@chai2,
There was a wild child born late in the 18th century, who was first found in 1797, and escaped, was brought back in, escaped again, and then showed up on his own about three years later, in 1800.
This article at Wikipedia gives the bare facts. But it leaves some things out. He had to be taught to eat cooked food, and apparently despised cooked vegetables all his life. He didn't want cooked meat at first, but eventually got used to, and even grew to like it. It took them a long time to teach him to wear clothing, even in winter. The doctor who raised him would go into his room at night, to wish him good night, and to "tuck him in." If he came back later in the night, though, he would usually find him sleeping (apparently comfortably) on the hardwood floor, with no pillow and no covers--once again, even in winter. I read a detailed account, but it has been many, many years.
I don't think it would be a very fun life.