Physical Anthropology
Human Origins
What is a Mammal?
• Class Mammaliaair-breathing vertebrate
animals characterized by the
possession of endothermy,
hair, three middle ear bones,
and mammary glands.
• Most mammals also
possess sweat glands and
specialized teeth, and the
largest group of mammals,
the placentals, have a
placenta which feeds the
offspring during gestation.
Mammal Origins
• The first mammals evolved from
Therapsids, mammal-like
reptiles, at the end of the
Triassic period (248-213 mya),
and coexisted with dinosaurs
throughout the Mesozoic Era
(248-65 mya).
• It was only after the dinosaurs
went extinct that mammals were
able to evolve beyond their tiny,
mouse like forms into the widely
specialized species that populate
the world today.
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Therapsids-mammal like reptiles
Early mammals characteristics:
1. enlarged brain; more developed
sense of smell & hearing
2. warm blooded
3. nocturnal
4. specialized teeth (4 types)
5. may have laid eggs (like extant
monotremes)
6. skeletal changes permit more
flexibility & faster motion
7. larger lungs for faster breathing
Earliest Mammals
|←--------- 4-5 inches long ----------→|
• Megazostrodon- extinct Mammaliaform, widely accepted as
being one of the first mammals, appearing in the fossil record
approximately 200 million years ago, is likely to represent the
final stage of the transition between cynodont, or "mammallike" reptiles and true mammals.
Coelacanth; a living fossil
Living Mammal Ancestors
Platypus & Echidna:
• Monotremes- means “onehole”, refers to presence of
“cloaca”, which serves
purpose of urination/defecation
& reproduction (reptiles, birds).
• Primitive, egg-laying mammals
that nourish their newly hatched
young with milk produced from
modified sweat glands.
• Only found in Australia & New
Guinea.
The next step: Marsupials
• Marsupials- pouchedmammals with short gestation
periods due to yolk-type
placenta, giving birth to
underdeveloped live young.
• More common than placental
mammals during Mesozoic era,
declined at mid to late Tertiary
period.
• Still common in Australia & South
America. S. American populations
decline after land bridge
connecting N. America introduces
placental mammals during late
Miocene, early Pliocene.
Eutheria: placental mammals
-Placenta, connected to
mother’s bloodstream,
directly nourishes young to
advanced stage.
-large opening at bottom of
pelvis for birth of larger, more
developed young.
-loss of epipubic bones
(present monotremes,
marsupials) which interfere
with enlargement of
abdomen during gestation
-oldest known fossil dates
back to 160 mya.
Monotreme vs. Marsupial vs. Placental
• For all or the above:
1. List all the advantages of each group.
2. List the disadvantages of each group.
3. Teacher will pick you to defend 1 group.
• Note: to be able to defend your advantages you
must be familiar with the
advantages/disadvantages of the other 2 choices.
Order: Primates
• Category of Mammals with:
-flexible hands & feet
-forward-looking eyes, which allows
for excellent 3-D vision
-enlarged brains relative to body
size
-can rotate arm in a circle around
shoulder joint
-many have opposable thumbs
Examples:
-smallest = mouse lemur (1 oz.)
-largest = mountain gorilla
(440 lbs.)
Primate evolution & origins:
• Primates evolved from mammals
of the late Cretaceous (c. 65
mya).
• Oldest know primate is
Plesiadapis , c. 55-58 mya.
• Most likely a tree-dweller, it is,
however, found in high numbers
suggesting ground-dwelling.
• Eyes not completely forward
facing.
• Teeth similar to rodents (large
incisors) but with grinding &
crushing molars for omnivority.
Prosimians “before ape”
Oldest living primate group
• Loris- nocturnal, found
in forests/woodlands of
S.E. Asia, slow-moving,
omnivores &
insectivores, “allergenic”
slightly toxic saliva
gathered from brachial
gland & applied to
young when left in nest,
wet nose, nails instead
of claws, tooth comb.
Slender Loris
Slow Loris
Prosimians
• Lemur- name means “ghost”, all
found in Madagascar arriving 6265 mya on vegetation rafts,
thought to have evolved from
lorisiforms 50-55 mya, very
diverse (100 species) with many
overlapping same terrain but
occupying different niche, size
range 1oz.-20lb. (400lb. extinct
lemur!), eyes not completely
forward facing, wet-nose, nails
instead of claws, “tooth comb”
used for grooming/feeding, “toilet
claw” longer second toe used for
scratching.
Prosimians
• Tarsier- found in S.E. Asia,
considered “early” monkeys,
one eyeball as big as entire
brain and with different
connections compared to
other primates, elongated
tarsus (foot) bones give its
name, elongated fingers with
longest = to forearm, toilet
claw, lack toothcomb,
although many nocturnal they
lack light reflecting membrane,
all carnivores with most being
insectivores.
What does it mean to be human?
• What
qualities/traits
set us apart from
other ape,
monkeys and
hominids that
have existed on
earth so far?
The first Hominid? Sahelanthropus tchadensis
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“Toumaï”- Extinct hominin species dated to about 7 million years ago.
Arguments for and against inclusion in Hominid family.
Older than human-chimpanzee divergence (6.3 to 5.4 million years ago).
Braincase volume = 320 cm³ to 380 cm³
Anteriorly placed foramen magnum
Ape-like U-shaped dental arcade, Hominid-like smaller canines
Is it related to Ardipithecus?
Orrorin tugenensis: “Original Man”
2nd oldest fossil hominid found to date
• Fossil specimens estimated to
be 6 to 5.8 million years old
• Small teeth relative to body size,
but thicker enamel (Ardipithecus?)
canines ape-like but reduced
• Bipedal, but grasping hands
(curved fingers) suggest tree
climbing, arboreal grasping
hallux (big toe).
• Femur more similar (?) to
humans (may be more direct
human ancestor than “lucy”!)
• Pushes great ape/hominid split
to at least 7 million years
Ardipithecus kadabba & Ardipithecus ramidus
Ardi = “ground floor” Pithecus = “ape” Ramidus = “root”
• A. kadabba, 5.6 mya
• A. ramidus (“Ardi”) - 4.4 mya,
bipedal but with arboreal grasping
hallux (big toe), reduced canines,
brain size similar to modern
chimps (300 and 350 cm3),
generalized dentition suggests
omnivory & frugivory, less sexual
dimorphism points to less male to
male competition, more pair
bonding, more parental
investment.
• Inhabited mosaic of woodland and
grasslands.
Genus Australopithecus
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Common ancestors to all great
apes?
Australopithecines:
“southern apes”
35% brain capacity of modern
humans
Bipedal hominids between
3ft. 10in. – 4ft. 7in. tall
Substantial dimorphism: in
humans males are ~15%
larger than females,
Australopithecine males may
have been 50% larger.
Oldest fossils ~4 mya.
Is dimorphism
alone enough to
determine whether
a hominid is more
ape-like or humanlike?
Australopithecus (Praeanthropus) afarensis
• A. (P.?) afarensis- “Lucy”
• Fossil range ~3.9-3.2 mya
• Reduced canines and molars,
although still relatively larger
than in modern humans
• Brain case ~380–430 cm3
• First proof that larger brain size
was not necessary for
bipedalism.
• No grasping toe, although
curvature of fingers and toes
similar to great apes.
• Evidence of stone tool using
Australopithecus africanus
Very likely our oldest direct ancestor?
• Lived ~3.0 - 2.4 mya
• ~485 cm3 cranial capacity
(largest Australopithecine brain
is A. ghari ~600 cm3)
• Pelvis more suited for
bipedalism than A. afarensis,
but has curved climbing fingers.
• May lead directly to
Paranthropus or Homo or
both?
• Slightly less sexual dimorphism
possibly as adaptation of
females to bear load of
pregnancy while upright.
Genus Paranthropus- “robust australopithecines”
Greek phrase meaning “beside human”
• First appear ~2.7 mya
• Bipedal apes descended from
Australopithecines
• Stood 4ft 3in - 4ft 7in, brain
case ~500-550 cm³
• Side branch to genus “Homo”,
inhabiting more wooded areas
• More dedicated herbivore,
similar to gorillas;
– sagital crest, large dentition;
skull highly specialized for
heavy chewing
P. aethiopicus P. boisei and P. robustus
• High sexual dimorphism:
– Males 68 kg (150 lb) and stood
1.3 m (4 ft 3 in) tall, Females
weighed 45 kg(99 lb) and stood
1.05 m (3 ft 5 in) tall
• Molars have twice the area of
human molars with most
enamel of any hominid
P. Boisei “Nutcracker man”
Fossil range ~ 2.3-1.2 mya
Genus Homo: homo means “same”
• Oldest examples from about 2.3 - 2.4 mya
• Genus Homo was originally distinguished from previous genus by
use of stone tools, but newer evidence puts tool use as early as
3.39 mya.
• Emergence of Homo coincides roughly with the onset of
Quaternary glaciation, the beginning of the most recent ice age.
• All species in genus Homo extinct expect Homo sapiens; us.
Homo gautengensis
the earliest member of genus Homo?
• Dating to about 2.5 mya, believed to be
the transitional species between genus
Australopithecus and genus Homo.
• Cranial capacity probably ~ 600 cm³, just
over 3 ft tall and about 110 lbs, probably
very similar to Australopithecines;
bipedal on ground and spending
considerable time in trees.
• Was "small-brained" and "large-toothed”,
probably relying on vegetable matter for
majority of diet.
• Produced and used stone tools and may
even have made fire.
H. habilis & H. rudolfensis
• H. habilis “handy man” 2.33 - 1.4 mya
• Brain size: ~710 cm³
• Less prognathism than previous Homo
species, molars reduced in size and
elongated suggesting more varied diet
• May or may not be first tool maker, but
hand/finger bones shorten and evolve
for finer precision
• Most likely used to tools to scavenge
carrion and not necessarily for hunting
• Debate as to differences between two
species and which is direct ancestor to
Homo sapiens
H. Ergaster –”workman”
• 1.8 -1.3 mya
• 700-900 cm³ brain case, ~6ft tall
• Evolves in Africa from H. habilis; debate
continues on whether H. ergaster is just
early H. erectus, or H. ergaster leaves
Africa and becomes H. erectus in Asia.
• Probably 1st hominid to harness fire,
although most likely not created.
• Less sexual dimorphism = less male
competition, more social organization,
larger brains, more sophisticated tools.
• Probably 1st hominid to use “human” voice
• H. ergaster likely continues lineage to
modern humans
• See H. erectus for more info *
H. Erectus (from/with H. ergaster?)
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1.89 million - 143,000 years ago
Brain case ~ 850-1100 cm³
Able to vocalize, “proto-language.”
*Probably first hominid to live in
small, familiar band-societies
similar to modern hunter-gatherers.
*First hominid to hunt in
coordinated groups, use complex
tools, and care for infirm or weak
companions.
*May be first hominid to light fire
Populates Asia & Europe
Longest lived hominid to date
Possible “side branch” to H.
ergaster?
H. mauritanicus/antecessor
• 1.2 million to 800,000 years ago
• Brain case ~ 1,000 cm³ , 5.5-6ft
tall, 200 lb., more robust than H.
heidelbergensis
• Descendant of H. ergaster in
Europe, or early H.
heidelbergensis?
• Most likely 1st hominid in
Northern Europe
• Language (left brain)
development leads to righthandedness (?)
• Evidence from European fossils
points to cannibalism
H. Heidelbergensis from/with(?) H. mauritanicus/antecessor
• 600,000 – 250,000 yrs ago
• Similar to H. ergaster but because of larger
brain-case (1100–1400 cm³) and more
advanced tools and behavior, given
separate species name.
• European populations tall (~6ft), African
populations Giant (~7ft)
• Most likely has true, albeit primitive,
language due to similarities to human
auditory sensitivities
• First hominid to bury their dead
• May be 1st to hunt with projectiles
• European populations evolve into H.
neanderthalensis, African populations into
H. sapiens.
H. neanderthalensis
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“Neanderthal Man”
200,000 – 25,000 years ago
~1450 cm³ brain case
Shorter, but more robust with strong
arms/hands: males ~5’6”, females ~5’1”
• Only found in Eurasia, well adapted to cold
weather.
• Evidence points to interbreeding w/ H.
sapiens between 80,000 and 50,000 years
ago (1-4% of Eurasians have H.
neanderthalensis genes)
• Debate as to whether extinction is caused
by climate change and/or volcanic activity,
competition w/ H. sapiens, or both, or
genetically absorbed into H. sapiens.
Genus Homo: possible lineage scenarios
1. H. habilis
H. ergaster
H. erectus
H. floresiensis
H. heidelbergensis
H. sapiens
H. neanderthalensis
2. H. ?
H. habilis
H. ergaster
H. erectus
H. mauritanicus
H. heidelbergensis
H. sapiens
H. neanderthalensis
3. H. ?
H. habilis
H. rudolfensis
H. ergaster
H. heidelbergensis
H. sapiens
H. erectus
H. neanderthalensis
4. H. habilis
H. erectus
H. mauritanicus
H. neanderthalensis
H. heidelbergensis
H. sapiens
5. H. habilis
H. ?
H. ergaster
H erectus
H. heidelbergensis
H. sapiens
6. H. ?
H. habilis
H. neanderthalensis
H. ergaster
H. erectus
H. mauritanicus
H. heidelbergensis
H. sapiens
H. neanderthalensis