When writing the future, I often reflect on the past to help me create my "world".
Take, for example, the simple decision of how tall to make your characters. Most writers just choose what attracts them most. "The tall, strapping man glided in on his space bike to flash his dazzling, perfect smile at the tall, willowy ladies through the space port viewer."
But, who's to say that it's realistic? Health and physical stature is environmentally dependent.
Let's continue with the height thing. Height is a global indicator of environmental health. Men during the early Middle Ages were almost as tall as modern man today. Basically, people living 1 to 2 thousand years ago had it as good as us climate and social economic- wise.
Trippy... I know, right? They were in a warm period like we are today. They had room to both grow plenty of crops and keep away from other people's germs. Plus, they didn't have the social networking to deal with so they may have been happier, since FB studies have shown people are less satisfied with their lives after a FB session.
It is believed a "perfect storm" of social and climate factors hit when people began losing inches. These factors included the mini ice age, the increased trend of trading routes and the growth of towns into full-blown cities. Due to close proximity of this new urbanization, communal disease flourished and agricultural production -- which was already declining due to the colder weather -- was overtaxed.
We went from an average of 68.27 inches to down to an average of 65.75 inches by the end of 18th century.
It was only during the 19th century that height started to really return. The war had decreased the population pressures in many cities (cold, I know, but a fact just the same) and health care advancements and environmentally conscious thinking has helped to recover the stature of humans, which again, is a sign of a healthy world.
So, in writing what do we take away from this? Well, when world-building I always think through what kind of world/setting are the characters both in and from. Are they from a heavy industrial society or from an agriculturally driven world? Are they rich or poor (which can make up a difference of 1-3 inches against the average)? Are they from a city/crowded space port or a rural area? If from a city/space port, how is the health care in that society?
What factors do you all look at when designing your "people" in stories?