Ears have been pierced in the Western world since ancient times, and have repeatedly gone in and out of fashion for various reasons. Here are a few specific things I know about the subject:

Ötzi the Iceman shows evidence of pierced and stretched ears, and he lived over 5000 years ago. The Bible mentions ear piercings a number of times, and indicates that the Hebrews who followed Moses out of Egypt had them. Exodus chapter 32 talks about how Aron made the golden calf out of melted down gold earrings.

In Roman times pierced ears were a sign of social status. The average worker did not have them as they would have gotten in the way, but the wives of wealthy Patricians did, and often wore gemstone earrings to show off their wealth and status.

During the Renaissance, European noblemen often pierced their ears, it was a sign of virility. Noblewomen did not often wear earrings during this era, as their elaborate wigs and hats tended to make earrings impractical. They became very popular again after 1800, when women's fashions simplified and those big heavy wigs and hats went out of fashion.

It remained popular until the 1920's when clip-on earrings became fashionable. From that time until the 1960's, clip-ons were seen as more proper for 'good girls'. During the counter-culture movement piercing the lobes caught on again, and it became common for young girls to get their lobes pierced at a doctor's office or at a jewelry store in a mall during the 1960's and 1970's. The age has slowly gotten younger and younger, and new Mothers now commonly pierce their little girl's ears when they are babies.

In the US, this has also been influenced by Latino immigrants. In Mexico and other Latino countries, baby girls are pierced by nurses before they even leave the hospital. There are cultural reasons for this and it is considered highly unusual in these countries for a baby girl's ears to not be pierced. Gold ear studs for a new baby girl are a common gift for expectant Mothers.