The Human Journey

Humans are not a stay-at-home species. While our ape cousins remain confined to the tropical forests they have inhabited for millions of years, we have spread across the globe. What makes us such successful migrants? Begin your exploration of the key factors that let us adapt to diverse landscapes, climates, food sources, and other challenges-allowing us to outcompete all rivals.

As resourceful as humans are, we can't survive alone. Cooperation is the key to success under new conditions. Consider the cautionary tale of the ill-fated Burke and Wills expedition, which set out to explore interior Australia in the mid-1800s. Despite being exceptionally well-equipped, the mission ended in disaster-largely because its leaders ignored Aboriginal knowledge of the environment.

Explore two innovations that fundamentally shaped our species. Fire-and its use for cooking-provided access to calorie-rich, easily digestible food, dramatically reducing the time needed for foraging. Carrying technology, from bags and baskets to water skins, allowed us to transport tools and essentials-an ability unique among animals. Both fueled a hunting lifestyle that drove human expansion.

Discover how trade supercharged human migration and laid the groundwork for complex societies. Early groups exchanged surplus goods with their neighbors in mutually beneficial swaps. Before long, highly valued personal adornments-like beads and jewels-entered the mix, giving rise to a market for inessential but beautiful objects that functioned as an early form of money.

Trace the great migration of our ancestors across the globe, starting with Homo erectus, who ventured out of Africa some 1.9 million years ago. Homo sapiens followed about 80,000 years ago, mixing with other hominin populations, notably Neanderthals and Denisovans. Around 20,000 years ago, humans crossed into the Americas, populating the continents in several waves during the last glacial period.

If humans are born to migrate, what compelled our ancestors to settle down roughly 12,000 years ago? Investigate the origins of agriculture and why this comparatively unhealthy, labor-intensive practice took off. Was farming such a good idea that it persuaded mobile foragers to change their ways, or did early farmers themselves push outward, claiming new land and transforming the world?

Modern Europeans descend from three genetically distinct ancient populations: pre-Ice Age hunter-gatherers, early farmers from the Middle East, and a later-arriving group of steppe herders from Eurasia known as the Yamnaya, who contributed the largest genetic share. Who were these mysterious nomadic pastoralists, and how did they shape the ancestry and languages of much of the world?

As the human population grew, a new kind of settlement emerged: the city. Explore the dynamics of these artificial entities, which became centers of trade, governance, and culture-and of disease. Drawing people from near and far, cities fostered unprecedented genetic exchange. Discover how rapidly they form in the modern world, where more than half of humanity now lives in urban communities.

Migration is humanity's oldest survival strategy-and one we'll need more than ever, as hotter temperatures and sea-level rise render parts of the planet uninhabitable. With the global human population now exceeding 8 billion, this relocation will be on a scale far exceeding that out of Africa, or the expansion into formerly frozen lands, or any of the other great migrations by our ancestors.

Consider the hurdles faced by people fleeing war, drought, tyranny, or other perils in search of a better life. Today, national borders are their biggest obstacle-yet historically, these boundaries are a very recent invention. How did they arise, and how did the concept of national identity take hold in a species that evolved to manage social life in groups of no more than about 150 individuals?

What are the economic stakes on both sides of migration-what do migrants stand to gain or lose, and how are receiving communities affected in turn? Learn that under most circumstances, migration can be a win/win proposition for all parties. Migrants often seek higher wages and opportunity; host regions gain needed labor, increased economic activity, and younger workers to help support retirees.

As we enter a century of unprecedented global human movement, how can we respond wisely? This final lecture explores the case for managing migration-not merely controlling it. With careful planning, we can build entirely new cities and foster sustainable, well-functioning communities-even as some regions are abandoned and others adapted to meet the realities of a changing climate.