MOND famously (notoriously?) cannot explain the observed motions of galaxies within groups and clusters (the oldest known evidence for dark matter). Even if you

MOND famously (notoriously?) cannot explain the observed motions of galaxies within groups and clusters (the oldest known evidence for dark matter). Even if you assume MOND is true, the galaxies are moving too fast, so you need an extra source of, well, dark matter.