Introduction: human evolution and interactions

Humans 15,000 years ago were foragers, or hunter-gatherers. They traveled great distances in search of food. There were no cars, phones or even wheels. How did people come to inhabit almost all areas of the world at this time? And how do we know about their movements and their way of life?

Different scholars have helped us understand human origins and migration, or movement, patterns: archaeologists, anthropologists, climatologists, historians, and language researchers are just a few. Most would agree that modern humans, Homo sapiens, evolved in Africa approximately 300,000 to 200,000 years ago. But we weren’t the only humans around during that time. Other human communities existed in various regions of Afro-Eurasia. They were made up of different species. Homo neanderthalensis (Neanderthals), Homo erectus, and Homo floresiensis were a few. But Homo sapiens—us—are the only human species that are still alive today. Homo sapiens have a smaller build than earlier human species. Their skull was a specific shape. You can see it in the image below. It compares a Homo sapiens skull and a Neanderthal skull. Evidence of our earliest existence comes from fossils found in the African country Ethiopia about 200,000 years ago. But some researchers think that our species was around for longer than this.

Homo sapiens migrated out of Africa around 80,000 to 60,000 years ago. Did Homo sapiens met all of these species at that time? We don’t know for sure. These migrations probably occurred at various times, to different places. Chances are there wasn’t just one large migration out of Africa starting at once. New evidence suggests that the earliest migration date may be 120,000 years ago. There is evidence that Homo sapiens interacted and mated with Neanderthals. Neanderthals mainly lived in colder climates and had a heavier build. Their foreheads were more sloped with a more obvious ridge at the front. Some modern humans have small amounts of Neanderthal DNA because of these interactions. Another human species known as Denisovans lived in Central Asia and Australia (Bae, et al).

They were just recently discovered. Studies show that some Homo sapiens mixed with both Neanderthals and Denisovans. They mainly lived in the area of modern-day Siberia.

Human communities on the move

We don’t know exactly when human communities left Africa. Eventually, some human species died out. This could be after mixing with Homo sapiens communities. Perhaps there were violent fights with modern humans. Or maybe climate and environmental changes hurt them. All of these early human communities moved around to follow their food. These foragers lived off the land by gathering, hunting, and fishing. Each community was likely kept rather small, no more than 20-50 people. These humans primarily used stone and bone tools. For this reason, archaeologists and historians have categorized the period as the Paleolithic era (Old Stone Age). Population numbers probably remained relatively small throughout the Paleolithic era. These human communities may have intentionally kept their population growth rates low. They could move more easily that way. It would be very difficult to carry many children at one time as you search for food.

These small groups collected food and resources from one area. Then they moved to another as food became scarce. The groups interacted with other communities. Networks of exchange were made to trade items they gathered or made. In addition, language networks connected people who lived nearby. Information could then be shared amongst groups. Some members of one community left to join others in order to start new family groups. Larger networks of people also came together for spiritual or religious purposes.

Over time, some groups migrated outside of Africa. These movements were possibly as a result of climate changes and scarcity of resources. Other reasons might have been simple curiosity, or conflicts with other groups.

Humans began moving perhaps as early as 120,000 years ago. They probably traveled in waves that occurred to different regions at different time periods. The earliest migrations might have occurred along the coasts of the Arabian Peninsula into India and then on to Southeast Asia. These groups stayed near the coastline. Abundant resources here, such as underwater animals, could help these groups survive. Early humans constructed rafts or small dugout boats. It helped them float across larger bodies of water. By about 50,000 to 45,000 years ago, these communities reached Papua New Guinea, Australia, and East Asia. Humans’ arrival in Australia may even be much earlier than this. Some studies push the date back to 65,000 years ago (Clarkson et al., 2017).

Evidence also shows that other groups left Africa. They moved north through the Arabian Peninsula and entered Europe and Central Asia by about 45,000 years ago. Some communities had migrated and adapted to much colder climates in northern Asia. They journeyed across the Bering Strait by as early as 20,000 years ago. Small groups may have then traveled along the coasts. They came into the Americas by about 15,000 years ago. Still others may have waited until the climate became warmer. Then they would journey by land into the Americas about 12,000 to 10,000 years ago. Regardless of the route taken, early humans made their way down to the southern tip of South America. That happened by about 15,000 to 10,000 years ago. Abundant food resources helped quicken the pace of migration. Underwater life and large game animals were available. Many of these large American game animals were eventually wiped out by traveling humans.

Human communities and the environment

Humans adapted to new environmental conditions as they moved around and populated the Earth. One reason they achieved success living in varied climates was because of a concept called collective learning. They shared and preserved of information across age groups. Humans learned new ways of dealing with their environment. They shared this information with others in their communities. Such tools and methods for survival were then passed down. Collective learning is, therefore, what allowed our human ancestors to survive and populate the Earth. They improved themselves in many ways.

But as humans moved, they changed. There were slight, random mutations to DNA that occurred as humans lived in certain areas for longer periods. DNA tells our bodies how to grow and work. It’s like a set of instructions for every living thing. DNA that gets passed from parent to child. These random mutations caused differences that you see in humans today. We are all of the same species. Some of us, though, have slightly different appearances such as skin and hair color. The shape of our eyes and noses would be others. For example, humans who migrated to colder climates needed more vitamin D from the Sun. Meanwhile, humans living near the equator needed more protection from the sun. Over thousands of years, these humans experienced random genetic mutations. Through these they gained some advantages when adapting to their new environments. Some, for example, saw their skin color lighten. That would allow more of the Sun’s rays to get in the skin and provide more healthy vitamin D. In fact, this process was happening before modern humans ever left Africa (Crawford, et al. 2017).

Humans also impacted their environments as they migrated. They hunted animals. Some creatures became extinct by humans. They set fire to wooded areas to drive out wildlife and more easily hunt. Their movements changed the environment and still do today.

Conclusion

The story of the origins of humans and their migration patterns out of Africa are almost constantly changing. Scholars continually make new discoveries that lead to revisions in the history of humanity. That is collective learning at work! As more fossils, tools, and genetic evidence are discovered, the story of early human communities may change. We may learn more about our ancient past.