Recently, my wife and I took our 8-month-old daughter on a trip involving five plane flights in one week. Many people would be reluctant to travel with a baby that small, but we had a compelling reason: We have Fig Newtons for brains. An intelligent person, or even a reasonably bright fungus, would know that two people cannot possibly carry both a baby and all the supplies the baby needs, including stroller, car seat, clothes, diapers, industrial-sized bale of wipes, stuffed bear, stuffed tiger, stuffed frog, stuffed paramecium, etc. The total weight of all these supplies can be hundreds of...