Raw meat is good because of
1. parasites/bacteria/disease (cooking kills that stuff)
2. cooking breaks down the meat and makes it easier to chew.
Update: how come cavemen were able to eat it in the past?
The genus Homo evolved about 2,000,000 years ago.
Fire and cooking happened before 1,000,000 years ago.
"Cavemen" had fire, and cooked their meat.
We are Homo Sapiens, evolved about 300,000 years ago.
We evolved *because* our ancestors cooked their meat.