As to whether power is the primary motivation of people, I have yet to witness even a small fraction of people try to exert themselves toward power. Most people are too timid and unsure of themselves to do that.
Beyond survival, it seems to me that human motivations become fairly erratic. Some are genuinely selfless, and some are selfishly generous. Though I have yet to meet someone who is truly without some degree of selfishness.
Humans are to my experience, beautifully flawed. The only constant is that humans need some way to pass the time: a hobby, games, television, reading, starting wars, exercising, painting, starting up businesses, meditating, and so on. The only common thread I see in every person is the need to do something.
Since survival doesn't fill the void of activity, other things must. The need to do something is so powerful that it will override the need to be happy or to have power. There is never a moment when I'm doing "nothing", though to some observers it might appear so. Even if you were to meditate and empty yourself of everything, you are still doing something.
After survival and then doing something, the most common thread I've seen is doing something for the sake of change. Often this is done to the detriment of a person's happiness. For example, many happy marriages can end not because they are unhappy with each other from the exhausting sameness. Look at the amount of vocabulary to describe this sense: burn out, needing excitement, boring, repetitious, same-o same-o (a literary construct that exists in French and Chinese to my knowledge, probably others), same shit different day, doing nothing, and so on.
In the end this vast array of activities and spontaneous changes in those activities leads humanity stumbling along in something we call progress.
