Human Evolution Flashcards
How are primates “advanced”?
more developed features & certain behaviours;
reduced teeth & olfaction
How are primates “primitive”?
evolved early in mammalian evolution;
retain features that most other mammals have lost
What features have primates retained that most other mammals have lost?
5 digits, clavicle
How do we know what primate features are shared, derived, or primitive?
compare to features in a primitive mammal (oppossum)
What are the two large divisions of primates?
prosimians & anthropoids
What type of primate are lemurs?
prosimians
Which species is the most primitive of the primates?
lemurs (prosimians)
What are the characteristics of lemurs/PROSIMIANS?
small cranium,
long snout,
long tail
What are the 2 smaller groupings within the anthropoids, from largest/most general to smallest/most specific?
hominoids, homonids
What are some characteristics of new world monkeys?
noistrils far apart,
prehensile tail (can grasph/hold things),
strictly arboreal,
eat fruits or insects
What are some characteristics of old world monkeys?
nostrils close together, though seat pad, quadripedal, mostly arboreal/some terrestrial, marked sexual dimorphism
What is sexual dimorphism?
phenotypic difference between males and females of the same species
What does arboreal mean?
living in trees
What are the unique characteristics of apes?
larger,
no tail
What type of ape is a gibbon and what are some of its characteristics?
lesser apes;
vocal, brachiate, monogamous
What does brachiate mean?
arm swinging - a form of locomotion to swing from tree to tree
What are some species of greater apes?
orangutans,
gorillas,
chimpanzees
What species are more closely related to us than to other primates?
chimps & bonobos
What are some characteristics of orangutans?
herbivores
What are some characteristics of gorillas?
herbivores,
strong sexual dimorphism
What are some characteristics of chimpanzees?
adaptable,
use tools,
can kill animals for food
Where do nearly all primate species live?
tropical places
Why are many primate species endangered?
habitat destruction,
hunted for food,
hunted & sold (bush meat),
killed because they eat crops
What body parts of primates have shared derived features?
hands & feet, mammary glands,
eyes, nose, teeth, brain (cerebral cortex)
What are some shared derived features of the hands & feet of primates?
adapted for grasping, manipulating digits, opposable thumb (pollex), tactile pads with ridges on palms/soles, flattened nails instead of claws
What is a pollex?
opposable thumb
What is a shared derived feature of the mammary glands of primates?
reduced to 2
What are some shared derived features of the eyes of primates and what do they give them?
sophisticated vision;
eye socket surrounded by bone,
binocular - forward facing, close-set eyes,
enlarged visual centres in brain
What are some shared derived features of the noses of primates?
shortened snout,
reduced olfactory abilities
What are some shared derived features of the teeth of primates?
simple cusp design of incisors & premolars,
reduced in number & size
What are some shared derived features of the brains (cerebral cortex) of primates?
enlarged in relation to body size,
unique fissures
What does binocular vision entail?
forward-facing, close-set eyes
What are the 3 hypotheses of the selective pressures that favoured the evolution of the shared derived features of primates?
arboreal theory,
visual predation theory,
angiosperm radiation theory
According to the arboreal theory, what selective pressure favoured the evolution of the shared derived features of primates?
life in trees
Are the 3 hypotheses of selective pressures that favoured the evolution of the shared derived features of primates mutually exclusive?
no
Which theory is the “classic view” of the evolution of the shared derived features of primates?
arboreal theory
What is the problem with the arboreal theory?
not all arboreal animals have the traits (the shared derived features of primates)
According to the visual predation theory, what selective pressure favoured the evolution of the shared derived features of primates?
improved prey-catching ability
According to the angiosperm radiation theory, what selective pressure favoured the evolution of the shared derived features of primates?
new feeding niches appeared with flowering plants (fruits & flowers)
Was the first primate like anything alive today and, if so, why might that be?
perhaps a tree shrew; convergent evolution (since tree shrews aren't primates)
In what might a tree shrew resemble the ancestor of primates?
appearance & ecology (insectivorous, arboreal)
Why must convergent evolution be used to explain why tree shrews might resemble the first primate?
tree shrews are NOT primates;
they LACK the shared derived features of primates
What are some extinct anthropoids, and where did they live?
Eosimias (Asia),
Aegyptopithecus, Dendropithecus, Proconsul (Africa)
What are some trends seen in anthropoids going from oldest to most recent?
larger body size,
more open, drier habitat (more terrestrial)
What selective pressures may have favoured larger body size in Anthropoid evolution?
cooling climate,
competition for food,
redator defence,
competition for mates
Why might the cooling climate have favoured larger body size in Anthropoid evolution?
larger size = lower surface to volume ratio,
so larger animals lose less heat
Why might competition for food have favoured larger body size in Anthropoid evolution?
larger animals can displace smaller ones (especially in groups)
Why might predator defence have favoured larger body size in Anthropoid evolution?
larger animals can fight back (especially when in groups)
Why might compeition for mates have favoured larger body size in Anthropoid evolution?
males compete for access to females (inrasexual selection);
evidence is seen in sexual dimorphism (body size ratio 5:4 to 2:1 (male:female))
When did the last common ancestor of monkeys and apes live?
~ 25 mya
When did the last common ancestors of humans and apes live, and what is this date based on?
~ 6-8 mya;
based on DNA
Why are dates of ancestral species very approximate?
based on DNA;
get revised with new evidence
What is the initial defining physical feature that distinguishes a homonid?
bipedalism
What are some possible advantages of bipedalism?
hands free to carry food & young, make/use tools,
less skin exposed to mid-day sun,
more efficient locomotion in open areas,
better view of surroundings
What are some anatomical changes associated with the change from quadripedal to bipedal locomotion?
pelvis changed shape/tilted forward to support erect position
femur shifted to support weight out to the side,
grasping foot became walking foot
(?)
What changes in the skull have occured with bipedalism?
foramen magnum facing downwards,
shortening of jaw & reduction of teeth,
development of chin
What is the foramen magnum?
“big hole” - where spinal cord enters brain
What homonid characteristics followed bipedalism?
decrease in sexual dimorphism, decrease in tooth size, reduction of face, nostrils point down, less olfaction, increase in brain size, ability to make sophisticated tools, development of language & culture
What finding showed evidence of upright posture and how?
the “Toumai” skull (Sahelanthropus tchadensis);
human-like features: walked upright, small canine teeth, short middle part of face, foramen magnum facing downwards
Where was the “Toumai” skull found and when did it live?
found in Chad, Central Africa;
lived 6-7 mya
What ape-like features did the “Toumai” skull exhibit?
small brain, sloping face, very prominent brow ridges, elongated skull
What lifestyle did “Ardi” (Ardipithecus ramidus) have and what does it suggest
lived in woods (not savanna), climbed & walked;
suggests a human-ape common ancestor that was not chimp-like
When did the Ardipithecus ramidus live?
4.4 mya
What species is the likely ancestor of Homo, when did it live, and what human-like characteristic did it have?
Australopithecus afarensis;
3.85-2.95 mya;
walked upright
What is one of the 3 known “robust” australopithecines?
Paranthropus boisei
When did the Paranthropus boisei live, and how does that relate with our ancestors?
lived 2.3-1.2 mya;
contemporary with our ancestors
Which species was an evolutionary dead-end and what does that mean?
Paranthropus boisei;
no descendants left
How does the structure of Paranthropus boisei relate to its diet?
eats tough leaves;
sagittal crest, massive jaw, high-crowned teeth (horse/cow-like)
What were sympatric in east Africa for a long time (and what was that time span)?
several species of homonids;
from ~1-3 mya
What diet is though to be important in human evolution and why?
meat:
hunted or scavenged,
more quickly digested,
non-toxic (unlike many plant items),
concentrated food source (calories, protein, fat, nutrients),
accomodation of larger brains (cooked food = reduced dentition = room for them)
What may have allowed reduction in dentition, and what would that have accomodated in humans?
the habit of cooking food;
accomodation of larger brains
Which species was known as the “handy man” and why?
Homo habilis (2.4-1.4 mya); earliest known hominid to make and use tools
What species was the earliest known homonid to make and use tools?
Homo habilis
What species was the earliest known user of fire, and where did it remain?
Homo ergaster (1.7 mya); stayed in Africa
What species was ancestral to both Homo erectus and Homo sapiences?
Homo ergaster
Which homonid lost sexual dimorphism, and what does that mean?
Homo ergaster;
males and females same size
What was unique about Homo erectus?
physically better adapted for more efficient bipedal movement;
first homonid to leave Africa
When did Homo habilis live?
2.4-1.4 mya
When did Homo ergaster live?
1.7 mya
When did Homo erectus live?
1.89 mya to 143000 ya
When did the first homonid first leave Africa, and which species was this?
Homo erectus;
1.8 mya
What species was known as “the Hobbit” and why?
Homo floresiensis (95000-17000 ya); only 1 m tall
What were the characteristics of Homo floresiensis?
walked fully upright; only 1 m tall; enlarged frontal lobes (but brain only 1/3 size of ours); no chin; made and used tools
Where were Homo erectus fossils found?
in Africa and across Africa
Where were Homo floresiensis fossils found?
Flores Island, Indonesia
When did Homo floresiensis live?
95 000 - 17 000 ya
What was the likely ancestor of Homo floresiensis?
Homo erectus
When did Homo heidelbergensis live?
700 000 - 200 000 ya (but may reach back to 1.3 mya)
Where did Homo heidelbergensis live?
Africa, Europe, possibly China
What species may be the last common ancestor of Homo sapiens and Homo neanderthalensis?
Homo heidelbergensis
What does DNA evidence suggest regarding Homo sapiens and Homo neanderthalensis?
that the 2 lineages diverged from a common ancestor sometime between 350 000 and 400 000 years ago;
Euorpean branch lead to H. neandethalensis and African brance lead to H. sapiens
When did Homo neanderthalensis live?
200 000 - 28 000 years ago
Which species inhabited Europe during the ice age?
Homo neanderthalensis
What were the characteristics of Homo neanderthalensis?
physically robust,
well-adapted to conditions,
accomplished hunters,
took care of elderly
What 2 Homo species overlapped and may have interbred?
H. sapiens and H. neanderthalensis
What were the Denisovans and what does DNA evidence suggest regarding their interaction with other Homo species?
members of a lineage closely related to Neandertals;
Neanderthals & Denisovans interbred with H. sapiens
Where and when did Homo sapiens evolve?
in Africa;
200 000 ya
What behaviours were performed by Homo sapiens?
culture, sophisticated tools,
hunting, art, care of injured, sick
What are the characteristics of “anatomically modern humans”?
slight sexual dimorphism,
globular, voluminous cranium (short, high, domed),
bony elements above eye (brow ridge) are reduced,
flatter face, tucked under cranium,
vertical forehead,
mental iminence (pronounced chin),
gracile skeleton (long slender bones)
What does maternal inheritance mean?
males do not pass it on in sperm
Why is mtDNA helpful compared to nuclear genes?
evolves quickly;
in nuclear genes, mutations accumulate more slowly & recombination mixes up genes, obscuring history
How does mtDNA differ from nuclear DNA?
single circular chromosome,
only 37 genes,
most of the nucleotides are non-coding
Who was Eve (according to the Eve hypothesis)?
woman to whose mitochondria all living humans can be traced back
(i.e. the 1st female Homo sapiens)
What does genetic divergence data suggest regarding Eve?
that she lived ~ 200 000 years ago
Which human populations are the most divergent, how do we know this, and what does this tell us?
sub-Saharan African populations;
highest mtDNA variability;
therefore the oldest
What is the FOXP2 gene associated with?
speech
When did a mutation in the FOXP2 gene occur?
near split of homonid-great apes
When did the frameshift mutation in genes for chewing muscles occur?
~ 2.4 mya
What may have allowed expansion of the brain’s cortex?
deletions in non-coding regions
What do many homonid fossils appear to represent?
evolutionary “dead-ends”
What are the characteristics of the Homonid evolutionary tree?
no evidence of “steady progress”;
no direct path to modern humans
What advanced behaviours are exhibited by primates?
high level of parental care,
high level of sociality,
cultural evolution
What are the characteristics of primates in relation to their high level of parental care?
few young, born helpless;
long gestation period, grow slowly;
long dependent period;
relatives often help
What are the characteristics of primates in relation to their high level of sociality?
most species live in groups,
complex social relationships,
dominance hierarchy,
learn from others, not just family
IDENTIFY THE PRIMITIVE AND THE SHARED, DERIVED FEATURES OF PRIMATES AND OF HOMONIDS
(learning outcome)
CLASSIFY PRIMATES AND PLACE THEM ON A PHYLOGENETIC TREE
(learning outcome)
IDENTIFY SPECIES OR GROUPS OF SPECIES OF NON-HUMAN PRIMATES AND ALSO HOMONIDS FROM A DESCRIPTION OF THEIR CHARACTERISTICS
(learning outcome)
DESCRIBE TRENDS IN THE EVOLUTION OF ANTHROPOID PRIMATES AND HOMONIDS, AND INIDCATE WHAT SELECTIVE PRESSURES MAY HAVE FAVOURED THE OBSERVED CHANGES
(learning outcome)
PLACE THE SPECIES OF HOMONIDS, AND THEIR NOVEL CHARACTERISTICS, IN RELATIVE CHRONOLOGICAL ORDER
(learning outcome)
INDICATE WHICH HOMINIDS WERE LIKELY DEAD ENDS AND WHICH MAY BE ANCESTRAL TO US
(learning outcome)
EXPLAIN WAHT MOLECULAR EVIDENCE HAS REVEALED ABOUT OUR EVOLUTION
(learning outcome)
