By Orlando R. Barone

Way back in Psychology 101, Dr. Ward discussed the evolutionary nature of emotions and attitudes. Anger, she told us, is useful for warding off dangerous animals whom we can beat up, while fear gives us the spunk to run away from larger beasts who look upon us as a tasty treat.

It made sense, and our current age is awash with folks opining about the evolutionary origins of every mood and impulse. Jealousy is an aid to keep mating couples together to raise the kids. Prejudice makes my tribe wary of your tribe, and is useful if your tribe has bad intentions.

Even altruism has a basis in our survival system. It binds families and tribes, making us more likely to band together against a world that would snuff us out if it could. That makes altruism selfish, of course, and somewhat less altruistic.

The whole thing sounds feasible, this evolutionary explanation of feelings and impulses. Even though the various hypotheses are difficult to test scientifically, I find the notion compelling. We possess these attributes, these tendencies, because they've kept us alive in an indifferent universe.

There is one stumper, however: Gratitude, the inclination to say "thank you" to someone who does something we think is generous or kind to us. How does gratitude give us an evolutionary advantage? It seems at first like a harmless yet useless feeling. Ungrateful louts don't appear to be at any particular disadvantage to those of us who are more softhearted toward paramedics and waitresses. We all get served.

So I asked my favorite philosopher, Sydney. She is my eldest granddaughter, now 13, and just about at the age when the words "thank you" can disappear from a teenager's lexicon. What good is it to offer thanks to people?

Sydney came up with three reasons to say thank you. (a) It's the nice thing to do. (b) It makes you feel like you did the right thing. (c) It can help build friendships and trust. I'm glad she put the least evolutionary and most altruistic reason first: It's the nice thing to do. It's how we make our hectic, device-driven lives a little less impersonal, a little gentler. Nicer.

Then there is the second reason. "Thank you," the words, spoken aloud to someone who has done you a kindness, reflect back on you. They affect you. You feel the circle close, as it should. Your acknowledgment of the other's gift gives you the feeling that you have done right, completed the transaction.

The third reason reminds me of the origin of our national day of Thanksgiving. The desolate pilgrims are saved from a terrible winter by kindly natives, and the two groups meet in a meal of thanks. It is a moment of friendship, a signal of trust.

Historians aver that the meal took place but the friendship did not take root. Trust gave way to suspicion, animosity, and finally enmity. The Thanksgiving story becomes a cautionary tale.

Gratitude, after all, derives from the same root as grace and gracious. Grace is a gift freely given; gratitude is a gift graciously accepted. The pilgrims are graced with the means to survive. In gracious humility they welcome the gift with the most intimate invitation a household can offer: a seat at the dinner table, a shared meal.

Some religious folk call it Eucharist, a fine gift, a bread of life. We invite those whom we want to call friend, those with whom we want to share a bond of trust, to come to our table, sit, relax, enjoy the turkey with all its trimmings.

This is Thanksgiving, a celebration of hope that our kind can evolve, can build a world of friendship and trust. It is a moment when we are permitted to believe it can really happen.

Orlando R. Barone is a writer in Doylestown.