Some of us are short or tall and it all has to do with the climate in which hundreds of generations of their people have spent their lives.
People who have lived in the cold climate of the Arctic need to save every bit of heat their bodies can produce. The more skin they have, the more heat they will lose.
That’s why Eskimos are normally short, with short legs and short arms. They have less body surface than most other humans and can stay warmer in their cold climate.
People who live in very hot places must be able to lose body heat, or they would be too warm. That’s why most Africans tend to be tall, with long arms and long legs.
This gives them a great deal of body surface through which their extra body heat can escape.