According to what I have read, the accepted theory is that all humans used to be lactose intolerant, i.e. after breast feeding is stopped. Some thousands of years ago it was because of a mutation which allowed the
LCT gene (which allows for making lactase) to remain turned on and humans were able to continue to consume milk.
The lactase deficiency also could be linked to certain heritages. Seventy-five percent of all African American, Jewish, Mexican American, and Native American adults are lactose intolerant. Analysis of the DNA of 94 ancient skeletons in Europe and Russia concluded that the lactose tolerant mutation appeared about 4,300 years ago and spread throughout the European population.
Different alleles for lactase persistence have developed at least three times in East African populations, with persistence extending from 26% in Tanzania to 88% in the Beja pastoralist population in Sudan.
Source:
en.wikipedia.org/wiki/Lactose_intoleranceRegarding the criticism of the verse, exactly what does the verse has to do with lactose intolerance? This is a straw man fallacy and probably a red herring too. The verse is talking about the blessing of Allah for creating a palatable drink, a drink consumable for humans (these are actually how other translators translate this verse, instead of "sweet to the drinker", source:
islamawakened.com/quran/16/66/). From between the impure and disgusting matters such as "waste matter [or excretions] and blood", consumable milk is produced.
The verse isn't claiming that there are no humans in the world for whom milk is non-consumable. Additionally, as it would appear that around 75% of all Jews are lactose intolerant (source:
www.haaretz.com/israel-news/science/.premium-1.664967,
www.momentmag.com/the-biggest-jewish-genetic-myths-of-all-time/), if Prophet Muhammad was making the Qur'an up, he would've known about this intolerance.