Human Evolution Midterm: Bipedalism

mosaic evolution

evolutionary change takes place in some body parts or systems without simultaneous changes in other parts

occasional bipedalism

• bipedal locomotion that is practiced sometime/or occasionally

  • Rely on a different form of locomotion, they are anatomically adapted to their primary form of locomotion (ex. Bears, great apes)

habitual bipedalism

bipedal locomotion that is practiced regularly/habitually . use their locomotion and bipedalism more equally

Obligate bipedalism

• bipedal locomotion is practiced all the time (ex. Humans and later hominins) cannot do other locomotion for a long period of time

____ and ____ bipedalism as the primary form of locomotion is seen only in hominins

Habitual and Obligate

Environmental determinism

links simple environmental changes directly to major evolutionary shifts in an organism

Savanna Hypothesis

during miocene, earth's climate grows drier and cooler

• In africa, forests shrink and “fringe” (grassland) habitats grow

• East africa, continental plate shifts (rifting) create more savanna environments

• Advantages: fewer trees, so arboreal locomotion is not as helpful for survival, upright posture allows to see over tall grasses

• Darwin and other scholars have no logical conclusion

Patchy forest hypothesis

 patchy forests grow in africa at end of miocene and beginning of pliocene

• Advantages: bipedalism uses less oxygen, so is more energy efficient that quadrupedalism in a patchy forest environment 

Thermoregulation hypothesis

 upright posture reduces exposure to sun and increases exposure to wind and air circulation

Provisioning Hypothesis

bipedalism freed hands to carry things, so males could carry food and resources to females

postural feeding hypothesis

upright standing and shuffling allows for better collection of fruit hanging from small trees in woodland environments 

kyphotic curve

curve in human spine at thoracic vertebrae

lordotic curve

curve in human spine at lumbar vertebrae

ape trunk is more _____ shaped

funnel

human trunk is more ___ shaped

barrel