ANTH 1
Introduction to Physical Anthropology
Study Guide #3
Last
Updated: May 8, 2006
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Physics
of Stability:
- relationship of height of center of gravity (CG) of
body relative to width/size of base of support
- High CG and small Base =
unstable (e.g., ballerina, some floor lamps)
- Low CG and large Base =
stable (e.g., sumo wrestler, high-chair, some table lamps)
- Biomechanical constraints on arboreal locomotion:
- branches are narrow, so
base of support for a primate is limited
- can modify height of CG
by: having shorter legs or flexing legs at elbow and knees
- can modify width of base
of support by moving legs/feet onto a nearby branch
- Lack of biomechanical constraints in terrestrial
environment:
- ground is continuous, so
base of support for a primate is unlimited
- because there are no
limits to the base of support, animals can afford to heighten CG;
- Can heighten CG by
lengthening legs
- advantage of long legs is
that speed is a function of:
- rate of stride (how
often legs move)
- length of stride
(distance covered by one leg)
Characteristics
of all hominids compared to other hominoids:
- The distinctive difference between hominids and apes relates to
locomotion: hominids are bipedal, whereas apes are quadrupedal
- modifications of skeleton
for bipedal walking
- vertebral column S-shaped
with anterior lumbar curve
- consequence of curvature
is to bring body mass directly above knees and feet at midline
- hip modified to balance
body over one supporting foot
- pelvis curved anteroposteriorly rather than along back of body or
from side to side, so
- gluteus maximus muscle functions as an extensor of the hip
- gluteus medius and minimus are abducters of trunk, keeping the trunk from falling
to the unsupported side; in apes these muscles are extensors of the hip
- femur modified to bring
knees to midline
- thus hominids have a
"carrying angle" that does not equal 90 degrees, whereas in
apes the carrying angle=90 degrees
- large calf muscles
compared to apes
- foot modified to bear
total body weight, rather than body weight being shared by four limbs as
in apes
- transverse arch, as seen
in all primates, and
- longitudinal arch,
unique to bipedal hominids
- very short toes (not
needed for grasping)
- big toe bound/adducted
to other toes
- Another distinctive difference relates to the loss of
the honing triad
- honing triad:
- canines large and
projecting;
- upper canine honed
against lower anterior premolar and lower canine; so worn on anterior
and posterior sides
- lower canine fits into
diastema between upper canine and lateral incisor;
- anterior premolar is unicuspid;
- large canines in
non-human primates used in male-male competition and in establishing
dominance heirarchies
- human canine complex:
- canines look like
incisors (incisiform)
- canines occlude apically
(at top), so worn only apically
- no diastema
- lower anterior premolar
is bicuspid
Plate
Tectonics:
- Structure of Earth: Core, Mantle, Crust (divided into
plates)
- Convection currents in mantle, in part, drive movements
of plates
- In Mesozoic all continents joined into Pangaea - earth
warm all over
- Division of Pangaea into Gondwanaland and Laurasia; then division of Gondwanaland into S.
America & Africa by opening of S. Atlantic, Madagascar breaks off,
Dating methods:
- Assumptions:
- Principle of Superposition
- strata higher in a column
are younger than those lower in the sequence
- Principle of
Uniformitarianism
- Relative methods
- Biostratigraphy
- Use biological organisms within
strata to correlate different sites
- Paleomagnetism
- the position of the poles
have changed through time; we are currently in a Normal Chron but there have also been Reversed Chrons
- Flourine dating
- bones that are buried at
the same time should have equal amounts of flourine
in them
- used to prove that Piltdown
Man was a hoax
- Absolute methods
- Non-radiometric
- dendrochronology (tree ring dating)
- 1 ring = 1 year
- date fossil trees
- Varves
- lake sediments
- varve made up of 2 bands:
bottom coarse-grained; top fine-grained
- 1 varve
= 1 year
- Radiometric methods
- atomic structure
- atom made of central
nucleus and surrounding shells
- nucleus = protons (+
charge) and neutrons (0 charge)
- shells = electrons (-
charge)
- protons and neutrons
have mass/weight whereas electrons do not
- elements differ from
each other in that their atoms have a different number of protons in
their nucleus (i.e., atomic number)
- the atoms of a
particular element (e.g., oxygen, carbon etc.) have the same number of
protons (atomic number), but may have different number of neutrons
(yielding different atomic weights); if there are variants of an atom
they are called ISOTOPES
- some isotopes may be
unstable and disintegrate over time in to the atom of another element;
disintegration occurs by protons capturing an electron and becoming a
neutron or by neutrons breaking into protons and electrons; in either
case the number of protons changes in the nucleus
- the HALF-LIFE of
radioactive isotopes refers to the amount of time it takes for one-half
of the atoms to decay in to the atoms of another element
- Potassium/Argon (40K/40Ar)
- half-life = 1.3 by
- date volcanic rocks, not
fossils themselves
- when volcanic rock is
hot all the argon in the rock "evaporates" off, so that when
the rock cools there is no argon in it; thus, whatever argon is found
in a volcanic rock is there because it was produced by potassium
decaying in to argon
- used to date age of
Earth as well as hominid localities
- examine the ratio of 40K
to 40Ar
- Carbon 14 (14C)
- half-life = 5730 years
- date fossils, not rocks
- a) plants absorb equal
amounts of 14C and 12C during their lives; when
plants die 14C decays in to nitrogen while 12C
remains stable
- used to date organic
things up to 50 kya
- examine the ratio of 14C
to 12C
- Climate Reconstruction:
- Oxygen Isotope Analysis
- 18O is heavier than 16O;
therefore, water (H2O) with 18O is lower in the
water column than is water with 16O
- microscopic organisms
that live in the water column use oxygen in constructing their
exoskeletons (shells);
- during cold periods when
glaciers exist, water is bound up in the ice and the sea level drops
- by examining the type of
oxygen in the shells of organisms that live near the top of the water
column, we can tell whether the period during which they lived was cold
or warm
Major Events in Primate
Evolution during the Cenozoic:
- Paleocene (65-55 mya):
- Possible (archaic)
primates appear; now considered by many to be non-primates; found in N.
America and
- Eocene (55-35 mya):
- True primates appear,
characterized by nails and grasping ability, postorbital bar,
stereoscopic vision, large brain
- Three groups recognized:
- adapids, which are ancestral to
living lemurs and lorises, found in N.
America, Europe, N. Africa and
- omomyids, which are ancestral to
living tarsiers, found in N. America and
- possible primitive
anthropoids from
- Oligocene (35-25 mya):
- Definitive anthropoids
appear, characterized by postorbital closure, closed metopic
suture and closed mandibular symphysis, color
vision, diurnal life style, sexual dimorphism
- Found primarily in Jebel el Qatrani Formation
of
- New World monkeys appear
in
- Miocene (25-5 mya):
- Old World Monkeys (OWM)
and apes appear in
- Living apes characterized
by lack of tail, suspensory abilities
- Pliocene (5-1.5 mya):
- OWM spread, apes decline,
hominids appear
- Hominids characterized by
suite of features related to bipedalism & incisor-like canines
- Pleistocene (1.5 mya - 10,000 ya)
- Homo spreads
- Characterized by larger
brain and capacity for culture
Hominin species:
- Mio-Pliocene Hominins
- Sahelanthropus, Orrorin,
Ardipithecus
- cranial capacity ~350 cc
- evidence of bipedalism
- Age:7- 4.5 mya
- Sites: E. Africa (
- Australopiths
- Primitive Group
- Australopithecus anamensis,
Kenyanthropus platyops, A. afarensis
- Primitive dental features
related to honing triad:
- diastema between upper
incisors and canine
- canine worn on apex and
posterior surface (intermediate between apes and other hominids)
- first premolar not fully
bicuspid
- cranial capacity on avg 450 cc
- trail of footprints
showing they were bipedal
- Age: ~4 - 3 mya
- Sites: E. Africa (
- Gracile group
- Australopithecus africanus, A. bahrelghazalia, A. garhi
- Dentally similar to us
- incisors and canines
large relative to cheek teeth
- premolars narrow
relative to molars: stepped condition
- cranial capacity on
average 450 cc
- Age: 4 – 2 mya
- Sites: S. Africa (Sterkfontein, Makapansgat,
Taung [Taung
child]), Central Africa (
- Robust group
- Paranthropus (P. robustus, P. boisei,
P. aethiopicus)
- Dental condition
- incisors and canines
relatively tiny compared to cheek teeth
- premolars relatively wide
compared to molars: continuous condition; megadontia
of cheek teeth serves to increase surface area for chewing seeds etc.
- large chewing muscles; so
large cheek bones (for masseter muscles) and a
sagittal crest (for temporalis
muscles)
- cranial capacity on
average ~500 cc
- Age: 3 - 1 mya
- Sites: P. boisei & P. aethiopicus
are from E. Africa (Olduvai Gorge, Lake Turkana);
P. robustus is from
- Leapord Hypothesis to explain
origin of S. African cave sites
- genus Homo
- Characterized by
- larger brain size,
expanded cranial vault
- smaller, straighter face
- less massive mandible
- rounded dental arcade
- narrow cheek teeth and
reduced third molar
- Homo rudolfensis
- Cranial capacity: 750 cc
- Maximum breadth of skull:
low
- Age: 2.3 – 1.9 mya
- Sites: E. Africa (
- Homo habilis
- hand capable of precision
grip and making tools.
- Cranial capacity: on
average 600 cc
- Maximum breadth of skull:
low
- Culture
- Oldowan Industry
- Chopper-Chopping tools
- core tools, with a few
flakes taken off
- scavengers
- Age: 1.9 - 1.6 mya
- Sites: E. Africa (Olduvai
Gorge,
- Homo ergaster
- Thin cranial bones
- Cranial capacity on
average 800 cc
- Maximum breadth of skull:
low
- Sites/Age:
- Europe:
- E. Africa (
- Homo erectus
- Morphology
- Thick bones
- cranial capacity approx
1000 cc
- platycephalic skul
with occipital and sagittal keels
- Maximum breadth of
skull: low
- strong brow ridges
- Culture
- controlled fire
- Tools: Acheulian Industry
- hand-axes typical tool
- bifacial core tools
- Big-game hunting
- clothes likely
- skin color? probably
becoming lighter (UV etc) as moved out of
- Age: 1.8 mya –
400,000 ya
- Sites:
- E. Africa (
- N. Africa (
- Asia: (
- Homo floresiensis
- Age: 40,000 –
18,000 ya
- SE Asia: Flores Island
- Homo antecessor
- Maximum breadth of skull:
low
- Age: 900,000 –
700,000 ya
- Europe (
- Homo heidelbergensis
- Cranial capacity approx
1250 cc
- Maximum breadth of skull:
low
- Intermediate in all
senses between Homo erectus, H. neanderthalensis
and H. sapiens
- Tools: Acheulean
- Sites
- E., S. & N. Africa
- Europe (
- Asia (
- H. neanderthalensis
- Morphology
- Platycephalic skull with cranial
capacity: approx 1575 cc
- Maximum breadth of
skull: intermediate, resulting in barrel shape
- occipital bun
- Hollow brow ridges;
round orbits Mid-facial prognathism
- very wide, large nasal
aperture
- sloping cheekbones
- incisors worn labially and shovel-shaped
- Stocky body build
(related to cold)
- Culture
- Buried dead (graves with
pollen)
- Tools
- Mousterian Industry
- flake tools, not cores
- LeVallois Technique - mass production
of tool types
- Homo sapiens
- Morphology
- cranial capacity: approx
1500 cc
- vertical forehead
- Maximum breadth of
skull: high
- chin
- Culture
- art
- tools
- blades, complex compound
tools (bow & arrow etc.)
Models
for Origin of Homo sapiens:
- Multiregional Model
- Out of
- Out of
Anatomy
of Human Speech.
- Chimps:
- have long, thin tongue
& short pharynx (supralaryngeal space);
- can drink and breathe at
same time
- Humans:
- as adults have short,
thick tongue & long pharynx
- as babies have short,
thick tongue, but a short pharynx