Part 1: Around the world in 40 minutes
I've set myself the
modest task today of trying to explain the broad pattern of human history, on
all the continents, for the last 13,000 years. Why did history take such
different evolutionary courses for peoples of different continents? This problem
is now ripe for a new synthesis because of recent advances in many fields
seemingly remote from history, including molecular biology, plant and animal
genetics and biogeography, archaeology, and linguistics. I'll try to answer this
question for you in 40 minutes, which averages out at less than 7 minutes per
continent. This talk is based on an 800-page book that I recently completed, and
I had to omit some details in order to compress 13,000 years of history into 800
pages, so naturally I'll have to omit more details today.
At the outset,
I want to acknowledge with pleasure my debt to the UCLA community over the last
30 years. For the material that I'm about to discuss with you, I thank
especially my colleagues in the School of Medicine for helping me understand
human diseases; my colleagues in many college departments for helping me
understand problems of history and evolution and linguistics; and the librarians
of UCLA's wonderful library system, without which it would have been impossible
to pursue the broad synthesis that I'll now attempt.
My theme, then, is
the different courses of history for peoples of different continents. As we all
know, Eurasians, especially peoples of Europe and eastern Asia, have spread
around the globe, to dominate the modern world in wealth and power. Other
peoples, including most Africans, survived, and have thrown off European
domination but remain far behind in wealth and power. Still other peoples,
including the original inhabitants of Australia, the Americas, and southern
Africa, are no longer even masters of their own lands but have been decimated,
subjugated, or exterminated by European colonialists. Why did history turn out
that way, instead of the opposite way? Why weren't Native Americans, Africans,
and Aboriginal Australians the ones who conquered or exterminated Europeans and
Asians?
This question can easily be pushed back one step further. By the
year A.D. 1500, the approximate year when Europe's overseas expansion was just
beginning, peoples of the different continents already differed greatly in
technology and political organization. Much of Eurasia and North Africa was
occupied then by Iron Age states and empires, some of them on the verge of
industrialization. Two Native American peoples, the Incas and Aztecs, ruled over
empires with stone tools and were just starting to experiment with bronze. Parts
of sub-Saharan Africa were divided among small indigenous Iron Age states or
chiefdoms. But all peoples of Australia, New Guinea, and the Pacific islands,
and many peoples of the Americas and sub-Saharan Africa, were still living as
farmers or even still as hunter/gatherers with stone tools.
Obviously,
those differences as of A.D. 1500 were the immediate cause of the modern world's
inequalities. Empires with iron tools conquered or exterminated tribes with
stone tools. But how did the world evolve to be the way that it was in the year
A.D. 1500?
This question, too can be easily pushed back a further step,
with the help of written histories and archaeological discoveries. Until the end
of the last Ice Age around 11,000 B.C., all humans on all continents were still
living as Stone Age hunter/gatherers. Different rates of development on
different continents, from 11,000 B.C. to A.D. 1500, were what produced the
inequalities of A.D. 1500. While Aboriginal Australians and many Native American
peoples remained Stone Age hunter/gatherers, most Eurasian peoples, and many
peoples of the Americas and sub-Saharan Africa, gradually developed agriculture,
herding, metallurgy, and complex political organization. Parts of Eurasia, and
one small area of the Americas, developed indigenous writing as well. But each
of these new developments appeared earlier in Eurasia than elsewhere.
So,
we can finally rephrase our question about the evolution of the modern world's
inequalities as follows. Why did human development proceed at such different
rates on different continents for the last 13,000 years? Those differing rates
constitute the broadest pattern of history, the biggest unsolved problem of
history, and my subject today.
To appreciate how far from obvious is the
answer to this question, imagine that an alien historian from Outer Space had
visited the Earth 50,000 years ago. If that visitor had been asked to predict
which continent's people would develop technology most rapidly, and who would
conquer whom, what do you think that the alien would have predicted? The alien
might well have answered "Africa," because human history in Africa had a
six-million-year head start over history on the other continents. Or, the alien
might instead have predicted "Australia," the continent with perhaps the
earliest evidence of anatomically and behaviorally fully modern humans, and the
continent with by far the earliest evidence for human use of watercraft. The
visitor would surely have written off Europe, where Homo sapiens still hadn't
even arrived as of 50,000 years ago. To that visitor, the state of the world as
we see it today would be incomprehensible. What were the reasons for the
unexpected outcome?
By now, you may have been starting to wonder: Oh, my
God! Did the Faculty Research Lecture Committee really blow it in their choice
this year? Is this guy going to give us excuses for the status quo, with all its
gross injustices? Are we about to hear an apology for racism?
No, I won't
be talking about differences in IQ, and I won't be asserting that Europeans
spread overseas because of being smarter than other peoples. Many Europeans
tacitly assume so, even though they may have learned that it's no longer
considered politically correct to say so in public. Technologically primitive
peoples are often assumed to be biologically primitive.
But many
attempts, especially in the U.S., to document innate IQ differences among
different peoples have been unsuccessful. My own impression, from my 32 years of
field work in New Guinea, is that New Guineans recently out of the Stone Age
appear on the average considerably more intelligent than Europeans -- partly for
the obvious reason that natural selection related to intelligence operates much
more ruthlessly in traditional New Guinea societies than in politically
organized Europe, so that New Guineans probably have an average genetic
advantage. In addition, most European and American children today suffer from
the crippling developmental disadvantage of spending much of their time being
passively entertained by radio, TV, and movies, while traditional New Guinea
children spend all of their waking time talking or otherwise actively engaged
with other children and adults.
We therefore have to turn the usual
racist assumption on its head. Instead of asking how industrial peoples came to
be smarter, we have to ask: why is it that modern Stone Age peoples, despite
probably being genetically smarter and certainly being developmentally
advantaged, nevertheless ended up technologically outstripped and conquered by
Eurasians?
In case you still feel uncomfortable about exploring this
subject, just reflect on the underlying reason why so many people accept racist
explanations of history's broad pattern: we don't have a convincing alternative
explanation. Until we do, people will continue to gravitate by default to racist
theories. That leaves us with a huge moral gap, which constitutes the strongest
reason for tackling this uncomfortable
subject.
Part 2: Why did a few
hundred Spaniards overthrow the Aztecs and Incas?
Let's proceed
continent-by-continent. As our first continental comparison, let's consider the
collision of the Old World and the New World that began with Christopher
Columbus's voyage in A.D. 1492, because the proximate factors involved in that
outcome are well understood. I'll now give you a summary and interpretation of
the histories of North America, South America, Europe, and Asia from my
perspective as a biogeographer and evolutionary biologist -- all that in ten
minutes. Here we go:
Most of us are familiar with the stories of how a
few hundred Spaniards under Cortés and Pizarro overthrew the Aztec and Inca
Empires. The populations of each of those empires numbered tens of millions.
We're also familiar with the gruesome details of how other Europeans conquered
other parts of the New World. The result is that Europeans came to settle and
dominate most of the New World, while the Native American population declined
drastically from its level as of A.D. 1492. Why did it happen that way? Why
didn't it instead happen that the Emperor Montezuma or Atahuallpa led the Aztecs
or Incas to conquer Europe?
The proximate reasons are obvious. Invading
Europeans had steel swords, guns, and horses, while Native Americans had only
stone and wooden weapons and no animals that could be ridden. Those military
advantages repeatedly enabled troops of a few dozen mounted Spaniards to defeat
Indian armies numbering in the thousands.
Nevertheless, steel swords,
guns, and horses weren't the only proximate factors behind the European conquest
of the New World. Infectious diseases introduced with Europeans, like smallpox
and measles, spread from one Indian tribe to another, far in advance of
Europeans themselves, and killed an estimated 95% of the New World's Indian
population. Those diseases were endemic in Europe, and Europeans had had time to
develop both genetic and immune resistance to them, but Indians initially had no
such resistance. That role played by infectious diseases in the European
conquest of the New World was duplicated in many other parts of the world,
including Aboriginal Australia, southern Africa, and many Pacific
islands.
Finally, there is still another set of proximate factors to
consider. How is it that Pizarro and Cortés reached the New World at all, before
Aztec and Inca conquistadores could reach Europe? That outcome depended partly
on technology in the form of ocean-going ships. Europeans had such ships, while
the Aztecs and Incas did not. Also, those European ships were backed by the
centralized political organization that enabled Spain and other European
countries to build and staff the ships. Equally crucial was the role of European
writing in permitting the quick spread of accurate detailed information,
including maps, sailing directions, and accounts by earlier explorers back to
Europe, to motivate later explorers. Writing may also be relevant to what seems
to us today the incredible naiveté that permitted the Inca Emperor Atahuallpa to
walk into Pizarro's trap, and that permitted the Aztec Emperor Montezuma to
mistake Cortés for a returning god. Since the Incas had no writing and the
Aztecs had only a short tradition of writing, they didn't inherit knowledge of
thousands of years of written history. That may have left them less able to
anticipate a wide range of human behavior and dirty tricks, while writing made
Pizarro and Cortés better able to do so.
Part 3: How domestication
of animals proved easiest for Europeans
So far, we've identified a
series of proximate factors behind European colonization of the New World:
namely, ships, political organization, and writing that brought Europeans to the
New World; European germs that killed most Indians before they could reach the
battlefield; and guns, steel swords, and horses that gave Europeans a big
advantage on the battlefield. Now, let's try to push the chain of causation back
further. Why did these proximate advantages go to the Old World rather than to
the New World? Theoretically, Native Americans might have been the ones to
develop steel swords and guns first, to develop ocean-going ships and empires
and writing first, to be mounted on domestic animals more terrifying than
horses, and to bear germs worse than smallpox.
The part of that question
that's easiest to answer concerns the reasons why Eurasia evolved the nastiest
germs. It's striking that Native Americans evolved no devastating epidemic
diseases to give to Europeans, in return for the many devastating epidemic
diseases that Indians received from the Old World. There are two straightforward
reasons for this gross imbalance. First, most of our familiar epidemic diseases
can sustain themselves only in large dense human populations concentrated into
villages and cities, which arose much earlier in the Old World than in the New
World. Second, recent studies of microbes, by molecular biologists, have shown
that most human epidemic diseases evolved from similar epidemic diseases of the
domestic animals with which we came into close contact. For example, measles
evolved from a disease of our dogs, influenza from a disease of pigs, smallpox
from a disease of cows, and falciparum malaria from a disease of birds such as
chickens. The Americas had very few native domesticated animal species from
which humans could acquire such diseases.
Let's now push the chain of
reasoning back one step further. Why were there far more species of domesticated
animals in Eurasia than in the Americas? The Americas harbor over a thousand
native wild mammal species and several thousand wild bird species, so you might
initially suppose that the Americas offered plenty of starting material for
domestication.
In fact, only a tiny fraction of wild mammal and bird
species has been successfully domesticated, because domestication requires that
a wild animal fulfill many prerequisites: the animal has to have a diet that
humans can supply; a rapid growth rate; a willingness to breed in captivity; a
tractable disposition; a social structure involving submissive behavior towards
dominant animals and humans; and lack of a tendency to panic when fenced in.
Thousands of years ago, humans domesticated every possible large wild mammal
species fulfilling all those criteria and worth domesticating, with the result
that there have been no valuable additions of domestic animals in recent times,
despite the efforts of modern science.
Eurasia ended up with the most
domesticated animal species in part because it's the world's largest land mass
and offered the most wild species to begin with. That pre-existing difference
was magnified 13,000 years ago at the end of the last Ice Age, when more than
80% of the large mammal species of North and South America became extinct,
perhaps exterminated by the first arriving Indians. As a result, Native
Americans inherited far fewer species of big wild mammals than did Eurasians,
leaving them only with the llama and alpaca as a domesticate. Differences
between the Old and New Worlds in domesticated plants, especially in
large-seeded cereals, are qualitatively similar to these differences in
domesticated mammals, though the difference is not so extreme.
Another
reason for the higher local diversity of domesticated plants and animals in
Eurasia than in the Americas is that Eurasia's main axis is east/west, whereas
the main axis of the Americas is north/south. Eurasia's east/west axis meant
that species domesticated in one part of Eurasia could easily spread thousands
of miles at the same latitude, encountering the same day-length and climate to
which they were already adapted. As a result, chickens and citrus fruit
domesticated in Southeast Asia quickly spread westwards to Europe; horses
domesticated in the Ukraine quickly spread eastwards to China; and the sheep,
goats, cattle, wheat, and barley of the Fertile Crescent quickly spread both
west and east.
In contrast, the north/south axis of the Americas meant
that species domesticated in one area couldn't spread far without encountering
day-lengths and climates to which they were not adapted. As a result, the turkey
never spread from its site of domestication in Mexico to the Andes; llamas and
alpacas never spread from the Andes to Mexico, so that the Indian civilizations
of Central and North America remained entirely without pack animals; and it took
thousands of years for the corn that evolved in Mexico's climate to become
modified into a corn adapted to the short growing season and seasonally changing
day-length of North America.
Eurasia's domesticated plants and animals
were important for several other reasons besides letting Europeans develop nasty
germs. Domesticated plants and animals yield far more calories per acre than do
wild habitats, in which most species are inedible to humans. As a result,
population densities of farmers and herders are typically ten to a hundred times
greater than those of hunter/gatherers. That fact alone explains why farmers and
herders everywhere in the world have been able to push hunter/gatherers out of
land suitable for farming and herding. Domestic animals revolutionized land
transport. They also revolutionized agriculture, by letting one farmer plough
and manure much more land than the farmer could till or manure by the farmer's
own efforts. Also, hunter/gatherer societies tend to be egalitarian and to have
no political organization beyond the level of the band or tribe, whereas the
food surpluses and storage made possible by agriculture permitted the
development of stratified, politically centralized societies with governing
elites. Those food surpluses also accelerated the development of technology, by
supporting craftspeople who didn't raise their own food and who could instead
devote themselves to developing metallurgy, writing, swords, and
guns.
Thus, we began by identifying a series of proximate explanations --
guns, germs, and so on -- for the conquest of the Americas by Europeans. Those
proximate factors seem to me ultimately traceable in large part to the Old
World's greater number of domesticated plants, much greater number of
domesticated animals, and east/west axis. The chain of causation is most direct
in explaining the Old World's advantages of horses and nasty germs. But
domesticated plants and animals also led more indirectly to Eurasia's advantage
in guns, swords, ocean-going ships, political organization, and writing, all of
which were products of the large, dense, sedentary, stratified societies made
possible by agriculture.
Part 4: Where Africa fits into the
scheme
Let's next examine whether this scheme, derived from the
collision of Europeans with Native Americans, helps us understand the broadest
pattern of African history, which I'll summarize in five minutes. I'll
concentrate on the history of sub-Saharan Africa, because it was much more
isolated from Eurasia by distance and climate than was North Africa, whose
history is closely linked to Eurasia's history. Here we go again:
Just as we
asked why Cortés invaded Mexico before Montezuma could invade Europe, we can
similarly ask why European countries colonized sub-Saharan Africa before
sub-Saharan countries could colonize Europe. The proximate factors were the same
familiar ones of guns, steel, ocean-going ships, political organization, and
writing. But again, we can ask why guns and ships and so on ended up being
developed in Europe rather than in sub-Saharan Africa. To the student of human
evolution, that question is particularly puzzling, because humans have been
evolving for millions of years longer in Africa than in Europe, and even
anatomically modern Homo sapiens may have reached Europe from Africa only within
the last 50,000 years. If time were a critical factor in the development of
human societies, Africa should have enjoyed an enormous head start and advantage
over Europe.
Again, that outcome largely reflects biogeographic
differences in the availability of domesticable wild animal and plant species.
Taking first domestic animals, it's striking that the sole animal domesticated
within sub-Saharan Africa was a bird, the Guinea fowl. All of Africa's mammalian
domesticates -- cattle, sheep, goats, horses, even dogs -- entered sub-Saharan
Africa from the north, from Eurasia. At first that sounds astonishing, since we
now think of Africa as the continent par excellence of big wild mammals. In
fact, none of those famous big wild mammal species of Africa proved
domesticable. They were all disqualified by one or another problem such as:
unsuitable social organization; intractable behavior; slow growth rate; and so
on. Just think what the course of world history might have been like if Africa's
rhinoceroses and hippopotamuses had lent themselves to domestication! If that
had been possible, African cavalry mounted on rhinos or hippos would have made
mincemeat of European cavalry mounted on horses. But it couldn't
happen.
Instead, as I mentioned, the livestock adopted in Africa were
Eurasian species that came in from the north. Africa's long axis, like that of
the Americas, is north/south rather than east/west. Those Eurasian domestic
mammals spread southwards very slowly in Africa, because they had to adapt to
different climate zones and different animal diseases.
The difficulties
posed by a north/south axis to the spread of domesticated species are even more
striking for African crops than they are for livestock. Remember that the food
staples of ancient Egypt were Fertile Crescent and Mediterranean crops like
wheat and barley, which require winter rains and seasonal variation in day
length for their germination. Those crops couldn't spread south in Africa beyond
Ethiopia, beyond which the rains come in the summer and there's little or no
seasonal variation in day length. Instead, the development of agriculture in the
sub-Sahara had to await the domestication of native African plant species like
sorghum and millet, adapted to Central Africa's summer rains and relatively
constant day length.
Ironically, those crops of Central Africa were for
the same reason then unable to spread south to the Mediterranean zone of South
Africa, where once again winter rains and big seasonal variations in day length
prevailed. The southwards advance of native African farmers with Central African
crops halted in Natal, beyond which Central African crops couldn't
grow.
In short, a north/south axis, and a paucity of wild plant and
animal species suitable for domestication, were decisive in African history,
just as they were in Native American history. Although native Africans
domesticated some plants in the Sahel and in Ethiopia and in tropical West
Africa, they acquired valuable domestic animals only later, from the north. The
resulting advantages of Europeans in guns, ships, political organization, and
writing permitted Europeans to colonize Africa, rather than Africans to colonize
Europe.
Part 5: Australia tests theories about evolution of human
societies
Let's now conclude our whirlwind tour around the globe by devoting five
minutes to the last continent, Australia. Here we go again, for the last time.
In modern times, Australia was the sole continent still inhabited only
by hunter/gatherers. That makes Australia a critical test of any theory about
continental differences in the evolution of human societies. Native Australia
had no farmers or herders, no writing, no manufacture of metal tools, and no
political organization beyond the level of the tribe or band. Those, of course,
are the reasons why European guns and germs destroyed Aboriginal Australian
society. But why had all Native Australians remained
hunter/gatherers?
There are three obvious reasons. First, even to this
day no native Australian animal species and only one plant species (the
macadamia nut) have proved suitable for domestication. There still are no
domestic kangaroos.
Second, Australia is the smallest continent, and most
of it can support only small human populations because of low rainfall and
productivity. Hence the total number of Australian hunter/gatherers was only
about 300,000.
Finally, Australia is the most isolated continent. The
sole outside contacts of Aboriginal Australians were tenuous overwater contacts
with New Guineans and Indonesians.
To get an idea of the significance of
that small population size and isolation for the pace of development in
Australia, consider the Australian island of Tasmania, which had the most
extraordinary human society in the modern world. Tasmania is just an island of
modest size, but it was the most extreme outpost of the most extreme continent,
and we'll see that it illuminates a big issue in the evolution of all human
societies. Tasmania lies 130 miles southeast of Australia. When it was first
visited by Europeans in 1642, Tasmania was occupied by 4,000 hunter/gatherers
related to mainland Australians, but with the simplest technology of any recent
people on Earth. Cultural features that mainland Aboriginal Australians
possessed and that Tasmanians lacked included the following. Tasmanians couldn't
start a fire; they lacked the boomerangs, spear throwers, and shields of
mainland Australians; and they had no bone tools, no specialized stone tools,
and no compound tools like an axe head mounted on a handle. Their only stone
tool was a crude hand-held scraper without ground edges. With only those
scrapers, Tasmanians couldn't cut down a tree or hollow out a canoe. They lacked
nets, traps, ropes, and sewing, hence even in Tasmania's cold winter climate
they lacked clothing other than a one-piece cape thrown over the shoulder.
Though they lived mostly on the sea coast, the Tasmanians -- incredibly --
didn't catch or eat fish. How did those enormous gaps in Tasmanian material
culture arise?
The answer stems from the fact that Tasmania used to be
joined to the southern Australian mainland at Pleistocene times of low sea
level, until that land bridge was severed by rising sea level 10,000 years ago.
People walked out to Tasmania tens of thousands of years ago, when it was still
part of Australia. Once that land bridge was severed, though, there was
absolutely no further contact of Tasmanians with mainland Australians or with
any other people on Earth until European arrival in 1642, because both
Tasmanians and mainland Australians lacked watercraft capable of crossing those
130-mile straits between Tasmania and Australia. Tasmanian history is thus a
study of human isolation unprecedented except in science fiction -- namely,
complete isolation from other humans for 10,000 years. Tasmania had the smallest
and most isolated human population in the world. If population size and
isolation have any effect on accumulation of inventions, we should expect to see
that effect in Tasmania.
If all those technologies that I mentioned,
absent from Tasmania but present on the opposite Australian mainland, were
invented by Australians within the last 10,000 years, we can surely conclude at
least that Tasmania's tiny population didn't invent them independently.
Astonishingly, the archaeological record demonstrates something further:
Tasmanians actually abandoned some technologies that they brought with them from
Australia and that persisted on the Australian mainland. For example, bone tools
and the practice of fishing were both present in Tasmania at the time that the
land bridge was severed, and both disappeared from Tasmania by around 1500 B.C.
That represents the loss of valuable technologies: fish could have been smoked
to provide a winter food supply, and bone needles could have been used to sew
warm clothes. What sense can we make of these cultural losses?
The only
interpretation that makes sense to me goes as follows. First, technology has to
be invented or adopted. Human societies vary in lots of independent factors
affecting their openness to innovation. Hence the higher the human population
and the more societies there are on an island or continent, the greater the
chance of any given invention being conceived and adopted somewhere on the
island.
Second, for all human societies except those of totally isolated
Tasmania, most technological innovations diffuse in from the outside, instead of
being invented locally, so one expects the evolution of technology to proceed
most rapidly in societies most closely connected with outside
societies.
Finally, technology not only has to be adopted; it also has to
be maintained. All human societies go through fads in which they temporarily
either adopt practices of little use or else abandon practices of considerable
use. Whenever such senseless taboos arise in an area with many competing human
societies, only some societies will adopt the taboo at a given time. Other
societies will retain the useful practice, and will either outcompete the
societies that lost it, or else will be there as a model for the societies with
the taboos to repent their error and re-acquire the practice. If Tasmanians had
remained in contact with mainland Australians, they could have rediscovered the
value and techniques of fishing and making bone tools. But that couldn't happen
in the complete isolation of Tasmania, where cultural losses became
irreversible.
In short, the message of the differences between Tasmanian
and mainland Australian societies seems to be the following. All other things
being equal, the rate of human invention is faster, and the rate of cultural
loss is slower, in areas occupied by many competing societies with many
individuals and in contact with societies elsewhere. If this interpretation is
correct, then it's likely to be of much broader significance. It probably
provides part of the explanation for native Australians, on the world's smallest
and most isolated continent, remaining Stone Age hunter/gatherers, while people
of other continents were adopting agriculture and metal. It's also likely to
contribute to the differences that I already discussed between the farmers of
sub-Saharan Africa, the farmers of the much larger Americas, and the farmers of
the still larger Eurasia.
Part 6: Environmental differences
outweigh biological differences
Naturally, there are many
important factors in world history that I haven't had time to discuss in 40
minutes. For example, I've said little or nothing about the distribution of
domesticable plants; about the precise way in which complex political
institutions and the development of writing depend on agriculture and herding;
about the reasons for the differences within Eurasia between China, India, the
Near East, and Europe; and about the effects of individuals, and of
environment-unrelated cultural differences, on history. But it's now time to
summarize the overall meaning of this whirlwind tour through human history, with
its unequally distributed guns and germs.
The broadest pattern of
history -- namely, the differences between human societies on different
continents -- seems to me to be attributable to differences among continental
environments, and not to biological differences among peoples themselves. In
particular, the availability of wild plant and animal species suitable for
domestication, and the ease with which those species could spread without
encountering unsuitable climates, contributed decisively to the varying rates of
rise of agriculture and herding; which in turn contributed decisively to the
rise of human population numbers, population densities, and food surpluses;
which in turn contributed decisively to the development of epidemic infectious
diseases, writing, technology, and political organization. In addition, the
histories of Tasmania and Australia warn us that the differing areas and
isolations of the continents, by determining the number of competing societies,
may have been another important factor in human development.
As a biologist practicing
laboratory experimental science, I'm aware that some scientists may be inclined
to dismiss these interpretations as unprovable speculation, because they're not
founded on replicated laboratory experiments. The same objection can be raised
against any of the historical sciences, including astronomy, evolutionary
biology, geology, and paleontology. The objection can of course be raised
against the entire field of history, and most of the other social sciences.
That's the reason why we're uncomfortable about considering history as a
science. It's classified as a social science, which is considered not quite
scientific.
But remember that the word "science" isn't derived from the Latin word
for "replicated laboratory experiment," but instead from the Latin word for
"knowledge." In science, we seek knowledge by whatever methodologies are
available and appropriate. There are many fields that no one hesitates to
consider sciences even though replicated laboratory experiments in those fields
would be immoral, illegal, or impossible. We can't manipulate some stars while
maintaining other stars as controls; we can't start and stop ice ages; and we
can't experiment with designing and evolving dinosaurs. Nevertheless, we can
still gain considerable insight into these historical fields by other means.
Then we should surely be able to understand human history, since introspection
and preserved writings give us far more insight into the ways of past humans
than we have into the ways of past dinosaurs. For that reason I'm optimistic
that we can eventually arrive at convincing explanations for these broadest
patterns of human history.