Human migration: sub-Saharan Africa and the Pacific | World History | Khan Academy

In this video, I want to explore the question of what impact does the environment have on human migration. We have a couple of specific examples here, and before we dig into those, I want to make a few broader points about the environment as a historical factor.

The first of those is simply that the environment does have impacts on what people are able to do, on how and where they're able to move. We might be looking at whether the climate is suitable for practicing agriculture. Food production is such an important part of human movement and human survival in new environments. We might look at transportation; in the Pacific Ocean, for example, getting from island to island requires that you have technology that allows you to travel over the ocean for long distances.

The second point to consider more broadly is that human beings, when they move to new areas, tend to have impacts on the environment. If they're bringing new plants or new animals to a place where they haven't previously existed, that's going to have some impacts on the new place. Finally, this isn't to say that the environment is wholly explanatory of why history played out the way it did, but we also don't want to dismiss the environment as a potential explanatory factor.

With those bigger points in mind, let's start by looking at a specific example in Africa known as the Bantu migration, or more often the Bantu expansion, into Sub-Saharan Africa. When I say Sub-Saharan Africa, that's just the region of Africa that is south of the Sahara Desert, and I'll shade that in here so that you can see where I'm talking about. Next, what I have is an overlay in yellow that shows the areas of Africa where a Bantu language is the predominant language spoken.

The question that raises is: why does so much of Sub-Saharan Africa speak a Bantu language? There aren't any written records of Bantu speakers and how they moved, and what they were thinking when they did move. But there is evidence in terms of how the languages relate to one another, and there's also archaeological evidence. One of the helpful things about studying the Bantu expansion is that, from about 500-400 BCE on, they were using iron tools. They had iron-making technology, and those tools, along with pottery that's distinctive to Bantu-speaking cultures, can help archaeologists trace how Bantu speakers spread throughout Africa over time.

So linguists who have studied how these languages relate to one another and archaeologists who have looked at evidence of how Bantu speakers migrated and moved throughout Africa are fairly confident that they originated somewhere here in West Africa. From there, they spread to the south, as well as to the east, over to what's known as the Great Lakes region of Africa, and then from there farther south again. That tells us how people moved through Africa and what pattern they followed.

The next question we want to try and figure out the answer to is: why did they migrate to the places that they did? Well, one thing that we know about Bantu-speaking peoples is that they tended to have fairly consistent and common agricultural practices. Among the crops that they were growing were millet and sorghum. Once they got to the Great Lakes region and started moving south, you also see them adopting cattle herding.

Pictures of the cattle that they would have probably had here show that these crops and these cattle have something in common. All of them tend to thrive in what's known as a tropical savanna or a semi-tropical savanna climate. Sub-Saharan Africa, with the exception of this rainforest region here and this high desert down in the south, is largely tropical or semi-tropical savanna. When we put the overlay back up of where Bantu speakers are the majority, we can see that it corresponds with those climate variations.

You see them populate really all of the areas that are favorable to their agricultural practices. That should make sense if we think about migration as a risk-reward calculation. You need to make sure that any place that you're migrating to is going to be able to provide you with food.

So, to bring that back to our big theme of how does environment impact migration, we really see in the Bantu expansion the role of climate affecting what kind of agriculture is possible, and that determines what areas look attractive for migration.

The next region we want to look at, the next migration we want to study, is that of people moving throughout the Pacific Islands. You can see the path this migration probably took here. When we talk about expansion in the Pacific, we're looking at something somewhat similar to the Bantu expansion in Africa. Again, we don't have any written records from the people who moved here, so we’re relying on linguistic or language-based evidence, as well as archaeological evidence.

This evidence helps us sort of divide up the Pacific into three distinct regions: Melanesia in blue, Micronesia in red, and Polynesia in purple. Again, these are all people who were originally speaking some form of Austronesian language, very similar culturally. But they can look at how there have been small changes in cultural artifacts, changes in languages, and even in the genetics of the people and the animals in different regions of the Pacific to kind of get a sense of where they were at what time. That gives us this probable route of migration that we saw.

Thinking again about environment impacting this migration into the Pacific Ocean, there are a couple of important factors. The first and obvious one is that getting across large stretches of ocean is going to pose a difficulty; it's an obstacle. The way that people overcame this obstacle in the Pacific was they came up with better sailing technology. I can pull up here a picture of a recreation of a catamaran. This technology was really important for traveling long distances in the ocean because, to get out in the open ocean, you need a sturdy, durable ship that's going to hold up to wind and waves.

So, even though this is a modern recreation, it gives us a good sense of what the technology was like, and you can see how that would be a more durable craft than, say, a canoe by itself. This allows people to travel between islands.

The other issue, environmentally speaking, that poses an obstacle to expansion in the Pacific is that a lot of these islands are really small. You're probably noticing that some of them are quite difficult to see on the satellite image, and they don't have a lot of arable or farmable land on them. So, they can't support large populations. This is probably one reason why there is continued expansion in the Pacific over a long period of time; because the islands themselves can't support very large populations, if the population grows to a certain point, some people have to leave.

To deal with this fact that the islands didn't provide a lot of natural food, people would bring their own food supplies with them. They'd bring things like sweet potatoes, yams, taro root, and they would bring animals as well. So, chickens—this is what's called a Southeast Asian red jungle fowl—and it’s the precursor to domestic chickens. It can give you a sense of what some of these chickens probably looked like. They brought pigs, and they also had a small breed of dog. The dog breed is extinct now, but we have some pictures that were drawn by some of the early European explorers of the Pacific.

So people would bring these items with them; they’d bring these animals with them onto these new islands. They would grow the crops, they would raise the animals, and use them as a food source. To go back to our original list of big takeaways, this gets into this idea of environmental impact—of bringing these new plants and animals.

So what happens is that people bring these plants, they bring these animals that are not native to these islands onto these islands, and use them. They farm them, they raise them for food, and in most cases, people are able to sort of strike a balance of maintaining a food supply with these crops and animals that they've brought and not destroying the island environment because, obviously, that would have consequences for their ability to continue to live there.

Hopefully, it's clear at this point that environment definitely played a role in these migrations and these expansions. Certainly, this isn't only about environmental factors, but in both cases, it would be very difficult to explain what happened if you didn't include these environmental factors.