lecture 4 and 5 human evolution Flashcards
when was the primate ancestor “super order” of euarchonta est?
80 MYA
when did “super order” of euarchonta split into prosimians and simians
50 MYA
another name for simians
anthropoids
“higher primates”
features of prosimians
- grasping fingers & toes
- binocular vision
most nocturnal
mostly arboreal
(live in trees)
features of simians
Direct ancestors of monkeys and hominoids
Originated in Africa or Asia
different adaptive radiations (over 40MYA)
where are new world monkeys from and example
south america
marmosets squirrel monkey
where are old world monkeys from and example
africa and asia
macaques, baboons
how do simsians differ from prosmians
overlapping fields of vision
opposable thumbs (not all genera)
lived in groups (social)
Mostly diurnal (active during the day)
what are the apes
group within simians
who are the apes
All are members of the superfamily Hominoidea (the Hominoids)
Two families of hominoid:
what are the Two families of hominoid
Hylobatidae (e.g., gibbons)
the ‘Lesser Apes’
Hominidae - the ‘Great Apes’
(eg orangatan, chimps, humans
how similar are we to chimpanzees
96% similarity overall
99% similarity in coding DNA
key new characteristics of apes
Larger brain relative to their body size compared to other primates
Flexible behaviour
Tail-less
Some highly social (social interactions)
hands
opposable thumb
feet
chimp and gorillas feet shaped for trees, human shaped for flat surfaces
human ancestsry
Hominoid the ‘Apes’ superfamily Hominid the ‘Great Apes’ family Hominine gorilla, chimp & human subfamily Hominin human & chimp tribe Hominina ‘human’ subtribe
chimp vs hominina anatomy
skull
c; posteriorly attatched
h; inferiorly
chimp vs hominina anatomy
spine
c slighly curved
h s shaped
chimp vs hominina anatomy arms
c longer than legs and used for walking
h shorter not for walking
chimp vs hominina anatomy pelvis
c long and narow
h bowl shaped pelvis
chimp vs hominina anatomy femur
c angled out
h angled in
who is Ardipithecus ramidus
A key step towards human evolution? Dated to around 4.4 MYA Chimp sized brain Broader diet than modern chimps At least partly bipedal
what did all austalopithicus have
Round jaw
Brain size 35% of modern humans
Stocky build
Large teeth and jaws
Various ways of moving,
but can walk upright
how many years ago was A. afarensis
4.2 - 2.8 mya
how many years ago was A. africanus
2.9-2.0 MYA
how many years ago was P. robustus
2.2-0.9 mya
how many years ago was P. boisei
2.3-1.6mya
past desendants had skulls with
flat face
large brow ridge
steepness of skull changing over time
example of skeleton A. afarensis
“lucy”
found in ethiopia 3.2 mya old
human teeth
ape like head
Australopithecus MAY be a direct ancestor of
the genus Homo
many species overlapped in time but…
where were they on space
some characteristics of modern humans around 2.5 mya found in skeleton of H. habilis
Found with many stone tools Short stature Disproportionately long arms BUT: Larger brain than Australopithecines 50% of current human brain size, ~750cc Shorter jaw
homoerectus “replaced” Homo habilis was how long ago
2.0mya
homo erectus stats
About 5 feet tall Long straight legs – excellent walkers Thick skull with steep forehead Larger brain – 1000 c.c.’s (similar to modern human) But still prominent brow ridge Rounded jaw - Ability to talk?
social development of H. erectus
Used crude tools
Built fires
Social groups
Cave dwellers/wooden shelters
neanderthal man stats
Appeared 600,000 years ago in Europe & W/C Asia
12-14cm shorter than modern humans
Large skulls, heavy bony ridges over brows
Bigger brains than modern humans
Common in Europe and Asia 70,000 years ago
neanderthals socially develpment
made diverse tools
Stone and wood
lived in huts and caves
took care of injured and sick
buried dead - symbolic thinking
what was the cro-magnon man
“Anatomically Modern Humans” = AMH
“Early Modern Humans” = EMH
Half way between Neanderthals and modern humans?
Looked like us, but lacked complete suite of modern human behaviours
Replaced Neanderthals by 30,000 years ago, but may have evolved 200,000 years ago (overlap in time)
Sophisticated tools
Complex social organisation
Facial expressions
Language
cro-magnon man developments
Usually 1 offspring
Made cave ‘paintings’
Loss of body hair
Pigmentation (trade off for lost body hair)
Lengthened thumb
- tool use
when did they (cmm) spread across siberia and N. america
13,000 years ago
newest discovered species?
Homo naledi 2015 south africa
what are the two main hypotheses to explain the origin of modern humans
- (Recent) out-of-Africa (or replacement hypothesis, recent single origin hypothesis…)
- multiregional (model of parallel evolution)
what is a brief outline of the out of africa hypothesis
anatomically modern human evolved within africa first and then left africa to colonise new continents
how long ago in the out of africa hyp. did amh evolve and then colonise the rest of the world
200-100KA (thousand years)
in the ooa hyp. what happened when the amh colonised
they “replaced” regional descendants of homo erectus
if ooa hyp. is correct what would we find was true about global populations today?
they should be more closely related
what is a brief explaination of the multiregional hypothesis
homo erectus left africa first, colonized new continents and then AMH evolved outside of africa in multiple different regions
for multiregional hypothesis when and where is the last common ancestor?
africa 1.5 million years ago
what other evidence involving H. erectus backs up multiregional?
H. erectus was scattered through europe asia and africa widespreadly
what explaination is there for similarities of modern people? (multi r )
product of occasional interbreeding between neighbouring populations
what hyp. does skeletal remains support?
hominina fossils 1.2 to 1.1 MYA in spain
multiregional
what does molecular genetics support?
mitochondrial dna indicates origins of AMH in africa with a time of genetic divergence 200,000 years ago
what is odd about the time of genetic divergence found with mtDNA?
it is inbetween the times hypothesized for either theory
why is comparision of y chromosomes useful?
little crossing over during meiosis means diversity in y chromosome is limited to mutations and can act as a marker for examining ancestry
what has y chromosome evidence found?
there is divergence from one common male african ancestor 60 KA
evidence that neanderthals could be a ‘link’ between erectus and sapiens
Neanderthals ‘split’ from descendants of African Homo migrants, but then extinct ~30 KA
Neanderthals ‘co-existed’ with AMHs for at least 1000 years
mtDNA typing shows sharp differences between AMHs and Neanderthals
what model does neanderthal evidence favour
out of africa
amhs replaced neanderthals
whats the third hypothesis
ASSimilation model
brief explaination of assimilation model
Important contribution of a recent common ancestor from Africa (~ out of Africa model)
But emphasises assimilation rather than replacement as colonised rest of world
Predicted that archaic people (e.g. Neanderthals) contributed about 10% of living people’s genome
what recent evidence may support the assimilation model?
neanderthal complete DNA sequecning shows 1 - 4% similarity with europeans and asians but not africans
what does this neanderthal dna sequencing suggest
EMH evolved into modern day humans but ALSO
left africa and cross bread with neanderthals and also evolved into modern day humans outside of africa
what newer evidence contradicts the assimilation theory
denisovan cave girl’s little finger
not neanderthal or modern
(found in siberia)
how old is the cave girls little finger
30-50KA
what is the fourth hypothesis
leaky replacement
what is the leaky replacement hypothesis
Neanderthals and Denisovan populations split about 200,000 years ago – share some DNA
When modern humans left Africa, interbred with Neanderthals, approx 100,000 years ago – these then evolved into modern day Asians and Europeans
A subset of this group went east, and interbred with the Denisovians – these form the basis of modern-day Melanesians
Interbreeding still limited
evidence for leaky replacement
2018 – Siberian Cave – “Denny”
Neanderthal (mom) x Denisovan (dad) hybrid
what is the fifth hypothesis
if neanderthals and modern humans shared a common ancestor approx 500,000 years ago then it could be a common ancestor, not interbreeding
new discovery opposite of out of afraica
into africa??????? wth lol
how much modern african dna can be traced to into africa migrations
25% !!!! wow
what distinguishes us from chimps
- bipedalism
- bisexual social groups
- large brain (complex learning)
- language, society culture
- food obtained though dol and shared efforts
similarities with other primates
Reproductive strategies
Enhanced communication/social behaviour
Tool use
tool use orangutans
use sticks to get insects out of their nests
tool use chimps
use rocks to smash open food
put leaves on their feet to walk over thorns
communication, chimps
social structure
not capable of speach
capable of learning sign language
possible reasons for human language development
Substitute for grooming (was a way to communicate) Hunting theories Language as a way of thinking Motherese (noises to calm infants) Tool making
how did language develop theory one
started with manual gestures
Moved to vocal either because of a conflict with tool use OR through associations of gesture and sound
how did language develop theory two
night is too dark for gestures
speach may derive from how we use our mouths to eat or swallow
changes in brain for walking changed for speech too
evidence for neanderthal speech
kebara 2 is a 60 ka male neand.
modelling of hyoid bone suggests this man had the capacity for speech
what happened at the start of the holocene
cultivation started of cereal grains e.g. wheat & barley
where were the agricultural centers
SW Asia, C&S America, SE Asian mainland
how long ago was livestock domesticated
9KA
what were drivers of human evolution?
fluctuating environments
vulnerabiltity to predation
fluctuating environments how did this drive evolution
changing food sources and environmental conditions, need to be smart and adaptative to survive
vulnerable to predation how did this drive evolution
had to think ways around this fire as protection stone tools as weapons communication (warnings) shelter
what is lamarkism
heritability of acquired characterisitics or instruction by the environment rather than selection by it
example of lamarkian evolution
ostritch callus
what could be a heritable mechanism for lamarkian evolution
epigenetics (darwinian mechanism)
evidence language has a genetic basis
Language and written disorders more highly correlated in monozygotic twins than dizygotic twins
what specific gene is related to language
FoxP2 gene found in many species (including humans) and removal/mutation in it usually associated with impaired communication.
So some genetic basis, but not necessarily all
