At last, an answer to the question asked a thousand times.

While only females have mammary glands, we all start out in a similar way in the embryo. The embryo follows a female template until about six weeks, when the male sex chromosome kicks in.

That’s according to New York physician Billy Goldberg, from his new book Why Do Men Have Nipples? Hundreds of Questions You’d Only Ask a Doctor After Your Third Martini, anyway. He also covers other burning questions such as why your teeth chatter when you’re cold, and whether you can really get diseases from sitting on a toilet seat.

You can order it from Amazon for about 7 quid.

Via: [Reuters]