In the shadow of the modern synthesis? Alternative perspectives on the last fifty years of paleoanthropology

Abstract

In a recent article in Evolutionary Anthropology, Tattersall1 discussed the development of human evolution in the last 50 years, specifically in the context of the history of evolutionary theory over the same time. His paper was rich in ideas and information, all clearly and elegantly stated, even if his admiration for most palaeoanthropologists’ grasp of issues in evolutionary theory was somewhat restrained. His summary of many issues in the complex world of fossil hominins cut a swathe through much that is often obscure. Furthermore, the paper was clearly meant to be provocative, and in this it is a masterly success. At the risk of oversimplification, Tattersall can be said to have made two main points. The first is that the last fifty years of palaeontological discovery and analysis have swept away the last vestiges of the unlinear and anagenetic models of human evolution and replaced them with a series of radiations and a pattern of diversity similar to that known for many other organisms. His second point is that this evidence should be seen as grounds for also clearing away the modern synthesis, which he sees as underlying a unilineal model. Multiple species, adaptive radiations, and diversity are taken to be evidence for macroevolutionary mechanisms and the dominance of a punctuated equilibrium process of evolutionary change. Indeed, it can really be claimed that these two points are, in his mind, merely the two sides of the same coin, inseparable and indivisible. Multiple species and complexity cannot be accommodated within the modern synthesis, a theory of evolutionary change that Tattersall clearly sees as the crusty port of the biological establishment, ritually and uncritically passed from one select person to another, gradually deadening their senses. His article left me in a dilemma. As someone who has championed the idea of multiple species, cladogenesis, adaptive radiations, and for well over a decade,2–5 I nodded wisely and cheered happily as he listed the fossil discoveries that have sealed, nail by nail, the coffin of unilinealism. But I am also a paid-up member of the modern synthesis, one who thinks that microevolutionary and adaptive processes account for the pattern we can see in the fossil record. If Tattersall were right, then I obviously could not have my evolutionary cake and eat it too. I would have to choose whether to sink all those wonderful hominin species together and champion a grand Darwinian unilinealism or else keep the species but throw away the theoretical glue that I saw holding them together. Which was it to be? Of course, the question is, does it have to be either/or? What I want to do in this paper is to challenge the dichotomous equations that Tattersall has set up: multiple species 5 macrovolution; the modern synthesis 5 unilinealism. On these sets of equivalence hang his whole thesis, and therefore his reading of the past and vision for the future of palaeoanthropology. I shall do this in three sections. The first will be historical. I shall argue that paleoanthropology, rather than being shackled for the last 50 years by the modern synthesis, has in fact remained blithely innocent of most theoretical issues, and that this, rather than rigid dogma, was the central problem. Second, I shall suggest that there is much within the classic microevolutionary synthesis that predicts the pattern we see. Much of Tattersall’s outline of what falls within the modern synthesis is a simplification of a far more diverse field, one to which macroevolutionary theory has added little of substance. Third, I suggest that the future of paleoanthropology lies in a very different direction from the one Tattersall marks out, a direction that is less tied to the earth sciences but more integrated into the life sciences, particularly evolutionary genetics and evolutionary ecology.