1) The concept of reinsurance, which is insurance for insurance companies, originated in the 17th century.

2) The Amazon rainforest produces more than 20% of the world's oxygen.

3) International relations encompass the study of relationships between nations, including diplomacy, treaties, and foreign policy. It examines the interactions and dynamics among different countries in the global arena.

4) The world's oldest known recipe is for beer and is over 4,000 years old.