Evolving Characters

Humans are said to 'learn' and to 'grow'. This is indicated by the old sayings, "Grow up," and "Act your age." And most humans do manage to remember what they've learned so far in their life, add to it whatever they've learned lately. Putting these things together, they adjust their thoughts, their decisions and actions. They learn, grow and mature.

In writing, characters are said to 'evolve', if the writer is any good.

I'm not sure why a different phrase is used for characters, who are created as representatives of human beings.

I mean, let's look at this. Wherever the story opens, the characters have a personality, and to have that, they have a backstory ... basic life events that have formed them into the 'person' they are. The author is supposed to have that all thought out, even if s/he doesn't actually say any of it in the story.

As the story proceeds, the character is challenged, reacts, learns and adjusts. Woops, I mean, he 'evolves'.

I don't know, to me, 'evolve' means 'become something new'. That sounds like a character who starts at Personality A suddenly makes a complete change to become Personality Z. I have trouble believing people do that, even when that person is a story character.

Person or character, I have a much easier time believing someone starts at Personality A and as a result of the challenge, reaction, learning and adjusting, winds up as Personality A1. A character who does that is much more believable to me.

What do you think?