11/22/20 1711Course BusinessMidterm 2 descriptive statsGroup Size 47Mean 37.1Standard Deviation 4.9Variance 24.0Highest Possible Score 50Highest Obtained Score 49Lowest Obtained Score 27Range of Scores 2390th Percentile Score 42.875th Percentile Score 41.050th Percentile Score - Median 37.425th Percentile Score 33.810th Percentile Score 30.1211/22/20 1723The Early (Probable) Hominins and Gracile AustralopithsTopics for Today• The earliest possible bipeds• The earliest positively-bipedal taxa: the gracile Australopiths (Genus Australopithecus)411/22/20 1735Earliest (probable) Hominins 7-5 million yeas ago.Hominin adaptive radiation 4-1 millionP. robustusP. boiseiP. aethiopicusPlay the Paleoanthropological version of CLUE, looking for the different characters in the narrative:• Who (species name)• With what (locomotor, dietary, and behavioral adaptations)• Where (geographic area, habitat coverage)• When (time range)611/22/20 1747Probable Hominins (various Genera); Gracile Hominins (Australopithecus)Robust Hominins (Paranthropus)P. robustusP. boiseiP. aethiopicusGorilla Pan HomoThe Earliest Probable HomininsMiocene ape8?LCA: last common ancestor shared betweenHomo and Pan11/22/20 175The Earliest Probable HomininsSahelanthropus tchadensis in ChadOrrorin tugenensis in KenyaArdipithecus ramidus in Ethiopia9Sahelanthropus tchadensis• 7-6 Ma, Chad• Discovered in 2001 by Ahounta Djimdoumalbaye, published by Michel Brunet• Habitat: lake, forest, riverine, wooded savanna• No postcranial bones1011/22/20 176Some Sahelanthropus morphology• Primitive (~ chimp- or gorilla-like):– Very large, thick browridge– Chimp-like cranial capacity (320-380 cubic centimeters=cc)• Derived (~ human-like):– Reduced prognathism– Small canines– Foramen magnum position?• Fossil is heavily distorted11Virtual Reconstruction1211/22/20 177Gorilla Pan HomoSahelanthropus tchadensis ?Miocene ape13The Earliest Probable HomininsSahelanthropus tchadensis in ChadOrrorin tugenensis in KenyaArdipithecus ramidus in Ethiopia1411/22/20 178Orrorin tugenensis• 6.1-5.8 Ma• Tugen Hills, Kenya• Bipedal?• Smaller molars than Australopithecus afarensis• Fragmented teeth, mandible, humerus, femora, and phalanges15Bipedal?inferior neck 4x thickerthan superior neckboth surfaces approx.equal in thicknesshuman (chimp)inferior neck 3x thickerthan superior neckOrrorinOrrorin tugenensis1611/22/20 179Gorilla Pan HomoOrrorin tugenensis ?Miocene ape17The Earliest Probable HomininsSahelanthropus tchadensis in ChadOrrorin tugenensis in KenyaArdipithecus ramidus in Ethiopia1811/22/20 171019Ardipithecus• Found first in 1992 by White et al. but only published in partial detail in 2009.• Two species:– A. kadabba: 5.8-5.5 Ma– A. ramidus: 4.4-3.9 Ma20Ardipithecus ramiduscranial morphology• Similar to Sahelanthropus• Cranial capacity 300-350 cc• Foramen magnum placed beneath the cranium• Base of cranium in evolutionary direction towards hominins• No canine honing facet– Reduced canine– Less sexual dimorphism than chimp but more than humans2011/22/20 171121Dental comparison of Chimpanzee vs. Human: evolutionary polarity of dental traitsChimpanzee vs. Human:• Prominent vs. reduced canines.• Presence of Canine-Premolar3 (CP3) homing complex vs. absence.• U-shaped dental arcade vs. parabolic dental arcade.• Thin enamel vs. thick enamel• Small molars vs. larger molars.21CP322Ardipithecus ramiduspostcranial morphology• Short broad pelvis• Abductable big toe but used as a stabilizer in bipedal locomotion• Primitive foot with some bipedal features• Intermembral index close to 1.0!• No suspensory or knuckle-walking adaptations2211/22/20 171223Ardipithecus ramidus reconstructed• Suggested to be a facultative biped terrestrially and a four-hand climber/clamberer arboreally23• Unique combination not seen in other apes, but includes many features similar to earliest apes (>12 million years earlier)• A. ramidus in some ways is unlikechimpanzees, suggesting that the LCA differs from the modern chimpanzee, confirming that after the chimpanzee and human lineages diverged, both underwent substantial evolutionary change. LCA may not have been as chimp like as previously thought!24Gorilla Pan HomoArdipithecus ramidusMiocene ape2411/22/20 1713ALA #10: A Take-Home assignment, turn in next week (Week 13); ~1 page in length1. What do Jill Pruetz and Andrew Whiten cite as unique cultural characteristics for their group of chimpanzees in Senegal?2. Can chimpanzees cooperate with each other? Briefly describe an experiment that shows this.3. Can chimpanzees anticipate the motives of others? Describe an experiment that shows this.4. What does the film cite as a possible limiting factor to nonhuman ape cooperation?5. What is the attention triangle and how does this relate to the human vs. nonhuman ape ability to teach?25www.dcl.umn.eduTitle: Nova: Ape Genius: What Separates Apes from HumansID#: 40075672611/22/20 1714272811/22/20 171529I suggest watching this on a computer, not a smart phone or tablet, but do what works3011/22/20 171631Problems with phylogenetic tree reconstruction with poor sampling3132? Ardipithecus ramidusChimpanzee Modern human?Orrorin tugenensis?? Sahelanthropus tchadensisMiocene apeGorilla Pan Human3211/22/20 1717ALA#11What other bones or skeletal features would support an interpretation that Orrorin tugenensiswas a biped (besides its proximal femur)?3334Chimp =Iliac bladesin CoronalplaneBiped =Iliac bladesin
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