Per his Wikipedia page. (Not always the best source but a quick one)
Bonnar was born in Hammond, Indiana and raised in Munster, Indiana, attending Munster High School.[2] Bonnar had an extensive background in combat sports, beginning with Wrestling when he was 10 years old, Tae Kwon Do at age 12, Brazilian Jiu-jitsu at age 22, and then added Boxing and Muay Thaiwhen he was 24 years old. He earned his black belt in Tae Kwon Do at the age of 16 and was a two-time Golden Gloves Champion in the Super Heavyweight division. He attended and graduated from Purdue University in 2000, earning a degree in Sports Medicine.[3]