Locomotion Flashcards
Give 7 reasons locomotion and postures are important
resting traveling infant carrying escaping from predators foraging social communication object manipulation/ carrying
Define locomotion and posture
locomotion
move from one place to another, displacement
postures
positions/attitudes,
no significant displacement
What is the positional repertiore
all of the locomotor and postural activities of an individual/ species.
one activity may be the most important
What is the substrate
: the surface on which an animal moves, it could be terrestrial (ground) or arboreal (lianas, branches)
What is gait
repeated cycles of limb movement during steady locomotion.
Different parts of the body in contact with the ground between and within cycles
What does frequency refer to when describing locomotion
Frequence: occasional vs habitual behaviours.
eg human: obligate terrestrial bipedalism vs chimp: occasional terrestrial bipedal walking
What is orthnograde and pronograde
Orthograde: upright. • Pronograde: longitudinal axis of the body parallel to the ground.
Orthograde can also be if climbing trees
Give the quotation from Stern and Oxnard (1973) showing the unique locomotor diversity of primates
“Primates stand, sit, lie, walk, run, hop, leap,
climb, hang, swing, swim, and engage in other
activities too numerous to mention. They may
do these things often or rarely, quickly or
slowly, with agility or clumsiness, on the
ground or in the trees (or, with swimming, in
the water), on thick branches or thin ones, on
vertical, oblique or horizontal supports, with
all appendages or only some.”
Why is there such a diversity of locomotor abilities in primates (2, elaborate on each)
differences in body size, i.e., small primates tend to be more arboreal,
and large primates are more terrestrial
habitats, primates in savannah will be more terrestrial while in the
forest there are multiple levels of the canopy that could be exploited by arboreal primates
What are the 6 main locomotor behaviours of primates according to Fleagle 2013
arboreal quadruped terestrial quadruped knuckle-walking quadruped leaping suspensory climbing bipedalism
Describe knuckle walking
fingers in a partially flexed posture
Describe suspension locomotion
limbs loaded in tension, spread their weight among small supports includes orthograde suspension
(brachiation, using arm swinging
Describe leaping
leaping (saltation)
cover distances in free flight,
move between discontinuous supports
Describe bipedalism
bipedalism
progress on a continuous
substrate, frees the hands
Describe terrestrial/arboreal quadrupedalism
progression on small supports using all four limbs
What is vertical climbing
• Vertical climbing: moving up vertical substrates.
How many modes and sub-modes of primate locomotion/postures are there
Hunt et al. (1996): up to 32 positional modes, including 52 postural sub-modes
and 74 locomotor sub-modes!
How does the inner ear differ depending on locomotor activity (generally)
Inner ear: size and orientation of the semicircular canals differ, large anterior
canal in humans
How does the vertebral column differ between human and non human great apes
non humans great apes
- « short-backed »
- reduced lumbar number (3-4)
- immobile lower spine
- straight spine
humans
- « long-backed »
- greater overall lenght (5 lumbar)
- flexible spine
- lumbar and cervical lordosis
- thoracic kyphosis
Describe the bipedal pelvis of a human
shortened ilium (body and blades, lower centre of mass), iliac blades
more laterally placed (bowl shape), large sacrum (no entrapment of the lumbar
vertebrae) in humans
Chimp entrapment of sacrum limits its flexibility
Describe the bipedal femur of a human
long neck (increase the mechanical advantage), bicondylar angle (feet below the center of gravity) and linear aspera (muscle attachments) in humans
Describe the bipedal adaptations of a human tibia
: articular facets longer, larger, more concave, medial>lateral facets (weight transfer to the feet) in humans.
Describe phalanges of other primates
• Hands: curved hand bones in arboreal primates.
What are the 2 key types of bone tissue
compact bone:
cortical
spongious bone:
trabecular
What is Wolff’s Law
what parts of the body have used this to examine bipedalism
Wolff’s law: bone tissues adapt to the loads
Bone form reflects mechanical loading history during life. • Bone remodeling: mechano-transduction (mechanical signals converted to
biochemical signals)
cortical thickness in the tibial plateau
(Mazurier et al., 2010)
trabecular bone in the humeral head
(Ryan and Shaw, 2012)
what are the 4 possibilities of positional behaviour before human bipedalism
arboreal climbing ancestor? knuckle-walker?
terrestrial quadruped ancestor? arboreal quadruped ancestor?
What is the evidence of bipedalism in Sahelanthropus tchadensis
(7.2-6.8 Ma)
what may contradict this
cranium reconstruction with a foramen magnum positioned anteriorly
(Zollikofer et al., 2005)
femur showing the linear aspera
(Guy et al., 2020)
ulna is curved
Why may orrorin have been bipedal
what contradicts this
femur showing the linear
aspera and thick cortical bone
in the femoral neck
(Galik et al., 2004)
arboreal activities in the upper limbs - phalanges and humerus
evidence for bipedalism in kadabba
give dates
Ardipithecus kadabba
(6.4-5.4 Ma)
human-like foot
(Haile-Selassie et al., 2004)
evidence for bipedalism in ramidus
give age
what may contradict this
Ardipithecus ramidus
(4.6-4.3 Ma)
short ilium mediolaterally expanded (Lovejoy et al., 2009) cranium reconstruction with a foramen magnum positioned anteriorely (Suwa et al., 2009)
arboreal activities in the upper limbs - hands and feet
what is the trend in early hominin locomotor activity
what is the most likely locomotion pre-bipedalism
evidence of bipedalism in the cranium and lower limbs and of arboreal activities in the upper limbs.
Terrestrial bipedality combined with climbing capacities. (Bipedalism did not emerge from knuckle-walking.)
What is Oldest evidence of habitual bipedalism in Australopithecus.
Australopithecus anamensis at Lake Turkana (Kenya) dated to 4.2-3.9 Ma
(Leakey et al., 1995)
KNM-KP 29258.
medial>lateral,
concave facets
What evidence is there of bipedalism in afarensis
Australopithecus afarensis footprints at Laetoli (Tanzania) dated to 3.7-3.5 Ma (Leakey
and Hay, 1979). • No evidence of forelimb support, human-like gait (heel-strike and toe-off
during stance phase of walking).
Lucy:
pelvis- wide sacrum, short iliac blades
femoral neck
long, thicker cortical bone inferiorly
high bicondylar angle
How is Lucy a locomotor mosaic
biped:
pelvis- wide sacrum, short iliac blades
femoral neck -long, thicker cortical bone inferiorly
high bicondylar angle
arboreal: hand - curved and long phalanges femur - relatively short distal humerus - well-developed lateral trochlear crest scapula - cranially oriented
latter 2 suggest above branch climbing
Give the mosaic features of the locomotor activity of africanus
biped: pelvis - wide and short iliac blades laterally flaring femur - long neck high bicondylar angle lumbar vertebrae - lordosis 6/5
arboreal:
inner ear - ape-like semicircular canals
hand - curved phalanges
What are the arboreal/ bipedal features of little foot
StW 573 - Australopithecus africanus (3.7-2.2 Ma)
proportions distinct
from humans and apes
long limbs
What suggests africanus had a variability in positional repertoire
variability in the inner ear morphology
(Beaudet et al., 2019)
variability in the sacrum
(Fornai et al., 2020)
variability in the vertebral morphology
(Beaudet et al., 2020) - (atlas – is very different, one similar to lucy but one more derived etc)
Describe the alleged locomotion of sediba
Australopithecus sediba (2.0 Ma): supports locomotor and postural diversity within Australopithecus
mosaic:
biped:
pelvis - very human-like
arboreal; scapula - cranially oriented humerus - marked crests foot - more primitive hand - curved phalanges
What is The problematic assignment of postcranial remains to Paranthropus?
stratigraphic association with Homo, → postcranial material not systemically found in association with
craniodental remains
What do we know about Paranthropine postcrania and thus the locomotor activity
The fragmentary material from Kenya and Tanzania.
biped:
human-like features:
fine grip precision, femoral lines
arboreal hominoid-like features:
scapula, proximal radius
specific features
straight and robust radius, thick
cortical bone in the humerus
What are the locomotor traits of Homo skeletons
Early Homo and the emergence of obligate bipedalism. • Obligate bipedalism and possible endurance running in Homo ergaster. • Primitive (arboreal?) traits in Homo habilis
How are H sapiens adapted to long distance running
Skeletal strength
Stabilisation
Thermoregulation
How is the H sapiens adapted to increase skeletal strength for running (2)
1) expand joint surfaces in lower body disproportionally cf. upper body (Homo has larger articular surfaces cf. Au. eg in femoral head and knee)
2) shorter femoral neck cf Pan and Au - reduces bending moments in femoral neck
How do Homo species improve stability for endurance running to counter the following problems:
1) trunk and neck of human runners are more forwardly inclined during running than walking
2) during the aerial phase of running, leg acceleration generates even larger torques that cannot be counter-acted by ground forces (as in walking).
3) head stablisation
1) enhance trunk stabilization, including expanded areas on the sacrum and the posterior iliac spine for the attachment of the large erector spinae muscles, and a greatly enlarged m. gluteus maximus
2) offset by the opposing torques produced by counter-rotation of thorax and arms (but not the head)
- greater degree of isolated rotation of the trunk relative to the hips compared to apes
- greater structural independence of the pectoral girdle and head
- wide shoulders + reduced forearms allows energy saving in arm swinging for counter-balancing
3) radius of posterior semicircular canal is significantly larger in Homo than in Pan or Australopithecus, presumably increasing the sensitivity of sensory perception to head pitching in the sagittal plane, which is potentially much greater during running than walking
nuchal ligament (convergent evolution with other running mammals eg horses and hares)
How does Homo achieve greater independence of head from pectoral girdle
chimps have extensive muscle connections between shrugged shoulders and head but humans have only trapezius
cranially orientated glenoid fossa (fine for walking) would impede counter-rotations of pelvis and arms
(this decoupling of the head and pectoral girdle may also be advantageous for throwing)
How has Homo sapiens improved thermoregulation for endurance running
- Elaboration and multiplication of eccrine sweat glands for evapo-transpiration, and reduced body hair
- narrow, elongated body form
- enhanced cranial venous drainage (venous blood that has been cooled by sweating in the face and scalp to cool, via countercurrent heat exchange in the cavernous sinus, hot arterial blood in the internal carotid artery before it reaches the brain)
Why do we think Orrorin was bipedal
why not
Femur:
• A large femoral head that is anteriorly twisted
• Elongated femoral neck
• A femoral neck that is compressed antero-posteriorly
• Inferiorly thickened femoral neck cortex (seen in humans - superior thickening seen in apes)
• An obturator externus groove
• A medially projecting lesser trochanter
• A well-developed gluteal tuberosity
Phalanges show similar curvature to afarensis with deep lateral fossae for insertion of flexor digitorum superficialis – strong hand flexing musculature
Give a feature of Sahelanthropus’ forearm
waisted trochlear notch - arboreality would require fully developed notch BUT this trait could not be selected for and independent of walking
Guy et al 2020
Describe the hands and wrists of ramidus
what about forearm
Primitive hands – short, grasping
thumbs and elongated fingers
• Wrist: arboreal palmigrady
Radius:tibia – similar length – consistent with above branch quadruped
Give the key features of ramidus’ pelvis (3)
What must be remembered about this evidence
1) Ilium shortened in height cf apes - ilium shifted to become more anterior and basin-like, away from the vertical ilium in Pan. This shift allowed the gluteal muscles to be positioned in a more advantageous position for centering ramidus’ centre of mass while walking
2) Has an incipient anterior inferior iliac spine – prominent in humans but not present in apes
3) Ape like ischium
Pelvis is crushed so limits reliability
Describe sediba’s back
has a lumbar lordosis and vertebral pyramidal configuration consistent with bipeds
long costal processes for psoas major attachment imply increased Tm for this muscle, aiding trunk stablisation in upright walking and vertical climbing
adapted for bipedalism and arboreality
Describe sediba’s shoulder
sternoclavicular joint suggests oblique orientation of clavicle and high scapula
cranially oriented glenoid fossa
retention of climbimg abilities likely signals full reorganisation did not occur until total commitment to terrestriality, which was when upper limbs became more prehensile and manipulative
Give key hypotheses for the evolution of hominin bipedalism
Multiple factors
Savannah-based theory
Traveling efficiency hypothesis
Postural feeding hypothesis
Provisioning model
Thermoregulatory model
Carrying models
Wading models
Who is a key proponent of the provisioning hypothesis of bipedality
What does it suggest
Support?
Problems?
Lovejoy -> male provisioning
slow LHS required males to go out and find food for females which requires hands for carrying etc
based on reduced canine dimorphism in Sahelanthropus and ramidus and ovulatory crypsis
but kadabba has large canine? and honing complex?
afarensis were sexually dimorphic and lived in large groups unlike extant monogamous primates eg gibbons
What is the Postural feeding hypothesis
Primates were only bipedal when reaching for branches/ high up food
Give evidence for the Postural feeding hypothesis
Australopithecus afarensis has similar shoulder to chimp and the lower limb/ hip is inefficient at movement, suggesting it may have been important postural originally
orangutans walk bipedally through branches using forelimbs to hold higher branches (75% of observations by Thorpe)
explains instability of afarensis’ ankle joint
What is the Traveling efficiency hypothesis
Is there any evidence?
the mixture of savanna and scattered forests increased terrestrial travel by proto-humans between clusters of trees, and bipedalism offered greater efficiency for long-distance travel between these clusters than quadrupedalism
metabolic cost of bipedal and quadrupedal locomotion are similar in chimpanzees (Pontzer, 2014)
What are key features of the savannah hypothesis
evolution of an orthograde posture would have been very helpful on a savanna as it would allow the ability to look over tall grasses in order to watch out for predators, or terrestrially hunt and sneak up on prey
thermoregulation
What is the wading model of the evolution of human evolution
evidence?
apes selected for bipedalism due to need to wade for foods containing essential fatty acids
captive bonobos found them to exhibit <2% bipedality on the ground or in trees but over 90% when wading in water to collect food
this explanation of A. afarensis locomotor morphology
is more parsimonious than others which have plainly failed to produce a consensus
Sahelanthropus may have lived near the Mega Lake Chad
not taken seriously (Meier, 2003)
eg Orrorin did not have an aquatic paleohabitat
What is the Multiple factors model of bipedalism
Because biological evolution is not a simple causation; there may be multiple answers to the evolution of bipedalism.
The postural feeding hypothesis (reaching for food/balancing) provides an explanation for the partial bipedalism of the earliest hominins.
The savannah-based theory describes how the largely bipedal hominins that started to settle on the ground became increasingly bipedal.
The provisioning model (food-gathering/monogamy) explains questions arising after the postural feeding hypothesis and before the savannah theory in an evolutionary timeline.
Endurance running explains shift to efficient bipedalism in Homo
Describe the angular relationship between foramen magnum (FM) and orbital (OP) planes in S tchadensis
quad and bipedal primates have face facing forward so have small angle compared to humans which have an angle between FM and face of 103 degrees (almost right angle) – Sahelanthropus has angle of 95 degrees also close to right angle – evidence of bidepalism
Does an anterior FM necessarily suggest bipedal walking
This does not necessarily mean that it walked upright on the ground, but at least we know their heads were more closely above the body, indicating a habitually upright posture.
What is the importance of the bicondylar angle
Which hominins have this
phenotypically plastic trait, meaning that it only appears through behaviour. Humans that were not able to walk as children never develop this trait.
Therefore, if we see it we know that the individual walked bipedally.
Orrorin afarensis africanus robustus boisei
What are the key features of a modern human pelvis
Which of these does ramidus have
1) A wide and short sacrum
2) Laterally oriented iliac crests that turn the gluteus minimus and gluteus medius into abductors
3) The ilium is shorter and broader in humans than in apes
4) Anterior inferior iliac spine
All of the above BUT has long (ape-like) ischium for adductor and hamstring attachment needed in arboreal climbing
