BOOKS ET AL.

19 OCTOBER 2012 VOL 338 SCIENCE www.sciencemag.org 330

I love big cities. Not only is there always

something interesting to do, but where

else can you experience so much human

diversity in such relatively compact areas? As

you walk down the street, your ears pick up

a multitude of languages and accents, your

eyes capture a huge range of human physi-

cal traits, and your nose catches the smells

of cooking from scores of ethnic restaurants

Why We Are What

and Where We Are

GEOGRAPHY

John P. Hart

The reviewer is at the Research and Collections Division, New York State Museum, 3140 Cultural Education Center, Albany, NY 12230, USA. E-mail: jhart@mail.nysed.gov

variety just as we are to be intrigued by the

similarities among them. And we are led to

wonder: What is the appeal of the tree meta-

phor? What general representational utility

makes this form so persistent, even as the

ideas it represents change?

In sum, Pietsch provides a comprehen-

sive visual document of an idea, which I rec-

ommend to anyone interested in the history

of science and scientifi c representations. It

collects diagrams that, although now (or

perhaps soon to become) obscure, helped

shape the development of one of the most

important ideas in modern science. With the

concept of evolution now often iconifi ed to

the point of misrepresentation, Trees of Life

reminds us that both the idea and its repre-

sentations were—and are—fl uid, debated,

and reconstructed.

References

1. C. A. Clark, God—or Gorilla: Images of Evolution in the

Jazz Age (Johns Hopkins Univ. Press, Baltimore, MD, 2008).

2. M. Landau, Narratives of Human Evolution (Yale Univ. Press, New Haven, CT, 1991).

3. R. J. O’Hara, Biol. Philos. 7, 135 (1992). 4. K. M. Catley et al., J. Res. Sci. Teach. 47, 861 (2010). 5. C. F. Matuk, D. H. Uttal, in Evolution Challenges: Inte-

grating Research and Practice in Teaching and Learning

About Evolution, K. S. Rosengren, S. K. Brem, E. M. Evans, G. M. Sinatra, Eds. (Oxford Univ. Press, New York, 2012), pp. 119–144.

6. D. A. Baum et al., Science 310, 979 (2005). 7. T. MacDonald, E. O. Wiley, Evol. Educ. Outreach 5, 14

(2012). 8. H. J. Lam, Acta Biotheor. 2, 153 (1936). 9. M. A. Ragan, Biol. Direct 4, 43, discussion 43 (2009). 10. L. E. T. Loesener, Nova Acta Phys.-Med. Acad. Caesareae

Leopoldino-Carolinae Ger. Nat. Curiosorum 89, 1 (1908).

and food carts. All of this refl ects the modern

world, in which rapid travel allows a mixing

of people from around the globe. But how did

the patterns of human variation that contrib-

ute to the modern cityscape arise? This is the

subject of a relatively new fi eld of human bio-

geography and of Alexander Harcourt’s book

of the same name.

In the spring of 1974, a group of promi-

nent anthropologists, biogeographers, and

population geneticists met at the Smithso-

nian Institution to discuss the potential of

using biogeographical theory and methods

to analyze geographical patterns of human

variation ( 1). Participants shared a sense of

great promise for the develop-

ment of an interdisciplinary

fi eld of human biogeography.

A wide range of investiga-

tions have since contributed to

the fl edgling discipline, even

if the researchers were not

specifi cally concerned with or

even aware of their contributions to the fi eld.

By summarizing a vast, disparate literature

from a variety of scientifi c disciplines (the

bibliography comprises 861 publications) as

well as offering new analyses and insights,

Harcourt (an anthropologist at the University

of California, Davis) captures the continued

potential of human biogeography as well as

its challenges.

Concerned with geographic patterning

within and between species, biogeography

itself is an old discipline, which Harcourt

traces back to 18th-century European

explorations and Alfred Russel Wallace’s

foundational work ( 2). Since then, we have

developed good understandings of the bio-

geography of many species.

For example, we know that maize (Zea

mays ssp. mays) evolved from a teosinte (Z.

mays ssp. parviglumis) native to central Mex-

ico and has spread around the globe over the

past 9000 years as the result of its interactions

with humans. It is highly variable both geneti-

cally and phenotypically across its range. Its

thousands of varieties differ in, for exam-

ple, plant size, number of days to matura-

tion, infl orescence shape, and kernel shape,

size, and color. We know that the histori-

cal patterning in variation was the result of

founder effects, drift, isolation, hybridization,

and natural and artifi cial selection in varying

environmental settings—that is, it refl ects the

history of genetic variation within and among

maize populations.

We are also a globally dispersed species.

Having evolved in Africa, Homo sapiens

dispersed within and from our home conti-

nent beginning some 55,000 years ago (to

use Harcourt’s compromise figure). Over

50,000 years later, we reached the farthest

reaches of the globe, islands in the Pacifi c

Ocean. As we spread out and encountered

widely ranging and changing environments,

we became highly variable both physically

and behaviorally. As in other species, this

variation is patterned.

Can the patterns of physical and behav-

ioral variation in humans be explained

with the same theories and methods used

to explain geographical patterning in other

species? That theme of the 1974 meeting

remains a primary question for a discipline of

human biogeography. Early in his narrative,

Harcourt notes that there is

more genetic diversity in a sin-

gle subspecies or population

of chimpanzees than in the

global human population. As

a result, he states that “much

of the biogeography that [he

discusses] has to do not with

genes determining human behavior, or even

infl uencing it, but with humans’ reactions to

the environment.” In other words, whereas

some of the patterning in human variation is

the result of genetics, much more of it (unlike

in most species) is not.

Perhaps what is most interesting about

the book and the field is that at this junc-

ture, human biogeography is most success-

ful in explaining patterns in physical traits,

whether they be adaptations to environmen-

tal pressures or to human niche construction.

It seems less adept at explaining variation in

cultural patterning. Although Harcourt rec-

ognizes that equating languages with cultures

is questionable, he bases most of his analy-

ses on that concept. The issue of appropriate

units of analysis was raised at the 1974 meet-

ing and has been ongoing in anthropology

and other sciences that contribute to human

biogeography. Harcourt offers ample justifi -

cation for his analytical methods. Given that

the selection of analytic units should be situ-

ational, readers are left to decide how mean-

ingful his results are.

Regardless of any such issues, Human

Biogeography is a remarkable achievement.

The book fi rmly establishes its subject as an

important discipline bridging the social and

biological sciences. By bringing together

such a vast corpus of analytical results, it will

undoubtedly attract more attention to the fi eld.

References

1. G. B. Kolata, Science 185, 134 (1974). 2. A. R. Wallace, The Geographical Distribution of Animals

(Macmillan, London, 1876).

10.1126/science.1227960

Human Biogeography

by Alexander H. Harcourt

University of California Press,

Berkeley, 2012. 327 pp. $60,

£41.95. ISBN 9780520272118.

10.1126/science.1227838

Published by AAAS

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