Mutational meltdown happens in a population of animals if their number is so low that negative mutations and deletions in their DNA accumulate.

Rule of thumb: 500 minimum viable population, 1k minimum to prevent negative genetic trends (inbreeding).

Is a similar rule of thumb thinkable for communities of practice in terms of maintaining the community itself, and in terms of keeping it varied / valuable enough on all [[Community building 20100210214508]] aspects Wenger et al list?