The Ape in the Tree: An Intellectual and Natural History of Proconsul

  • Alan Walker &
  • Pat Shipman
Harvard University Press: 2005. 312 pp. $26.95, £17.95, €24.90 0674016750 | ISBN: 0-674-01675-0

The ape in the tree is Proconsul, a fossil ape known exclusively from East Africa. It has many things to recommend it as a subject for a book: it is the earliest known ape in the fossil record (dating from 18–20 million years ago); it is represented by the most complete remains of any fossil ape (several partial skeletons); and, since the first remains were found some 75 years ago, it has been studied by many people of different levels of eminence. It is therefore a good subject on which to build any number of scientific edifices, whether historic, taxonomic, ecologic, phylogenetic or to do with functional morphology.

What's more, it has been at the centre of feuds, deaths, disputes over ownership, and rivalries between some of the biggest personalities in anthropology. In many of these, Alan Walker has been involved at first hand, and he brings a strongly personalized view of these events to this book. It is first and foremost an account of his own involvement with the discovery and description of some of the best specimens of Proconsul yet found. The account is actually written by Alan's wife, Pat Shipman, but it is curiously written in the first person singular as if by Walker, and we learn as much about him in this book as we do about the place of Proconsul in the evolution of the apes.

One of Walker's many gifts is his ability to illuminate subjects he is interested in and to bring new ideas to bear. His stated aim in this book is to provoke curiosity about apes and the part they have played in our evolutionary past. He recognizes that we should not view fossil apes in some sense as ‘failed apes’. There is a tendency among some workers, both past and present, to try and identify fossil apes with their living survivors — chimpanzees, gorillas and orangutans — so the common ancestor of humans and chimpanzees, for example, is seen by some as having been chimpanzee-like.

Walker does not address this particular issue directly, for he is dealing with a fossil ape that lived close to the time when monkeys and apes diverged (about 20 million years ago), but he states unequivocally that the common ancestor of monkeys and apes was neither monkey nor ape but a being in itself that had its own suite of characters and its own way of life. This enlightened approach, free of the straitjacket of descendent species, is the most successful aspect of this book in documenting the way of life of Proconsul in all its aspects.

Having said this, Walker makes it clear right from the start that this is no scientific treatise, but a semi-popular account of early ape evolution. His mentor was John Napier, a larger-than-life character who had enormous influence on primate studies in the middle of the twentieth century. One of Napier's major works was a monograph — The Fore-limb Skeleton and Associated Remains of Proconsul africanus (British Museum (Natural History), 1959) — on the partial skeleton of Proconsul from Rusinga Island, which provides a detailed morphological description with the emphasis on the function of the animal as a whole. Napier's approach to functional morphology was hugely influential and made a great impression on Walker, who has carried on and extended this approach with the help of a succession of bright, enthusiastic students.

The study of functional morphology is based on interdisciplinary collaboration: morphology is interpreted in terms of function, function in terms of behaviour, and behaviour in terms of interaction with the environment. This requires a high level of collaboration that is entirely in line with Walker's stated intention to “give as many opportunities to up and coming young people as I could”. He is an inspired and inspiring teacher, but it is my regret, and the subject's loss, that he has not himself produced a monographic treatment of Proconsul and its place in ape evolution to match Napier's. The present book is not an adequate replacement, however entertaining it may be.

There is also a failure to extend the approach of functional morphology to its third aspect: interaction with the environment. There is little more than anecdotal discussion about the environment that Proconsul lived in, other than saying that there was forest and trees for it to move around in. The apparent link to forest environments is important for Walker's reconstruction of Proconsul's way of life, for it implies a reliance on tree-living. Primates that live in woodland rather than forests, by contrast, are more terrestrial, as the tree canopies are too open and too poor in resources to support fruit-eating mammals all year round.

Walker does not mention a wealth of published environmental evidence, much of it done in the 1970s, a period of study excised from his account of Proconsul studies, and some that he does mention is now thought to be wrong. For example, much of the evidence for the environment at Rusinga, based on both plants and mammal faunas, shows that the area was dominated by seasonal deciduous woodlands with patches of forest that were almost certainly ephemeral both in time and space. The strong evidence for forest environments comes from other sites: Songhor and Koru, based on abundant mammalian faunas, and Mfangano, based on the fruits of tropical forest trees. The evidence for forest at Rusinga is based on localized outcrops of forest faunas, abundant woody climbers, which typically would have been growing locally along water courses, and leaves with apparent (not yet analysed) forest affinities. The so-called fruit-and-nut bed, which Walker mentions several times as providing evidence of forest, is actually dominated by plant species with deciduous woodland affinities. The idea of Proconsul as a slow climber subsisting mainly on a diet of soft fruits, as indicated by its functional morphology, is less viable if it lived in a deciduous woodland environment, rather than a forest.

Walker's semi-popular account of this important fossil ape will be an accessible and entertaining read for the educated layman. It will also be a useful guide to students learning about how research is conducted, although they need to be aware of the idiosyncracies in this highly personalized account. We can live in hope that Walker will do justice to his great abilities and will yet produce a definitive account of this ape in the tree.