ANTH 1Introduction to Physical Anthropology
Study Guide #3

Last Updated: May 8, 2006

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 humans (living and fossil) compared to other apes:

  • The distinctive difference between humans and apes relates to locomotion: humans are bipedal, whereas apes are quadrupedal.

Modifications of skeleton for bipedal walking include:

  • 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 humans 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, India heading North towards Laurasia; Laurasia splits into N. America and Eurasia by opening of N. Atlantic; then India smacks into belly of Asia, uplifting Himalaya Mts.

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

Chronometric (aka 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
  • 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 Europe
  • 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 China
  • omomyids, which are ancestral to living tarsiers, found in N. America and Europe
  • possible primitive anthropoids from E. Asia
  • 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 Fayum, Egypt
  • New World monkeys appear in South America later in Oligocene
  • Miocene (25-5 mya):
  • Old World Monkeys (OWM) and apes appear in E. Africa; apes dominate
  • Living apes characterized by lack of tail, suspensory abilities
  • Pliocene (5-1.5 mya):
  • OWM spread, apes decline, hominids appear
  • Hominins characterized by suite of features related to bipedalism & incisor-like canines
  • Pleistocene (1.5 mya - 10,000 ya)
  • Homo spreads

Hominin species:

  • Mio-Pliocene Hominins (Sahelanthropus, Orrorin, Ardipithecus)
  • cranial capacity ~350 cc
  • evidence of bipedalism
  • Age:7- 4.5 mya
  • Sites: E. Africa (Kenya, Ethiopia), Central Africa (Chad)
  • 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 (Kenya, Ethiopia, Tanzania)
  • 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 (Chad), E. Africa (Ethiopia)
  • 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 S. Africa (Swartkrans, Kromdraai)
  • 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 (Lake Turkana)
  • 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, Lake Turkana)
  • Homo ergaster
  • Thin cranial bones
  • Cranial capacity on average 800 cc
  • Maximum breadth of skull: low
  • Sites/Age:
  • Europe: Georgia at 1.8 mya
  • E. Africa (Kenya: Olduvai Gorge, Lake Turkana) at 1.7 mya
  • Homo erectus
  • Morphology
  • Thick bones
  • cranial capacity approx 1000 cc
  • low, long skull 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 Africa
  • Age: 1.8 mya – 400,000 ya
  • Sites:
  • S. Africa (Swartkrans)
  • E. Africa ( Ethiopia: Middle Awash; Kenya: Olduvai Gorge, Olorgesailie)
  • N. Africa (Algeria: Ternifine)
  • Asia: (China: ZhoukoudianCave; Java)
  • Homo floresiensis (the Hobbits)
  • Age: 40,000 – 18,000 ya
  • SE Asia: FloresIsland
  • Homo antecessor
  • Maximum breadth of skull: low
  • Age: 900,000 – 700,000 ya
  • Europe (Spain,Italy)
  • 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
  • TimeRange: 800,000 – 25,000 ya
  • Sites
  • E., S. & N. Africa
  • Europe (England, Germany, France, Hungary, Greece)
  • Asia (China)
  • Homo neanderthalensis
  • Morphology
  • Long, low 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
  • TimeRange: 300,00 – 30,000 ya
  • GeographicalRange: peri-Mediterranean
  • Homo sapiens
  • TimeRange: 200,000 ya - present
  • GeographicalRange: World wide
  • 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 Africa Model (Population Replacement Model)
  • Out of Africa Again and Again Model
  • 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