Why are so many natives lactose intolerant? The genetic and evolutionary story
                                
                                
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                                    4 min read                                
                            
                                Approximately 65% of the global adult population has a reduced ability to digest lactose, while estimates suggest this figure is nearly 100% among some American Indian communities. The reason why so many natives are lactose intolerant is rooted not in a medical disorder, but in human evolutionary history and ancestral dietary habits.