Adventures in the Bone Trade: The Race to Discover Human Ancestors in Ethiopia's Afar Depression
Adventures in the Bone Trade: The Race to Discover Human Ancestors in Ethiopia's Afar Depression by Jon Kalb, published by copernicus
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According to an article later published in Nature, Johanson found the expedition's first hominid fossils that same day, discovering four partial leg bones: two joining at the knee and two upper femurs, or thighbones. He said the finds were made at two adjoining localities, L128 and L129, just west of camp along the drainages of a small stream called Denen Dora, near the base of the Hadar section, thus making the fossils among the oldest at the site. The associated fauna at that level, we then estimated, would make the hominid bones at least 3 million years old, or middle Pliocene. Most significantly, Johanson concluded from their morphology that the hominid had walked upright; given their age, the leg bones thus represented the oldest known evidence of human bipedality. From their similar size and proximity to one another, he guessed that the leg bones came from a single individual. It was an important discovery and cause for great celebration—except that Johanson made no mention of the find to Dennis or me when we returned to the camp that afternoon.
Instead of returning to Denen Dora the next morning to renew surveys of L128 and L129, Johanson took his student, Tom Gray, Dennis, and a few others to renew surveys of a different locality, L116. This was the single richest fossil locality yet found at Hadar, one located in the higher (and therefore younger) part of the stratigraphical section at the north end of Hadar. I had found the locality before leaving for Bati and had shown it to Johanson as a potential dissertation project for Gray in taphonomy, the study of processes that affect the preservation of animal remains, then a hot topic in East African research. It was late in the afternoon of October 31, after the group had moved on from L116, that Johanson told Dennis and me in camp that he had discovered hominid fossils at Denen Dora. He showed us the leg bones, which he retrieved from a small box. At the time, we assumed that he had just found the fossils, and we thought his subdued behavior was odd for someone who had just made a great discovery. He would allow no photographs of the specimens until he had "confirmed they were hominid in London or Nairobi" following the field season, and he even raised the possibility that the fossils "might be baboon." Later, when I looked at the expedition catalog, I found that Johanson had entered the fossils simply as "primate"—not "hominid." Our standing procedure was to catalog fossils to the nearest taxonomic level to which they could be identified. Yet in Lucy, Johanson's book about the Hadar discoveries, he said that after picking up the specimens and examining them, he immediately recognized that they were hominid.
That evening, because it was Halloween, we celebrated the discovery by making popcorn. I was not sure whether Johanson's find was a "trick" or a "treat."
In Lucy, the story continues the next day, when Taieb returned from Camp 270 with Bonnefille and Corvinus. Late that afternoon Johanson led Gray to an Afar stone grave, where they removed a leg bone (a femur) to compare with the fossil leg bones, to be "absolutely sure" that the Denen Dora fossils were hominid. Later, apparently in the secrecy of his tent, Johanson compared the specimens, concluding that this was all the confirmation he needed to ensure the hominid status of the fossils: The Afar leg and the corresponding fossils leg bones were "virtually identical." Whether Taieb was aware of the nocturnal grave robbing I do not know—I seriously doubt it—but until the end of the expedition, I believed that confirmation of the hominid identity of the fossils was to await comparative studies in London or Nairobi.
In retrospect, I gave Johanson the benefit of the doubt in many of his actions, as regards scientific matters, but on this occasion, in the context of his overall behavior, I suspected there was something rotten in Denmark.
The arrival of Corvinus and Bonnefille gave Johanson new opportunities to exercise his leadership skills. Whereas he chose to regard Corvinus as incompetent, he paid special attention to Bonnefille, with whom he still had a personal relationship from their days together in Omo.
I thought Corvinus was very competent, both as a field archeologist and as a geologist, for which she was trained in the rigorous German tradition of prehistory studies. During two field seasons with the expedition, she documented dozens of stone tool localities in the greater Hadar area. Her surveys west of Hadar during the next field season, in the upper Gona River area, resulted in the discovery of artifact-bearing deposits that have since yielded the oldest human artifacts known, 2.5 to 2.6 million years old. In Lucy, Johanson credited the initial discoveries at Gona to others, including himself, failing to recognize Corvinus's pioneering work there, or at Hadar, which she described in two papers published in Nature.
Johanson's particular complaint about Corvinus was her interest in the Acheulean bifaces found on the slopes of the much older deposits. The tools were characteristic of the middle Pleistocene type, about 400,000 to 700,000 years old. He regarded them as "junk." This was not an altogether unjustified criticism, at first glance, because the stone tools were worn and patinated and were found on the surface. But what Johanson did not appreciate was that the stone tools were not quite that worn.
After Corvinus arrived at Hadar, she began carefully to search the higher levels of the site, where she thought the bifaces might have originated. In particular, she looked for their source along the contact of the plateau gravels with the underlying older Hadar strata. Soon she began finding large numbers of handaxes in even better condition than the original finds, although they were still found on the surface. Interestingly, they were not in the higher Hadar levels but at lower elevations closer to the Awash. Although she did not find their source during that field season, the next year (1974) she hit the jackpot. Of all places, it was in the Denen Dora hills, the same general area as Johanson's hominid locality. She found fresh, sharp handaxes and associated flakes and chips raining down from a sand layer within a 10-meter wedge of stream deposits. The sequence unconformably overlay the fossil-rich Pliocene beds and was unconformably overlain by the plateau gravels. The wedge thinned and disappeared toward higher elevations, which explained why Acheulean tools were rare in the upper Hadar levels. Corvinus described the artifacts as probably representing a stone tool factory site situated on the edge of a floodplain. The river had carved into the Pliocene beds during the middle Pleistocene, depositing a fluvial terrace; in the later Pleistocene, rivers fed by intermittent highland storms eroded any overlying strata, leaving the wedge of remnant sediments buried under the gravels.
The contempt that Johanson showed for Corvinus's work on the Acheulean was mild compared with his views on another set of stone tools she found at Denen Dora in 1974. These came from on top of and from within the plateau gravels, which she also described in her Nature papers. She identified these "plateau artifacts" as protobifaces, modified pebbles, choppers, and crude flakes, which she characterized as a "degenerate biface-flake industry." The term degenerate referred to handaxes and other stone tools that were poorly manufactured compared with the more sophisticated Acheulean tools originating beneath the gravels. The quality of tool-making thus appeared to decline from the lower to the upper levels: Well-crafted handaxes and refined flakes beneath the gravels became "proto-handaxes" and "crudely made flakes" within and above the gravels. By analogy, Corvinus compared these disparate technologies with those described by Mary Leakey from the middle and upper beds of Olduvai. There, Acheulean bifaces lay at the same level as stone tools of a more primitive tradition called Developed Oldowan. But at Denen Dora, Corvinus described an Acheulean industry that was overlain by a "pre-Acheulean industry" made by "a somewhat later group of people."
Could this make sense? Yes and no.
Corvinus was simply saying, although in confusing terms, that the later group of stone toolmakers put less effort into their craft than had the earlier group. It is also likely that at least some of the more worn primitive stone tools in the Denen Dora gravels originated from older (genuinely pre-Acheulean) deposits swept up by streams in the later Pleistocene. Pliocene tools from the higher levels of Gona, for instance, could have been eroded and transported by Pleistocene streams to lower levels at Hadar and elsewhere and redeposited with the younger stream gravels.
Overall, Corvinus's work was far more right that wrong. And, as we shall see, she laid the groundwork for archeological discoveries in the Afar of an epic nature. But these were made in 1975, the year after the forces of evil caused her to abandon her pioneering work at Hadar. The last I heard, she was investigating Acheulean sites in the diamond fields of South Africa, but that was years ago.
During the first few weeks of November, Dennis and I continued work on the stratigraphy of Hadar. At one point I took Bonnefille across the Awash to see the stratigraphy along the Meshellu stream. She collected samples of a thin layer of lignite, a very low grade of coal, that I hoped would correlate with a similar layer on the north bank of the Awash, thus linking the stratigraphy on both sides of the river. Her specialty was the study of fossil pollen, called palynology. She was interested in the lignite for the abundance of pollens these deposits often preserve, which are invaluable for identifying paleofloras and reconstructing past environments.
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