Forbidden Archeology: The Hidden History of the Human Race

By the end of his first season at Hadar, Johanson was in trouble. His National Science Foundation grant money, which was supposed to have lasted two years, was almost gone. Johanson worried he would be labeled incompetent. Furthermore, he had not found any of those glamorous hominid fossils. Johanson noted: “I had not exactly promised hominids when I put in my request for funds from the National Science Foundation, but I knew when I wrote up my grant proposal that if I did not include a strong pitch for hominids I would get no money at all; the likelihood of being sent to Ethiopia to collect pig’s teeth was remote” (Johanson and Edey 1981, p. 154).

Despite his financial problems, Johanson continued scouting for fossils. One afternoon, he found the upper portion of a tibia, a long bone between the knee and the ankle. The bone was obviously from some kind of primate. Nearby, Johanson found a distal femur, the lower end of a thighbone. From the way the femur and tibia fit together, Johanson believed he had found the complete knee joint not of some ancient monkey but of a hominid, an ancestor of modern humans. The deposits yielding the fossils were over 3 million years old, making this one of the oldest hominid finds ever made (Johanson and Edey 1981, p. 155).

Johanson felt that “his whole reason for being there, the core of his own most secret motivation” had been justified (Johanson and Edey 1981, p. 159).

In scientific publications that followed, Johanson reported that the Hadar knee (AL 129) was 4 million years old and belonged to a primitive australopithecine with a fully human bipedal gait (Johanson and Coppens 1976).

In support of his contention that AL 129 was characteristically human in structure, Johanson cited the presence of a valgus knee. A valgus knee is one in which the femur slants outward from the knee to the hip, at an angle from the lower part of the leg. Humans have a valgus knee. In African apes, the femur rises straight from the knee to the hip, in line with the lower part of the leg.

At 15 degrees from vertical, the angle of valgus in AL 129 was, however, much higher than the adult human mean of 9 degrees (Stern and Susman 1983, p. 296). This suggests that the locomotor behavior of AL 129, even if terrestrial and bipedal, might have been quite different from that of adult humans. In human children 3 to 4 years of age, the degree of valgus is as great as that in the AL 129 femur (Stern and Susman 1983, p. 296). The high angle is reflected in a child’s knock-kneed stance and somewhat awkward gait. The creature with the AL 129 knee may have stood and walked in similar fashion.

Furthermore, Jack T. Stern and Randall L. Susman of the State University of New York at Stony Brook noted that the presence of a valgus knee is not exclusively associated with terrestrial bipeds. Orangutans and spider monkeys, both of which spend most of their time in trees, have valgus knees (Stern and Susman 1983, p. 298).

As we have seen (Section 11.8.5), C. E. Oxnard and others have found that the functional morphology of the australopithecines has orangutan affinities. The valgus knee in AL 129 could thus represent yet another orangutanlike feature in Australopithecus. The totality of orangutan resemblances suggests arboreal behavior in Australopithecus, which Oxnard, Zuckerman, and the Leakeys did not consider ancestral to modern humans.

In his account of the discovery of AL 129, Johanson did not mention that primates other than humans have a valgus knee. It seems there are two possible explanations why he did not. Either he was unaware that orangutans and spider monkeys have the same outward slanting femur as humans, or he was aware of this but deliberately neglected to mention it because it would have complicated the case he was trying to make.

According to Brigitte Tardieu (1979), key features of the AL 129 femur and tibia, other than the degree of valgus, fell outside the modern human range. “These traits . . . led her to conclude that despite clear adaptations to terrestrial bipedality in the small Hadar hominid, the precise mechanism of this bipedality could not be specified and that it must have occurred along with some degree of arboreal behavior,” said Stern and Susman (1983, p. 298).

Stern and Susman (1983, pp. 298–299) themselves concluded: “Since, aside from the degree of valgus, the knee of the small Hadar hominid possesses no modern trait to a pronounced degree, and since many of these traits may not serve to specify the precise nature of the bipedality that was practiced, we must agree with Tardieu that the overall structure of the knee is compatible with a significant degree of arboreal locomotion.”