Reduced cartilage GAGs explain knees

A Nature study using barcoded regulatory assays and human–ape hybrid stem cells finds humans produce ~25–33% of the glycosaminoglycans (GAGs) found in great‑ape cartilage, which makes human cartilage thinner and less shock‑absorbing. That molecular regulatory shift plausibly explains humans’ unusually high burden of osteoarthritis, disc disease, and other skeletal degeneration compared with other great apes. — If true, this rewires how we think about musculoskeletal disease — from lifestyle explanations toward evolutionary‑genetic origins, with implications for screening, regenerative medicine, and ageing policy.