Orrorin tugenensisTimespan: 6.2 – 5.8 mya

Region: East Africa (Kenya)

Specimens: 13 specimens, >5 individuals

Discovered: Senut 2001

Holotype: BAR 1000'00

Lineage: Unknown

Environment: Open woodland

Diet: Unknown

Speculation/theories: • Claim as earliest evidence for bipedalism• Claim more “humanlike” than australopithecines, may be direct ancestor of Homo w/

australopithecines only a side-branch• Upper-limb morhology suggests adaptation to climb but lower limb morphology

suggest bipedalism; adapted to both• body size likely equivalent to female chimp; disproving notion earliest hominids small

D I A G N O S T I C F E AT U R E S

postcranial

• femur similar to A. afarensis• femur head spherical & rotated anteriorly; femur neck elongated and oval in section;

◦ compared to modern humans, head small relative to shaft – but proportionately larger than AL-288-1 (A. afarensis)

• morphology of proximal femur more human-like than australopithecines or African apes• femur and humerus 1.5x larger than AL 288-1 (A. afarensis)• humerus w/ vertical brachiordialis crest• proximal manual phalanx curved

◦ similar to extant climbing primates & A. afarensis

dentition

• dentition small relative to body size• molars smaller than australopithecines', closer in size to Ardipithecus• anterior teeth less hominid-like and more ape-like – similar morphology to female chimp• thick molar enamel

• jugal teeth smaller than australopithecines• upper central incisor large & robust, not shovel-shaped

◦ smaller than australopithecines but similar to Ardipithecus

• upper canine short w/ shallow, narrow vertical mesial groove (common in Miocene & African apes but unlike australopithecines or Ardipithecus)

• corpus mandibularis has great depth (archaic feature in hominids)• buccal notch well-developed• no cingulum on molars

K E Y S P E C I M E N S

• BAR 1000'00 + “Millenium Man”: left femur, pieces of jaw w/ teeth, arm bones, finger

BAR 1000'00: fragmentary mandible

BAR 1000'a'00: fragment of left mandible w/ M3

BAR 1000'b'00: fragment of right mandible w/M2-3

BAR 1002'00 (young adult) – femur: femoral head, neck, and 2/3 of shaft

M A J O R S I T E S• 4 sites in Lukeino Formation, Tugen Hills, Baringo District Kenya:

B I B L I O G R A P H Y

Galik, K. et al (2004) External and Internal Morphology of the BAR 1002'00 Orrorin tugenensis Femur, Science Pickford, M.& B. Senut (2001) 'Millennium Ancestor', a 6-million-year-old bipedal

hominid from Kenya - Recent discoveries push back human origins by 1.5 million years, South African Journal of Science 97: 22-22.

Pickford, M. et al (2002) Bipedalism in Orrorin tugenensis revealed by its femora, Comptes Rendus Palevol 1: 191-203.

Richmond, B.G. & W. L. Jungers (2008) Orrorin tugenensis femoral morphology and the evolution of hominin bipedalism, Science 319: 1662-1665.

Senut, B. et al (2001) First hominid from the Miocene (Lukeino Formation, Kenya), Comptes Rendus de l'Académie des Sciences 332: 137-144

Thorpe, S.K.S. et al (2007) Origin of human bipedalism as an adaptation for locomotion on flexible branches. Science 316: 1328-1331.