Comment by strken

In hindsight, this explanation was a bit sparse, so here is the actual text from TFA:

> your baby will still be somewhat less fit compared to you and your hopefully-hot friend on average, but now there is variance, so if you cook up several babies, one of them might be as fit or even fitter than you, and that one will likely have more babies than your other babies have

This is a nearly word-for-word explanation of mutation-selection balance, e.g. check out the Wikipedia explanation:

> an equilibrium in the number of deleterious alleles in a population that occurs when the rate at which deleterious alleles are created by mutation equals the rate at which deleterious alleles are eliminated by selection

Regression to the mean is a statistical phenomenon about, well, measurements that regress to the mean. In the given quote, the average baby isn't regressing to the mean, the average baby is carrying a higher number of deleterious alleles and is less fit across the board. TFA then describes fitter babies having more babies themselves, which is irrelevant to regression to the mean but an integral part of mutation-selection balance.