Lactic acid fermentation
Since they consumed more milk products, these societies developed lactase pesistence: The milk-digesting enzyme lactase was present in their body during the whole lifetime: They could also drink unfermented milk as adults. Even today there are regional differences: Estimates are that about 65% of the world polulation still lacks this enzyme. The first societies came from regions in eastern Turkey to central Europe; the gene is more common there, as well as in the United States, which was settled from Europe. In Asian countries,  lactose intolerance is much more present.