Human Fetuses Develop Useless Hair

One of my favorite cases of embryological evidence for evolution is the furry human fetus. We are famously known as “naked apes” because, unlike other primates, we don’t have a thick coat of hair. But in fact for one brief period we do—as embryos. Around sixth months after conception, we become completely covered with a fine, downy coat of hair called lanugo. Lanugo is usually shed about a month before birth, when it’s replaced by the more sparsely distributed hair with which we’r...

 An Origami Metaphor for Fetal Development

The sheets of tissue that fold, invaginate and turn inside out in a developing embryo do indeed grow, and it is that very growth that provides part of the motive force which, in origami, is supplied by the human hand. If you wanted to make an origami model with a sheet of living tissue instead of dead paper, there is at least a sporting chance that, if the sheet were to grow in just the right way, not uniformly but faster in some parts of the sheet than in others, this might automatically cau...