The implanted stem cells, however, were human. (The fact that that the treatments did not cause "fever or substantial changes in immune cell levels (lymphocytes, neutrophils, and monocytes), which are commonly monitored for xenograft-related immune responses," is itself surprising.)

> promises of extending life have always fallen short of hype, and odds are this will too

Correct, though I'd say because this is early-stage medical research. Not because it's targeting longevity. I'd be similarly sceptical of an N = 16 early-stage drug trial for the flu.

In terms of replicatability, it is also not always the sample size, it is the effect size. Small samples do affect ability to generalize, but the point is that sample size isn't everything.

Which effect size do you find lacking?