FOOD!

Food is nearly as defining of a culture as language. People gotta eat right?

Food is usually influenced mostly by whats available to the region. People living in temperate plains likely live on wheat products and livestock; those in the coastal tropics would naturally have more fish  and fruit in their diet.

Another factor is trade. Some cultures openly trade with others, and would have more variety and spices available than those who are more xenophobic or just undiscovered. Without trade, the Americas would likely never have known of soy sauce and curry.