 Within the setting of the story, what makes one character more attractive than the other?
"There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel— and yet each planetary race can interbreed with a minimum of ten others ! "Outside of your own world, there's nothing like your species, except superficially, and that's true of all other creatures, intelligent or not, with the sole exception of mankind. Actually, the four of us here, though it's accidental, very nearly represent the biological spectrum of human development. It's reasonable to assume that, if men were set down on a hundred such worlds, they'd seem to fit in with native life-forms on a few of them. Man was the most numerous though not always the most advanced—Ribboneers had a civilization as high as anything in the known section of the Milky Way, and there were others—and humans were more than a little feared. The theory is that humans who can mate with each other were once physically close. When we project back into time those star systems on which humans existed prior to space travel, we get a certain pattern. And while stars in a given region tend to remain together, there's also a random motion. It was a paradox that some biologically higher humans hadn't developed as much as lower races and actually weren't prepared for the multitude of life-forms they'd meet in space.
 Evolutionary status
 Having a pure genetic line  Reasoning capacities  Evolutionary status  Lineage to the big ancestor