I WONDER IF THIS HAS ANYTHING TO DO WITH WHY HATS WENT OUT OF STYLE? White Americans’ heads are getting bigger — literally, study shows.

Researchers at the University of Tennessee’s Forensic Anthropology Center (what Mary Roach calls “the body farm” in her book “Stiff”) routinely examine skulls to try to determine sex and race of the craniums so if police officers discover just a skull, there are guidelines for gleaning info about it. The database of skulls and bodies has steadily increased to include people who were born and died in the 20th century, whereas prior the skulls were from people born in the 19th century. . . .

“The basic thing that we observed over the course of looking at crania that belong to people born from 1820s to 1980s, is that the cranium has gotten higher and narrower,” says Richard Jantz, who is married to Lee.

“If you just look at a side view of the skull, what you would see is the distance from top to bottom increased, and if you look at a front view of the skull, you would see the distance from side to side decreased.”

Bigger heads typically mean bigger brains, and while Richard Jantz and his colleagues did not look at brain size, he suspects brain size also increased. There are several theories why brains might be brawnier.

Better nutrition is one.

UPDATE: A better theory from reader Mary Forman: “Maybe those hats were interfering with head growth!”