Human migration: causes, types, history and impacts

About 40,000 years ago, Homo sapiens opened up the temperate zones of Eurasia; 12,000 years ago, he was present in all large areas of the continents. The emergence of the Sahara triggered a migration of Bantu from western to southern Africa between 3000 and 1000 BC. In the period between 200 and 1500, the Chinese spread in all directions from their areas of origin, especially into South Asia. Around 500, Arab tribes migrated in large numbers over long distances, reaching East Africa and elsewhere. Jewish migration, often resulting from discrimination, oppression, and persecution, was evident, among other things, in the exodus from Egypt in 1250 BCE, in diaspora Judaism caused by foreign domination and the outcome of the Jewish War, and in the remigration to Palestine driven by the Nazi period and the Holocaust.

Early migratory movements in the European region include the Greek colonization of the Mediterranean in the 1st millennium BC and the migration of peoples at the transition between Late Antiquity and the Early Middle Ages. European expansion began with the 16th century, as a result of which colonialism and the modern slave trade developed and the indigenous population of the Americas collapsed. Mass emigration from Europe, particularly to the Americas and especially to the United States, began in the 19th century with continued strong growth in the European population and internal migration.

From the worldwide warlike or war-like conflicts of the 20th century, forced migrations in the form of deportations and expulsions increasingly emerged, for example as a consequence of the Russian Revolution, the Asia Minor Catastrophe, the Stalinism of the Soviet Union, the deportations of Jews and forced labourers as well as the expulsion of Poles and ethnic minorities by the Third Reich or in the westward shift of Poland after the Second World War or the partition of India. At the end of the 20th century - after the end of the East-West conflict - global migration seems to increase in complexity. The classic forms of migration - immigration, guest labour and flight - appear less in pure form than in variants.

Migrating people are more mobile than others, states Annette Treibel, and wants this to be understood not only spatially, but also psychologically and socially: "They divert their dissatisfaction with living conditions into the decision to migrate". If migration takes place within a country, it is internal migration. If state borders are crossed, it is emigration from the perspective of the country of origin and immigration from the perspective of the receiving country. Transit countries are used for temporary residence during the transition from the country of origin to the country of destination.

Involuntary migrants are refugees, forcibly displaced persons or people displaced by natural disasters. However, the distinction between voluntary and involuntary migration is relative, because certain constraints (e.g. scarcity of resources, insecurity) are almost always contributory factors in a decision to migrate. Refugees are people who have fled wars, political or religious persecution, or even natural disasters and environmental damage (environmental migration). The latter migration push is likely to become more important, especially in the wake of global warming, although present-day estimates vary widely. Sea-level rise alone threatens to directly endanger rice production and supply for some 200 million people in low-lying regions of Asia. There is also a significant link between the destruction of cultural property and flight or migration, as Blue Shield International President Karl von Habsburg explained during a cultural property protection mission in Lebanon in April 2019 with the United Nations Interim Force in Lebanon: "Cultural property is part of the identity of the people who live in a particular place. If you destroy their culture, you also destroy their identity. Many people are uprooted, often have no prospects and as a result flee their homes." At the same time, refugee migration often follows personal circumstances: While the poorer can only afford to flee to neighboring regions, the better off are more likely to reach more distant regions. Whether such "involuntary migrants" should be considered migrants at all is a matter of debate.

Both civilians and military personnel may flee warlike conflicts in large numbers.

According to the Geneva Convention of 28 July 1951, refugee migration is the spatial movement of a person who "owing to a well-founded fear of being persecuted for reasons of religion, nationality, membership of a particular social group or political opinion, is outside the country of his nationality and is unable or, owing to such fear, is unwilling to avail himself of the protection of that country."

Economic reasons are not recognized for the definition of a person as a refugee in the Geneva Refugee Convention. However, migration usually takes place with the hope of improving one's living situation. In such cases, the problem of distinguishing between voluntariness and "economic coercion" arises. Individuals are to varying degrees able and willing to endure frustration (frustration tolerance). And even if they are not willing to remain in the status quo, they have different options for action: They can change their environment or try to escape it.

Prosecution for desertion and conscientious objection leads many fugitives to seek protection from persecution abroad. Often only a few deserters succeed in this escape. In many countries, desertion is not directly recognised as a reason for protection. In the Federal Republic of Germany, for example, there is no right to asylum for deserters: "In the Federal Republic's case law on granting asylum, it is insisted that every state has the right to conscript its citizens for military service." Even the danger of being used again in war in the area of origin "does not protect deserters from deportation." There is a possibility of recognition in the jurisdiction "if it can be shown that recruitment is based on membership of a particular ethnic group, that is, it constitutes discrimination."

Labour migrants are people who emigrate from their home country to a foreign country for the purpose of employment. The migration usually takes place from industrially less developed countries to industrial nations. Therefore, these migrants are sometimes colloquially and disparagingly referred to as economic migrants. Economic migrants do not meet the criteria for refugee status. They are therefore not entitled to international protection as refugees in the sense of asylum law.

Educational migration is playing a growing role, although it is not an entirely new phenomenon. Today, more and more countries are making efforts to create attractive conditions of education, study and research in order to attract people who are willing and qualified to migrate. According to an OECD study published in 2015, Germany is the industrialised country with the highest number of people moving abroad to study; the most visited destination country for German students is Austria.

Transmigration refers to the commuting of migrants between places of residence in different cultures. Transmigrants are characterised, among other things, by high formal qualifications and spatial mobility while retaining social ties to the society of origin. Linked to the term are questions of identity formation (keywords: "third-culture kids", biculturalism). Studies show that migrants' qualifications influence their identity and that it is particularly the highly qualified who do not (or no longer) define their identity in national terms. For industrialised countries, internationally positioned companies or research institutions, the migration behaviour of well-educated professionals is of interest. They are considered to be the ones who create and transport innovation leads due to their qualifications and experience, but also because of their global networking.

Sociologist Christoph Butterwegge speaks of a polarisation of migration into "misery and refugee migration" on the one hand and "elite and expert migration" on the other, "in which the highly qualified, scientific-technical, economic and political leaders as well as artistic and sporting celebrities settle here today, there tomorrow, whether because their places of employment rotate, professional advancement is facilitated by a global presence or tax advantages invite modern nomadism." Misery migration is subject to much more restrictive and repressive forms of regulation than elite and expert migration.

In addition, "old-age migration" or "retirement migration" is becoming increasingly important. In contrast, "marriage migration" is the most important reason for immigration of third-country nationals in Germany.

German law on foreigners defines migrants as a "generic term for people of non-German origin" and includes not only foreigners but also "naturalised German citizens and ethnic German repatriates".