These magnitudes are considered small because they do not explain much of the heritable variation.

This heritable variation is known from heritability studies based on monozygotic twins.

Darwin tells us that evolution occurs by reproduction with heritable variation and natural selection.

Could we now state all possible physical systems that might be capable of replication, heritable variation, and natural selection?

Mutations are the feedstock of heritable variation in a population.

There are forces which add heritable variation to the population, such as mutation and recombination.

Twin and family studies have shown a substantial genetic component to this disorder, with heritable variation estimated at 50 to 70%.

The only widespread agreement on characters seems to be that variation used for character analysis should reflect heritable variation.

While mutation is the ultimate source of heritable variation, its permutations and combinations also make a big difference.

Thus, robustness reduces the amount of heritable genetic variation on which selection can act.