I just finished reading the book by Peter Peregrine, What Happened in Prehistory? Peregrine is an anthropologist at the Lawrence University in Wisconsin. I have known him primarily because he spearheaded the construction of the Atlas of Cultural Evolution database and was co-editor of the nine-volume Encyclopedia of Prehistory. (I am interested in these works because we have recently embarked on building our own historical database). Such extensive experience with cross-cultural research means that he has at his fingertips a lot of comparative archaeological data, and I was curious to see how he would synthesize it.

There was also an additional reason to read Peter’s book – it was self-published as an eBook on the Kindle and Nook platforms. As I am planning to write my own eBook in the near future, I was interested to see what an anthropological book might look like on Kindle.

Whatever my ulterior motives, I enjoyed reading this book and I learned a lot from it. I have no formal training in Anthropology, and while I have delved into various – and sometimes esoteric – parts of it, it is also really useful to get a general overview from an established practitioner in the field. Such an overview provides a kind of a mental map on which other, more specialized topics can be placed. So I definitely recommend it. One peeve I have, however, is that it would be relatively easy to provide endnotes, which would not detract from the book’s readability, but could also allow the reader to pursue interesting tangents more easily. There is, however, a Bibliographic Essay at the end.

The title of the book echoes the seminal oeuvre of Vere Gordon Childe, What Happened in History?

In his 1942 book Childe famously proposed that there were two major revolutions in the early human history, the Neolithic Revolution when plants and animals were first domesticated, and the Urban Revolution when first true cities and states arose. To this two revolutions, Peregrine adds two more, which preceded those identified by Childe. The total is four; thus the title of this blog.

The first major evolutionary transition in human prehistory that Peregrine discusses is Behavioral Revolution. Behavioral Revolution, which unfolded roughly 2 million years ago, resulted when the Homo genus (to which we belong) differentiated itself from our great ape relatives.

It started with the early Homo people (such as habilis), but really came into its own with the rise of Homo erectus 1.8–1.6 million years ago.

Reconstruction of Homo erectus by Elisabeth Daynès (source: http://johnhawks.net/)

The hallmarks of this transition were walking upright on the hind legs (“bipedalism”), making tools with hands that were freed as a result of bipedalism, culture (as seen in the cumulative development of the stone tool technology), semi-permanent camps or home bases to which foragers and hunters (or scavengers) returned at the end of the day, and families, marriage (“pair-bonding”), and extended care of children. At some point (still unclear precisely when) this species of humans started using fire.

The next major transition, according to Peregrine, was the Cognitive Revolution. It is associated with the emergence of modern humans (Homo sapiens) some 200 thousand years ago followed by their explosive spread from Africa in the last 50 thousand years. It involved another qualitative jump in the size of the brain, evolution of language, the arts, and more generally symbolic thinking. So I think a better name for this transition would be Symbolic Revolution (rather than cognitive revolution). The Behavioral and Symbolic Revolutions would also nicely correspond to the two ‘cultural’ modes of evolution in the Jablonka and Lamb (Evolution in Four Dimensions) classification.

Symbolic revolution (source: Wikimedia)

Although each of these revolutions unfolded over tens and even hundreds of thousands of years, there is no question in my mind that they were truly revolutionary transitions. In each case one species (first Homo erectus, then anatomically modern humans) swept out of Africa and wiped out all of our other relatives. There were at least 20 various Homo species (and, quite likely more await to be discovered) living during the last 2 million years. All of them are gone except for us. To me, this is a clear case of ‘species-selection’ – group selection at the level of whole species.

The next two revolutions, the Neolithic and Urban, also resulted in an explosive spread of first, agriculture, and then states, each eventually taking over the world. Unlike the first two revolutions, these ones involved competition (and selection) between human groups within the same species.

Nevertheless, I am struck by the similarities in how each revolution unfolded. Homo erectus was an enormously successful species, which rapidly (on an evolutionary time scale) spread over the whole of the Old World. The anatomically modern humans were even more successful, getting to all continents and major islands, with the exception of Antarctica. Over just 10,000 years ‘Homo agrarius’ pushed hunter-gatherers into marginal environments, and now this way of life is essentially extinct. The spread of human societies organized as states was even more rapid, and was basically complete by the nineteenth century when the European Great Powers claimed all land that had not been already claimed by some state or another.

The future of Homo urbanus? Planet Coruscant, the capital of the Galactic Empire in the Star Wars Saga (source)

So what was the mode of these revolutions – how did we, agricultural and urbanized anatomically modern humans drive all those other types of people extinct? In his book Peter Peregrine presents a number of hypotheses for each case, but doesn’t come to any definitive conclusions. To me the answer is clear – the fundamental mechanism was multilevel selection involving both genetic and cultural traits. This means that the key part of each revolution was competition between different types of groups, which resulted in ones driving the others to extinction. Details varied, but violence was probably a large part in each transition.

Think about the spread of anatomically modern humans. The pattern is always the same. They arrive in a world region, and all other species of humans go extinct. Most of ‘megafauna’ (large mammals) goes extinct. In fact, we can think of the Neanderthals as a kind of megafauna. The evidence is not conclusive yet, but I think as we accumulate data, it will become increasingly clear that we (well, our ancestors) basically killed and ate the Neanderthals. As well as raped them in some cases. It’s not anything to be proud of. But I think that is what happened in prehistory. Perhaps we should call this the ‘Jeffrey Dahmer hypothesis’ of Neanderthal extinction.

“Wilma,” a DNA-based reconstruction of a Neanderthal female (National Geographic)