bipedal locomation

Question 1

two other ways to describe the bipedal gait?

Answer 1

• serial monopedalism

- locomation using one foot at a time through a series of controlled falls

Question 2

something to notice about the bipedal gait and sort of how it works?

Answer 2

body’s weight shifts from one foot to the other as an individual moves through the swing phase to heel strike and toe off

Question 3

what is bipedalism?

Answer 3

refers to locomotion on two legs

Question 4

what is facultative bipedalism?

Answer 4

animals including chimps and gorillas that assume bipedalism on a temporary basis in order to perform a particular function practice this type of locomotion

Question 5

what is habitual bipedalism?

Answer 5

aka - obligate bipedalism
is rare
assumed as the a regular means of locomotion
examples: kangaroo, ostrich, kangaroo rat, t-rex

Question 6

advantages of bipedalism

Answer 6

• raises the head and allows a better field of vision
• improved detection of distance of danger and resources
• access to deeper water for wading water
• allows to read higher food sources
• arms became free to be used for other things

Question 7

disadvantages of locomotion?

Answer 7

• animal more visable to predators
• exposes soft underbelly
• interferes with the ability yo instantly change direction while running
• makes climbing difficult
• possibly slower

Question 8

disadvantages of bipedalism in humans

Answer 8

• Frequent lower back problems, hernias, hemorrhoids, and other circulatory problems.
• Consequences of a serious leg or foot injury seriously hinders a biped and they are an easy meal for some carnivore

Question 9

how is the skull adapted for bipedalism?

Answer 9

• skull is set right above the spine

- foramen magnum is shifted forward

Question 10

how are the lumbar vertebrae adaptations for bipedalism?

Answer 10

• the lumbar curvature helps to bring the centre of gravity closer to the midline and above the feet - maintains balance
• maintaining balance is one of the most critical issues that must be solved in order to walk on two legs
• a biped must balance of one leg while lifting the other foot off the ground and swinging it forward during the walking cycle

Question 11

how is the sacrum and adaptation for bipedalism?

Answer 11

• sacrum is relatively broad in modern humans with large sacroiliac joint surfaces
• extant chims have a smaller joint surface
• these size differences are related to the different pattern of weight transmission through the pelvis seen in quadrupedal and bipedal locomotion

Question 12

how is the pelvis adapted to bipedalism?

Answer 12

• allows different function of gluteal muscles
• In apes, the flat portion of the iliac ala is roughly parallel with the plane of the back, while in humans it is shifted laterally and flares more on the sides.
• The ilium of the human pelvis is broad, giving it a bowl shape – supports intestines.
• modern humans have a broader pelvis - bowl shape
  
  • for large brained and wise shouldered babies to pass through
  • efficient bipedalism

Question 13

how is the knee adapted to aid bipedalism?

Answer 13

• relates to the need to keep the body’s centre of gravity balanced over the stance leg during the stride cycle
• in humans the hips are wide apart but the shaft of the femur is angled - knee joint is closer to the midline than the hips
• this ensures that the knee is brought more to the centre of gravity
• knee has locking mechanism

Question 14

what is the bicondylar angle?

Answer 14

angle at which the femur occurs

Question 15

what is another name for the knee joint?

Answer 15

valgus knee

Question 16

how are the hands and feet adapted for bipedalism

Answer 16

• curvature in phalangeal shaft correlates with the frequency of arboreal behavior
• • curved fingers and toes = more time grasping and suspending themselves e.g. in trees
• humans dont have a divergent big toe - grasping ability is not required in the toeH

Question 17

how are the arms and legs adapted to aid bipedalism

Answer 17

Most quadrupedal and arboreal primates have either longer arms relative to their legs, or arms and legs of equal length, while most bipeds have relatively longer legs than arms.

Question 18

why bipedalism arose according to charles darwin?

Answer 18

bipedalism is an adaptation resulting when a quadrupedal ape is forced to assume a terrestrial adaptation. This adaptation was partly caused by the advent of a hunting subsistence pattern, where the hands needed to be free to carry weapons and meat. Additionally, Darwin thought that a change in habitat from woodland to savannah left early hominids without the refuge of trees, resulting in less importance of climbing and a greater need for efficient movement on the ground.

Question 19

what are some problems with darwin’s hypothesis for why bipedalism arose?

Answer 19

• evidence for tool use is only found much later in the records
• trees didnt disappear from the african landscape
• early hominins still exhibited morphological adaptations for tree climbing

Question 20

what are two models for how early hominins becae bipeds

Answer 20

savannah model
dense woodland model
#both focused around and hypothesized the environ conditions at the time

Question 21

explain the savannah model l

Answer 21

• environments opened up
• (forests began to retreat in the face of expanding savanna grasslands at the end of the Miocene around 8 million years ago)

Question 22

what were some assumptions for the savannah model:

if you were bipedal…

Answer 22

• food and water would be easier to spot
• more likely to spot predators before they got too close for safety
• hands were free and could defend yourself
• body would be less exposed to the sun

Question 23

what caused the savannah hypothesis to be challenged?

Answer 23

the discovery of biped hominins in dense woodland areas

Question 24

explain the dense woodland model

Answer 24

• hominins would have been more likely to evolve in a familiar environment in which fewer dangers would be face
• we then moved to the savannah armed with new skills and traits as the forests disappeared

Question 25

what is a possible environ pressure that could have lead to bipedalism (not explained by the dense woodland model)

Answer 25

-orangutans walk bipedally on thin branches
One study notes “Bipedalism is used to navigate the smallest branches where the
tastiest fruits are, and also to reach further to help cross gaps between trees.”

-Could this be the reason for the first emergence of bipedalism? To assist with
movement in the tree tops?

Question 26

how does the dense woodland model fall short

Answer 26

The Dense Woodland model also falls short as it does not explain why our ancestors would
have developed the high level of bipedalism seen in Ardipithecus and possibly earlier species
such as Orrorin tugenensis and Sahelanthropus tschadensis in a closed environment that
did not place any new adaptive demands on them.

Question 27

explain the nouveau savannah hypothesis:

Answer 27

–A savanna is not without trees, but is a landscape with a grassy cover, where trees are sparse enough to allow grass growth.

–A savanna is not inevitably synonymous with a pure grassland, but rather may be made up of a variety of open and wooded habitats.

–Ardipithecus and other early hominins may thus have dwelled in seasonal mosaic environments — that is, on the savanna.