Rhaina Cohen

When Paul Kugelman was a kid, he had no shortage of friends. But as he grew older and entered middle age, his social world narrowed.

"It was a very lonely time. I did go to work and I did have interactions at work, and I cherished those," he says. "But you know, at the end of the day it was just me."

Kugelman's story isn't unusual: researchers say it can be difficult for men to hold on to friendships as they age. And the problem may begin in adolescence.

Women in the Middle Ages were excluded from many realms: the law,