Search

Although many studies relating stature to foot length have been carried out, the relationship between foot size and body mass remains poorly understood. Here we investigate this relationship in 193 adult and 50 juvenile habitually unshod/minimally shod individuals from five different populations—Machiguenga, Daasanach, Pume, Hadzabe, and Samoans—varying greatly in body size and shape. Body mass is highly correlated with foot size, and can be predicted from foot area (maximum length × breadth) in the combined sample with an average error of about 10%. However, comparisons among populations indicate that body shape, as represented by the body mass index (BMI), has a significant effect on foot size proportions, with higher BMI samples exhibiting relatively smaller feet. Thus, we also derive equations for estimating body mass from both foot size and BMI, with BMI in footprint samples taken as an average value for a taxon or population, estimated independently from skeletal remains. Techniques are also developed for estimating body mass in juveniles, who have relatively larger feet than adults, and for converting between foot and footprint size. Sample applications are given for five Pliocene through Holocene hominin footprint samples from Laetoli (Australopithecus afarensis), Ileret (probable Homo erectus), Happisburgh (possible Homo antecessor), Le Rozel (archaic Homo sapiens), and Barcin Hoyuk (H. sapiens). Body mass estimates for Homo footprint samples appear reasonable when compared to skeletal estimates for related samples. However, estimates for the Laetoli footprint sample using the new formulae appear to be too high when compared to skeletal estimates for A. afarensis. Based on the proportions of A.L. 288-1, this is apparently a result of relatively large feet in this taxon. A different method using a ratio between body mass and foot area in A.L. 288-1 provides estimates more concordant with skeletal estimates and should be used for A. afarensis.

In 1978 and 1979 at Laetoli, Northern, Tanzania, Mary D. Leakey and assistants excavated the most compelling evidence for the existence of bipedalism in Pliocene (3.5 Ma) hominids. They have stimulated controversy over the extent to which the three individuals had feet and gaits that are like those of humans versus having ape-like features and gaits. A short trail of bipedal tracks discovered in 1977 at Laetoli site A are probably not those of a hominid and more closely resemble the prints of bears. One of the original researchers on the Laetoli prints claimed that she could identify individual modern humans from their footprints, partial footprints and shoe prints because each individual has distinctive foot morphology on a par with the individuality of fingerprints. Courts of law should not have allowed her unproven (and now discredited) method to be used forensically prior to thorough review by scientific peers.

I selectively and critically review the state of knowledge about human evolution and the place of humans vis-a-vis living apes, with emphasis on bipedal posture and locomotion, expansion of the brain and associated cognitive capacities, speech, tool behavior, culture, and society. I end with a personal perspective on God and Heaven.

Electromyographic studies on brachial muscles in a gorilla indicate that its elbow joint may be especially adapted for knuckle-walking and suspensory behavior. A close-packed positioning mechanism that minimizes muscular effort during full extension of the elbow joint is indicated by remarkably low levels of EMG in the brachial muscles, particularly during knuckle-walking and suspensory behavior on a trapeze. Extension of the elbow joint is facilitated by reduction of the olecranon process of the ulna, a feature that is attributable initially to aspects of an arboreal heritage in protogorilla and secondarily to selection for efficient knuckle-walking. Although notable differences exist between gorilla and man in known activity of the brachial muscles, the two species are strikingly similar in many basic features. Available evidence suggests that they share a common heritage of arboreal adaptation, including vertical climbing, hauling, hoisting, and suspensory behavior, perhaps more recently than some authors would care to admit. Knuckle-walking probably played an inconsequential role in the protohominid career. Selection for tool use, expecially involving powerful and rapid extension of the elbow joint, is the most reasonable explanation for the relatively more protuberant olecranon process in man by comparison with apes.

Data on footprints and gait of 54 Hadzabe, 6-70 years of age expand understanding of pedal morphology of unshod people and assist the development of ideas about the evolution of hominid bipedality and upright posture. Contrary to published data on gaits and pedal morphology of unshod populations, Hadzabe (also known as Hadza) from northern Tanzania exhibit values of stride length, relative stride length, and walking speeds that exceed those of rural and small-town populations. In all observable plantar features, including foot indices, an interdigital space between the hallux and second toe, fanning of the foot anteriorly, and foot angles (in-toeing and out-toeing), Hadzabe feet are comparable with those of never-shod Machiguengas in Peru ´ . On average, Hadzabe hallucal gaps and ball widths are narrower than those of Machiguengas and other unshod short people. Hadzabe feet are also charac- terized by valgus halluces versus the varus halluces of never-shod Machiguen- gas and certain West Africans. Although characterized by a valgus toe, Had- zabe hallucal angles, which do not exceed 208, are lower than those of Northern Hemispheric urbanites and shod rural populations of the Southern and North- ern Hemispheres. Hadzabe also exhibit less medial and lateral rotation of the hip joint than Machiguengas do. The heel and the longitudinal arch impressions of the Hadzabe footprints closely resemble those of the Laetoli bipeds in the manner of weight distribution during locomotion. The striking similarity of footprint impressions, especially the heel and the longitudinal arch, between Hadzabe and Laetoli hominid footprints clearly imply that the pedal features of the Laetoli printmakers are remarkably humanoid. Am. J. Hum. Biol. 9:303-321, 1997. q 1997 Wiley-Liss, Inc.

When walking at normal and fast speeds, humans swing their upper limbs in alternation, each upper limb swinging in phase with the contralateral lower limb. However, at slow and very slow speeds, the upper limbs swing forward and back in unison, at twice the stride frequency of the lower limbs. The change from "single swinging" (in alternation) to "double swinging" (in unison) occurs consistently at a certain stride frequency for agiven individual, though different individuals may change at different stride frequencies. To explain this change in the way we use our upper limbs and individual variations in the occurrence of the change, the upper limb is modelled as a compound pendulum. Based on the kinematic properties of pendulums, we hypothesize that the stride frequency at which the change from "single swinging" to "double swinging" occurs will be at or slightly below the natural pendular frequency (NPF) of the upper limbs. Twenty-seven subjects were measured and then filmed while walking at various speeds. The mathematically derived NPF of each subject's upper limbs was compared to the stride frequency at which the subject changed from "single swinging" to "double swinging." The results of the study conform very closely to the hypothesis, even when the NPF is artificially altered by adding weights to the subjects' hands. These results indicate that the pendulum model of the upper limb will be useful in further investigations of the function of the upper limbs in human walking.

We obtained electromyographic recordings from the supinator, biceps brachii, pronator quadratus, and pronator teres muscles of a chimpanzee and a gorilla and from the supinator, pronator quadratus, and biceps brachii muscles of an orangutan as they stood and walked quadrupedally on horizontal and inclined surfaces, engaged in suspensory behavior, reached overhead, and manipulated a variety of foods and artifacts. In Pan troglodytes and Pangorilla, as in Homo sapiens, the supinator muscle is the prime supinator, with the biceps brachii muscle serving to augment speed or force of supination. Primacy of the pronator quadratus muscle over the pronator teres muscle during pronation is less clear in the African apes than in humans. Possibly, pongid radial curvature or forelimb elongation or both factors are related to the somewhat different patterns of activity that we observed in the pronator muscles of Pan versus those reported for Homo sapiens. In Pongo pygmaeus, as in P. troglodytes and P. gorilla, the pronator quadratus muscle acts as a pronator and the supinator muscle acts to supinate the hand at the radioulnar joints. The biceps brachii muscle isactive at low levels as the organgutan supinates its hand with the elbow flexed.

The probable misfit between feet, particularly toes II–V, of 3.0-million-year-oldAustralopithecus afarensis from Hadar, Ethiopia, and the 3.5-million-year-old hominid footprints at Site G, Laetoli, Tanzania, casts doubt thatA. Afarensis made the Laetoli trails. We suggest that another species ofAustralopithecus or an anonymous genus of the Hominidae, with remarkably humanoid feet, walked at Laetoli. It would be imprudent to declare thatHomo was present at Laetoli 3.5 million years ago (my) because there is no evidence of brain expansion, advanced tool manufacture, or other non-locomotor hallmarks of the human condition at Site G.

In addition to showing that bipedalism notably preceded the appearance of stone tools and ballooning brains in the paleontological record, the 3.5 million-year-old footprint trails at Laetoli Site G, Tanzania, provide an unprecedented opportunity to discern the pedal morphology and gaits of Pliocene Hominidae. Although plantar prints had been collected for unshod people, studies of gait had been performed only on subjects who habitually wore shoes. Initial inferences about the Laetoli printmakers seemed to be limited by this comparative data. Therefore, we expanded the base for interpreting fossil hominid footprints with a study of > 70 never shod Machiguenga in Cuzco Department, Peru. In all discernible plantar features, including foot indices, an interdigital space between the hallux and second toe, anterior “fanning” of the foot, a medial longitudinal arch, and overall morphology, the Laetoli G impressions are matched by Machiguenga footprints. No features of gait, viz. foot angles, stride widths, or step lengths, demonstrate that the Laetoli creatures were naturally less efficient bipeds than we are. On average, Machiguenga stride widths are narrower than those of Laetoli G-3 and shod Yankees but only slightly narrower than those of Laetoli G-1: this may be ascribed to custom, to differences in the substrates upon which they walked, or to both factors. The Laetoli hominids progressed slowly by modern human standards, but their inferred paces are within the range of walking Homo sapiens.

We do not know how many genes mark levels of separation among apes and people; we cannot discretely recognize their phenotypic expressions; and they probably are not of equal value to sort apes from people and apes from other apes. Until the developmental and functional biology of our genomes are much better understood (Naylor and Brown, 1998; Hamdi et al., 1999), I recommend a measure of dispassionate conservatism among colleagues who would resolve puzzles regarding our bushy phylogeny and the largely uncharted lineages of extant apes. Estimates of the number of genes in the human genome and presumably also in those of chimpanzees and other great apes range between 30,000 and 150,000 (Venter et al., 2001; Claverie, 2001; Cohen, 1997; Fields et al., 1994; Hattori et al., 2000; O’Brien et al., 1999; Reeves, 2000). Accordingly, if humans and chimpanzees share 98.4% of their genes, between 480 and 2400 of them could be different. However, if Britten (2002) is correct that the overall difference is 5%, then there are 1500–7500 different genes. And if the human-chimpanzee difference in DNA is has been underestimated “possibly by more than a factor of 2” (Britten et al., 2003, p. 4664), the difference could be more than 3000– 15,000 genes. Currently, we are poorly equipped to state how many of these genes, in what combinations, and how interacting with the several preand postpartum environments that shape organisms throughout their careers might be determinate in gauging the distances among them following furcation of the human lineage, whether it be from a dichotomy of humans and chimpanzee/bonobos (Bailey et al., 1992; Diamond, 1988; Horai et al., 1995; Ruvolo, 1996; Goodman et al., 1998), a tritomy of African apes and humans (Marks, 1995; Deinard and Kidd, 1999; Samollow et al., 1996; Rogers, 1994), or a polytomy that also included extinct collateral lineages for which there is no genetic material (Corruccini, 1994).

s of the International Symposium Evolution of Middle-to-Late Miocene Hominoids in Africa, July 11-13, 1999, H. Ishida, ed., Takaragaike, Kyoto, Japan. Simons, E.L., 1963, Some fallacies in the study of hominid phylogeny, Science. 141: 879-889. —— 1969, Late Miocene hominid from Fort Ternan, Kenya, Nature. 221: 448-451. Simons, E.L., and Fleagle, J.G., 1973, The history of extinct gibbon-like primates, in: Gibbon and Siamang,vol. 2, D.M. Rumbaugh, ed., Karger, Basel, pp.121-148. Simons, E.L., and Pilbeam, D.R., 1965, Preliminary revision of the Dryopithecinae (Pongidae, Anthropoidea), Folia Primatologica. 3: 81-152. Walker, A., 1969, Lower Miocene fossils from Mount Elgon, Uganda, Nature. 223: 591-593. —— 1992, Louis Leakey, John Napier and the history of Proconsul, Journal of Human Evolution. 22: 245254. Walker, A.C., and Pickford, M., 1983, New postcranial fossils of Proconsul africanus and Proconsul nyanzae, in: New Interpretations of Ape and Human Ancestry, R.L. Ciochon and R.S. Corruccini, eds., Plenum, New York, pp. 325-351. Walker, A.C., and Rose, M.D., 1968, Fossil hominoid vertebra from the Miocene of Uganda, Nature. 217: 980

Hidemi Ishida: 40 Years of Footprints in Japanese Primatology and Paleoanthropology.- Hidemi Ishida: 40 Years of Footprints in Japanese Primatology and Paleoanthropology.- Fossil Hominoids and Paleoenvironments.- Seven Decades of East African Miocene Anthropoid Studies.- Evolution of the Vertebral Column in Miocene Hominoids and Plio-Pleistocene Hominids.- Terrestriality in a Middle Miocene Context: Victoriapithecus from Maboko, Kenya.- Late Cenozoic Mammalian Biostratigraphy And Faunal Change.- The Ages and Geological Backgrounds of Miocene Hominoids Nacholapithecus, Samburupithecus, and Orrorin from Kenya.- Functional Morphology.- Patterns of Vertical Climbing in Primates.- Functional Morphology of the Midcarpal Joint in Knuckle-Walkers and Terrestrial Quadrupeds.- Morphological Adaptation of Rat Femora to Different Mechanical Environments.- A Hallmark of Humankind: The Gluteus Maximus Muscle.- Primates Trained for Bipedal Locomotion as a Model for Studying the Evolution of Bipedal Locomotion.- Locomotor Energetics in Nonhuman Primates.- Computer Simulation of Bipedal Locomotion.- Theoretical Approaches.- Paleoenvironments, Paleoecology, Adaptations, and the Origins of Bipedalism in Hominidae.- Arboreal Origin of Bipedalism.- Neontological Perspectives on East African Middle and Late Miocene Anthropoidea.- The Prehominid Locomotion Reflected: Energetics, Muscles, and Generalized Bipeds.- Evolution of the Social Structure of Hominoids.- Are Human Beings Apes, or are Apes People too?.- Current Thoughts on Terrestrialization in African Apes and the Origin of Human Bipedalism.