Humans (and other life forms) were designed to react swiftly to immediate threats to their existence. Any forms designed without this capability failed to flourish. You have to leap out of the way of the lion or you won't be able to stick around to make babies.
However, we are proving our unconsciousness to threats just as mortal but not as immediate. The challenge we face is to engineer our own evolution so that we become continuously capable of reacting to future dangers.