[cyberax]

> Not sure why you think weight is such a key variable.

I worked in cancer research-adjacent area (on computational biology). The problem with mice was that cancers in mice necessarily contain fewer cells than human cancers.

So a lot of treatments can simply clear these cancers completely, without giving them a chance to evolve resistance. Yes, you can try to compensate for that, but it just is not reliable.

In addition, mice are notoriously naturally susceptible to cancer. So their cancers, counter-intuitively, are often less evolved as a result.

> And when you say “brain” who could been a dozen different things.

I basically mean "degenerative brain diseases", very much including aging.