Biological Anthropology The Early Hominids

Hominid Species Ardipithecus ramidus Homo habilis Homo erectus Australopithecus afarensis Australopithecus africanus Australopithecus boisei Australopithecus robustus Homo habilis Homo erectus Homo sapiens

Ardipithecus ramidus A revolutionary find Why “revolutionary”? Let’s see what we know before her…

Australopithecus afarensis 1973 – “Johanson’s knee” First suggestion of bipedalism

Figure 11.13 The knees of A. afarensis are more like the knees of modern humans than the knees of chimpanzees. Consider the lower end of the femur, where it forms one side of the knee joint. In chimpanzees, this joint forms a right angle with the long axis of the femur. In humans and australopithecines, the knee joint forms an oblique angle, causing the femur to slant inward toward the centerline of the body. This slant causes the knee to be carried closer to the body’s centerline, which increases the efficiency of bipedal walking.

Australopithecus afarensis 1974 – “Lucy” 47 out of 207 bones

Australopithecus afarensis 1975 – “First Family” Over 200 fragments from at least 13 individuals

Australopithecus afarensis 1978 – Laetoli footprints 3.6 my BP (K/Ar) Clear bipedalism Divergent big toe

Australopithecus afarensis Fully bipedal, but… Arms longer than legs Divergent big toe (?) 3.5 – 4.0 ft tall

Figure 11.08 Here, Lucy’s skeleton stands beside the skeleton of a modern human female. The parts of the skeleton that have been discovered are shaded. Lucy was shorter than modern females and had relatively long arms and a relatively small brain.

Figure 06.06

Australopithecus afarensis Cranial capacity: 375-425 cc

Australopithecus afarensis Rounded dental arcade (not parabolic) app. 33% have large canine with diastema Simian shelf present

Figure 11.10a The teeth and jaws of A. afarensis have several features that are intermediate between those of apes and modern humans. (a) The dental arcade is less U-shaped than in chimpanzees, but less parabolic than in modern humans.

Australopithecus afarensis Ca. 4-3 my BP Found only in East Africa No known culture

Australopithecus africanus First find made in 1924 by quarryman M. de Bruyn Cleaned and identified by Raymond Dart

Australopithecus africanus Dental evidence indicated a juvenile age “Taung child”

Australopithecus africanus Finds in Southern and Eastern Africa Dates between app. 3.0-2.0 my BP

A. africanus: bipedalism Full biped Pelvis smaller & upright Parallel toes Developed arch in foot

A. africanus: dentition No large canines No diastema Simian shelf V-shape jaw

A. africanus: cranial capacity 400 – 600 cc

Osteodontokeratic culture osteo = bone donto = teeth keratic = hair, horn Postulated by Raymond Dart as early culture of Australopithecus africanus May be the culture of all Australopithecus species

Australopithecus boisei Australopithecus robustus Two very different types of hominids

Where were they found? boisei East Africa (Olduvai!) robustus South Africa

What are their dates? boisei ca. 2.5 – 1.0 my BP robustus

Cranial capacity boisei mean ca. 510 cc robustus mean ca. 510 cc

Bipedalism Human-like bipedalism Smaller in stature

dentition Huge jaw Small incisors & canines Large premolars & molars Parabolic dental arcade Simian shelf

Chewing apparatus Sagittal crest No diastema

“Dietary Hypothesis” suggests two groups Gracile A. afarensis A. africanus Robust A. boisei A. robustus

Dietary Hypothesis Graciles Omnivorous diet Robusts High fiber diet

Figure 05.34a

“Ardi” Ardipithecus ramidus a 4.4 million year old relative?

Found in Eastern Africa First fossils discovered in 1992 Includes a partial skeleton And remains of at least 35 other individuals

An unexpected mix of traits…

Ardipithecus locomotion hands and arms indicate she could climb like a chimp, but walked on her palms (not knuckles) Chimp skeleton A. afarensis skeleton rigid feet are more like an Old World monkey’s than an apes Ardi legs and pelvis indicate that she could move on two legs like a biped

Ardipithecus cranial capacity 300 – 350 cc reconstruction based on CT scans of fossil fragments

Ardipithecus dentition Modern human Modern chimp Ardi’s canines are blunt – like a humans A move away from multi-male, multi-female mating patterns?

Ardipithecus dentition Modern human Modern chimp The wear patterns and isotope analysis of teeth suggest a varied vegetarian diet

Why is Ardi so “revolutionary”? Our earliest ancestor may not have looked like a modern chimp Ardi undermines the “savanna hypothesis”