Why some meats have a doneness range and others have one fixed number
Beef, lamb, and fish all have a genuine spectrum of doneness preference — rare through well-done are all considered safe to eat (assuming the meat is handled properly beforehand), so the "right" temperature is really a matter of taste. Poultry and ground meat are different: USDA guidance gives these a single safe minimum temperature (165°F for poultry, 160°F for ground meat) rather than a preference range, because of higher bacterial risk — poultry skin and ground meat's larger surface-area-to-volume ratio (from grinding) both carry more risk of contamination throughout the meat, not just on the surface, which is why there's no "medium-rare" option for either.
Why pork's target dropped over the years
Older cooking guidance called for pork to reach 160°F or higher, largely due to trichinosis concerns that were far more common decades ago. Modern USDA guidance lowered the safe minimum to 145°F with a 3-minute rest, reflecting improved farming and processing practices — this means well-cooked pork today can be noticeably juicier and pinker than older recipes assumed, without any food-safety compromise.
FAQ
Why does ground meat need a higher temperature than the same cut whole?Grinding mixes any surface bacteria throughout the meat, rather than leaving it only on the exterior (which searing/cooking to a lower internal temp would normally handle safely for a whole cut) — that's why ground meat needs a higher, more uniform internal temperature.
Does resting time matter for all of these? Yes to some degree for larger cuts — a brief rest lets temperature and juices even out, though it matters less for thin cuts like a burger patty than for a thick roast.