“Human Biogeography, is an outstanding publication that serves as an unrivaled synthesis and nexus of two disciplines – human diversity and biogeography.” –Mark Lomolino, co-author of Biogeography

“This is the first book to explain and illustrate what human biogeography is all about. Moreover, Human Biogeography gives us a highly persuasive demonstration that anyone looking for answers about our diversity as a species and our impact on the planet must take biogeography into account. An outstanding work of scholarship supported by an immense depth and breadth of knowledge. ” –John Edward Terrell, Regenstein Curator of Pacific Anthropology, Field Museum of Natural History

Alexander H. Harcourt is Professor Emeritus in the Anthropology Department at the University of California, Davis. He is the coauthor of Gorilla Society and coeditor of Coalitions and Alliances in Humans and Other Animals.

Human Biogeography

By Alexander H. Harcourt

UNIVERSITY OF CALIFORNIA PRESS

Copyright © 2012 Regents of the University of California
All rights reserved.
ISBN: 978-0-520-27211-8

Contents

Acknowledgments, vii,
1. Biogeography and Humans: An Introduction, 1,
PART ONE. WHY AND HOW ARE WE WHERE WE ARE? HISTORICAL BIOGEOGRAPHY OF HUMANS,
2. Origins and Dispersal, 15,
3. Climate, and Hominin Evolution and Dispersal, 53,
4. Barriers to Movement, 77,
PART TWO. ENVIRONMENTAL INFLUENCES ON HUMAN NATURE, DIVERSITY, AND NUMBERS,
5. How Are We Adapted to Our Environment?, 89,
6. Use of Area, 155,
7. A Biogeography of Human Diet and Drugs, 193,
PART THREE. INTERACTION AMONG CULTURES AND SPECIES,
8. We Affect Our Biogeography, 207,
9. Other Species Affect Our Biogeography, 215,
10. We Affect Other Species’ Biogeography, 225,
References, 245,
General Index, 303,
Author Index, 313,

CHAPTER 1

Biogeography and Humans

An Introduction

Ethnology is the science which determines the distinctive traits of mankind; which ascertains the distribution of those traits in present and past times, and seeks to discover the causes of the traits and of their distributions.

—modified from T. H. Huxley, 1865, “On the Methods and Results of Ethnology,” Fortnightly Review

This book is about how and why our species, Homo sapiens sapiens, is distributed around the world in the way it is—why we are what we are where we are. It is therefore both anthropology and biogeography. Anthropology is literally the study of humans, and it is nicely summarized in Thomas Huxley’s description of what he termed ethnology. Biogeography perhaps needs a bit more explanation.

One part of the field of biogeography investigates why organisms are where they are. How did they get there? Why are they where they are and not somewhere else? Why is this sort of organism here, and that sort of organism there? Scientists and others have been asking these questions for centuries.”God” used to be the answer, and still is for half the American population. But in science, biogeography took off with the explorations of the 18th century [104; 463, ch. 2; 464]. The early work can be seen as culminating in Alfred Russell Wallace’s two-volume The Geographical Distribution of Animals [803; 804].

A modern example of biogeography is the quantitative, statistical approach of phylogeography, a subfield of biogeography that relates data on the distribution of organisms to data on their evolutionary trajectories, their phylogeny [26; 27; 74; 348; 463, ch. 11, 12; 646; 663; 668; 784]. For anthropology, phylogeography is exemplified by the large amount of work on the origins of native Americans.

A major branch of biogeography is now often known as macroecology [101; 253; 463, ch. 13–15], although other terms have been used for all or part of the discipline, such as areography or geographical ecology [469; 629]. Macroecology as a branch of biogeography relates diversity (e.g., number of species or cultures in a region) or density (e.g., individuals per square mile) or the traits of organisms (e.g., body size) to various quantitative measures of space on a large scale. For example, why do taxonomic and cultural diversity vary with latitude? Do animals and human cultures at higher latitudes have larger geographic ranges? Why are organisms at higher latitudes stockier than those from the tropics? Do large islands have more species or cultures than do small islands?

A perusal of this book’s table of contents will give an idea of the range of biogeography as a discipline. Mark Lomolino et al. provide in chapter 1 of the 4th edition of their great synthesis of biogeography a detailed account of its questions and its integral relation to so many other disciplines [463]. Their chapter 2 is a nice introduction to the history of biogeography, a fuller and engaging account of which is provided by Janet Browne’s The Secular Ark [104].

WHY HUMANS?

In many respects, humans are biogeographically just another species. Why then concentrate on humans? In brief, I hope that both biogeography and anthropology can benefit from a more specific and extensive concentration on the topic of the biogeography of humans than so far attempted [757; 758].

What can anthropology contribute to biogeography? The answer is the huge amount of data and understanding that anthropology has of regional variation, both past and present, in our own species and its close relatives. Is there another species on which we have as large a sample of relevant data as we do for humans? Sample sizes of hundreds of individuals and scores of molecular markers are commonplace in studies that directly or indirectly concern the distribution of humans. Globally, the sample is 10 times as large and increasing all the time [125; 529; 627; 762]. Some of the medical anthropological data is barely available for most other species, let alone in the detail that anthropology has. We even have a biogeography of the distribution of bacteria on the human body [154].

On top of its enormous amount of data, anthropology can use areas of evidence not available to biogeographers and macroecologists of other taxa. Linguistics is an example [124; 125]. Yes, the calls of bush-babies (Galagonidae) can differ regionally and inform us about taxonomic relationships [554]. But no bushbaby taxonomist has anywhere near the detail available to historical linguistic anthropology [124; 125]. And while there is some nice prehistorical analysis of pack rat middens [763], it is, of course, utterly negligible by comparison to the information that archeology can provide.

Yet as far as I can tell, little of this anthropological knowledge reaches the biogeographical literature. For instance, although the title of Ian Simmons’ Biogeography: Natural and Cultural [705] sounds as if it fully integrates the two disciplines, in fact Simmons treats only the topic of chapter 10 of this book, the effect of humans on other species’ distributions. In biogeography’s bible, Mark Lomolino et al’s Biogeography (now in its 4th edition), only 15 of its 760 text pages treat human biogeography [463]. Yes, we are just one of thousands of species, but does not the amount we know about us deserve more than the 2% of space devoted to us?

An additional benefit to the field of biogeography of attention focused on human biogeography might be that because of our intrinsic interest in ourselves, the topic of biogeography as a whole would receive more than the minor amount of attention it does in the popular press [441].

What can biogeography contribute to anthropology? Biogeography in all its forms has exploded in the last half century, and perhaps especially in the last two decades [463]. It seems to me that anthropology has yet to fully embrace that immense increase in knowledge and understanding.

It is not the case that biogeography is ignored in anthropology [224; 228; 435; 757; 758]. Rather, its treatment is scattered through anthropological works and usually addressed under headings such as human origins, or human variation or adaptation [757; 758]. Despite the quote from Huxley at the start of this chapter, which is effectively an explicit statement that much of anthropology is the biogeography of humans, it is not treated as such. Consequently, relevant biogeographic patterns and principles developed largely by analysis of nonhumans have perhaps not been as fully integrated into our understanding of humans as they could have been.

Advantages of integration of other disciplines with anthropology are, as always, to increase understanding of, on the one hand, the biological heritage and influences that we have in common with so many other species and, on the other hand, to help delineate what is unique about the human species.

HUMAN TAXONOMIC TERMINOLOGY

Hominoid, hominid, and hominin are terms still sometimes used interchangeably to describe humans and our ancestors. Table 1.1 shows the proper taxonomic divisions and indicates continuing debate—for instance, whether Pan (chimpanzees) should be included in the same tribe as Homo [841]. The term hominin in English is confusing because it could mean either Hominini or Hominina. Not only that, but whether the chimpanzees, Pan, are included in Hominini is debated. In this book, I use hominin to mean Hominina, i.e., only humans and our direct, non-ape ancestors. By human, I mean Homo sapiens. I need to say that because some authors use the word human to mean any Homo.

Colin Groves provides an expert yet readable account of taxonomic rules in what some term the bible of primate taxonomy, his Primate Taxonomy [292]. Richard Klein provides an exhaustive description of all of the hominids, including debate about their nomenclature, in the 4th edition of his The Human Career [425].

For want of another place to say it, let me add here that I use the terms gene and allele more loosely than some might like. In my defence, precise jargon meanings of the words differ, and have changed over time, and considerable debate exists over the units of selection [694, ch. 7].

HUMAN VARIATION

The observation that individuals differ is one of the foundations of the theory of evolution by natural selection [165]. Not only do individuals differ, but so does the average person in different parts of the world. Humans from different parts of the world differ morphologically, molecularly, genetically, and culturally, and some of the differences have clearly existed for millennia. The causes of those differences are the topic of this book, and of much previous work in anthropology [124; 125; 241; 332; 530; 540; 640; 722].

A focus on differences between humans from different parts of the world raises the topic of race and all its unpleasant connotations. Humans are distressingly good at not only detecting differences between “us” and “them” but also inventing differences and then at stigmatizing those unlike ourselves [622].The contrast between us and them, whether real or perceived, is the basis of much that is worst in human nature. People from many parts of the world, even now, perceive people from different parts of the world as inferior in one or more traits. Unfair discrimination does not, however, remove the fact that regional differences exist.

It can be medically vital to recognize regional differences [61; 115; 304; 708; 722; 771; 817; 857]. Several contrasts in susceptibility to various aspects of the environment exist between peoples from different regions of the world. Do not force milk products on adults from regions where adults are not used to drinking milk: they cannot digest the milk, and they will get sick from it. This is not an artificial example: western famine-relief programs used to ship milk powder as food aid, which at best was useless but at worst could have exacerbated malnutrition [193, ch. 5]. Know that if a child in New York is sick and its parents came from west Africa, or Greece, or lowland New Guinea, or Ferrara province in Italy, the child could well have one of a variety of hemoglobin variants that seem to provide protection against the consequences of malarial infection in the parents’ country of origin [115; 124, ch. 2; 540, ch. 4; 640, ch. 7; 771]. Know that codeine might be less likely to cure the headache of someone from Europe or Africa than from Asia [817]. It is not racist to recognize these differences. Understanding their causes can be helpful.

Nevertheless, between a Maasai herdsman and the average Scandinavian farmer a continual gradation of skin color exists. It would be impossible to say where African stops and European starts [640, ch. 5]. As Darwin wrote, “It may be doubted whether any character can be named which is distinctive of a race and is constant” [166, part I, p. 225].

Indeed, we know that more variation exists genetically within any one population of humans than between populations from different parts of the world [665]. Not only that, but a large number of studies from a variety of labs and continents on a variety of bits of the genome all agree that more genetic variation exists within chimp subspecies, even a single population of chimpanzees, than within the whole global population of humans (Fig. 1.1) [247; 730]. In other words, for a species spread over the whole globe, humans are extraordinarily homogeneous genetically.

In sum, spatial gradation in traits and extraordinary genetic homogeneity make “race” as the word is used in normal discourse a sociopolitical concept, not a biological concept.

I suggested at the start of the explanation of why I have written a book about human biogeography that biogeographically humans are just another species. That suggestion of identity will for some social anthropologists still raise the red flag of genetic determinism. Such anthropologists have always made the mistake of confounding genetic influence with genetic control. Let me emphasize that much of the biogeography that I write about has to do not with genes determining human behavior, or even influencing it, but with humans’ reactions to the environment. There should not be any hard-core anthropologists remaining who deny any influence at all of the environment on human physiology, behavior, society, culture. But if there are, they need to produce alternative explanations than the ones from physical anthropology and biogeography that I review here to explain why biogeographically we seem to do the same as so many other species.

ORGANIZATION OF THE CHAPTERS

I have organized the book into three parts. The first considers why humans are where we are. It is historical biogeography, phylogeography. The second relates our distribution to the nature of the environment. The topic is adaptation, or functional biogeography, including macroecology. And the third addresses the biogeographic effects of interactions between cultures and between species.

The biogeographic history of human origins and our spread around the world from Africa is the first topic (chapter 2). People from different regions are different. In part, that is because their origins and history of settlement were different. The similarities and differences in the biological and cultural traits that lead to this inference allow us to track the spread of humans, first from Africa, and subsequently to the rest of the world.

Change of climate has been a main correlate of major evolutionary events since life began. The same is probably true of human origins and our dispersal around the globe (chapter 3). Quantitatively substantiating the connection between climate and human history is a different matter, however. Except for climate’s inevitable role in delaying human migration into and through the arctic north, a lot more data and statistical sophistication are needed to prove climate’s influences.

Barriers stop movement of individuals and therefore help maintain different sorts and variety of organisms on either side of the barrier (chapter 4). The most common sort of barrier is a hard geographic barrier, such as water or high mountains. However, the behavior of individuals also can be a barrier to movement. A contrast in cultures can be an extremely effective impediment to the movement and mating of individuals; hence, ghettoes in cities.

Even if people from different regions did not have different origins, and even if there were no barriers to movement, people in different parts of the world would still be different, because of adaptation to different environments (chapter 5). For instance, people with short limbs are probably better adapted to cold environments than are those with long limbs. It is not just the average trait of this sort that sometimes varies with the environment in apparently some sort of adaptive way, so also does the diversity of traits within a region. Thus, in just the same way as diversity of many organisms is greatest in the tropics, so is diversity of human cultures. We can use our understanding of the causes of the gradient in cultural diversity to test hypotheses for the biodiversity gradient, and vice versa. And of course, human numbers vary with the nature of the environment: there are not many of us in Antarctica or the Sahara.

The size of areas available to organisms and species, or used by them, is a major explanatory and organizing principle in biogeography (chapter 6). The area available affects the number of individuals that can inhabit an area, and hence it affects both the sort of species and culture in a region and the diversity of species and cultures. The area used by species and cultures, their geographic range, varies with latitude, probably in part via latitudinal contrasts in productivity of the land and thus the size of area needed for persistence of a species or culture.

Different cultures and people from different regions exploit the environment in different ways—for example, by having different diets. Different diets sometimes correlate with a different physiology, and so we get regional differences in physiology, a perhaps too-little-investigated aspect of biogeography (chapter 7).

In the final three chapters, I consider the biogeographical effects of competition within and between species. Competition between humans from different parts of the world affects human diversity across the globe (chapter 8). Human nature and diversity is affected by other species. Because the nature of these other species varies regionally, human nature and diversity varies regionally (chapter 9). And, of course, humans affect other species, driving many to extinction but increasing the numbers and geographic ranges of many as well. Which species are affected and how depends on the nature of the species, on where they are, on regional differences in what sorts of humans arrived, on when and where humans arrived, and in what numbers humans arrived (chapter 10).

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