But here is an example of where moving away from our ancient ways may have hidden costs. What else besides nutrition is stored in that milk? There’s some evidence that breast milk contains circadian cues. If true, then milk delivered at 2 am, straight from the breast, would not only satiate the baby, but also send the signal that it is now time to sleep. Milk expressed at noon, in contrast, would send the opposite signal. When feeding the baby at night, then, it’s best to provide nighttime milk. It won’t hurt, and may very well help.

Do not put screens in front of children, especially screens that have animate objects on them. As Bret and I posit in our book, babies and young children who are entertained by screens will learn to flatten their emotional range; they do not expect humanoid forms to respond to them.

Do eradicate all blue light from the space where you and your baby sleep. Early morning sunlight is so very blue, and those who are regularly exposed to bright outdoor light early in the day are more productive, and more fit, than those who are not. But expose yourself to blue light late at night, when our ancestors would have been gathered around a campfire — or navigating by the pale light of the moon — and find yourself struggling with sleep, and therefore with productivity, creativity, and health.

Do feed your children real food, tempting though it is to lean on processed meals.