FIGURE 2.3 Replica of a 1.8-Ma Paranthropus boisei cranium found by Mary Leakey in 1959 at Olduvai Gorge, shown with a replica of a 1.2-Ma mandible of the same species from Peninj, Tanzania. SOURCE: Image courtesy Human Origins Program, Smithsonian Institution.

FIGURE 2.3 Replica of a 1.8-Ma Paranthropus boisei cranium found by Mary Leakey in 1959 at Olduvai Gorge, shown with a replica of a 1.2-Ma mandible of the same species from Peninj, Tanzania. SOURCE: Image courtesy Human Origins Program, Smithsonian Institution.

White et al., 2006), and gradual change from A. anamensis to A. afarensis has been documented (Kimbel et al., 2006). Although their food processing anatomy differed, this lineage of bipedal hominins had brain to body mass ratios that are about the same as those of extant great apes. Their limb proportions differed from those of both chimpanzees and humans, and their pelvic and hip structure suggests a somewhat different mode of bipedal locomotion from that of our own genus Homo. Confirmation of bipedal locomotion comes from fossilized footprints at Laetoli in Tanzania (Leakey and Hay, 1979). Australopithecus species exhibited differences in body size and canine dimensions between males and females (i.e., sexual dimorphism). A. afarensis is well known from cranial and postcranial parts and includes the famous partial skeleton ”Lucy” from ~3.2 Ma. A related hominin—A. africanus—is well known but poorly dated from South African cave sites. One individual is of a nearly complete skeleton (Clarke, 1998; 2002), which promises to deliver much important information about this southern form. The youngest member of this genus, A. garhi, was recovered from 2.5-Ma deposits in Ethiopia (Asfaw et al., 1999), but little is known about it except that the trend throughout this lineage to larger jaws and teeth continued.

Extremely large-toothed hominins appear in the record around 2.7 Ma. These are sometimes placed in Australopithecus but are more commonly assigned to their own genus, Paranthropus (Figure 2.3). These “robust” creatures, so-called



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement