Chapter 10 Hominid Origins

1. Chapter 10 Hominid Origins • The Bipedal Adaptation • Early Hominids in the Plio-Pleistocene • The East African Rift Valley • The Earliest East African Hominids • Australopithecus from East Africa • Early Homo

2. Chapter 10 Hominid Origins • Central Africa • South African Sites • Interpretations: What Does It All Mean • Continuing Uncertainties • Putting It All Together • Interpreting the Interpretations

3. The Bipedal Adaptation • Efficient bipedalism among primates is found only among hominids. • All the major structural changes required for bipedalism are seen in early hominids from East and South Africa. • Some researchers believe these early humans also spent considerable time in the trees.

4. The East African Rift Valley Valley associated with mountain building, faulting and volcanic activity over several million years. • Early sediments were thrown to the surface where they were discovered. • Volanic sediments make it possible to date the sites. • Dating provides information about the chronology of early human evolution.

5. Earliest Traces of East African Hominids • Tugen Hills - Discovered in 2000, the form has been dubbed “Millennium Man”. • Middle Awash - Early fossils first described in 2001. Dating places the fossils in the late Miocene.

6. Ardipithecus from Aramis • Dated at 4.4 million years old, oldest collection of hominids discovered. • The remains provide anatomical evidence of bipedalism. • Excavators suggested they be assigned to a new genus and species, Ardipithecus ramidus.

7. Astralopithecus From East Africa • Dating from 4.2 to 1.4 m.y.a. these are included in the genus Australopithecus. • Fossilized hominid footprints were found in an ancient volcanic bed. • Despite agreement that they were bipedal, some researchers feel they were not bipedal in the same way as modern humans.

8. Australopithecus afarensisfrom Laetoli and Hadar • Several hundred specimens representing 60 to 100 individuals have been removed. • More primitive than other australopithecine fossils from South or East Africa: • Teeth - canines are large and pointed • Small brain

9. Early Homo • The earliest appearance of Homo may be as ancient as the robust australopithecines. • Leakey named these specimens Homo habilis ("handy man") • H. habilis differs from Australopithecus in cranial cavity and dental proportions.

10. Steps in Interpreting Fossil Sites • Selecting and surveying sites. • Excavating and recovering fossil hominids. • Designating individual finds with specimen numbers for clear reference. • Cleaning, preparing, studying and describing fossils.

11. Steps in Interpreting Fossil Sites • Comparing with other fossil material. • Comparing fossil variation with known ranges of variation. • Assigning taxonomic names to fossil material.

12. Subsets of Fossil Data • Set I. Basal hominids (6.0-4.4 m.y.a.) • Set II. Early primitive Australopithecus (4.2-3.0 m.y.a.) • Set III. Later, more derived Australopithecus (2.5-1.0 m.y.a.) • Set IV Early Homo (2.4 -1.8 m.y.a.)