Ecological Imperialism: The Biological Expansion of Europe 900-1900 by Alfred W. Crosby (1986)

If we seek the roots of the success of European imperialism, we must be off to the Middle East, to Abraham, to Gilgamesh and the cultural ancestors of all of us who eat wheaten bread, smelt iron, or record our thoughts alphabetically… We – you who read and I who write this sentence – are part of that continuity; these words are in an alphabetical form of writing, a very clever Middle Eastern invention produced by peoples even more directly influenced by the Sumerian example than we are. The Sumerians and the inventors of the alphabet, and you and I, no matter what our genetic heritage, are in one category: heirs of post-Neolithic Old World cultures. All Stone Age peoples, including the few living, and all pre-Columbian Amerindians, however sophisticated, are in another. The indigenous populations of the Neo-Europes were in the second category until Europeans arrived from beyond the seams of Pangaea. The transition from one category to another was a harrowing one, and many individuals and even peoples faltered and failed. (Ecological Imperialism, pp.21-22)

Until I started reading it I hadn’t realised this book was published in 1986 (I was brought up short by the references to the Soviet Union and that world population was ‘thrusting towards 5 billion’ – it is, of course, now 7.4 billion). 1986 is a long time ago, especially in science, where new discoveries and perspectives arise each year. A lot of the argument – that European triumph over the rest of the world was as much to do with biological advantages as military skill or morality or civilisation etc – was familiar to me from Jared Diamond’s best-seller Guns Germs and Steel. Now I look closely I see the latter was published in 1998. Maybe it had the advantage of following up ideas Crosby pioneered.


Crosby takes a doggedly chronological approach and starts several hundred million years ago with our knowledge of Pangaea, the supercontinent consisting of all the world’s land surface compacted into one unit that existed during the late Paleozoic and early Mesozoic eras. Pangaea began to break up into our present continental units 175 million years ago, each continent driven apart by fault lines where new molten magma was forced to the earth’s surface, creating new crusts. Life forms on the newly separated continents evolved along different lines.

Some areas remained connected by land bridges for a while, but, after a long sequence of ice ages, the final ice age ended about 13,000 years ago, the ice caps melted, and the land bridges connecting Britain to Europe, Russia to America across the Bering Sea, and New Guinea to Australia, were flooded. The continents were sealed off in their isolation.

By about 100,000 years ago the human brain had evolved to the same size as it is today. By 40,000 years ago our species, Homo sapiens, had arrived. We spread out of Africa, across Asia, walked into Australia and across the land bridge into America. Then the seas flooded.

The Neolithic revolution

Crosby moves swiftly on to the Neolithic revolution(s). This began when humans started to grind and polish rather than chip their stone tools, and went on to include the development of agriculture, the domestication of farm animals, the beginning of food surpluses which gave rise to denser settlements and social hierarchy, eventually to cities with rulers who wanted records of their possessions and so to writing. The revolution was complete as humans learned how to smelt metal and work it into tools that stayed sharper for longer.

To some extent ‘the rest is history’, the history of successive empires which used these technologies to conquer (and generally enslave) their neighbours – the Sumerians, Akkadians, Babylonians, Persians, the Greek and Roman Empires, the astonishing success of the Islamic caliphates, the long slow growth of the Chinese empires, alongside the rise of a Japanese state and more obscure (to us) empires in Thailand, Burma, the East Indies. Europe, abandoned by the Romans, slowly regrouped with strong leaders carving new empires, notably Charlemagne’s north European empire, crystallised by about 800, with King Alfred and his successors’ efforts to unify England under one king, complete by about 900.

All this is interesting but the key fact for the history of European empire was the fact that all the other human populations not directly linked to the Middle East (where the Neolithic revolution took place, starting in Sumeria, modern Iraq) fell behind and were outstripped. In Saharan Africa the empire of Mali arose and in South Africa several empires, latterly the Zulus. But in Australia and New Zealand, across the Pacific islands and in North America there was no Neolithic Revolution. The people continued the old style of hunter-gatherer living. Only in Central America was there a semi-revolution – when the conquistadores arrived they found the Aztecs could smelt metal – but only to use as decoration, not weapons; and they had invented the wheel – but only as a decorative toy, not to carry heavy weights long distances. Why? Because they had no domesticated large mammals to pull any wheeled vehicle (unlike us Eurasians, blessed with domesticable horses, cattle, oxen and so on).

Thus when the Portuguese, the Spanish, the French, the Dutch and – right at the end – the British set sail in their advanced ships, with highly developed sailing and steering technology, maps, knowledge of the winds, horses, armour, cannons and guns, it was all too often to encounter indigenous peoples who were still living in the Stone Age and were easy to fight, kill, round up and enslave, shoot and loot and dispossess of their land.

Eurasian biology

There is not as much biology as the title suggests, in fact the book is rather disappointing from this point of view, and not as focused and memorable as Diamond’s book. Why was agriculture more successful in the West? Because:

  • There was a broader variety of domesticable edible plant species to begin with e.g. wheat, barley, peas and lentils.
  • Wheat was highly productive of edible seed from the start, encouraging agriculture and surpluses, whereas new World maize was far less productive and took a lot longer to be developed.
  • The growing seasons of a temperate climate are more supportive for arable crops (unlike tropical rainforest or desert).
  • And for the simple but amazing reason that the Eurasian land mass runs East-West with a broadly similar climate all through it – what can be grown in the Caucasus can be grown in France or southern Britain and grown on the Russian steppe. Agriculture, and agricultural innovation, could spread unhindered across this vast area (albeit very slowly). There just wasn’t the same geographic scope for the Central Americans to spread and share innovations because they were blocked by the Mexican desert to the north and Amazon rainforest to the south. North America turned out to be fantastically fertile but having never had a Neolithic/agricultural Revolution the native Americans weren’t in a position to realise this. Similarly, the Aborigenes in Australia remained a relatively small scattered population of doggedly hunter-gatherer tribes in a vast and generally inhospitable land.

Which brings us to animals and the bald fact that Eurasia simply happened to possess more and more easily domesticable animals – horses, sheep, pigs, goats, chickens, reindeer, ducks. At the opposite end of the scale no-one managed to tame Australian fauna – the kangaroo, dingo, koala bear. Native Americans hunted and killed bison but never tried to produce tame populations of them in fenced farms – they didn’t need to.

We had all kinds of advantages. An apparently minor one, which becomes more important the more you think about it, is that Western people have a gene which allows us to digest milk after we’ve stopped being babies. Many other peoples – Amerindians, Aborigenes – don’t.

Few adult black Africans or East Asians, and fewer yet of the adult indigenes of Australasia or the Americas, can tolerate milk in any but small amounts after infancy. In fact, it makes them quite sick. (p.27)

In many times and places the ability to drink cow or goat’s milk in bleak winters or times of dearth made the difference between survival or extinction for all kinds of Western settlements. Just one way in which we had more biological and technological resources than the first peoples we met.

Eurasian disease

The main biological component, however, was disease. For thousands of years Westerners lived in towns and cities large enough to foster urban diseases like smallpox and measles. Not that these were a weapon in any way consciously deployed against native peoples or that only hurt non-Westerners: Crosby shows how waves of plague and other diseases decimated the West again and again and again before any imperial voyages began. Some historians attribute the collapse of the Roman Empire to a deadly plague which decimated its population.

The Plague of Justinian (541–542) was a pandemic that afflicted the Eastern Roman (Byzantine) Empire, especially its capital Constantinople, the Sassanid Empire, and port cities around the entire Mediterranean Sea. One of the deadliest plagues in history, this devastating pandemic resulted in the deaths of an estimated 25 million (at least 13% of the world’s population). (Wikipedia)

Plague continued to ravage Europe for centuries, notably the Black Death of the 1340s when up to 200 million Europeans died, the famous recurrence in the 1660s which killed about a quarter of London’s population. Well into the 19th century Londoners were dying of cholera, typhoid and diphtheria and of course the early 20th century witnessed one of the worst pandemics of all time.

The 1918 flu pandemic (January 1918 – December 1920) was an unusually deadly influenza pandemic, the first of the two pandemics involving H1N1 influenza virus. It infected 500 million people across the world, including remote Pacific islands and the Arctic, and resulted in the deaths of 50 to 100 million (three to five percent of the world’s population), making it one of the deadliest natural disasters in human history. (Wikipedia)

Generations of Eurasians had survived these remorseless plagues and epidemics, and become hardened and immune. But when European explorers arrived at any settlement of humans outside the infection zone, the result was inevitably devastation, and there is a long melancholy list of native peoples in America north and south, in the Pacific islands and Australia who were wiped out by European disease.

Disease was also a major factor in limiting where white Europeans could realistically settle. Crosby gives examples of the high death rates of white people in the Tropics, which complement the accounts I’ve read in John Darwin’s Unfinished Empire and Tom Pocock’s harrowing Battle for Empire. In the early 19th century over half the British troops stationed on the Gold Coast died of disease. Joseph Conrad reported that only about 7% of white men served out their three year contracts in King Leopold’s Congo, the rest dying or being forced home by disease. Of the first freed slaves resettled to Sierra Leone about 40% died from disease. Compare with Pocock’s report that, of the 14,000 British soldiers and sailors who took part in the five-month-long siege of Havana, Cuba in 1762, no fewer than 10,000 died or were disabled by disease. Similarly, between 1793 and 1796 the British Army stationed in the Caribbean lost about 80,000 men, about half to yellow fever alone.

No wonder John Darwin points out that the best survival strategy for white settlers in the Caribbean was to pay local agents to run their plantations for them, and leave as quickly as possible. Even temperate climates were harsh for the first white settlers: in the first winter, half of the original Pilgrim Fathers who landed in New England died of disease, exposure or malnutrition.

Just one more reason why the Neo-Europes are pretty limited geographically, to the more temperate parts of America, southern South America, and Australasia, where not only do diseases not thrive, but the native populations were so thinly spread that they hadn’t incubated and helped evolve vicious strains of communicable disease. The direction of fatal diseases was almost all in the other direction, from Old World to New.

Eurasian biota

And not just disease. Europeans brought the livestock and plants they knew they wanted to farm – horses, cows, sheep; wheat, barley, peas – but also unintended passengers which played havoc with local biota. The most notorious example is the rabbit, which ran rampant in Australia, eating all the crops, but we also took the European rat wherever we went, and the rat is a key vector for disease. And among the seeds of useful crops were seeds of all kinds of European weeds. The common plantain was brought to America by Europeans and, apparently, nicknamed the ‘Englishman’s foot’ by native Americans. That infestive weed the dandelion is now found in all temperate climates around the world.

The spread of European disease, weeds and pests throughout the world is one of the greatest examples of the ‘law of unintended consequences’.

Pre-imperial European colonising attempts

I feel I’ve read quite a lot about the European conquest of India or Africa, therefore I found Crosby’s earlier chapters the most interesting, where he describes in detail the Norse voyages of exploration, to Iceland, Greenland and then onto Vinland, with detailed discussion of the crops and livestock the Vikings took with them, and the reasons for their initial success and ultimate failure, a combination of insufficient numbers, economic unviability (nobody wanted the goods the colonies could produce), conflict with the natives – the skraelings as the Vikings called the inhabitants of America.

He gives an account of the Crusades, again analysing the reasons for their ultimate failure – they came up against well-populated, well-organised native states and cultures, and not enough Europeans wanted to emigrate there. Result: collapse, withdrawal. The last Crusader territory was abandoned in 1202.

He claims that European Imperialism really begins around 1400 with the settlement of the Canary, Azores and Madeira Islands and this is a story I’d never read about before. It set the pattern for everything which followed – including long bloody campaigns against the natives – the Guanches – the eventual extermination of their populations through war but mostly waves of infectious disease, the setting up of sugar cane plantations with their insatiable appetite for manual labour solved by the importing of slave labour (often not black African, but North African Berbers or Jews or heretics from Europe).

This economic, social and technological model was to be exported to innumerable other ‘plantations’ in the centuries ahead. And it shows the general rule: a technologically more advanced society will tend to conquer, enslave and completely re-order a technologically inferior culture remodeling it to supply its economic needs. This rule applies in all times and places: wherever a more powerful population can overpower and dominate a weaker one – it will.

World winds and global exploration

The middle chapters give a highly detailed account of the early explorations by the Portuguese and Spanish pioneers, notably de Gama, Magellan and Columbus, but focusing not on armaments or economics but on winds. The story is told as the slow steady and thorough exploration of the world’s wind systems – in an age of sail, effectively the discovery of the world’s motorway systems – complete with several complex and fascinating maps. Obviously the era of great Explorations was a pre-requisite for European expansion but this chapter has nothing directly biological about it. It’s an example of the way the book has a chatty, discursive feel, and Crosby writes in a relaxed, slangy, sometimes jokey style quite unlike the sensible academic prose of John Darwin or the impassioned opinionating of Niall Ferguson. One of his catch phrases is ‘and what have you’. Thus:

The Asians and their plants and animals had existed in and around thousands of villages and cities for thousands of years, and along with them had evolved many species of germs, worms, insects, rusts, molds, and what have you attuned to preying on humanity and its servant organisms. (p.135)

The Neo-Europes

The second half of the book turns to look in closer detail at its main subject: the success of the ‘Neo-Europes’, lands with temperate climates, inhabited overwhelmingly by whites descended from European settlers and which, in an angle I hadn’t thought about before, are characterised by producing, consistently year after year, surpluses of food, something almost all the rest of humanity fails to do. He’s talking about North America, Australia and New Zealand, and the southerly part of South America.

The timing of these migrations is fascinating because it was slow slow slow – and then a torrent. Thus in 1800, after two centuries of colonisation, North America still only had a population of about 5 million whites and a million black slaves; southern South America only half a million whites; Australia 10,000 white settlers.

Then bang! The nineteenth century is the great century of mass white emigration. Between 1820 and 1930, over 50 million people emigrated to the Neo-European lands, about a fifth of the entire population of Europe! Why? The agricultural revolution fuelled a population explosion which put pressure on land and resources; war and instability; persecution of minorities in increasingly nationalist countries – and the rapid growth of transport, better long distance sailing and then steamships, train networks across the Neo-European lands opening up vast new frontiers for settlement; mass media i.e advertising campaigns giving tantalising pictures of the wealth to be won abroad.

The chapters which follow deal with the fauna and weed we exported – chief among which seems to have been plantain and sow thistle; the animals we exported – cattle, pigs, sheep, rabbits, rats; the illnesses white men took with them, most devastatingly smallpox whose ravages, destroying half or third of entire populations, again and again, rendering populous countrysides empty just as the colonists arrived.

The longest chapter in the book takes New Zealand as a case study of the colonisation of a New Europe, by all the elements discussed – flora, animals, disease, whitey – with the usual baleful impacts on local ecosystems and above all the poor Maori people. But, as Darwin pointed out, the Maori story is a bit different because they were annexed by the British Empire after requesting it themselves, and signing a formal treaty. This Treaty of Waitangi (1841) was later to form the basis of claims against the government and is the subject of dispute to this day.

The final chapter of ‘Explanations’ draws all the previous discussions together. One giant conclusion leaps out. At several places in the text, Crosby had mentioned that fossil and bone records suggest that the original large animals in America, Australia and New Zealand died out at just around the time the first humans arrived in these places. Humans arriving with stone axes and arrow tips came across enormous walking meals which were unafraid of humans – and they devastated them. When Crosby was writing this was still a controversial theory. But if true, it has the supplementary effect of providing a strong additional reason why the Neo-Europes were so vulnerable to invasion from Old World flora, fauna, disease – because all these places were still reeling from a first decimation of large mammals, their predators, their pest and the diseases they carried. Without realising it the Europeans arrived in countries with, biologically speaking, yawning gaps in their ecosystems – and their imported animals – pigs, horses, cattle, sheep, rabbits, rats – as well as the wheat and innumerable weeds – stormed into the vacant slots. From nature’s point of view the Amerindians, Aborigines and Maoris on the one hand, and the European invaders on the other, are not adversaries, with natives passive and whites active: they are both invaders of the same destructive species, the first wave acting as shock troops to clear the way for the second wave which arrived with its complex technologies, economies, biota and overwhelming numbers.

Quite a radically different way of seeing imperial history from the usual “bad white imperialist destroys eco-friendly native paradise” picture.

Rare words

  • endogeny – development or growth from within.
  • helminthic parasites – helminths, also commonly known as parasitic worms, are large multicellular organisms, which when mature can generally be seen with the naked eye. They are often referred to as intestinal worms even though not all helminths reside in the intestines.
  • indigenes – a person or thing that is indigenous
  • ‘Neo-Europes’ – a country or territory with a temperate European-style climate, inhabited by whites descended from European settlers e.g. America, Canada, Australia, New Zealand
  • northing – distance travelled or measured northward, especially at sea.
  • pelagic – Any water in a sea or lake that is neither close to the bottom nor near the shore can be said to be in the pelagic zone.
  • virgin soil epidemic – a term coined by Crosby himself, who defines it as epidemics ‘in which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically almost defenseless’ i.e. decimated by illnesses they have never encountered before.
Landscape with an Episode from the Conquest of America by Jan Mostaert (c. 1535)

Landscape with an Episode from the Conquest of America by Jan Mostaert (c. 1535)


Ecological Imperialism: The Biological Expansion of Europe 900-1900 by Alfred W. Crosby was published by Cambridge University Press in 1986. All quotes and references are to the 1993 Canto paperback edition.

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