By motivation I mean such things as hunger, escape from danger, thirst, reproduction, etc.
Again, your words suggest consciousness of cells. Why do you think cells experience hunger, thirst, or a need to escape from danger. We do know that cells replicate, but there is nothing to suggest that there is any conscious motivation to do so. Rather, it is simply something they do.
While we are at it, how do you explain consciousness, rationalization, creativity, empathy, love, hate, jealousy, free will, etc.?
I don't make any claim to be able to explain consciousness. Science is only now just beginning to examine consciousness, so we are still in the dark ages. There are various ideas, but none proven.
There are a few things above that I can comment on.
1. Rationalization is the largely unconscious attempt to justify and action or idea. The person doesn't say to themselves, "Hey, I'm now going to just LIE to myself." In the case of immoral actions, humans are driven by cognitive dissonance to provide a justification so that they can continue to think of themselves as good people. In the case of ideas, it is due to something called Confirmation Bias, a defect of logic that seems to simply be part of our brain wiring.
2. Regarding creativity, scientists are still studying this. We know that it comes from the brain, and the most popular hypothesis is that it is rooted in the frontal lobes. But the jury is still out.
3. Regarding empathy, it is a biological instinct, and talent that most (though not all) humans are born with, and which is either developed or decreased by our experiences. Along with our innate sense of fairness, these two instincts are the foundation for human moral thought.
4. Love? This word is used for so many different things, that I'm not sure which one you are referring to. I'm going to take a shot, but if I understood you wrong, you have only to clarify and I'll be happy to reply once more.
I think of love not in terms of feelings, but of actions. For example, let's say a parent comes home for a 10 hour shift plus an hour long commute. They want nothing more than to grab something to eat, and have time alone watching their favorite TV show or playing the latest video game. But they have three kids. So instead of resting the way they want, they put in the effort to hug their kids, prepare dinner for them, help them with their homework, oversee that they all have their baths, and put them to bed. This is not what they want to do. In fact, inside their own mind, they grumble about it. They do not FEEL loving at that moment. But they ACT loving. THAT is REAL love.
In other words, I tend to think of love as acts of altruism. Behavioral biologists such as Robert Sapolsky teach us that altruism as evolved because of GROUP SELECTION. This is different than individual selection or sex selection. In Group Selection, traits which help the entire group survive and get pass on and become more frequent. It's interesting because the group selection of altruism is in direct conflict with the individual selection for selfishness. This is why you find some humans that are loving, and others that are selfish jerks.
5. Hate can be defined as intense dislike. I found the following summary of its reasons very helpful:
"Hate that's directed externally is typically caused by a personal threat or experience that triggers a strong sense of fear, mistrust, loss of power, or vulnerability. "
6. You could write an entire book on jealousy, which would be interesting given that it is the source of so many negative actions, from a bad mood to murder. In its milder form, it is simply envy: "Gee I sure wish I had won that award instead of Susie." In its extreme form, it becomes a pathological obsession and hatred that can even drive a person to violence. Psychology Today magazine has this to say: "Jealousy is a complex emotion that encompasses feelings ranging from suspicion to rage to fear to humiliation. It strikes people of all ages, genders, and sexual orientations, and is most typically aroused when a person perceives a threat to a valued relationship from a third party. The threat may be real or imagined." People do not choose to be jealous, and in many cases it seems impossible to reason with the jealous person. However, there are those people who have greater self insight, and you can talk to them, and work to ease their feelings.
7. Free will is another big topic. I have to say that I spent most of my life arguing for free will, as I believe it to be a necessary part of moral responsibility. I mean, if someone doesn't freely choose an action, like if they are experiencing hallucinations and delusions, can you really hold them responsible? My religion is one of right action (Judaism), and a lot of what we call free will is embedded into Jewish views.
However, things I have learned throughout my life have chipped away at my belief in free will. Probably the one factor that effected me the most was a series of classroom videos on Behavioral Biology by Dr. Robert Sapolsky from Stanford University (you can see the series for free on YouTube). I first watched them some 10 years ago. As with many new ideas, I listened, but had to chew on it for a LONG time. I think it was about a year ago that I had to admit to myself that I no longer believed in free will.
Factors determining behavior have quite a range: environment (including upbringing, social interactions, influences, and socioeconomic status), genetics, epigenetics, threat of punishment or promise of rewards, womb environment (including viruses, hormones, neurotransmitters, position in the womb, whether one has a twin of the same sex or opposite sex, etc.), learning, maturation, evolution, culture (including the culture of a person's ancestors), and more (basically I can't remember them all, LOL).
Today, although I'm still strong on law and order (offenders need to be removed from society so that they don't continue to inflict harm) I do not think of imprisonment as retributive justice, but simply necessary to protect us, and would like to see significantly better programs to rehabilitate.