Do quantum gravity effects prevent the smallest black holes from forming?

If gravity has a built-in minimum length scale ℓ — as many quantum gravity theories predict — then primordial black holes below a mass roughly c²ℓ/G simply cannot form in the early universe. This raises the threshold density fluctuation needed to birth a black hole, meaning the observed abundance of primordial black holes could directly constrain that fundamental length. It links cosmological observations to the deep structure of spacetime.