Book Review/Science in the Media Climate-Driven Evolution

Henry Harpending* Department of , , Salt Lake City, Utah, United States of America

There are several rather distinct tradi- humans and related species in time and tions in the contemporary study of human space. They see humans responding to the evolution. One is the detailed study of physical and biotic factors like geography, anatomical differences among fossils. A climatic shifts, the availability of exploitive second emphasizes classical ecology with technologies, or the availability of domesti- detailed attention to ancient climates and cates. In this literature, humans are mem- environments and comparative biogeogra- bers of communities, and these communities phy. A third has a focus on behavioral are like organisms evolving to become better ecology (i.e., what used to be called and better at provisioning their members. ). It appears to this outsider This group or species view of evolution that these are not so much competing contrasts sharply with the implicit model of traditions as they are nearly independent the behavioral ecologists in which reproduc- and seemingly unaware of each other. tive competition between individuals within They each have much to contribute, they groups is the important dynamic. are each prominent in particular current The Humans Who Went Extinct is firmly in disagreements in the field, and they each the third, that is, classical ecological have glaring weaknesses. tradition. This admirable book is a Anatomical details are central to the summary and interpretation of human literature on Australopithecines and their evolution from the first bipeds several relatives, primates in Africa on the human million years ago to the earliest settled side of the ancient chimp–human split from agricultural populations after the end of five to ten million years ago to about two the Pleistocene. The title does not do and half million years ago when we start justice to the scope of the book: there is calling the fossils Homo rather than Australo- only a weak focus on the extinction of the pithecus. The anatomists are also in the thick Neanderthals. It is an excellent summary Finlayson C (2009) The Humans Who of debates these days about the hobbit, the of the classical ecological approach to Went Extinct: Why Neanderthals died small hominid remains found on the island with a dazzling portrayal out and we survived. : Oxford of Flores. Details of the wrist are apparently University Press. pp. XI+273. ISBN of the relevant paleoclimatology, paleo- (cloth): 978-0-19-923918-4. US$29.95. critically important in distinguishing wheth- ecology, and biogeography. doi:10.1371/journal.pbio.1000383.g001 er these creatures are derived from Austra- These traditions ought to be comple- lopithecines, from Homo erectus (perhaps mentary; instead they are rather isolated having undergone island dwarfism), or are from each other. The discipline would be The ecologists explain this in terms of simply pathological dwarves. A weakness of enriched if we acknowledged that the geography and climate, the availability of the anatomical tradition is the treatment of narratives that each tells are models and domesticates, increasing demand from a anatomical details as if they were selectively that models should be evaluated and larger human population, and a lot of neutral, mere traits that can be tabulated to falsified with data. There are numerous chance. Some in the behavioral ecology generate answers by consensus. There is not situations where models from the ecolog- tradition see settled agriculture as a much awareness of quantitative genetics. ical and behavioral traditions compete consequence of the formation of regional The behavioral ecology tradition em- directly, and such situations ought to be polities with militias that suppress local phasizes mating competition and inter- exploited for direct tests of the competing raiding and warfare, leading to population group struggles as the important drivers of models. growth, land scarcity, and increasing labor human evolution. With roots in econom- Why did settled farming appear after inputs into subsistence. These models ics, comparative animal behavior, and the the Last Glacial Maximum in several areas could both be true or both false, but new of interaction of the world, but never in the prior they ought to be tested as competing started by W.D. Hamilton in the 1960s, interglacial about 120,000 years before? hypotheses. social interactions themselves are the prime drivers of human evolution. For decades there has been a kind of faith that Citation: Harpending H (2010) Climate-Driven Evolution. PLoS Biol 8(6): e1000383. doi:10.1371/journal. pbio.1000383 there was some ‘‘environment of evolu- tionary adaptedness’’ (EEA) in the past to Published June 8, 2010 which humans are well adapted and that if Copyright: ß 2010 Henry Harpending. This is an open-access article distributed under the terms of the we could know about this EEA then we Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. could understand human nature. The ecologists look to ancient environ- Funding: No specific funding was received for this work. ments, climate, and climate change to Competing Interests: The author has declared that no competing interests exist. explain changes in the distribution of * E-mail: [email protected]

PLoS Biology | www.plosbiology.org 1 June 2010 | Volume 8 | Issue 6 | e1000383 Another playground of competing ex- warming means the return of Africa fauna established understanding that agriculture planations in extant narratives is the to the Middle East. Several modern led to sedentary lifestyles. The spectacular ‘‘creative explosion’’ in Europe and West- looking skulls from the Middle East (Skuhl, site of Go¨bekli Tepe in Southwestern ern Asia about 35,000 years ago. There Qafzeh) then simply represent a tempo- Anatolia with its monumental architecture appear quite suddenly in the archaeolog- rary intrusion of African fauna into the is a particularly dramatic example. Finlay- ical record new ways of making stone Levant ca. 120 kya. Finlayson destroys this son points out that the rich foragers of the tools, worked bone, decorations like beads, understanding of mine, pointing out that American Northwest Coast were likely on evidence of clothing, and art including the faunal associations of the early mod- the same path evolutionary path. sculptures like the famous Venus figurines. erns in the Levant, and of the slightly later The book is wordy and repetitious in One explanation is that some cognitive or Neanderthals, were much the same. places. It would have benefitted from the perhaps social threshold was crossed Another staple of my lectures is that the heavy hand of an editor in several ways: it marking the origins of true humanness. appearance of anatomically modern hu- would be shorter and more concise and The creativity, the evidence of regional mans in Europe is marked by a new adequate space would have been given to exchange of materials, the art and fine technology called Aurignacian (distin- the maps, which are obviously important technology—all these mark here the very guished by the use of blade tools) brought and informative but which are printed at first real members of our species. A by the moderns. Finlayson casually de- such a scale that they are nearly impossible second, perhaps more cynical, explanation stroys this staple too, pointing out that to interpret. The author commands a is that whenever we see gaudy art, fine there is no known association between the dense set of information about ancient weapons, and fancy technology among Aurignacian and modern human remains. climates and geochronology, but readers technologically primitive societies today, The Aurignacian could very well have unfamiliar with the information will have a these traits mark societies where men don’t been made by Neanderthals. difficult time following the narrative in have to work very hard provisioning their Even worse, I repeat the standard many places. Again, a heavy-handed families. Think of the societies of the US narrative that moderns out-competed Ne- editor might have insisted on more Northwest, where salmon runs only take anderthals and were somehow responsible timelines and diagrams in the text. up several months per year, with the rest for their extinction. Not so fast, says The book is somewhat dense for an of the caloric input from berries and Finlayson, suggesting that climate change introductory course, but it would be just gathered foods presumably gathered most- drove the Neanderthals away and they may right for an advanced course on human ly by women. The result is beautiful totem never have even encountered the modern evolution. An ideal advanced course might poles and watercraft and other decorative human invaders. His candidate for an use Klein [1], an encyclopedic yet acces- arts. Another familiar example is the tribes unequivocal archaeological marker of mod- sible survey including the anatomical of the US Great Plains after they took up erns is the Gravettian cultural tradition with details of the fossil record, the volume mounted predation of bison following the itsorigininwesternAsia,atraditionthatwas under review for the classical ecological introduction of the horse. A small hunt able to exploit open country herd prey on approach, and Boyd and Silk [2] for the could feed many people for weeks, leaving the expanding tundra. males free to develop an impressive This book is packed with new data, behavioral ecology. warrior culture with lots of gaudy decora- insights, and perspectives, with the dom- As a population geneticist, I must explain tions and weapons. In the view of cynics, inant theme being about how climate has why I have not discussed genetics in this then, the creative explosion is a mere driven human evolution. The narrative review. In the heady times of mitochondrial signature of a society where men could starts with the handful of very early DNA in the 1980s it seemed that genetics parasitize women. The makers of the apparent precursors of the Australopithe- would answer important questions about Venus figures are not foreshadowing cines and the later appearance of Homo human evolution. Since then, we seem to Rodin, they are foreshadowing Playboy erectus with its larger brain and slightly know less and less: the mutation rate of magazine. Can these models be tested? advanced tool-making technology. The mtDNA slows down as larger time intervals I am no expert in the classical ecological conventional story is that this new version are considered, and it has become clear that tradition; so much of Finlayson’s fascinating of Homo evolved in Africa and left about haploid markers like mtDNA and the Y book was new to me. For example, one and one half million years ago, but chromosome are not very reliable markers Finlayson calls on his knowledge of bioge- Finlayson points out that there is plenty of of origins and ancestry. The most important ography to propose that Australopithecines, room for a hypothesis of an Asian origin of finding about our genetics from the nuclear like azure winged magpies, occupied a wide this taxon. Several chapters discuss the genome was the apparent small effective size belt across Central to Eastern Asia in an earliest modern humans in Europe and in of our species, on the order of 10,000 ecosystem in which they flourished. This Southeast Asia and Oceania, again with a individuals. We knew in the 1980s that this proposal is not in our standard textbooks, narrative emphasizing climate change and was due to some severe bottleneck or but the great paleontologist GHR von shifting ecological zones as drivers of the bottlenecks in human history, but since then Koenigswald always maintained that he process. The discussion of the terrifying it has become apparent that other demo- found many Australopithecine teeth in his climatic instabilities of the Pleistocene, graphic phenomena, like waves of advance collections from Chinese pharmacists. particularly in western Eurasia, is partic- and selective sweeps of advantages genes A staple of my lecture notes on the ularly valuable. The appearance of seden- and haplotypes, could generate the apparent modern human diaspora is that when the tary communities soon after the end of the small effective size. In other words, we know earth is cold the Middle East is ecologically Pleistocene occurred well before the ap- much less today from genetics than we Europe with its Palearctic fauna, while pearance of agriculture, contradicting our thought we did two decades ago.

References 1. Klein RG (2009) The human career: human 2. Boyd R, Silk JB (2009) How humans evolved. biological and cultural origins, Third Edition. 1024 p. New York: W.W. Norton;xxv, 474, A39 p.

PLoS Biology | www.plosbiology.org 2 June 2010 | Volume 8 | Issue 6 | e1000383