The Claim
Lactase non-persistence is the ancestral human phenotype and is present in approximately two-thirds of the global adult population.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
Most adults worldwide cannot digest lactose after infancy because their bodies stop producing the enzyme lactase, a trait inherited from human ancestors.
See the scientific wording
Lactase non-persistence is the ancestral human phenotype, affecting approximately two-thirds of the global adult population.
After infancy, most people naturally stop producing the enzyme that digests milk because a specific region of DNA near the milk-digesting gene becomes covered in chemical tags that block the gene from being turned on. These tags build up over time and prevent the gene from receiving signals from distant control switches, so the enzyme is no longer made. Only a small number of people have a genetic difference that keeps these tags from forming, allowing them to keep making the enzyme into adulthood.
What the research says
4 studiesStudy: Lactase non-persistence is directed by DNA variation-dependent epigenetic aging
Most adults can't digest milk because their bodies naturally stop making the enzyme that breaks it down — this is how humans evolved. Only some people have a genetic quirk that lets them keep digesting milk as adults.
Study: A worldwide correlation of lactase persistence phenotype and genotypes
Most adults worldwide can't digest milk because their bodies naturally stop making the enzyme lactase after infancy — that’s how humans evolved. This study shows that even though some groups can digest milk as adults, most people still can't, which means the original human trait was not being able to digest milk after childhood.
Most adults worldwide can't digest milk because their bodies naturally stop making the enzyme after infancy — that's the old human trait. The study shows that in groups without a history of drinking milk, most adults still can't digest it, proving this is the original human condition.
Study: What is normal and abnormal in lactose digestion?
Most adults worldwide can't digest milk because their bodies naturally stop making the enzyme lactase after infancy — this is normal and inherited, and the study confirms that about two-thirds of people have this trait.
Related videos
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 4 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.