Download 1 Inaugural Lecture Human Migration: Disciplinary Contributions to

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Inaugural Lecture
Human Migration: Disciplinary Contributions to its History
Patrick Manning
Andrew W. Mellon Professor of World History
October 14, 2008
Thanks to Provost Maher for hosting this session, to Arts & Sciences Dean
Cooper for his confidence in the potential of world historical studies at Pitt,
to colleagues in the Department of History for welcoming an opinionated
senior faculty member into their midst, and to the University Center for
International Studies and its range of activities.
Inaugural lectures. Not long after arriving at Pitt I attended an impressive
inaugural lecture by Angela Gronenborn, Rosalind Franklin Professor of
Structural Biology, in which she traced 50 years of change in structural
biology, revealing spectacular results. (Biology is a field that works at
multiple levels, from the molecular level to that of whole phyla, so that it
presents a certain parallel to the range of historical studies—from biography
and microhistory up to worldwide patterns.)
So I have decided to structure this lecture as a review of the past 50-60
years. The results will be less spectacular but I think the increase in
knowledge and inflections in the direction of study are just as intriguing.
Migration History in World History
World History
The field of history entered the past 60 years by renewing its long-time
emphasis on national and political history. But new types of work then
expanded in area studies (with greater attention to Asia, Latin America, and
Africa), followed by the emergence of new methods and a wider range of
fields (social history, studies of gender and the environment), and then by
expanded study of interconnections within these subfields of history.
The idea of world history was available all along, but only now is it
becoming a research field, with a research agenda and institutions for formal
study.
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World History addresses a wide range of space, time, and topics. In addition,
world history draws on data and interpretive frameworks from almost every
academic discipline. Rather than try to make statements encompassing the
whole of world history, I will offer illustrations from the study of migration,
a subfield of world history into which I have put particular effort. I’ll seek to
convey some of the general patterns and changing implications of human
migration, and I’ll emphasize the contributions of many academic
disciplines to our understanding of migration.
Background to Migration Studies
Historical studies of migration 50 years ago centered on Atlantic
migration of the nineteenth and twentieth century. Oscar Handlin’s narrative
of The Uprooted became a classic study of the modification of the American
nation through the arrival of Irish and then continental migrants driven off
their homeland and starting anew across the Atlantic.
 “The Uprooted” – Atlantic migration [image]
Another well-known theme was that of the wandering German tribes
who brought down the Roman Empire in the early centuries of the Christian
era. As a child I studied this very image from H.G. Wells’ Outline of
History—written in the aftermath of World War I—which I pulled down
from my parents’ bookshelf in the years after World War II, another time in
which large-scale conflict caused people to think in more global terms than
usual.
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 In the 1970s William McNeill, the early leader in establishing the
field of world history, prepared a typology of migration. His vision
emphasized the distinctive character of migration at different times in
history. I’ll return to this overview later with a different approach to
migration history.
I want to turn rapidly to locate insights into migration from other disciplines,
and show how they have changed the historical understanding of
migration.
Insights from Social Sciences
I’ll start with the social sciences and with the field of economics.
The economist Brinley Thomas, in his 1954 Migration and Economic
Growth, showed how clearly the ebbs and flows of Atlantic migration
correlated with the ups and downs of the business cycle on both sides of the
Atlantic. That is, migration rose when there were greater economic
opportunities in the lands of settlement.
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 Sociology – 20thcentury migration. Networks; families; Portes, Doug
Massey
READ TRIMMER AND EXPAND SOCIOLOGY
The field of Demography joined migration studies, especially in the
1980s. Demographers had previously focused on rates of birth and death,
abstaining from studying migration because the comings and goings of
migrants disturbed the stable populations that were the core of their analysis.
The arrival of electronic spread sheets made the calculation of life tables far
easier, so demographers expanded their analysis to include migration and
other changes in status besides birth and death. The particular benefit of
demographic study was its attention to the age- and sex-specific character of
migration and other human activities.
Among the early benefits of demographic analysis was the
confirmation that migrants were usually young adult males, so that
immigrant populations were usually dominantly male, while the populations
remaining at home were dominantly female. This observation had particular
importance in studies of slave trade in the period from the fifteenth to
nineteenth century, where the Atlantic slave trade carried young males
especially, but where the parallel but smaller slave trade to Old World
regions carried more young females than males.
The field of historical linguistics is a minor subfield in linguistics
overall, but it is of great importance for migration studies and it has achieved
substantial advances in the past 50 years. The key figure was Joseph
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Greenberg, who classified the languages of Africa as of 1948 and later
classified the language groups known as Eurasiatic, Amerind, and IndoPacific. In sum, Greenberg proposed classifications for seven of the world’s
twelve major language groups. In addition to language classification,
historical linguists have conducted important studies of borrowings: the
movement of terms from one language to another, presumably in association
with the movement of the items referred to.
Applying the results of language classification to migration studies,
the big advances in the past 50 years have been the continuing study of IndoEuropean migrations to South Asia; the Bantu migrations in Africa, which
Greenberg showed to have begun in southeastern Nigeria but which
eventually expanded to occupy the southern third of the African continent;
and the Austronesian migrations, which began in south China but gradually
expanded, especially by maritime migration, to most of Southeast Asia, most
of the Pacific, and also to Madagascar.
Along with some others, I have taken the classification of languages
as an indication of the path of early human migrations. This approach
requires assuming that the major language groups of today reflect divisions
in linguistic communities from as much as 70,000 years ago. Historical
linguists are themselves divided on the methodology of language
classification and on the question of how far back we can trace ancestral
language communities. My point is that linguists need to get themselves
together, resolve their differences, and provide scholars in other fields with a
more unified picture of language change.
Here is a summary of a linguistically-based approach to the
population of the earth by Homo sapiens. The first map shows the projected
homelands of the nine language groups of the tropics. The distribution of
these language groups makes clear the hypothesis that humans migrated to
the east out of Africa, along the Indian Ocean coast, and relying heavily on
boats, presumably made of bundled reeds, until they reached Australia and
New Guinea. This migration would have been accomplished by at least
50,000 years ago.
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The second map shows the three principal language groups of
temperate Eurasia and the Americas. This zone, occupied in the time after
40,000 years ago, had a fundamentally different ecology than the tropics,
and it took a long time for humans to develop the techniques for living there.
Once restless humans learned the techniques for living in lands with sharp
temperature changes and with very different flora and fauna, the process of
occupation went rapidly.
An interesting riddle, to which we do not yet have a clear answer, is
that of by which route humans moved from the tropics to the temperate
zone. It could have been at any point—any south-to-north passageway—
between the Atlantic and the Pacific. My own analysis gives particular
attention to the route north along the Pacific coast of China.
Insights from Natural Sciences
These are some of the advances from social-science fields of
economics, sociology, demography, and linguistics. While the social
sciences have contributed important new methods and hypotheses to the
understanding of migration, the natural sciences have brought even greater
contributions to migration history. This tale must begin with genetics.
 Genetics –
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The key breakthrough in genetics was a truly remarkable experiment.
Once it became possible to establish the sequence of amino acids in DNA
molecules, a group in Berkeley designed a very efficient experiment. They
used mitochondrial DNA—small pieces of DNA that exist outside the
nucleus of human cells, and which are passed down only through the female
line. Then they selected 147 women, many from the San Francisco Bay
Area, different in that they had ancestry in Africa, Europe, Asia, and the
Americas. Then the researchers analyzed and compared the mitochondrial
DNA of their subjects and found that the variation in DNA among those of
African ancestry was greater than that among all other subjects. Based on
these results, the team asserted that the ultimate female ancestor of Homo
sapiens had lived in Africa some 200,000 years ago. On one hand, this
result was expected from evidence in genetics and other fields. On the other
hand, a decade of debate took place. The final conclusion was to confirm the
initial hypothesis—that is, the pattern is so robust that it was able to emerge
even from this simply though laborious test.
After some years, geneticists were able to develop a parallel but more
complex analysis tracing human ancestry through the male line. The Ychromosome, passed through the male line and only to males, now enables
us to trace ancestry through the male line as well as the female line.
Here is a portrayal of recent results on the analysis of Y-chromosome
composition over the course of 100,000 years, based on study of change in a
single nucleotide or amino acid in the DNA chain.. The orange dot for
Africa and the tropics is for people who have the nucleotide shared with
chimpanzees, going back far indeed. The green dots and blue dot represent
later mutations. In both cases the mutations are thought to have occurred in
Africa, but to have become important in populations later on. Finally, the
pink dot represents a mutation that took place in Asia and spread to the
Americas. The result gives a general but clear indication of the path of
human expansion.
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Genetic analysis is applicable to more recent times as well, in this
case over the past 500 years. For such analyses, geneticists trace the
mutations in groups of nucleotides rather than individual nucleotides, as
the cumulative change in multiple sites is more rapid and enables
distinguishing changes in shorter times. In the two graphs shown here, we
have samples of five populations of Brazilian females at left, and the
equivalent five populations of Brazilian males at right. The two populations
at the left of each graph are phenotypically “black,” while the three
populations at right are phenotypically “white.” The genetic analysis is able
to tell whether the male and female ancestors of these individuals are mainly
African, European, or Native American, and the results vary in interesting
ways.
For females now known as “black,” the great majority of their female
ancestors are African; a few are European and rather more are Native
American. For females now known as “white,” their female ancestors are
dominantly white, yet large minorities of their female ancestors are Native
American or AfricaN.
For black males, over half of their male ancestors are European;
nearly half are African and a small number are Native American. For white
males, virtually all of their male ancestors are European, and a very few are
Native American. Overall, the results show that European males had
numerous children with women of all origins; some African males had
children with some of the African women; and Native American males had
few children.
Females (B&W);
Males (B&W)
Overall, these genetic results confirm the importance of mixes of
various sorts in any population and provide information on social
hierarchies.
 Climatology - Geology –
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Geology and climatology have produced many important results in
recent years, but I will focus on some of those that have come from ice cores
taken from Greenland.
First, attention to volcanic ash at various levels of the ice cores gives
indications on the timing and intensity of volcanic explosions, which spread
dust into the air which, at worst, limited sunlight, reduced temperatures, and
brought drought and famine. In this graph, historian William Atwell has
summarized the apparent intensity of northern hemisphere volcanic
explosions in the 13th century. The results show peaks in the 1220s and
1250s.
Atwell’s research has located reports of erratic weather for each of
those times. Both periods were times in which there were major wars and
expansion of the Mongol empire. In addition, Atwell has suggested the
identity of the volcano in each case.
The ice cores provide data for much earlier times. This graph shows
estimates of Greenland temperature for the past 20,000 years—that is, from
the low point of the last Ice Age until the present. The graph highlights the
phenomenon known as Younger Dryas (named after a plant), in which
temperatures fell sharply for the period between about 13,000 and 11,000
years ago, before rising rapidly again. This information has led agronomists
to conclude that this phenomenon was important in provoking the rise of
agriculture. That is, populations that were intensively gathering grains, roots,
and fruits in the previous period of rapid warming—prospering along with
the plant life as temperatures grew—had to respond to the collapse in
temperature and the shrinking availability of food supplies either by
shrinking their communities or by developing systems for cultivating as well
as harvesting foodstuffs. This would help explain why at least six regions
around the world developed agriculture at very much the same time.
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Here’s my view of the places and the crops that were most important
in the rise of agriculture at this time.
 Archaeology The field of archaeology, a very multidisciplinary field of study, can
be included in both the social sciences and the natural sciences, but I have
chosen to emphasize its natural-science dimension. Archaeologists explore
the physical remains of human settlements. It is slow and expensive work,
but of immense value when skillfully conducted. I do question the standards
by which archaeological funds are allocated. That is, because of social
pressures, most archaeological study still focuses on regions where ancient
civilizations are best known—the Mediterranean, Europe, and now North
China—leaving in relative neglect the tropical regions where so much of
humanity has lived, as well as regions outside the tropics where important
developments arguably took place. Here are two exceptions: archaeological
findings on the eastern shores of the Pacific and in Central Asia.
For the Pacific, maritime archaeologist Jon Erlandson has developed
the notion of the “kelp highway” to explain a migratory path that was open
to maritime peoples of the Pacific as much as 35,000 years ago. Offshore
kelp forests provided a hospitable atmosphere for flourishing communities
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of fish, birds, and marine mammals. The archaeological sites go back at least
10,000 years.
The shells shown here are mussel, abalone, and sea urchins,
compounded into a midden on San Miguel Island. But village sites are 50100 meters below ocean surface. Still, middens were strewn at a distance
from shore, including on nearby cliffs.
 Archaeology of horse domestication. Between Ukraine and
Kazakhstan, over a long time with breakthroughs 7000 years ago.
Domesticating males, breeding females. Breeding horses for size and
strength; breeding mules early on. Bit and bridle. Wagons already for
oxen; chariots and spoked wheels developed in this region. Burials of
horses, chariots, and charioteers.
 Unique development because of the immediate impact of chariot
warfare c. 1500 BCE, and the spread of horses as a core element of
warfare, eventually for every continent.
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 Horses spread war and large-scale statecraft across region after region
of the world.
This completes my initial review of ideas—theories, data, and
hypotheses relevant to migration history—deposited into historical studies
by analysts working in various fields of social and natural sciences.
Historians’ advances in migration studies
Meanwhile historians, during this past 50 years, have expanded their
studies and added nuance to their interpretations, partly in response to the
enriched data made available by other disciplines
For much of that time, one of the major arenas of migration history
was study of slave trade and slavery, especially that of the Atlantic world but
also including other regions. This was part of the expansion in historical
studies of black peoples in the era of civil rights and decolonization, and it
was facilitated by the advances in social and demographic history. The
Atlantic slave trade became clearly understood as the largest human
migration in the period up to 1850. And the concept of migration now had to
expand and give explicit attention to the role of forced migration, as a result
of studies of slave trade and the studies of the more recent Holocaust in
Europe.
For the great migrations of the nineteenth and twentieth centuries,
growing attention to Asia revealed that the great Atlantic migration of
Europeans was only part of a larger process. Much as Philip Curtin had
tallied the magnitude of the Atlantic slave trade in a 1969 book, Adam
McKeown tallied the magnitude of global migration from 1840 to 1940 in a
2001 article.
The top layer of this graph shows the number of transatlantic migrants
from Europe, by five-year period, from 1840 to 1940. The next layer shows
the number of migrants from China and India to Southeast Asia—also
traveling by sea—in the same period. The bottom layer shows the number of
migrants to North Asia—especially Manchuria but also to Siberia and
Central Asia—from China and Russia. (Most but not all of the latter group
traveled on land). Roughly 50 million migrants in each of these instances—
150 million total—through there were numerous return migrants in each
case.
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Overall, this summary of a century’s global migration shows that the
pattern was not so much movement from Europe to America as it was
movement from the densely populated parts of the world to sparsely
populated regions that promised a decent living. Remarkably, the graph
indicates that the number of migrants into Southeast Asia during this century
exceeded the number of migrants into the United States.
Equally important, these results make clear how greatly this explosion
of migration depended on the development of steamships, which dominated
passenger routes from about 1850, enabling more dependable schedules and
a decline in shipboard mortality. So 1850 marks both the near elimination of
transoceanic slave trade—involuntary migration—and the expansion of
voluntary overseas migration.
Migration in Biology
So far I have reviewed examples of new data and new understandings
of migration, strewn across the continents and the oceans and encompassing
most of a hundred thousand years. Let me turn now to the question of
whether it is possible to assemble these scattered insights into a larger and
more coherent picture. I will argue that there is indeed a broader pattern
unifying much of the history of human migration, but I’ll propose this
argument by way of a detour through another instance in which ideas, data,
and inspiration came to history from the natural sciences.
Hugh Dingle, an entomologist at the University of California, Davis,
published a 1994 book entitled Migration: The Biology of Life on the Move
which reviewed the literature on migration of birds, insects, mammals, fish,
and other organisms. Working at the level of the organism, and synthesizing
and criticizing the literature in each field, he came up with definitions and
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general principles that showed the common issues and characteristics in
migration for numerous taxa.
Here is Dingle’s definition of Migration: “movement that takes the
individual organism beyond its habitat, is persistent in time, is straitened (in
contrast to multidirectional movements at a more local scale), is undeterred
by the availability of resources such as food, includes distinctive behavior on
departure and arrival, and involves a reallocation of energy to sustain the
voyage.”
This definition includes to-and-fro migrations, nomadic and
opportunistic migration, one-way migration, migration with the aid of wind
or mobile animals, and migration in alternate generations (as in some
insects)
Dingle emphasizes that his is a behavioral definition of migration,
focusing on behavior and experience of individual organism, rather than an
ecological definitions of migration focusing on points of departure and
arrival—he criticizes the analysts of birds as being too focused on geography
to give attention to the individual changes in the process of migration. Then
he criticizes the analysts of mammals for using the term “dispersal”, which
they adopted because students of birds claimed that “migration” could only
refer to the to-and-fro movements of birds. The problem with “dispersal” is
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that it tends to suggest that migrating young mammals moved progressively
far from each other, when in fact they commonly congregated at points
along their migration.
o Dingle described “habitat” as “the area that provides the resource
requirements for a discrete phase of an organism’s life.” Organisms
might move about their habitat, for instance to find mates, but
migration is the movement from one habitat to another.
o Dingle then poses two types of questions in order to articulate his
analysis. First are “why questions” about why organisms migrate;
second are “How questions” about the behavior through which
organisms accomplish their migrations.
o For the answers to why questions, Dingle suggests five general
points: (1) seasonal migration is resource-based; (2) requirements of
life history create migratory paths; (3) ephemeral or patchy habitats
reinforce migration; (4) variety in migratory behavior within species
is functional; (5) there exists a genetic basis for migratory life
histories.
o For the answers to how questions, Dingle emphasizes the changing
physiology of organisms and the environmental stimuli to which they
respond.
Here is just one illustration from the book.
Consider this contribution.
Both the specifics of Dingle’s observations on migration and the
general approach that enabled him to conduct this study are of relevance to
human migration history and world history. He provides a model for largescale interpretation, addressing numerous and differing fields, identifying
what is common and what is distinct. Dingle theorizes—not about details of
specific organisms but about larger patterns. He feels free to criticize the
definitions and analyses used within academic fields based on broader
considerations.
As I see it, in the growing mass of new evidence about change over
time, the role of the historian is more than to summarize results of other
fields; it is more than to provide background for the analysis taking place in
other fields. The historian should synthesize, theorize and criticize, entering
active discourse with scholars in other fields.
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Reinterpreting human migration
Here, then, are the main points I offer in developing a general model for
human migration inspired by Dingle’s approach.
o First, I define human communities. Human communities have far
more variation among them than is the case for other species,
especially because of our development of language and because we
have come to inhabit such varied ecologies. So I define human
communities as those who share a single language. This definition
has significant implications which I can only hint at here.
o Second, I define Habitat: Humans are exceptionally adaptable to
varying environments, so it is difficult to speak of human habitat in
general terms. Define human habitat as an ecological zone in which a
community can function with a given set of customs.
o Third, I distinguish categories of human migration. Only the last
category is distinctive to humans
o Home-community mobility (as for other organisms)
o Colonization (extending the range of a community)
o Whole-community migration (nomads following animals, fish,
or vegetable resources; expulsion via disaster)
o Cross-community migration—movement of individuals to other
communities.
o Cross-community migration
o Young adults
o Cross community lines
o Launched for positive and negative reasons (GIVE THEM)
o Learn language and customs
o Networks to facilitate migration
o Fifth, I distinguish types of cross-community migrants (these are
familiar categories, but they are now set in a broader context):
o Settlers
o Sojourners
o Itinerants
o Invaders
o
o Why questions:
o Social rather than biological mechanisms appear to be central in
regulating human migration
o Why do individual humans want to migrate?
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o What structures and forces pressured humans to migrate?
o How questions:
o How is migration accomplished?
o How do migrants get through seasoning?
Reinterpret migration history with this framework
Process:
o Distinguish colonization from cross-community migration
o Continuity of cross-community migration – and learning
o History of migration is re-enactment of cross-community migration,
moving into empty lands, and migrating into settled areas.
o Settlement of the Americas
Turning points in migration history
mostly associated with advances in maritime technology
o Occupation of the tropical shores, relying on reed boats, 70,000
years ago
o Occupation of temperate Eurasia, relying on skin boats, 40,000
years ago
o Occupation of the Pacific shores, relying on the kelp highway,
10 – 30,000 years ago
o Agriculture, 13,000 years ago
o Domestication of horses, 7000 years ago
o Navigation of all the oceans, from 16th century
o Steamships, from 1850
o Large-scale urbanization, 20th century
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This is the framework I propose. Some aspects of human migration
are easily explained by the principles that work for all sorts of organisms.
But the dominant aspect of human migration, emphasizing cross-community
migration, is a distinctive human pattern, and it can be observed
systematically in human behavior. Only a minority of individual humans
migrate, but all human communities rely on cross-community migration, in
varying degree, to sustain themselves. Further, cross-community migration
is one of the principal engines of social evolution, by building in constant
incentives to learn and to innovate at the individual level.
Migration today
o Migration today may appear in a different light from the upbeat
picture I have given of its role in human society.
o We are more acquainted with fears of migrants as those who might
pour in and undermine an established society
o We are also more acquainted with the vision of migrants as people of
little knowledge, little skill, and low income, hardly able to contribute
innovation and advance as they move.
o Probably I do need to revise my analysis to account more fully for
migrants who are kept at low levels of society, though the history of
the Atlantic slave trade gives impressive accounts of innovation and
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creativity even in the midst of cruelty and oppression of migrant
populations.
o I also need to account for the many cases of invaders who have left
paths of destruction before they got around to addressing benefits.
o But I want to finish with the example of university students as crosscommunity migrants. Young adults move to new place, learn new
languages (now including computer languages and esoteric theories);
they learn from others, convey their own ideas, and may invent new
ideas. As their university sojourn reaches an end they may return
home, stay where they are, or move on. Learning of the most updated
sort is grafted onto an old and trusted mechanism for facilitating
learning.
o An ancient and, really, instinctive behavior is here adapted to the most
current needs of a postindustrial society.
Conclusion
I don’t claim that all of knowledge is to explain migration or that migration
explains everything in human experience, but I do claim that movement and
migration are very important in making sense of the human experience.
I claim that analysis at multiple scales, using the perspectives of multiple
disciplines, can clarify and demonstrate the generality of patterns,
identifying more precisely where the uniqueness lies.
That’s what I wanted to present, so thank you for your interest.