A publication of the Archaeological Institute of America
As a child, I attended segregated schools, first a convent and then a boarding school. My early education was designed to instill a sense of security, stability, and lack of change. We were taught literature, history, the Christian religion, art, and music, with a little math thrown in. Science was not considered relevant for a girl's future. As an adult, and having overcome the limitations of my schooling by attending a technical college and then a university, I have found that the essence of life is its instability, insecurity, and constant change. And, importantly, that science is the basis of much of life as we know it today. My career has taken me to sites in the Turkana Basin in northern Kenya, which range in date from 27 million years ago to the present, and my research, which has focused on the evolution of a variety of mammalian groups over the past eight million years, has illustrated an array of changing faunas, climates, and environments. Evolutionary innovations have led to some astonishing adaptations: the elephant's trunk, the giraffe's neck, and the ruminant's stomach. But none approaches the development of the human brain. Its expansion is the most provocative and least understood of all, with consequences arguably more profound and far-reaching than for any other mammalian species.
My first experience with discoveries that revealed the brain's evolutionary expansion took place in 1972 with the thrilling recovery of a fossil skull at East Turkana, where I was taking part in a field expedition led by my husband, Richard Leakey. The initial find was just a few fragments of cranium which we began to reassemble. As members of the field team collected more pieces through a massive sieving operation, I had the privilege of reconstructing the most exciting three-dimensional jigsaw puzzle I have ever attempted. As each small fragment found its place, the braincase gradually came together. The brain was surprisingly large, although a lot smaller than ours. Using the camp rain gauge and some beach sand we made a rough estimate of the cranial capacity, which came close to the 775 cc that more conventional estimates later proved it to be. Gradually, too, the face took shape and was unexpectedly large compared to the cranium. This specimen--we eventually called it simply ER 1470 after its inventory number--is an early example of our own genus Homo and represents a species now known as H. rudolfensis. It is 1.9 million years old and is equivalent in age to some of the earliest known stone tools. In 1975, I helped Richard excavate another skull. Over three days, he patiently extracted this incredibly fragile fossil from the grip of a matrix of grass roots that had penetrated the delicate bone. When the specimen was finally excavated, it was seen to have an even larger cranial vault and a face proportionately much smaller than that of 1470. This second skull was H. erectus (sometimes named H. ergaster to distinguish it from the Asian species). It has a cranial capacity of 848 cc and is 1.8 million years old, approximately the same age as H. erectus specimens from Java which represent the earliest evidence for hominids outside Africa. In 1983, another skull was discovered buried in the sand on the western shore of the lake. This skull has a braincase comparable in size to that of modern humans and a very reduced face. It is only a few hundred thousand years old and is Kenya's only specimen of an archaic H. sapiens. More recently members of my own expedition at Kanapoi, southwest of Lake Turkana, made some of the most exciting discoveries of my career, fragments of the earliest known australopithecine, which we named Australopithecus anamensis. At this early date, no expansion of the braincase is evident, and this 4.1-million-year-old bipedal human ancestor most likely had a brain that was no larger than that of an average modern African ape. This series of fossils, dating from more than 4 million to only a few hundred thousand years ago, combined with discoveries others have made, illustrates the immensely long evolutionary history of our family. It demonstrates too that brain enlargement was the latest in a series of significant adaptations, and one that is largely associated with the emergence of H. erectus and evolution of the earliest H. sapiens.
Parallel to these exciting discoveries in the field, I have experienced the consequences of this extraordinary evolutionary adaptation. In 1967, I was analyzing data for my Ph.D., enthusiastically using the latest technological invention of the day, a machine which, for the first time, performed complex statistical analyses impossible on a slide rule. The newly invented mainframe computer, which took up a large room and required hours of programming to iron out frequent bugs, was fed miles of plain paper tape and disgorged an equal length of tape punched with tiny holes. Not so long after this, in the 1970s, I acquired my own desktop, an immense improvement on the mainframe, which allowed me not only to dispense with my typewriter, but also to carry out extremely complex calculations. In the 1980s I was thrilled to purchase my first laptop with an eight megabyte memory, and last year I acquired a Macintosh G3 with 160 megabytes. I can now store all my data on one machine, carry out complex analyses, and print endless copies of a manuscript at the push of a button. The computer, together with advances in other technologies, such as CT tomography, scanning electron microscopy, digitized measurements, and photography, has revolutionized the way we study the past.
For more than half a century I have observed and marveled at the contrasts between the slow morphological evolution shown in the fossil record and the accelerating technological evolution of the twentieth century. Studies of the past put the present into perspective. As natural selection has shaped the human form, "commercial selection" in large part shapes technological advance. Recent technological developments have led to an unprecedented global population explosion with the resulting rapid deterioration of global resources. This population explosion has contributed in large part to the rapid acceleration of technological development. With the increasing adoption of capitalist economies throughout the world, more and more inventors, designers, and producers are making better and better products for more and more people to buy. As a result research today is focused on satisfying economic needs and funding for research that has no immediate commercial relevance is becoming increasingly hard to find. In the past 50 years, as women have proved their value as significant contributors in scientific disciplines, we have become accepted and recognized as creditable scientists. Perhaps in the next 50 years, scientific inquiry, for reasons that are not only economic, will be more widely recognized as valid. With the increasing pace of technological advance it is sobering and instructive to recall from where we came.
MEAVE LEAKY is head of the Division of Palaeontology at the National Museum of Kenya in Nairobi.