Testicle belts and other nerve-racking encounters on path through life

The Miocene epoch lasted from about 23.8 million to 5.3 million years ago. It was a time of warm global climates, towards the end of which our evolutionary lineage diverged from that of our closest living relatives, the chimpanzees. One of the groups of mammals that reached an unprecedented diversity during the Miocene was that of the apes. The Miocene world was the true "planet of the apes".

The Ape in the Tree , by Alan Walker and Pat Shipman, is an engaging chronicle that centres on the discovery and scientific interpretation of one of those early apes. This book does not dwell on the usual subjects of popular palaeo-anthropological writing, the bipedal or semi-bipedal creatures that have peopled the East African landscape and beyond for the past 5 million to 6 million years. It reaches further back in time, to an earlier relative, closer to the last common ancestor we share with all the other modern apes, the chimpanzees, the gorillas, the orang-utans and the gibbons. That early relative is Proconsul , named after a Victorian performing chimpanzee called Consul, and it lived in the Miocene of East Africa.

The first Miocene fossils to reach the British scientific establishment from the Kenyan shores of Lake Victoria were sent to London's British Museum in 1909 by Dayrell Botry Pigott, then assistant district commissioner of the Kavirondo region of western Kenya. Regrettably, Pigott did not live to realise the significance of his action. Of the many risks encountered by British officials in the more remote parts of their empire at the dawn of the 20th century, the one that brought an end to Pigott's life was not the most obvious. Pigott was an early casualty on the fringe of what would become one of the most enduring palaeontological adventures of the 20th century. He fell victim to a crocodile a few months after sending the fossils.

The Ape in the Tree combines adventure story with accounts of the painstaking work that underpins scientific progress. It tells of the associated history of scientific thoughts, of their development in the light of new evidence and of their subjection to preconceptions and personal ambition. Authenticity is guaranteed, as one of the authors, Walker, has been involved with the story of Proconsul for some 40 years. His anecdotes convey the excitement of digging up evidence of ancient life and the associated frustrations ("This is the list of break-downs on a brand-new machine, just for my memory when I talk to the manufacturers..."), unsettling moments ("When I looked at the belts closely, I realised they were leather strings from which dangled peculiar wrinkled objects: the testicles of the men they had killed. Their stares and their belts made us rather nervous."), and occasionally dangers ("'Get that plane up fast, Richard (Leakey)!'").

While the tales of personal adventures carry the text and entertain, Walker and Shipman also take care to elaborate on the tools that are available to palaeontologists in their quest to tease life out of the fossilised remains of ancient species. Scientific concepts are explained to enable non-expert readers to take part in the unravelling of the past. The authors tell of the chemistry of the ancient Kisingiri volcano, which was directly responsible for the unparalleled preservation of the Lake Victoria fossils. They explain how the ancient rocks are dated and how evolutionary relationships between species are estimated.

They also relate the basic techniques used to infer the behaviour of extinct species, from comparisons of two-dimensional measurements between species to recent imaging technologies, such as CAT scans, that are used to analyse the internal structures of fossils without damaging them. The Ape in the Tree invites reflection on what it means to be human, on the way scientific research is conducted and on how its results are interpreted. As is often the case with books that are about both the science and those who do the science, it benefits from the fact that research is first and foremost a human endeavour. As such, it also provides an opportunity to become acquainted with the human facets of many of the big names that have influenced biological anthropology over the past century and of some who still influence it today. As for Proconsul and all the other Miocene apes, they may have been extinct for millions of years, but the story of their scientific exploration is far from over. As if to underline this, an epilogue was added to the book at proof stage to tell of one of the most recent and spectacular finds - another ape in an increasingly crowded tree.

Christophe Soligo is a researcher in the Human Origins Group, Natural History Museum.