DATA
Links & Resources
TEACHING HUMAN EVOLUTION
Evolution takes a long time and involves complex interactions among a multitude of variables. Similarly, walking and running involve complex interactions among muscles, bones, and metabolism. We use numerical & mathematical modeling and simulation to understand these complex systems. Testing simple models allows us to understand how these complex real-world systems work.
Foraging
Efficiency & Selection on Economy
It is often assumed that
natural selection will act to maximize the economy of
locomotion and other activities in order to maximize the
energy available for growth and reproduction. However,
recent modeling efforts suggest that selection to
improve locomotor economy in terrestrial animals is
strongly dependent on foraging efficiency (see image
above). For most living species, selection for
additional improvement in locomotor economy appears to
be quite low, because the foraging efficiencies they
obtain are already quite high.
Papers & Presentations
Pontzer,
H.
2012. Relating ranging ecology, limb length, and
locomotor economy in terrestrial animals. Journal
of Theoretical Biology 296, 6–12.
Modeling Locomotion
in Fossil Hominins
Applying laboratory-tested models
of walking and running gait and cost to the hominin
fossil record allows us to understand how extinct
species moved about the landscape and used their
habitat. Our modeling efforts suggest that bipedalism
likely provided little, if any, energetic advantage for
early hominins: the number of legs used to walk and run
has no effect on cost. However, it appears that
selection did favor improved locomotor economy after
bipedalism evolved, with evidence from the australopith
pelvis indicating a more efficient gait than is seen in
living apes. We have also applied this approach to
modeling cost in dinosaur locomotion.
Papers & Presentations
2009 Pontzer, H., Allen, V.,
Hutchinson, J.R. 2009. Biomechanics of running
indicates endothermy in bipedal dinosaurs. PLoS
ONE
2009 Pontzer, H., Raichlen, D.A., Sockol, M.D.
2009. The metabolic cost of walking in humans,
chimpanzees, and early hominins. J Hum Evol.
56, 43-54
2008 Raichlen, D.A., Pontzer, H.,
Sockol, M.D. The Laetoli footprints and early hominin
kinematics. J Hum Evol. 54, 112-11
l
Collaborators: David
Raichlen, John
Hutchinson
Determinants of
Cost in Terrestrial Locomotion
Following on experimental work in
other labs in the 1990's, our work on the metabolic cost
of locomotion in terrestrial animals has shown that
energy cost is driven primarily by the volume of muscle
activated each step to support body weight. The primary
anatomical determinants of cost are therefore: body
weight (heavier animals use more energy), limb length
(longer limbs reduce the energy spent per kg body mass),
muscle fasicle length (long muscles are more expensive),
and the effective mechanical advantage of the limb
joints (better mechanical advantage means lower cost).
Current efforts are examining how these anatomical
variables interact, and how mechanical work contributes
to cost.
Papers & Presentations
2009 Pontzer,
H.,
Raichlen, D.A., Sockol, M.D. 2009. The
metabolic cost of walking in humans,
chimpanzees, and early hominins. J Hum
Evol. 56, 43-5
2007
Pontzer, H. Limb length and
the scaling of locomotor cost in terrestrial
animals. J Exp Biol. 210, 1752-1761.
2007 Pontzer, H. Predicting the
cost of locomotion in terrestrial animals: a test of
the LiMb model in humans and quadrupeds. J Exp
Biol. 210, 484 - 494
2005
Pontzer, H. A new model predicting locomotor cost from
limb length via force production. J
Exp Biol. 208, 1513 – 1524
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Collaborators:
David
Raichlen
This work has been supported by the National Science Foundation
Ecological
Pressures and Energy Budgets
Classic life history theory
suggests that energy budgets (the amount of energy used
each day by an organism) are a fixed function of body
size, and that differences in growth and reproduction
rates reflect differences in energy allocation within
this fixed budget. Our recent work suggests that, in
fact, energy budgets can expand or contract over
evolutionary time in response to ecological pressures.
Expanding the energy budget provides more energy for
reproduction but increases energy needs and the risk of
starvation; contracting the energy budget reduces the
energy available for reproduction but decreases
ecological risk. Our current work is exploring how
ecology affects the evolved energy budgets of humans,
apes, and other mammals.
Papers & Presentations
2011
Pontzer H., Raichlen D.A., Wood B.M., et
al. Hadza forager energetics and the
evolution of the human metabolic strategy.
AJPA. S52, 242
2010
Pontzer, H., Raichlen, D.A., Shumaker, R.W.,
Ocobock, C., Wich, S.A. Metabolic adaptation for low
energy throughput in orangutans. PNAS.
107, 14048-52.
2009
Pontzer, H., Kamilar,
J.M. Great ranging associated with
greater reproductive investment in mammals.
PNAS.106, 192-196.
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This work
has been supported by the National
Science Foundation and the
Wenner Gren Foundation