In the world of bio-mechanics, over-pronation is an excessive inward turning of the feet. 80% or more of the U.S. population exhibit some degree of pronation. The opposite of this phenomenon is supination - a turning outward of the feet. Excessive pronation and excessive supination can cause stress on the plantar fascia and lead to plantar fasciitis. Many running shoes have an anti-pronation design, and thus the issue of over-pronation can be relatively easily addressed. Orthotics are often prescribed as well.
You are correct in that SOME cases of over-pronation are inherited; but biomechanically, your tendencies also develop over time based on the shoes you wear, your activities and the types of stresses to which your feet are exposed. If you suspect biomechanical issues, you should have your gait assessed by a doctor or therapist.
Hope this info helps.