Somers, I totally disagree with the the concept
"If they can walk they can wrestle".

Only because one can walk does not mean he has balance, sufficient coordination, or emotionally ready to physically mix it up with someone else on the mat.

It's ok, I know many people who thinks the same and start their kids at 4, and 5. Some of those people are also surprised when kids that I've coached who are 10,11,and 12 years of age and have been wrestling for only 2 and 3 years are beating some of those kids that started wrestling when they were 4 and 5.

Bottom line, in the long run it doesn't make a different if you start them at 4 or 9. Actually it does, the 9 year old is better prepared to learn the sport.