"So what purpose does that serve?" you may ask. Well, picture this: Years ago, a field of fluffy white sheep, with one fainting goat in their midst. Of course the sheep are being eyeballed by coyotes or other predators. So the coyotes attack, thus startling the fainting goat (and the sheep). You can imagine what comes next. Thanks to that wonderful, genetic trait (or in this case, unfortunate) the goat tips over, making it easy prey for the coyotes, thus allowing the sheep to flee.
Females are polyesterus. Unlike other goats, they can breed year round. In some cases, they have babies twice, or up to three times a year. They are good moms, and usually have twins, but sometimes there are triplets, and even quadruplets and quintuplets!
Back in the 1980's, the fainting goats were close to extinction. However, today their numbers are estimated at close to 10,000 and they are no longer endangered.
American Tennessee Fainting Goat Association