Are pounding tools the missing link for the origins of technology?

All populations of modern humans (Homo sapiens) have repertoires of tool use and tool making (e.g., Ambrose, 2001). All well-studied extant populations of chimpanzees (Pan troglodytes) have repertoires of tool use and tool making (e.g., McGrew, 1992, 2010; Whiten et al., 1999; Sanz et al., 2010). No other living primate has lengthier inventories of tools than humans and chimpanzees (see van Schaik et al., 2003; Ottoni & Izar, 2008; Gumert et al., 2009 for inventories of tools in Pongo pygmaeus, Cebus spp. or Macaca fascicularis). During the Early Pleistocene, populations of hominins living in East and South Africa most likely had wider tool-use repertoires than the ones we have currently identified, which are only the non-organic, that is, non-perishable ones. Thus, archaeologists are mainly left with stone tools and fossilized bones to reconstruct the tool-use repertoire of the earliest hominins (e.g., Semaw et al., 2003; Plummer, 2004). In West Africa, for at least 4300 years, chimpanzees have been using stone tools, namely hammers and anvils, to access the kernels of hard-shelled nuts (Mercader et al., 2007).

Since studies began at Olduvai Gorge, Tanzania, and Koobi Fora, Kenya, stone tools have played a crucial role in inferring the evolution of early hominin behavior, beginning with research on the earliest stone tool industries (Leakey, 1971; Isaac, 1984). Leakey’s typological approach to the Oldowan was based on a continuous sequence of artifacts corresponding to the succession of cultures identified through the Olduvai stratigraphy. Metrics and types were applied to categorize lithics, to provide relative timelines and to make comparisons across industries/assemblages (mainly the Oldowan from Olduvai and KBS from Koobi Fora). In the 1980s lithic studies progressed, as artifacts needed to be understood and described in contexts, as they represent only one part of the hominin activity budget (Isaac, 1981). Isaac inspired a new research direction: integration of lithic studies into a paleoecological approach. This interdisciplinary approach aimed to get closer to site-formation processes and functions, and to understand ranging patterns in hominins (Isaac & Harris, 1997). Isaac (1984, 1986) also proposed an alternative terminology to describe the earliest stone assemblages. All artifacts were placed into three main categories (flaked, detached, pounded) with the aim of finding a simple alternative to terminologies based on post hoc, function-inferred labels (Leakey, 1971).

INTRODUCTION

Scenarios of ape–human divergence have often represented hominins as savanna-adapted (e.g. Dart 1959; Robinson 1972; Coppens 1988; Wheeler 1992), whereas the chimpanzee (Pan troglodytes) has been represented as rainforest-adapted. This dichotomy has eroded from both sides of the divide. Kano (1972) and McGrew et al. (1981) noted that the longest-studied chimpanzees, those at Gombe and Mahale, live in a grassland–woodland–forest mosaic, not tropical forest, and that other populations range into even drier, more open habitats (see the ‘savanna ape model’ in Moore 1996). The habitats of the earliest hominins were at least partly forested (Bonnefille 1984; WoldeGabriel et al. 1994, 2001). A less severely drawn contrast between ape and hominin habitats now seems a better fit with the evidence: Chimpanzee habitats range from closed-canopy rainforest to savanna, whereas early hominins likely occupied somewhat drier habitats, ranging from forest to woodland to savanna. This overlap means that primatologists can study the behavior of chimpanzees living in habitats nearly identical to those in which Mio-Pliocene hominins lived.

Study of chimpanzee diet, habitat use, ranging, and positional behavior in peripheral habitats will help establish whether water availability, food availability, food dispersion, vegetative cover, or climate limits the pan-African chimpanzee distribution. Better understanding of the factors that limit chimpanzees may help to identify niche differences between Mio-Pliocene apes and hominins.

Study of chimpanzees at the edges of the species' range may also have conservation implications. Documentation of the minimum requisites of the species is valuable for rehabilitation, relocation, and green corridor projects.

Each manuscript in this volume brings back to me the memory of a scene I witnessed with A. Suzuki in 1965. We were in western Tanzania, 50 km east of the escarpment in no man's land, when we came across an orderly procession of 43 chimpanzees, marching across the Miombo woodland with scarcely a leaf left on the boughs in the dry season (Itani & Suzuki, 1967).

It seems now that everything we must know about chimpanzees was condensed and suggested in the procession we witnessed, but we were unable to decipher the mystery at that moment. The manuscripts in this volume may present the possible answers for those who read this book; and this must have been the reason the manuscripts made me hark back to the scene of 30 years ago.

It was Thomas Huxley (1863), who first articulated the prologue to a plausible scenario recognizing the significance of great apes, especially the importance of inquiring into their relation to the human species, in the first chapter of Evidence as to Man's Place in Nature.

Later, well into the twentieth century, the first milestone was laid along the path towards the composition of a comprehensive scenario on the relationship between humanity and the apes. The milestone was The Great Apes by Robert & Ada Yerkes (1929).

INTRODUCTION

Until 1987, the received wisdom in psychobiology was that laterality of function in Homo sapiens was unique, and so qualitatively different from all other species, including even our nearest relations, the great apes. Humans were said to be overwhelmingly right-handed at species (or population) level, that is, about 90% of persons show right-hand dominance for virtually all kinds of hand-use. In contrast, other hominoids were said to be randomly lateralized, either showing no consistent, overall preference for left or right, or being individually lateralized to either the left or right side in about equal numbers.

The published data available on apes at the time seemed to support these views of 50 : 50 randomness, but findings were sparse. Finch's (1941) benchmark study showed a population of 30 chimpanzees in which all but one were lateralized, but to an equal extent for left and right.

The Great Apes, in Africa and Southeast Asia, are endangered. My expertise relates to chimpanzees, and so I will concentrate on them and on forest conservation in Africa. In most cases, the same issues also apply in the conservation of bonobos and gorillas. At the turn of the century, there were hundreds of thousands of chimpanzees living in what are now 25 African nations throughout a more or less unbroken belt of forest from the far west coast of Africa to the eastern shores of Lake Tanganyika. There are still many chimpanzees in the area that was the heartland of their historic range – in the contiguous forests of Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon and Zaïre. There are still vast areas of forest in some of these countries. But for how much longer? Forests and woodlands worldwide are disappearing as a result of commercial logging and the ever-increasing growth of human populations that tend to compete with and to destroy, rather than to live in harmony with, the natural world. When an area of forest is despoiled, the chimpanzees who live there disappear too: the territorial nature of wild chimpanzees ensures that communities squeezed out by habitat destruction cannot easily integrate with others, away from the devastated areas. Chimpanzees have already become extinct in four of the nations where they once lived and their numbers have shrunk alarmingly in many others.