Lecture 14 - Ardipithecus & Aramis

Question 1

why does paleoenvironment of Ardipithecus matter

Answer 1

if bipedal walker (and other things), and if Savanna Hypothesis is true, then we should see Lucy in Savanna environments - but not necessarily the case for Ardipithecus

Lucy upsets the notion of the Savanna Hypothesis

Question 2

Ar. ramidus

Answer 2

• relatively small brain, prognathism as in apes
• more forwardly-placed foramen magnum, consistent with bipedalism
• reduced canine size
• loss of C-P3 honing
• minimal sexual dimorphism

Question 3

Ar. ramidus
pelvis, evidence for bipedalism?

Answer 3

• mosaic of characters for both bipedality and climbing
• short and broad ilium (unlike chimps)
• ischial surface is primitive
• educated guesswork of reconstruction models

Question 4

Ar. ramidus
foot

Answer 4

• strange
• divergent big toe
• lacked other features for suspension/vertical climbing/knuckle walking
• facultative biped

Question 5

why is it risky to assume the LCA of chimps/humans are the same

Answer 5

• chimps have been evolving on their own for 6 Ma, ridiculous to assume LCA had chimp features
• pancestor model: LCA presented in Pan family
• Ardipith knocked theory down - implies that suspensory adaptations btwn chimps + gorillas are homplastic (evolved independently)

Question 6

Aramis description

Answer 6

Afar Depression (sea level)
* hot dry desert
* highly contested in paleoecological reconstruction
* depending on what parts of data is focused, evolution of Ar. can be argued in woody or grassland

Question 7

geological setting of Aramis

Answer 7

13C increases farther east, indicating slightly more open habitat
* primate fossils not found in open habitats
* Aramis found more west

Question 8

faunal analyses of Aramis

Answer 8

• antelope remains - * large amount of Tragelaphin bovids
• occupation from dense forest to open grassland
• modern taxa = browsers, overwhelming abundance of browsers argues Ar. had to be in a woody environment

Question 9

Cerling’s response

Answer 9

• used modern sample locations to screenshot canopy cover/organic matter amount
• plotted Aramis values - percent woody covers were modest
• so potentially open land