Human Evolution Flashcards
Evolution of the Homininae - Themes
Evolutionary themes (in order of
occurrence)
Locomotion
cooling drying climate; expansion
of savannahs
Diet
thin to thick enamel
reduced canines
reduced prognathism
Brain
cranial capacity
fluctuating climate
Mosaic pattern of human
evolution (NOT progressive)
Long gaps
Different rates
Chimps are nearest living relatives
Nearest common ancestor ca 6-7 MA
Share ca 99% of coding DNA (closely
related)
Shared traits due to
shared common ancestor
* e.g. Y-5 molars
no tail
convergent evolution
male cooperation(?)
* warfare(?)
Prognathism
Condition in
which part of
the face below
the nose is
pushed out
Brachiation (4)
Method of
movement that uses the arms to
swing from branch to branch
this is a distinction in the early hominin line from its ancestor
Diastema = Space between the upper canine
and incisor that accommodates the lower canine
must have a place for gap for canine, due to large canine
chimp skeleton male
- Hindlimbs shorter
than forelimbs - Long pelvis
- Knuckle walking
- Protruding face
- Spinal cord and the
vertebrae enter into
the cranium
posteriorly
Australopithecus Group
Erect & bipedal
Relatively long forelimb (ape-like
Sexually dimorphic (chimp-like)
* Small brains (chimp-like)
Intermediate teeth
- slight diastema
reduced canine
thicker enamel than ape
Locomotory transition: Arboreal suspensory to
bipedal (3.8 mya)
Australopithecus: warming, drying climate
> forest to savannah woodland
1. Postural adaptation for
feeding
- Thermoregulatory
(reduce surface area for insolation) - Energetics of movement over open ground
- Carrying objects
- Wading hypothesis
Australopithecus
afarensis
(4.2 - 2.9 mya)
LUCY
40% complete skeleton
Adult female
105-150 cm; 29-42 kg
Sex dimorphic
Skull/dentition
small braincase
prognathism
reduced canine
little bit of a diastema
Pelvis broad & narrow
Femoral neck long
Femur slants inward
› early bipedal
BUT arms somewhat longer
relative to legs than in humans
* slept & foraged in trees
Paranthropus (3 - 1 mya)
S & E Africa
Bipedal
Small brains
Robust masticatory
apparatus but not
entire bodv
Small incisors
Reduced canines
Massive cheek teeth
Large masticatory
muscle
as per bony attachment
on sagittal crest and
mandible
3 major genera
australopithecus
paranthropus
homo
australopithecus
biped, gracile, small brain
paranthropus
biped, robust crania, small brain
homo
biped, gracile, relatively larger brain
earliest homo
H. Habilis and H. rudolfensis
east africa
forelimb proportions similar to A. afarensis
slightly enlarged brain (wide variation in body size larger too)
reduced facial size and smaller teeth
parallel sided dental arcades
chimp mandible, bottom jaw forms a rectangular shape, this is because their faces are prognatic, most apes are like this
parabolic dental arcades
human mandible, bottom jaw forms a u shape, face is becoming flatter and flatter, and we are losing that prognatism
reduction in jaw size and facial flattening
our faces became more flatter because of our diet and invention of cooking the food that we ate become softer, and easier for our ancestors to chew the foot items, this allowed the facial flattening and contributed to our teeth getting smaller.
stone tools
cutting marks on bones = human hunting
concentrations of bones and stones suggesting central place foraging - carying meat back to a camp
(shows homo hobolis had base camps)
the pilo-pleistocene
Rapidly cooling climate
ice sheets & land bridges;
more of ocean ways are in
ice sheets
changes in vegetation
Cooling selects for
increased body size
Environment of evolution
of Homo ergaster and H.
erectus
Reduction in hominin
diversity
bipedal femurs
longer shaft, longer neck, and change in distal morphology, pan has small upper part, australopheitics has larger upper boney part, homo has largest femur
‘Nariokotome Boy’: H. ergaster
~1.8 mya
Approx. 12 years old
micro lines in teeth
Brain 850-1000+ cc
Tall (approx. 1.9 m at adult)
Fully committed to terrestrial
life
long legs
narrow hips
narrow shoulders
barrel-shaped chest
short arms
Longer development period
* later eruption of molars
Homo ergaster & H. erectus
H. ergaster in Africa from 2.0 - 0.6 mya (?)
Mostly Acheulian tools
- controlled fire
hunting of large mammals
Some disperse from Africa early to Eurasia and Asia
H. erectus in Asia approx. 1.8 - 0.1 mya
less complex tools than H. ergaster
controlled fire
dead end group but persists longer than H. ergaster
Bipedal locomotion precedes tools and big brains
Tool use/modification precedes period of greatest
encephalization
‘Slowed down’ life history may begin in H. ergaster
teeth human like in size and proportion
Meat consumption, handaxes, fire
First major dispersals of hominins from Africa to Eurasia
* H. ergaster at approx. 1.8 mya to Eurasia
anagenesis definition
transformation of a single species over time
homo heidelbergensis
similarity with homo ergaster
brow ridge
homo heidelbergensis major derived feature
more rounded, higher skull, which is a major difference between homo heidelbergensis and homo ergaster
when did homo heidelbergensis
roughly 600,000 and 200,000 years ago was originally found in africa, but migrated into europe and asia
difference between modern humans and homo heidelbergensis in skull morphology
higher cranial bolt
brow ridges
in terms of overall shape, human skull is more globular, homo heidelbergensis is more oval shaped
differences in mandible traits within humans and homo heidelbergensis
in homo heidelbergensis, smooth mandible, homo sapeins has an out jutting of the mandible and the fusion of the two parts of the mandible, the chin
skull characteristics used to identify neanderthals
large elongated skull, ridges that are supraorbital ridges, bump at the end of skull which is very diagnostic
nederthals had an anatomy for colder climate, smaller forehead
what are neanderthals and homo sapiens
they’re sister species, derived from a common ancestor
there is aslo evidence for admixture (we was both fuckin lol)
neanderthal lifestyle
probably buried their dead, lived in caves, hunted big game, hunter gathers, evidence of cannibalism
Cro Magnon: Early
H. sapiens (50-30 kya)
lifestyle
Decorative art, figurines, more
complex tools (Upper
Paleolithic), raw material
transport, shelters, burials etc.
Obstetrical Dilemma
Human pelvis bowl-shaped
adapted for bipedality
- but restricts size of birth
canal
BUT giving birth requires a
birth canal wide enough to
allow baby’s head through
Dramatic increase in brain
size after becoming bipedal
created a problem ->
obstetrical dilemma
Maternal Adaptations
Increase in neonatal
cranium > selective
pressure on
size of opening of female
pelvis resulting in sexual
dimorphism of the human
pelvis
softening of pubic
symphyses at end of
pregnancy
Neonate adaptations
Bones of cranium not
fused
able to slip >
allow
compression
during birth
space for rapid
postnatal brain
development
Life history of
Homo sapiens
Short to normal gestation for size
Altricial (‘undeveloped’) at birth
Rapid post-natal brain growth
Long juvenile period for size
Relatively short inter-birth interval
delayed age at sexual maturity
post-reproductive life span
