for all our "brains" we still can't match the raw power and strength on jungle animals.

I recently spent a week on safari in Tanzania's wild life reserves like the Serengeti. There you see the big cats predominantly resting, sleeping or else slowly ambling short distances, e.g., to have a drink of water. They certainly don't 'train' to be fit to chase and catch their prey. They probably can't 'afford' the extra energy that would go into training/exercise as we know it. (Even when they have sex it's short and with a minimum of effort. They wake, copulate, roll over and go to sleep again.)
By the same token, their potential prey spent their days leisurely grazing and not 'training'. yet when it comes to the crunch the healthy specimen can escape the predators and its usually only the weak, sick or young get get chased down and killed.

So I guess I'm with trifreak101 that it comes down to genetics.

Evolution... if that word hasn't been said yet... or if you're very Christian then God just made creatures that way. But if we consider Darwin, animals have whatever power they need to fend off predators, catch prey, or perform one of the basic functions of being an animal...
Before somebody names an animal however that has far more power than it conceivably could use, or not enough, remember the process of evolution takes a long time.
Humans however, are distinguished from animals in that we have developed past the point of acting on pure animal instinct (or hopefully most of us have), and therefore we all engage in different activities, and so there is no model specification for a human (touching on Nietzsche's Ubermensch theory a bit here). What I'm trying to say is there is no set of core activities that all humans must perform, or that this is a very small list. Therefore if you want to be ripped you will only get there by developing your body in that way, through work, sport, and any other physically demanding activities you might expose your body to.
Hope that makes sense... it's evolution, baby!