Each day as I travel through downtown Tucson, I am amazed at how quickly the most ancient of human behaviors have changed. For as long as there have been Homo sapiens - roughly 200,000 years - people have filled their lives principally with two activities: talking directly with other people, and doing physical things.

Fear and greed are potent motivators. When both of these forces push in the same direction, virtually no human being can resist.

It's rare - too rare, I have to say - for botanists to become doctors.

Everyone prefers some foods over others, but some adults take this tendency to an extreme. These people tend to prefer the kinds of bland food they may have enjoyed as children - such as plain or buttered pasta, macaroni and cheese, cheese pizza, French fries and grilled cheese sandwiches - and to restrict their eating to just a few dishes.

As an undergraduate at Harvard in the 1960s, I was fascinated by my visits to psychologist B.F. Skinner's laboratory.

Gardening is not trivial. If you believe that it is, closely examine why you feel that way. You may discover that this attitude has been forced upon you by mass media and the crass culture it creates and maintains. The fact is, gardening is just the opposite - it is, or should be, a central, basic expression of human life.

I tried to change the conventional paradigm, for example, by insisting on the reality of mind-body interaction, by stressing the importance of natural therapies, by focusing attention on lifestyle issues, by looking at worthwhile aspects of alternative medicine. Many people have been threatened by that. Doctors especially tend to think that they know everything about the human body, and don't realize that medical education has really omitted many very important subjects.