I was wondering this at the zoo the other day. If we did evolve we went from a very vulnerable creature into a very sturdy ape like creature and then back to a very vulnerable creature. Was there a reason we could not have developed our intellect and still kept the strength of apes and their dexterity in the feet. Why didn't we keep the fur, the ability to keep warm without clothing. Was there a choice, we came to a fork in a road and it said choose left and you lose all of your survival gear and become a weak a frail creature that is super smart or choose right and stay an ape. There wasn't a middle option.
Think about this, at some point in human evolution our young would have been born able to walk or run and had instincts that could keep it alive if the parents were gone barring a predator eating it. Now if we left a baby overnight after it was born it might not survive because it is solely dependent on the parents for everything. Also everything on the planet seems to have the ability to kill us, its almost as if we survived on dumb luck. Even as adults we are frail in comparison to virtually every other life form out their.
Now that we have evolved into these superior intellectual beings we aren't even good at that. Look at how we have a need to do everything to excess. Other animals dont generally kill of their entire food supply or attempt to drain the water supply as quickly as possible. Other animals also have means of thinning the heard and not by natural causes. We wreck entire ecosystems by introducing new species of all kids to them.