pakistan, and Bangladesh, spanning diverse timescales (~3300 BCE–1650 CE), geographic regions, and ethnolinguistic and subsistence groups to patterns of LP in South Asia.

Sorry to hear that David.

We have open positions if you want to send me your CV/chat, send me an email.