This got long, so, here's a TL;DR: Observational studies on humans are basically the best you're gonna get for most purposes. Other animal models (primates, do

This got long, so, here's a TL;DR: Observational studies on humans are basically the best you're gonna get for most purposes. Other animal models (primates, dogs, rodents) have problems, but rodents are the best compromise. By using rodents to screen new interventions, we actually end up benefitting humans sooner than if we'd just started with people in the first place. --- Right. IMO anyone criticizing observational studies on humans needs to overcome the idea that it's hard to do controlled studies on humans, and when it is possible (e.g. vaccine trials), the studies don't last very long, because you can't really control peoples lives that long and there tends to be significant attrition over time. Theoretically, chimps would be the next best thing, but experimenting on chimps is ethically questionable as well, and they also live a long time. That's great for chimps, but not so great for biological studies where you want to observe the effects of an intervention over an entire lifecycle. Monkeys would be the next best thing after chimps, but experimenting on monkeys has the same issues as with chimps. Among common experimental animals, that basically leaves dogs and rodents. Dogs are relatively large and hard to deal with compared to rodents, and their relatively long lives (compared to rodents) makes them difficult to selectively breed. Even if we modified the embryos using CRISPR or something to include genes that were of interest, a dog's gestation period is about 3 months whereas for rats and mice it's about 3 weeks. Likewise, Beagles (one of the more common experimentally used dogs due in part to their relatively small size and friendly disposition) live for about 12-15 years, whereas wild-derived mice and rats both live around 2-4 years in captivity. The general public is also much less concerned when rodents get euthanized as part of an experiment than when dogs do. Whether that should be the case or not is somewhat debatable, but, nonetheless it is. It's all a big trade off between fidelity and logistics, but shouldn't an audience like HN's consisting of a disproportionate number of software people compared to the general public actually appreciate that? ;) So, rats and mice a really the only reasonable choice if you need to experiment on a live mammal in less time than it takes to actually get a PhD. But, then that triggers the chorus of "in mice" replies we see to pretty much every biomedical article on preclinical research here. And, there are undoubtedly interventions that would work on humans that don't work on mice, just as there are many interventions that work on mice but don't transfer to humans. We miss out on those, but the ones that do make it through rodent trials and into humans got there by a process that weeds out a lot of things that couldn't possibly work, which ultimately means humans benefit sooner by starting with mice than if we just used people in the first place.