In the previous posts, I explored why my dad has lactose intolerance and concluded that it was because his Indian ancestors were likely late to domesticating livestock. Yet, both of my parents are South Asian, so why would my father be lactose intolerant while my mother is not?
I have read that in the Indus River Valley civilization, the inhabitants domesticated cattle. Therefore, they developed the ability to digest lactose through the evolution of their genes (Mallikarjun, 2011).
My mother has fair skin from Punjab and my father has dark skin from Madhya Pradesh. Although they are both North Indian, logic dictates that my father must have significant South Asian DNA due to his skin color in addition to Madhya Pradesh’s proximity to South Asia. Another study I found confirmed that people in North India, where the Indus Valley Civilization was located, and from where Aryans from the North invaded the South Asian native Dravidian populations, were less likely to have lactose intolerance than people from South India (Tandon, 1981).
Using this data it makes sense that my mom, who is from an area of India that was most likely invaded by the Aryans, would be lactose tolerant. My Dad, who likely has more ancestry from southern India where there was relatively less contact with the Aryans and domesticated animals, is lactose intolerant.
Mallikarjun, Y. “Indians Share Milk-Digesting Trait with Europeans.” The Hindu, The Hindu, 8 Sept. 2011, https://www.thehindu.com/sci-tech/health/diet-and-nutrition/indians-share-milkdigesting-trait-with-europeans/article2436885.ece.
R K Tandon, Y K Joshi, D S Singh, M Narendranathan, V Balakrishnan, K Lal, Lactose intolerance in North and South Indians., The American Journal of Clinical Nutrition, Volume 34, Issue 5, May 1981, Pages 943–946, https://doi.org/10.1093/ajcn/34.5.943
R K Tandon, Y K Joshi, D S Singh, M Narendranathan, V Balakrishnan, K Lal, Lactose intolerance in North and South Indians., The American Journal of Clinical Nutrition, Volume 34, Issue 5, May 1981, Pages 943–946, https://doi.org/10.1093/ajcn/34.5.943
Evolutionary Anthropology 