We have many ways. The Genographic project at the National Geographic Society uses DNA markers to sort people by the pathways taken by their ancestors from central Africa to their traditional location. Once it was thought that blood types indicate more than just structure of the blood. Bumps on the head and months of birth have gotten attention. The most basic classification of humans is probably their sex and we have endless research, discussion and even laws relating to that division. It is not a 100% absolutely totally complete division since there are individuals of ambiguous sex but for many purposes, it works pretty well to pretend that all humans are female or male.
I wrote the other day of my surprise at reading Huston Smith's mention of a ancient Hindu system of human personality classification. A close friend wrote this morning about having seen references in my writing about my interest in and use of personality classification several times over the years. In the 1980's, a friend told me to attend some lectures with him about the Myers-Briggs/Keirsey/True Colors system of recognizing and collaborating with people's habitual way of seeing the world. It was quite helpful and we used it from then on.
The most common complaint about classification of people is probably about pigeon-holing, a practice that nothing to do with birds. It is deciding that since I am a man, I must like hot dogs and beer, or sports. I want to maintain the freedom to be what I want to be and not be told what I can and can't do, or should or shouldn't do, because of my gender, age, educational level, Zip code, etc.
But I and others have found it helpful to learn that people with a strong emotional component often get angry with others they perceive to be uncaring. Without that abstract learning, I might be quite perplexed as to why a given individual seems to dislike me. Or, to use another example, the Myers-Briggs classification of people into quick, firm deciders and the other group of information gatherers who mull over a choice opened my eyes to tendencies in myself and relatives that showed similarities and differences that could be accommodated better if noted and understood.
It is very common in discussing people's tendencies to emphasize that people change and may suddenly develop a new tendency or drop a habitual one. It is true that generally we can all employ all kinds of views and approaches to life. Not only is there change everywhere in the larger world, there is also plenty inside each of us.
