Typically, Day (1985, p. 125) concluded: “There is now no serious dispute as to the upright stance and bipedal gait of the australopithecines.”
But what proof did he have that an australopithecine made the Laetoli footprints? There is no reason to rule out the possibility that some unknown creature, perhaps very much like modern Homo sapiens, was the cause of them.
R. H. Tuttle (1981, p. 91) stated: “The shapes of the prints are indistinguishable from those of striding, habitually barefoot humans.”
Tuttle (1987, p. 517) concluded: “Strictly on the basis of the morphology of the G prints, their makers could be classified as Homo sp. because they are so similar to those of Homo sapiens, but their early date would probably deter many palaeoanthropologists from accepting this assignment. I suspect that if the prints were undated, or if they had been given younger dates, most experts would probably accept them as having been made by Homo.” Tuttle (1987, p. 517) also stated: “They are like small barefoot Homo sapiens.”
Furthermore, Tuttle held that the A. afarensis foot could not have made the prints. Of the AL 333-115 foot, he said: “The shafts of the proximal phalanges are markedly curved ventrally. This feature is characteristic of certain full-time and part-time arboreal apes and monkeys. . . . It is difficult to imagine a foot with such markedly curved phalanges fitting neatly into the footprints at Laetoli” (Tuttle 1981, p. 91). The same would be true of any australopithecine foot.
Stern and Susman (1983) objected to this. Convinced that the apelike A. afarensis foot had made the Laetoli footprints, they proposed that the ancient hominids had walked across the volcanic ash with their long toes curled under their feet, as chimpanzees have sometimes been observed to do. Curled-under toes would explain why the A. afarensis footprints at Laetoli so much resembled those made by the relatively short-toed human foot.
Could an australopithecine walking with curled toes have made the humanlike prints? Tuttle (1985) found this extremely unlikely. If the Laetoli hominid had long toes, then, said Tuttle, one would expect to find two patterns of toe impressions—long extended toes and short curled toes, with extra-deep knuckle marks. Tuttle (1985, p. 132) observed: “Neither pattern exists at Laetoli G so we can infer that their lateral toes were quite short.” This meant the long-toed afarensis foot could not have made the prints.
Even Tim White, who believed Australopithecus afarensis made the footprints, stated: “The Stern and Susman (1983) model of toe curling ‘as in the chimpanzee’ predicts substantial variation in lateral toe lengths seen on the Laetoli prints. This prediction is not borne out by the fossil prints” (White and Suwa 1987, p. 495).
Stern and Susman did in fact claim that a few of the Laetoli footprints gave signs of toes longer than in humans. Tuttle (1985, p. 132) admitted that “the right foot of G-1 sometimes left peculiar marks distal to the toe tips.” To Stern and Susman, the marks forward of the “toe tips” represented the actual toe tips of uncurled toes. But Tuttle had another explanation for the marks. He wrote: “These are best explained by . . . the tendency for G-1 to drag its foot on lift off probably due to pathology of the lower limb” (Tuttle 1985, p. 132). The fact that the peculiar markings appeared only on one foot of one individual, and then only sometimes, lends support to Tuttle’s explanation.
Stern and Susman (1983) also suggested that the Laetoli prints did not have a deep rounded impression at the base of the big toe, representing the ball of the foot in humans. They regarded this as evidence that the foot that made the prints was not human. But Tuttle (1985, p. 132) observed that “humans commonly leave prints devoid of these features as may be seen in prints on the beach.” And, as we have seen, Robbins (1987, p. 501) said the prints she studied did have a “humanlike” ball region.
Directly challenging Johanson, White, Latimer, and Lovejoy, who asserted Australopithecus afarensis made the Laetoli prints, Tuttle (1985, p. 130) said: “Because of digital curvature and elongation and other skeletal features that evidence aboreal habits . . . it is unlikely that Australopithecus afarensis from Hadar, Ethiopia, could make footprints like those at Laetoli.” Such statements have provoked elaborate counterattacks from Johanson and his followers, who have continued to promote the idea that A. afarensis could have made the tracks.
Tim White, for example, published a study (White and Suwa 1987) of the Laetoli prints in which he disputed Tuttle’s contention that their maker was a hominid more advanced than A. afarensis.
White asserted: “there is not a single shred of evidence among the 26 hominid individuals in the collection of over 5,000 vertebrate remains from Laetoli that would suggest the presence of a more advanced Pliocene hominid at this site” ( White and Suwa 1987, p. 496). But, as we have seen in our review of African hominid fossils, there are in fact a few “shreds” of evidence for the presence of sapiens-like creatures in the Pliocene, some not far from Laetoli. Also, it is well known that human skeletal remains are quite rare, even at sites where there are other unmistakable signs of a human presence.
Like Tuttle, White rejected the curled-toe hypothesis of Stern and Susman. Instead, White tried to fit the foot of A. afarensis to the Laetoli prints. This was very difficult because no complete foot skeleton of A. afarensis had been found at the Hadar site. A partial foot skeleton, however, had been recovered. This was the AL 333-115 foot skeleton, which included only bones from the front part of the foot—phalanges and metatarsal heads.
According to White, the best tracks at Laetoli were in the G-1 trail, representing the smallest of the three individuals of the G group. Even White admitted that the phalanges of AL 333-115 were “obviously incompatible with the G-1 tracks” (White and Suwa 1987, p. 497). Stern and Susman, and Tuttle, found them incompatible with any of the tracks. White, however, pointed out that the AL 333-115 individual represented one of the larger, presumably male, members of the First Family group and proposed that the foot of Lucy, one of the smaller, female individuals, might have fitted the G-1 Laetoli prints.
But the only bones recovered from Lucy’s foot were an ankle bone and two toe bones. White therefore decided to use a partial Homo habilis foot skeleton (OH 8) from Olduvai Gorge to reconstruct the rear part of Lucy’s foot. White reduced the OH 8 foot by 10 percent to bring it down to the size of Lucy’s ankle bone (talus). He then scaled the large AL 333-115 toes bones down to the size of Lucy’s few toe bones, and used them to make up the rest of the foot ( White and Suwa 1987, p. 502). According to White, this speculatively reconstructed foot matched the prints.
White predicted that “the discovery of a complete foot skeleton at Hadar or Laetoli will conform in its basic proportions with the reconstruction described in this paper” ( White and Suwa 1987, p. 512). But this prediction remains to be fulfilled. It is interesting that the most complete afarensis foot skeleton now available (AL 333-115) definitely does not fit any of the prints.