Humankind: Why We Are What We Are Where We Are by Alexander Harcourt

October 3, 2013
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The peoples of different parts of the world differ genetically, anatomically, physiologically. Good biological reasons explain the differences, reasons that apply to other animals too – adaptation to the environment, different founding populations, random genetic change, and barriers to movement. That is a summary of the last two chapters. So far, so good.
But humans are defined by culture. Culture separates us from the animals. Yes, chimpanzees in different parts of Africa use different tools, or use the same tool in different ways, or to collect different foods. But that minimal difference is such a far cry from what we mean by culture in humans that many consider that applying the word ‘culture’ to the regional differences in behavior that we see among chimpanzees demeans the sense of the word as it applies to humans. So to repeat, culture separates us from other animals.
Yet, as I will show in this chapter, cultures geographically do the same as species. Not only that, but the same biological reasoning that can explain the geographic distribution of species can also explain the geographic distribution of cultures. In other words, even when we are talking about culture, a phenomenon that supposedly separates us from the animals, humans biogeographically do the same as animals. Biogeographically, man to phrase it alliteratively, is merely a monkey.
Before I go further, I need to say that anthropologists discuss interminably what they mean by the word ‘culture’. That is no different from biologists who have written over the decades thousands of articles and chapters on what a ‘species’ is – how to define it, how to distinguish species, how to decide when something a species, a subspecies, or a race. They are still writing. Anyone from outside would think that biologists do not know what a species is.
Nevertheless, biologists can usually ignore all the argument, and with highly sophisticated analysis produce deep insights into the process of evolution in general, the biology of the distribution of species in particular. In other words, despite the details of definition, we can for much of the time agree that the general concept works.
I used to study gorillas in the forests of Africa. When I started, most people agreed that one species of gorilla lived in Africa, separated into three so-called sub-species. Now, as far as I can gather, most gorillaologists like to write as if two species exist. I disagree. I have seen both so-called species, heard both, smelt both (the gorilla male has a powerful and characteristically smelly sweat), and I say that they are one species. But whether we write or think or analyze data as if two or one species of gorilla exists does not matter for almost any biological purpose. Indeed, one of biology’s most famous evolutionists, George Gaylord Simpson, said that we should use whichever definition of ‘species’ is most suitable for the study we are undertaking.
As far as I can tell, it is pretty much the same with cultures and societies and languages. Yes, important debate occurs about exactly what a ‘culture’ is, what a ‘society’ is, where one stops and another starts, what is a dialect, what is a language, what is a language family. Different authors use different definitions. Language can define culture. Mode of life can define culture. Dress, tools, attitudes, nature of marriages, or perceived origins can define a culture, or separate cultures. Yes, if different studies of supposedly the same culture produced contrasting answers, a first question would be whether what they meant by a culture affected the answer. On the whole, though, the sensible starting attitude is G.G. Simpson’s. And on the whole, that is what authors do.
I have no preference for any one definition of culture. I use without questioning their validity whatever classification of ‘culture’ the original authors used. But I have an important reason for using two main sources of information on ‘cultures’.
One, Ethnologue, compiled by the Summer Institute of Linguistics, is freely available on the web, and is a fascinating compendium of all the world’s languages, listing number of languages and their speakers per country. The other is Lewis Binford’s highly academic, detailed compilation and analysis of all sorts of information on the world’s hunter-gatherer societies, many of them now gone. The title of his book is a mouthful, ‘Constructing Frames of Reference: An Analytical Method for Archaeological Theory Building Using Hunter-Gatherer and Environmental Data Sets’. Ordinarily I would not touch with a barge pole any book with that sort of title. But this one is totally fascinating in its breadth, depth, analysis, and results.
Language groups and hunter-gather societies are very different sorts of information. Yes, the hunter-gatherer societies will each have to a large extent their own language. But of course the nature of a hunter-gatherer society is different from that of the society of the speakers of most extant languages. That means that the two sources of data are fundamentally independent, especially because the number of hunter-gatherer societies in Binford’s encyclopedic book is so much smaller than the number of languages in Ethnologue, less than five per cent. If I find that the data in both sources produce the same biogeographic patterns, then not only do the details of definitions of ‘culture’ not matter too much at the biogeographic scale at which I am writing, but we can be more certain of the validity of the patterns, and perhaps even of their explanations. And for the most part, the two sources do produce the same biogeographic patterns.
A major biogeographic pattern that most of us with the slightest interest in natural history are aware of is the amazing diversity of life in the tropics compared to higher latitudes. The biodiversity of the tropics is a byword. Take Ecuador, where my eldest sister lives. Ecuador is the same size as Britain. Britain has fifteen hundred species of plants with probably no more than a couple or so still to be discovered, given the density of botanists in Britain. Ecuador has more than twenty thousand species of plants, with quite possibly hundreds more still to be identified if oil companies and others leave any of its forests for future generations. Britain is a cat and dog loving nation. Cats and dogs are carnivores. Britain has less than ten native carnivores. Ecuador has nearly thirty. It is not just Ecuador that is rich in species and Britain that is poor. These sorts of huge differences in the diversity of tropical compared to temperate countries can be repeated all over the world.
If many of us know about the extraordinary diversity of species in the tropics, few of us seem to have heard of the extraordinary diversity of cultures in the tropics. I will compare Ecuador and the UK again. An energetic linguist could hear if they travelled the length and breadth of the country twenty three indigenous languages in Ecuador, compared to just twelve in the UK, including in the UK, Cornish, Gaelic, Manx, Romani, Scots, and Welsh.
On a continental scale, the people of tropical South America speak four hundred and eighty seven indigenous languages compared to just one hundred and seventy six in their neighbor to the north, the USA. That is over two and a half times as many languages spoken in tropical South America than in the USA. We get the same contrast between Africa and its northern neighbor, Europe. Linguists have counted two thousand one hundred indigenous languages in Africa, but only two hundred and thirty in Europe, namely a nine-fold difference in cultural diversity compared to only a three-fold difference in their areas.
In sum, the extraordinary biodiversity of the tropics is matched by an extraordinary, to Western eyes, cultural diversity.
Ecuadorian Huarani man with red and yellow feather headband. Ecuador, the same size as the UK, has twice the number of indigenous cultures and several times the number of indigenous species that the UK has.
Go to any one spot in the tropics, say Yasuni National Park of Ecuador. Stand in the middle of those forests and look and listen. You will see and hear immediately around you far more species of plant and animal than if you went into a North American or British forest. That is one way that the tropics are more diverse than higher latitudes. At any one spot, you will see and hear more species.
Then set off on a path north through the forest for a trip of twenty kilometers. Or south or west or east. And again, stop and stare and listen. You will find that you are seeing and hearing new species. But do the same in, say, the Great Smoky Mountains. National Park in North Carolina and Tennessee, and even though the Park harbors three main types of forest, you will not notice much change, especially if you still find yourself in the Park’s spruce forest.
And at an even larger scale, travel fifteen hundred kilometers south along the east slope of the Andes from Yasuni in Ecuador to Manu National Park in Peru, another Park that I and my wife have been lucky enough to visit, and you will see a whole new complement of species. Travel the same distance anywhere in western Europe, and the wilderness will look and sound much the same at either end of the trip.
One reason for these differences between tropical and temperate regions is that in the tropics, species and cultures cover a smaller area than they do at higher latitudes. Take African primates as an example of what non-human species do. African primates’ geographic ranges, measured as the north-south distance of a genus’ range, are on average fourteen hundred kilometers long at the equator, but over five thousand kilometers long ten degrees away from the equator.
Human cultures show the same pattern. At around ten degrees from the equator, human languages occupy a geographic range of about one thousand square kilometers. Go to near the Arctic circle, at sixty degrees latitude, and they occupy over five thousand square kilometers. We find the same with hunter-gatherer societies. They cover roughly twenty-five hundred square kilometers at the equator, but thirty-two hundred square kilometers at sixty degrees latitude.
Similar as they are in some biogeographic ways, cultures and species are different in one biogeographic respect. The tiniest patch of tropical forest is full of plant and animal species. Watch a column of army ants for a couple of hours near any one of the research stations in Yasuni National Park in the Ecuadorian Amazon rain forest, and you are likely to see over ten species of birds following the column and catching the insects disturbed by the ants – in the same way that cattle egrets follow cattle to get the disturbed insects. Sit still in that patch for a day, and you might see five species of ungulate and, if you are lucky, ten species of monkey. But in that same patch of forest and for many square kilometers around, you would ever see only one native human culture, the Huarani peoples.
The fact is that humans are notoriously territorial. We do not often find people of different cultures occupying the same bit of land. Read accounts of early travelers in the Americas and Africa and they are filled with stories of battles between the peoples whose lands the explorers are moving through. Here is Andrés Reséndez reporting in his ‘A Land So Strange’ from Cabeza de Vaca’s account of his journey across southern USA. “the Mariames engaged in female infanticide to deny potential wives to the surrounding groups who were their sworn enemies”. “The Susuolas were at war with other groups in the area”. “these Indians made war on one another, constantly engaging in elaborate ambushes”. “Since Indian men could not venture west for fear of being killed”.
Other countries of the world are no less belligerent. The Scots and the English battled one another for centuries, coming together only when both were threatened by another European country, often France until the twentieth century, when Germany took over as a main enemy. If you want to see primitive territoriality these days, go to a European football match (soccer match, for American readers). Tribalism and territorial disputes have always been alive and active in Europe.
If overall the tropics are more diverse biologically and culturally than are higher latitudes, within the tropics we find hot spots of extra high diversity. For non-human primates, the Cameroon highlands and the mountains bordering the eastern Congo Basin are two such areas.
For cultures, a well-known, to anthropologists, hotspot outside the tropics is the west coast of the United States, from northern California through Oregon and into Washington. Early records indicate that west of the Sierra Nevada and Cascade Mountains, a total of sixteen language families and forty-four languages used to exist. That is a density of nearly twenty languages per quarter of a million square kilometers. Such a high density is what we expect for the tropics, not for forty degrees latitude north well into the temperate zone. Columbia, for instance, has seventeen languages in the same area. By contrast, go east from coastal north-west USA, east of the Sierra and Cascade mountain ranges, and we find just four language families and ten languages, roughly the number expected for temperate latitudes. I will come later to why west coast America might have had such a high density of cultures.
I mentioned in chapter 4 that New Guinea has more languages for its size than any other area in the world. It certainly has many – over one thousand indigenous languages in less than one million square kilometers. However, plenty of other countries have a higher density of languages, and what is density but amount or number per size? So how can I say that New Guinea has the most languages for its size, when other countries have higher densities of languages?
The crucial phrase in the previous sentence is ‘for its size’. If we want to compare regions for diversity, we must compare regions of similar size, because smaller regions have, on average, higher densities of languages than do large areas. Exactly the same is true of density of animal and plant species. Number of languages and species do not increase or decrease on a one to one ratio with change in size of area. A rough rule for species is that a loss of ninety percent of area results in a loss of only half the number of species. So, if we had one hundred species in one hundred square kilometers of forest, or one species per square kilometer, and the forest was reduced to just ten square kilometers, we would find fifty species remaining, or five species per square kilometer now.
Therefore, if we want to compare countries or regions or areas for density of languages or species, we have to ask whether they have more or less than the average for their size. Now indeed New Guinea takes first prize. It has over ten times the density of languages for its size as do similarly forested tropical countries of roughly the same area, such as the Central African Republic, Columbia and Thailand.
So, we find high densities of not only species but also cultures in the tropics and lower densities at higher latitudes. We find that both species and cultures exist in smaller geographic ranges in the tropics than they do at higher latitudes. These general biogeographic patterns apply whether we are talking plants, ungulates, monkeys, or humans. That is all facts. Not much argument about them. But why? How is it possible that cultures, languages, products of the human mind, do the same biogeographically as species?
New Guinean
The jargon term for the observed pattern of decreasing biodiversity from the tropics to higher latitudes is, ‘the latitudinal gradient in biodiversity’. Biologists have known about the pattern for over two centuries, and still research and write about it. One of the earliest writers was Johann Georg Adam Forster, who travelled on the second of Captain Cook’s voyages around the world in the late 1700s. The ‘latitudinal gradient in biodiversity’ is rather a mouthful, so in honor of J.G.A. Forster I abbreviate it to the ‘Forster effect’.
For some reason, anthropologists became interested in the scientific analysis of tropical diversity far later than did biologists, even though Johann Forster the Younger was renowned in his time for his descriptions of the cultures that Cook’s expedition encountered. Indeed, so renowned was he that he was made a member of Britain’s Royal Society in his early twenties. We should probably not read too much into the fact that he died of a stroke in his late thirties. Be that as it may, anthropology’s late start mans that anthropologists have written far less on why humans show the Forster effect than biologists have written on why other species show it.
The bible of biogeography, Mark Lomolino’s and co-authors’ simply titled ‘Biogeography’, contains a dense three-page table listing details of thirty one explanations for why most sorts of organisms are more diverse in the tropics than outside the tropics, indeed why within the tropics they are more diverse at the equator than they are even a few degrees from the equator. They do not mention humans once. In chapter 5 of my ‘Human Biogeography’, I provide a one-and-a-half-page Table in which I condense Lomolino and co-authors’ thirty-one explanations to thirteen general explanations, and add a column devoted to explanations for the Forster effect among human cultures. Here, I will give the skeleton of my single preferred explanation for the effect in humans.
Except at the height of summer, land outside the tropics is not as productive as land in the tropics, where the climate is relatively warm and wet year-round. Because of the lower annual productivity of high latitudes, individuals there need to range farther to find sufficient resources than they do in the tropics. The density of individuals in populations is therefore lower, which means that for a population to persist at a viable size in the long term, the high-latitude population, whether we are talking species and cultures, needs a larger geographic range than do tropical species and cultures. Needing a larger geographic range, the species and cultures cannot be packed so tightly, and hence diversity of species and cultures is lower at high latitudes than in the tropics.
Biologists evaluate a region’s productivity in various ways. A common one is to estimate the weight of leaves produced in a given area over a year. Another is to calculate the total weight of plants and or animals that have lived for a year in a given area. Calculations indicate that at 60º latitude, up by Anchorage in Alaska, the Hudson Strait in Canada, Oslo in Scandinavia, and the middle of Russia, the land is one fifth as productive as it is at 10º from the equator.
Year-round productive High latitudes unproductive for
tropics (Uganda) six months per year (Scotland)
If the argument is correct, then measures of productivity itself, as opposed to degrees of latitude, should correlate with the density of individuals in a culture’s population. Productivity should correlate also with distances moved by individuals, and hence with the geographic range size of cultures. And productivity should correlate also with the diversity of cultures.
Such is indeed what we find. As productivity goes down, cultures’ population densities decrease, distances moved either daily or in camp movements go up, range sizes of cultures increase, and the diversity of cultures in the region decreases. The relationships are especially strong among hunter-gatherers, presumably because fewer extraneous factors, such as trade, affect how many people can live in an area. To give some real figures, an average Alaskan culture might live at a density of less than one people per square kilometer, move camps over a total distance of about four hundred kilometers in a year, and live in a geographic range of perhaps fifteen hundred square kilometers. Go down to equatorial South America, and the averages are roughly eighteen people per square kilometer, moving camps over a total distance of about one hundred and sixty kilometers in a year, whilst living in a geographic range of one thousand square kilometers.
Hunter-gatherer societies have larger geographic ranges in general than do languages, because most languages are spoken by agriculturalists, and without agriculture’s dense supply of food, the hunter-gatherers need more land to survive. I will not forget Robert Bettinger, an archeologist in my department, pointing out on a field trip that I joined to the White Mountains of the California-Nevada border the wild grass seed heads that the native Indians used to harvest. A single maize plant in the corner of a kitchen garden would produce more calories, I reckoned, than all the grass heads in my whole field of vision on that slope in the White Mountains.
These tropical – high latitude comparisons are general ones. Of course exceptions exist. So, for example, we find high densities of people along the base of the Himalayas. The land there is fertile as a result of the continually renewed soil from erosion of the nearby mountains, and a fertile soil allows intense agriculture to support large populations. The high productivity there correlates with a high density of cultures, which nicely substantiates the explanation for how the high productivity of the tropics correlates with a high diversity of cultures in the tropics.
I have already mentioned the exceptionally high density of cultures along the north-west coast of the United States. As one flies inland from the west coast, say from San Francisco to Las Vegas, the color of the land below changes abruptly from green to brown at the crest of the Cascade Mountains and the Sierra Nevadas. The rain clouds coming from the Pacific Ocean to the west drop most of their content on the Pacific coastal mountains’ and western slopes of the Cascades and Sierras, leaving almost nothing to fall to the east. To the west is what has been called the USA’s breadbasket, the fertile and well-watered Central Valley of California. To the east is near desert. Indeed, the San Francisco – Las Vegas flight goes over Death Valley.
The contrast in the past density of native American cultures matches the contrast in productivity that passengers with window seats can see now from the airplane. Seven times as many cultures occur in California as in an equivalent area of Nevada, where densities are as low as in the Arctic. Most of Nevada was Uto-Aztecan range. In California we had Yukian, Pomoan, Wintuan, Maiduan, Palaihnihan, Shastan, Nadene, Algic and more.

Map of west coast Native American cultures. In the original, all the patches are different colors, i.e. different languages. Uto-Aztecan is the culture of the large area in the center of the map.
Cultures that still rely quite heavily on hunting and gathering persist in South America, Africa and Asia. They are gone, of course, from much of North America and Europe. Imperialist agricultural societies have replaced them there. So is imperialism over the ages in its various forms, the Mongols and the British Empire for example, all the explanation that we need for a low diversity of cultures with large geographic ranges in the poorly productive lands of high latitudes? No, it is not. As I said, hunter-gatherer ranges are largest precisely where one might expect that imperialist cultures would have severely constrained them, namely outside the tropics. Also, how can imperialism explain the fact that of the top twenty-five most bio-diverse countries, two thirds are also the most culturally diverse, as judged by number of languages?
Before I go on, let me repeat that many other explanations exist for the Forster effect than the one I have just given. A drawback with some of them, though, is that whilst they might work for non-human animals they do not work for languages. For instance, one persuasive argument for the Forster effect among animal and plant species is that tropical species have had more time than high latitude species to evolve their extraordinarily varied forms because the tropics have not periodically been scraped bare by massive ice sheets.
The problem with applying that argument to humans is that cultures can evolve extremely fast. Take the example of the number of American Indian languages that I discussed in chapter 4 in another context. As I described there, humans have been in South America for probably no more than fifteen thousand years. Yet, we find an average density of languages there, seven per one hundred thousand square kilometers, that is not much less than the density in Africa or Asia, eleven per one hundred thousand square kilometers, where humans have lived for tens of thousands of years.
I mentioned in chapter 3 Dan Janzen’s explanation for the generally small geographic ranges of tropical species. Many small geographical ranges of species correlates with the finding of a relatively high density of species in the tropics. Janzen’s argument, which could also apply to human cultures, was that tropical species experience mountains as barriers more than do temperate species, because the tropical species rarely experience freezing weather. Consequently, they are not so adapted to withstand cold, with the result that they cannot cross high mountain ranges. High latitude species, by contrast, must survive winters, which means that they can withstand the cold of high elevations as well as of high latitudes, and therefore their geographic ranges are not constrained by mountains.
The argument might explain high tropical biological and cultural diversity in mountainous areas of the tropics. Its problem as a general argument, though, is that if you want to see examples of high tropical biological and cultural diversity, go to the Amazon or Congo forests – and yet they are effectively flat for hundreds of kilometers in all direction, across hundreds of thousands of square kilometers. Mountains cannot explain the bio- and cultural diversity of these forests.
The human history of the world is a non-stop account of invasion and counter-invasion. Nations and cultures come, expand at the expense of others, and go. Dynasties extend their reach over neighboring peoples, the Mongols erupted out of central Asia and almost conquered western Europe, the globe used to be mostly pink, reflecting Britain’s imperialistic reach. So, why have a few powerful tropical cultures not expanded at the expense of their neighbors, so producing ranges of the same size as those of temperate nations?
I do not know what an historian might answer. But as a biogeographer, I can suggest disease as a hurdle. Disease organisms, like most other species, are more diverse in the tropics than outside, and each covers a smaller geographic range. That means that a peoples would not have to move far before they encountered diseases to which they have not evolved resistance. And so they would be confined to their relatively small ancestors’ geographic range.

Culture, whatever we might mean by it, is to a large extent a product of our mind. Our minds, not the environment, determine our language, for example. Yes, the environment plays a part in our dress – no brightly colored feathers in the Arctic. But the fact that I speak English whereas a Parisian speaks French, the fact that I might wear a peaked cap whereas a Frenchman might be more likely to wear a beret has little or nothing to do with the environment or our biology.
Nevertheless, in many ways human cultures behave biogeographically as do many non-human animal species and even plant species. Humans are more culturally diverse in the tropics in the same way that many animal and plant species are more diverse in the tropics. Not only is the pattern the same, but the same hypotheses explain our tropical cultural diversity as well as they do the tropical biodiversity of non-human animal species. When we are talking about the global distribution of human cultures, we could be talking about the distribution of thousands of other animal species, even plant species. Biogeographically, man is merely a monkey, a mantis, even a magnolia.

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