Evolutionary pressures determine species advantages and adaptations.

In the tropical zones food is prevalent. The pressure is territory. You can have as many babies as you want because resources are plenty and environment is pleasant. The pressure becomes other tribes, so you develop higher aggression and short quick twitch muscles and your females develop more testosterone to aid in fighting.

In cold climates you have larger territories with sparse resources and the need to plan. You develop higher spatial awareness, long term planning and critical thinking skills, and cooperation within a tight knit small family group.