In 2013, Paul Salopek set out on a very long walk. It is the path some of our human ancestors walked when they migrated out of Africa, about 60,000 years ago by some estimates. Salopek is a journalist and National Geographic Explorer. His walk will last at least 10 years.
Salopek has named his expedition the Out of Eden Walk. His route will take him from the African country of Ethiopia to the Middle East. He'll head through Central and Southeast Asia, and across China. The land bridge our ancestors used to cross from Asia to North America has long since disappeared. So, Salopek will take a ship across the Pacific Ocean. He will then walk along the West Coast of the United States and Mexico. He will cross Central America to South America and walk along its western coast to the southernmost tip of the continent. Just as our ancestors did, Salopek will travel mostly along oceans and seas.
As he walks, Salopek will be documenting the places he travels and the people he meets. Salopek will also tell the stories of the very earliest humans to our more recent past. Some of the places he walks through will have clues that can help us understand early humans.
In the Beginning
Salopek chose Herto Bouri, Ethiopia, for the starting point of the Out of Eden Walk. This desert site is the location of the 160,000-year-old Herto man fossil. It is thought by many scientists to be the oldest fully recognizable modern human remains ever found.
Herto man is proof that modern humans (Homo sapiens) lived in Africa at least 160,000 years ago. Evidence shows that these modern humans did not leave Africa until between 60,000 and 90,000 years ago. Most likely, a change in climate helped push them out. Experts suggest that droughts in Africa led to starvation. Humans were driven to near extinction before they ever had a chance to explore the world. Changes in climate and the presence of fertile land in the Middle East probably helped draw the first humans out of Africa.
Food Is Life
Finding and processing food was very important to our human ancestors. It isn't surprising that they made tools to help them with these tasks.
Gona is an archaeological site in Ethiopia. It is covered with the earliest tools known, some 2.6 million years old. The tools found at Gona used to be crude, sharp objects. They weren't made by modern humans such as Herto man.
Modern humans are known by the scientific name of Homo sapiens. Along with other types of human that came before us, we belong to the group called hominins. The tools at Gona were made by early hominins. Scientists think these beings were scavengers who used their tools to cut up carcasses and bones. It is likely that most of their food was plants.
Early humans were mobile hunter-gatherers. They would move from place to place and search for food. About 10,000 to 13,000 years ago, this lifestyle changed. In a valley called Wadi Natuf, in what is now part of the state of Palestine, some humans stopped their roaming and settled down in one place. They created tools to harvest grains. Eventually, they began to grow food instead of gathering it. The concept of claiming land was born.
The change from hunting and gathering to farming had many advantages. Yet, there were also downsides. Mass outbreaks of diseases, like today's flu, were more intense in human settlements. When large groups of people gathered in one place, it made it easier for diseases to spread.
In the country Georgia, Dmanisi is a town between Europe and Asia. The site has been a popular crossroads for almost two million years. The evidence is in layers of archaeological remains. The 1,400-year-old remains of the medieval city of Dmanisi are found in the top layer. Below that are the remains of a 5,000-year-old settlement. And below that? The 1.8-million-year-old fossil remains of one of our early ancestors. These are some of the earliest hominin remains found outside of Africa.
Salopek visited the nearby National Museum to see these remains for himself. Finding the Dmanisi skulls changed scientists' understanding of human evolution. The theory of evolution explains how living things develop and change. Over millions of years, species will die out or lead to new species.
The Dmanisi fossils showed a mixture of features from three different hominin species. These helped scientists to better understand how these species related to each other.
Even more importantly, one of the skulls showed the earliest known evidence of caring behavior. The skull belonged to an older man, whose jawbone showed that he had only one tooth while he lived. Almost two million years ago, he would not have been able to survive alone without teeth. Yet, his bones show that he lived for years after losing them. This tells scientists that someone—another hominin—had taken care of him.
Something in Common
The Out of Eden Walk will take Salopek 33,796 kilometers (21,000 miles). He will cross five continents and more than 30 countries. Along the way, he will come across many different languages, stories and ways of life. Yet, everyone he talks to will have something in common. They will all be able to trace their family tree back to Africa.