If we had their bellys then we might not be so sensitive to E-Coli...and we also might not ever live beyond 20 years. Sometimes, evolution is a bitch.
Actually, to a certain extent, it is possible to acclimate one's system to deal with raw meat, as long as it is very fresh and the animal wasn't ill. It's not so much that our protohuman ancestors had the ability to fight off highly infectious bacteria (though they did have a stronger chance of doing so), it's that they ate relatively fresh kills for the most part.
Keep in mind too, they didn't have to contend with anti-biotic resistant bacteria, the way we do. Also keep in mind, as Karan mentions, they had very low life expectancy. Since they lived on a diet of raw meat from birth, their ability to deal with lesser bacterias, that might make us sick, was much better. Even so, if they encountered slightly rotted meat or the flesh of an animal that was diseased, chances are it would be their last meal.
To be honest, having eaten raw meat, on a couple of occasions, it's not terribly appetizing. The first time, could be passed off on the fact that it was wild game, my first deer. But the second time, it was shortly after we slaughtered an organically raised cow. A cow that produced some of the best flesh I have ever eaten, when it was cooked. And we were eating some of the tenderloin, so it wasn't a lousy cut. Trust me, cooked is better, for more than one reason.
Through the years, the rules keep changing. Maybe we should all have scorecards.
Lots of information that came to me from my parents is not now (maybe never was) true.
I didn't know that 160 degree rule. But then, I don't eat much meat.
The life-span then was about 30 years; little wonder.