# Guided practice: Causes and effects of human migration

Migration is the movement of people from one place to another with the intent to settle. Learn more about why it was important!

## Оршил

• Migration is the movement of people from one place to another with the intent to settle
• Causes: In preindustrial societies, environmental factors, such as the need for resources due to overpopulation, were often the cause of migration
• Effects: As people migrated, they brought new plants, animals, and technologies that had effects on the environment

## Causes of migration

Human migration is the movement of people from one place to another with the intention of settling in the new location. When large numbers of people relocate, historians ask questions about why these people moved and what impacts their movements had.
Broadly speaking, there are two categories of factors that influence people’s decisions to migrate. Push factors occur where someone is currently living and make continuing to live there less attractive. A push factor could be political unrest, a lack of job opportunities, or overcrowding. Pull factors occur in a potential destination and make it an attractive place to migrate to. A pull factor could be better job opportunities or having relatives or friends who have already moved to this location.
Stop and consider: What is human migration?
Дараах сонголтуудаас нэгийг нь сонгоорой.

## Causes of migration in Africa

In the preindustrial era, environmental factors like droughts, natural disasters, and climate all influenced human decisions about where to migrate. The expansion of Bantu-speaking peoples through Central Africa illustrates this relationship between environment and migration. Before we look at the movement of Bantu people, it is important to note that Bantu does not refer to a single community of people. It is a language family whose speakers also shared many cultural practices. There are several hundred distinct Bantu languages, of which Swahili is most widely spoken today.
People speaking Bantu languages spread from West Africa throughout Central and Southern Africa starting around 2000 BCE—see the first map below, where yellow depicts regions containing predominantly Bantu-speakers. Bantu-speakers migrated to and settled in places where the climate was well-suited to Bantu agricultural practices - see second map below.
Satellite image of Africa. Lighter green areas are regions with enough moisture to support typical Bantu agricultural practices. These regions have subtropical or tropical savannah climates. Compare this to the previous map showing the extent of Bantu settlement.
Satellite image of Africa. Lighter green areas are regions with enough moisture to support typical Bantu agricultural practices. Compare this to the previous map showing the extent of Bantu settlement. Image credit: Wikipedia, public domain.
Stop and consider: Based on these two maps, what might have caused Bantu-speakers to expand to the areas that they did?
Bantu expansion seems to match up really closely with regions of Africa that have a subtropical or tropical savannah climate. Moving to areas with a similar climate to what they were used to allowed Bantu-speakers to continue raising the crops they knew well. This in turn ensured a stable source of food in a new location.
The crops raised by Bantu-speaking farmers, such as millet and sorghum, grew best in the tropical savannah that covered much of sub-Saharan Africa. This made these regions the most attractive locations for new settlement. Sometime before 500 BCE, bananas were introduced to mainland Africa. Because bananas could grow in rainforest climates, the adoption of banana cultivation opened even more territory to Bantu expansion.
Bantu-speakers also possessed ironmaking technology, which allowed them to create stronger, more effective tools and weapons. Bantu-speakers had widely-shared agricultural practices and types of tools. This fact makes it easy to follow the spread of Bantu throughout central Africa. The presence of iron tools, for example, allows archaeologists to distinguish Bantu living sites from non-Bantu sites, such as those of the Pygmies in rainforest regions, and the Khoisan in more arid regions.
Stop and consider: Why would ironworking have given Bantu speakers an advantage over other peoples they encountered as they migrated?
Iron was stronger than other available metals. This meant iron tools were generally better for both agriculture and fighting. Bantu-speakers who could make iron thus had advantages over other groups in their ability to fight and produce food.
A photograph of finger millet, a staple grain.
Finger millet, a staple grain. Image credit: Wikipedia
Photograph of Sorghum bicolor. Sorghum bicolor is native to Africa. The grains it produced were used as a food source.
Sorghum bicolor is native to Africa. The grains it produced were used as a food source. Image credit: Wikipedia, CC BY-SA 3.0.
As Bantu-speakers successfully migrated into a new region, the population increased. This put pressure on local resources and prompted some people to seek new living space. Although estimates of population for sub-Saharan Africa are speculative, they do seem to confirm the trend of increased population growth occurring with the spread of agriculture and iron technology.start superscript, 1, end superscript

## Causes of migration in the Pacific

The most important factor limiting how many people can live in a given area is the ability to produce food. On the many small islands of the Pacific Ocean, limited space and limited production capacity helped cause migration. We don’t have population figures for the prehistoric Pacific, but we are able to make some guesses based on other evidence. The general relationship appears to have been that the larger the island, the more people it could support.start superscript, 2, end superscript
A map of Pacific migrations, 3000 BCE to 1200 CE.
A map of Pacific migrations, 3000 BCE to 1200 CE.
Image credit: Wikimedia, CC BY 3.0
The obvious obstacle to travel in the Pacific was the long stretches of open ocean between islands. Pacific Islanders used a combination of technology—such as catamarans and outrigger canoes—and knowledge of the environment and astronomy to navigate between islands.
Photograph of a modern replica of a Polynesian sailing canoe. Vessels like this could carry about a dozen people and supplies. The double canoe configuration made the craft much more stable at sea.
Modern replica of a Polynesian sailing canoe. Vessels like this could carry about a dozen people and supplies. The double canoe configuration made the craft much more stable at sea. Image credit: Wikimedia
Stop and consider: What technology allowed people to migrate to new islands in the Pacific?
Select all that apply.
Select all that apply.

Edible plants, such as various palm fruits and root vegetables, occurred naturally on many islands in the Pacific. But, these were not reliable food sources, so people who migrated throughout the region brought along other crops to raise on new islands. Starchy vegetables such as taro, yams, and sweet potatoes were commonly grown by Pacific Island populations because these plants generally grew well in wetter climates.
Pigs, chickens, and dogs were all raised as food sources in the Pacific Islands; they also travelled with humans. Rats tagged along on many these ocean voyages as well, although they probably were not brought along deliberately. These animals were usually able to survive and reproduce with limited human involvement. However, striking a balance between maintaining the animal population for food and raising and preserving crops was important. For example, many communities constructed storage bins raised on stilts to keep animals out of the food or small fences of reeds or rocks around garden plots.start superscript, 3, end superscript
Stop and consider: Why was population growth a major cause of migration in the Pacific?
Because many Pacific islands were small and did not naturally produce a lot of food, they could not support large populations. This limited the amount of space and resources, which limited the human population that could live on a given island.

## Effects of migration

In central Africa, the spread of Bantu-speaking people had effects on the environment. Introducing new crops and farming techniques altered the natural landscape. Raising cattle also displaced wild animal species. Agriculture improved the ability of Bantu-speakers to reproduce and expand more quickly. But, agriculture also had more noticeable impacts on the environment than hunting and gathering.
The plants and animals that people spread and cultivated throughout the Pacific allowed them to survive. However, these actions also had impacts on the island environments. The introduction of non-native plants and animals, as well as human activity, altered the ecosystems of the islands they chose to live on.
What were some effects of bringing new plants and animals to new environments?
Introducing new plants and animals tended to change environments. Growing plants as crops required active farming. Animals required food, which either required more farming, or letting the animals eat the naturally-occurring plants. In some cases, animals also ate or displaced local species.
In the most extreme example human effects on a Pacific island, the people who settled Easter Island destroyed the environment to the point where it was hardly habitable. Both humans and the rats that had travelled with them hunted and wiped out local bird populations. The Easter Islanders cut down all the large trees, which made agriculture more difficult as fertile topsoil eroded. It also meant they couldn't build boats to leave the island. Because of human actions, the island was no longer able to support a large human population.
Stop and consider: What was most responsible for altering the environment of Easter Island?
Дараах сонголтуудаас нэгийг нь сонгоорой.

Easter Island was the worst case scenario, but it showed what could happen if an island became overpopulated. On most islands, people were able to balance their survival needs with preserving their new homes. We see the effects of these migrations still today. In the Pacific, the people, plants, and animals living on the many islands are the result of earlier migrations. In the case of Bantu-speakers in Africa, there was plenty of land to expand into, but they had to overcome other groups. The large number of Bantu-speakers across the continent is evidence of their successful migrations.
Article by Steven Schroeder.
Notes:
1. Jerry Bentley, et al, Traditions and Encounters, Vol. 1 (New York: McGraw Hill, 2015), 284.
2. Douglas L. Oliver, Polynesia in Prehistoric Times (Honolulu: Bess Press, 2002), 32-35.
3. Oliver, 232, 239.