This document summarizes the journey of early humans spreading from Africa to populate the world, and then discusses two catastrophic events that impacted humanity - a climate change event approximately 15,000 years ago, and the Columbian Exchange that occurred after 1492 when Europeans arrived in the Americas. It notes that early humans migrated from Africa to the Middle East, India, China, and Europe around 10,000 years ago. It then describes theories about what caused a major climate downturn approximately 15,000 years ago, including volcanic eruptions. Finally, it briefly outlines the effects of the arrival of Europeans in the Americas in 1492, including the introduction of new crops and the beginning of slavery.