Human migration (derived from Latin: migratio) is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic people have retained this form of lifestyle in modern times. Migration has continued under the form of both voluntary migration within one's region, country, or beyond and involuntary migration (which includes the slave trade, trafficking in human beings and ethnic cleansing). People who migrate into a territory are called immigrants, while at the departure point they are called emigrants. Small populations migrating to develop a territory considered void of settlement depending on historical setting, circumstances and perspective are referred to as settlers or colonists, while populations displaced by immigration and colonization are called refugees. The rest of this article will cover sense of a "change of residence", rather than the temporary migrations of travel, tourism, pilgrimages, or the commute.
According to International Organization for Migration, "no universally accepted definition for (migrant) exists. The term migrant was usually understood to cover all cases where the decision to migrate was taken freely by the individual concerned for reasons of "personal convenience" and without intervention of an external compelling factor; it therefore applied to persons, and family members, moving to another country or region to better their material or social conditions and improve the prospect for themselves or their family. The United Nations defines migrant as an individual who has resided in a foreign country for more than one year irrespective of the causes, voluntary or involuntary, and the means, regular or irregular, used to migrate. Under such a definition, those travelling for shorter periods as tourists and businesspersons would not be considered migrants. However, common usage includes certain kinds of shorter-term migrants, such as seasonal farm-workers who travel for short periods to work planting or harvesting farm products."  Also, human migration happened when the Paleo-Indians entered America. For key stage 3
According to the International Organization for Migration's World Migration Report 2010, the number of international migrants was estimated at 214 million in 2010. If this number continues to grow at the same pace as during the last 20 years, it could reach 405 million by 2050. While some modern migration is a byproduct of wars (for example, emigration from Iraq and Bosnia to the US and UK), political conflicts (for example, some emigration from Zimbabwe to the UK), and natural disasters (for example, emigration from Montserrat to the UK following the eruption of the island's volcano), contemporary migration is predominantly economically motivated. In particular, there are wide disparities in the incomes that can be earned for similar work in different countries of the world. There are also, at any given time, some jobs in some high-wage countries for which there is a shortage of appropriately skilled or qualified citizens. Some countries (e.g., UK and Australia) operate points systems that give some lawful immigration visas to some non-citizens who are qualified for such shortage jobs. Non-citizens, therefore, have an economic incentive to obtain the necessary skills and qualifications in their own countries and then apply for, and migrate to take up, these job vacancies. International migration similarly motivated by economic disparities and opportunities occurs within the EU, where legal barriers to migration between member countries have been wholly or partially lifted. Countries with higher prevailing wage levels, such as France, Germany, Italy and the UK are net recipients of immigration from lower-wage member countries such as Greece, Hungary, Lithuania, Poland and Romania.
Some contemporary economic migration occurs even where the migrant becomes illegally resident in their destination country and therefore at major disadvantage in the employment market. Illegal immigrants are, for example, known to cross in significant numbers, typically at night, from Mexico into the US, from Mozambique into South Africa, from Bulgaria and Turkey into Greece, and from north Africa into Spain and Italy.
The pressures of human migrations, whether as outright conquest or by slow cultural infiltration and resettlement, have affected the grand epochs in history and in land (for example, the decline of the Roman Empire); under the form of colonization, migration has transformed the world (such as the prehistoric and historic settlements of Australia and the Americas). Population genetics studied in traditionally settled modern populations have opened a window into the historical patterns of migrations, a technique pioneered by Luigi Luca Cavalli-Sforza.
Forced migration has been a means of social control under authoritarian regimes, yet free-initiative migration is a powerful factor in social adjustment and the growth of urban populations.
In December 2003, The Global Commission on International Migration (GCIM) was launched with the support of Secretary-General of the United Nations Kofi Annan and several countries, with an independent 19-member commission, a threefold mandate and a finite lifespan ending December 2005. Its report, based on regional consultation meetings with stakeholders and scientific reports from leading international migration experts, was published and presented to Kofi Annan on 5 October 2005.
International migration challenges at the global level are addressed through the Global Migration Group, established in 2006.
Different types of migration include:
See main article: Early human migrations and Historical migration. Historical migration of human populations begins with the movement of Homo erectus out of Africa across Eurasia about a million years ago. Homo sapiens appear to have occupied all of Africa about 150,000 years ago, moved out of Africa 70,000 years ago, and had spread across Australia, Asia and Europe by 40,000 years BC. Migration to the Americas took place 20,000 to 15,000 years ago, and by 2,000 years ago, most of the Pacific Islands were colonized. Later population movements notably include the Neolithic Revolution, Indo-European expansion, and the Early Medieval Great Migrations including Turkic expansion. In some places, substantial cultural transformation occurred following the migration of relatively small elite populations, Turkey and Azerbaijan being such examples. In Britain, it is considered that the Roman and Norman conquests were similar examples, while "the most hotly debated of all the British cultural transitions is the role of migration in the relatively sudden and drastic change from Romano-Britain to Anglo-Saxon Britain", which may be explained by a possible "substantial migration of Anglo-Saxon Y chromosomes into Central England (contributing 50%–100% to the gene pool at that time."
Early humans migrated due to many factors such as changing climate and landscape and inadequate food supply. The evidence indicates that the ancestors of the Austronesian peoples spread from the South Chinese mainland to Taiwan at some time around 8,000 years ago. Evidence from historical linguistics suggests that it is from this island that seafaring peoples migrated, perhaps in distinct waves separated by millennia, to the entire region encompassed by the Austronesian languages. It is believed that this migration began around 6,000 years ago. Indo-Aryan migration from the Indus Valley to the plain of the River Ganges in Northern India is presumed to have taken place in the Middle to Late Bronze Age, contemporary to the Late Harappan phase in India (ca. 1700 to 1300 BC). From 180 BC, a series of invasions from Central Asia followed, including those led by the Indo-Greeks, Indo-Scythians, Indo-Parthians and Kushans in the northwestern Indian subcontinent.  
From 728 BC, the Greeks began 250 years of expansion, settling colonies in several places, including Sicily and Marseille. In Europe, two waves of migrations dominate demographic distributions, that of the Celtic people and that of the later Migration Period from the North and East, both being possible examples of general cultural change sparked by primarily elite and warrior migration. Other examples are small movements like that of the Magyars into Pannonia (modern-day Hungary). Turkic peoples spread from their homeland in modern Turkestan across most of Central Asia into Europe and the Middle East between the 6th and 11th centuries. Recent research suggests that Madagascar was uninhabited until Austronesian seafarers from Indonesia arrived during the 5th and 6th centuries AD. Subsequent migrations from both the Pacific and Africa further consolidated this original mixture, and Malagasy people emerged.
Before the expansion of the Bantu languages and their speakers, the southern half of Africa is believed to have been populated by Pygmies and Khoisan-speaking people, today occupying the arid regions around the Kalahari Desert and the forest of Central Africa. By about 1000 AD, Bantu migration had reached modern day Zimbabwe and South Africa. The Banu Hilal and Banu Ma'qil were a collection of Arab Bedouin tribes from the Arabian Peninsula who migrated westwards via Egypt between the 11th and 13th centuries. Their migration strongly contributed to the Arabization and Islamization of the western Maghreb, which was until then dominated by Berber tribes. Ostsiedlung was the medieval eastward migration and settlement of Germans. The 13th century was the time of the great Mongol and Turkic migrations across Eurasia.
Between the 11th and 18th centuries, there were numerous migrations in Asia. The Vatsayan Priests from the eastern Himalaya hills, migrated to Kashmir during the Shan invasion in 1203C. They settled in the lower Shivalik hills in 1206C to sanctify the manifest goddess. In the Ming occupation, the Vietnamese expanded southward in a process known as nam tiến (southward expansion). Manchuria was separated from China proper by the Inner Willow Palisade, which restricted the movement of the Han Chinese into Manchuria during the Qing Dynasty, as the area was off-limits to the Han until the Qing started colonizing the area with them later on in the dynasty's rule.
The Age of Exploration and European colonialism led to an accelerated pace of migration since Early Modern times. In the 16th century, perhaps 240,000 Europeans entered American ports. In the 19th century, over 50 million people left Europe for the Americas. The local populations or tribes, such as the Aboriginal people in Canada, Brazil, Argentina, Australia, Japan and the United States, were usually far overwhelmed numerically by the settlers.
While the pace of migration had accelerated since the 18th century already (including the involuntary slave trade), it would increase further in the 19th century. Manning distinguishes three major types of migration: labor migration, refugee migrations, and urbanization. Millions of agricultural workers left the countryside and moved to the cities causing unprecedented levels of urbanization. This phenomenon began in Britain in the late 18th century and spread around the world and continues to this day in many areas.
Industrialization encouraged migration wherever it appeared. The increasingly global economy globalized the labor market. The Atlantic slave trade diminished sharply after 1820, which gave rise to self-bound contract labor migration from Europe and Asia to plantations. Overpopulation, open agricultural frontiers, and rising industrial centers attracted voluntary migrants. Moreover, migration was significantly made easier by improved transportation techniques.
Transnational labor migration reached a peak of three million migrants per year in the early twentieth century. Italy, Norway, Ireland and the Guangdong region of China were regions with especially high emigration rates during these years. These large migration flows influenced the process of nation state formation in many ways. Immigration restrictions have been developed, as well as diaspora cultures and myths that reflect the importance of migration to the foundation of certain nations, like the American melting pot. The transnational labor migration fell to a lower level from 1930s to the 1960s and then rebounded.
The United States experienced considerable internal migration related to industrialization, including its African American population. From 1910–1970, approximately 7 million African Americans migrated from the rural Southern United States, where blacks faced both poor economic opportunities and considerable political and social prejudice, to the industrial cities of the Northeast, Midwest and West, where relatively well-paid jobs were available. This phenomenon came to be known in the United States as its own Great Migration. With the demise of legalized segregation in the 1960s and greatly improved economic opportunities in the South in the subsequent decades, millions of blacks have returned to the South from other parts of the country since 1980 in what has been called the New Great Migration.
200px|thumb|Balkan Turks in 1912The twentieth century experienced also an increase in migratory flows caused by war and politics. Muslims moved from the Balkan to Turkey, while Christians moved the other way, during the collapse of the Ottoman Empire. Four hundred thousand Jews moved to Palestine in the early twentieth century. The Russian Civil War caused some three million Russians, Poles and Germans to migrate out of the Soviet Union. World War II and decolonization also caused migrations. 
The Jewish communities across Europe, the Mediterranean and the Middle East were formed from voluntary and involuntary migrants. After the Holocaust (1938 to 1945), there was increased migration to the British Mandate of Palestine, which became the modern state of Israel as a result of the United Nations Partition Plan for Palestine.
Provisions of the Potsdam Agreement from 1945 signed by victorious Western Allies and the Soviet Union led to one of the largest European migrations, and the largest in the 20th century. It involved the migration and resettlement of close to or over 20 million people. The largest affected group were 16.5 million Germans expelled from Eastern Europe westwards. The second largest group were Poles, millions of whom were expelled westwards from eastern Kresy region and resettled in the so-called Recovered Territories (see Allies decide Polish border in the article on the Oder-Neisse line). Hundreds of thousands of Poles, Ukrainians (Operation Vistula), Lithuanians, Latvians, Estonians and some Belarusians were expelled eastwards from Europe to the Soviet Union. Finally, many of the several hundred thousand Jews remaining in Eastern Europe after the Holocaust migrated outside Europe to Israel and the United States.
See main article: Partition of India. In 1947, upon the Partition of India, large populations moved from India to Pakistan and vice versa, depending on their religious beliefs. The partition was promulgated in the Indian Independence Act 1947 as a result of the dissolution of the British Indian Empire. The partition displaced up to 12.5 million people in the former British Indian Empire, with estimates of loss of life varying from several hundred thousand to a million. Muslim residents of the former British India migrated to Pakistan (including East Pakistan which is now Bangladesh), whilst Hindu and Sikh residents of Pakistan and Hindu residents of East Pakistan (now Bangladesh) moved in the opposite direction.
In modern India, estimates based on industry sectors mainly employing migrants suggest that there are around 100 million circular migrants in India. Caste, social networks and historical precedents play a powerful role in shaping patterns of migration. Migration for the poor is mainly circular, as despite moving temporarily to urban areas, they lack the social security which might keep them there more permanently. They are also keen to maintain a foothold in home areas during the agricultural season.
Research by the Overseas Development Institute identifies a rapid movement of labour from slower- to faster-growing parts of the economy. Migrants can often find themselves excluded by urban housing policies, and migrant support initiatives are needed to give workers improved access to market information, certification of identity, housing and education.
Some people usually move from the Thar Desert, over to Dharavi in Mumbai, whilst shortly living in small towns and cities along the way.
Migration for work in the 21st century has become a popular way for individuals from impoverished developing countries to obtain sufficient income for survival. This income is sent home to family members in the form of remittances and has become an economic staple in a number of developing countries, namely the Philippines and those in Latin America. There are a number of theories to explain the international flow of capital and people from one country to another.
This is the newest theory of migration and states that the main reason for labor migration is wage difference between two geographic locations. These wage differences are usually linked to geographic labor demand and supply. It can be said that areas with a shortage of labor but an excess of capital have a high relative wage while areas with a high labor supply and a dearth of capital have a low relative wage. Labor tends to flow from low-wage areas to high-wage areas. Often, with this flow of labor comes changes in the sending as well as the receiving country. Neoclassical economic theory is best used to describe transnational migration, because it is not confined by international immigration laws and similar governmental regulations.
Dual labor market theory states that migration is mainly caused by pull factors in more developed countries. This theory assumes that the labor markets in these developed countries consist of two segments: primary, which requires high-skilled labor, and secondary, which is very labor-intensive but requires low-skilled workers. This theory assumes that migration from less developed countries into more developed countries is a result of a pull created by a need for labor in the developed countries in their secondary market. Migrant workers are needed to fill the lowest rung of the labor market because the native laborers do not want to do these jobs as they present a lack of mobility. This creates a need for migrant workers. Furthermore, the initial dearth in available labor pushes wages up, making migration even more enticing.
This theory states that migration flows and patterns cannot be explained solely at the level of individual workers and their economic incentives, but that wider social entities must be considered as well. One such social entity is the household. Migration can be viewed as a result of risk aversion on the part of a household that has insufficient income. The household, in this case, is in need of extra capital that can be achieved through remittances sent back by family members who participate in migrant labor abroad. These remittances can also have a broader effect on the economy of the sending country as a whole as they bring in capital.
Relative deprivation theory states that awareness of the income difference between neighbors or other households in the migrant-sending community is an important factor in migration. The incentive to migrate is a lot higher in areas that have a high level of economic inequality. In the short run, remittances may increase inequality, but in the long run, they may actually decrease it. There are two stages of migration for a worker: first, they invest in human capital formation, and then they try to capitalize on their investments. In this way, successful migrants may use their new capital to provide for better schooling for their children and better homes for their families. Successful high-skilled emigrants may serve as an example for neighbors and potential migrants who hope to achieve that level of success.
World systems theory looks at migration from a global perspective. It explains that interaction between different societies can be an important factor in social change within societies. Trade with one country, which causes economic decline in another, may create incentive to migrate to a country with a more vibrant economy. It can be argued that even after decolonization, the economic dependence of former colonies still remains on mother countries. This view of international trade is controversial, however, and some argue that free trade can actually reduce migration between developing and developed countries. It can be argued that the developed countries import labor-intensive goods, which causes an increase in employment of unskilled workers in the less developed countries, decreasing the outflow of migrant workers. The export of capital-intensive goods from rich countries to poor countries also equalizes income and employment conditions, thus also slowing migration. In either direction, this theory can be used to explain migration between countries that are geographically far apart.
Certain laws of social science have been proposed to describe human migration. The following was a standard list after Ravenstein's proposals during the time frame of 1834 to 1913. The laws are as follows:
Lee's laws divides factors causing migrations into two groups of factors: push and pull factors. Push factors are things that are unfavourable about the area that one lives in, and pull factors are things that attract one to another area.
See also article by Gürkan Çelik, in Turkish Review: Turkey Pulls, The Netherlands Pushes? An increasing number of Turks, the Netherlands’ largest ethnic minority, are beginning to return to Turkey, taking with them the education and skills they have acquired abroad, as the Netherlands faces challenges from economic difficulties, social tension and increasingly powerful far-right parties. At the same time Turkey’s political, social and economic conditions have been improving, making returning home all the more appealing for Turks at large. (pp. 94–99)
The modern field of climate history suggests that the successive waves of Eurasian nomadic movement throughout history have had their origins in climatic cycles, which have expanded or contracted pastureland in Central Asia, especially Mongolia and the Altai. People were displaced from their home ground by other tribes trying to find land that could be grazed by essential flocks, each group pushing the next further to the south and west, into the highlands of Anatolia, the Pannonian Plain, into Mesopotamia or southwards, into the rich pastures of China.