What's the difference between human evidence and animal research?

Research usually starts in cells in a dish (lab or “in vitro” studies), then moves to animals, then to small human studies, and finally to large controlled trials in people.

Each step filters out ideas that don't hold up. Many results that look impressive in mice or rats never appear in humans — bodies, doses and lifespans differ too much.

So when you read that a peptide “healed tendons” or “reversed ageing”, the first question is: in what? On this site every claim is labelled with the level of evidence behind it.