Do you have a source for the IVC use of milk? I'm not familiar with any direct evidence that the IVC consumed milk or milk products. They did rear animals that

Do you have a source for the IVC use of milk? I'm not familiar with any direct evidence that the IVC consumed milk or milk products. They did rear animals that can be milked, but it doesn't necessarily follow that the IVC used them for milk rather than meat. The lactase persistence variant found in India, 13910T, is the same as prevalent in Europe, and likely arrived with Steppe pastoralists - after the fall of the Indus Valley Civilization. If the IVC had widespread lactase persistence mutations developing independently of the Steppe, you'd expect other variants to show up in the population, but it doesn't. Lactase persistence in India also closely tracks Steppe ancestry, suggestive that the IVC were largely lactose intolerant. They did have significant cattle, and were the birthplace of Zebu cattle domestication.