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Human Evolution Darwins shocking idea... It is...probable that
Africa was formerly inhabited by extinct apes closely allied to the
gorilla and chimpanzee, and as these two species are now mans
nearest allies, it is somewhat more probable that our early
progenitors lived on the African continent than elsewhere. (from
The Descent of Man)
Dryopithicus found in 1856
Java man Homo erectus found 1896
Primates = Apes + Humans Catarrhini
Old World Monkeys baboons macaques
Great Apes gibbon, orangutan,
gorilla, chimpanzee, human
human & ape synapomorphies:
new world monkeys old world monkeys
24 source trees inferred from mitochondrial DNA, nuclear DNA,
and retroposon characters
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Hominid the group consisting of all modern and extinct Great
Apes (that is, modern humans, chimpanzees, gorillas and orangutans
plus all their immediate ancestors).
Hominin the group consisting of modern humans, extinct human
species and all our immediate ancestors (including members of the
genera Homo, Australopithecus, Paranthropus)
Human evolution:
Among all hominoids, evolutionary changes in humans allowed them
to take bipedal terrestrial locomotion the furthest!
several anatomical adaptations underlie human bipedalism: curved
lower spine, shorter, broader pelvis; angled femur; lengthened
lower limbs, enlarged joint surface areas; extensible knee joint,
platform foot, enlarged great toe; movement of foramen magnum
toward center of basicranuim
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origin of bipedalism? the family tree - based on fossils
http://humanorigins.si.edu/evidence/human-fossils/species/human-family-tree
The Fossil Record:
Sahelanthropus tchadensis aka Toumai found in 2001 in Chad,
dating ~7 mya, mostly complete cranium with a small brain (between
320 and 380 cc) comparable in size to that of chimpanzees.
oldest member of the family so far:
skull was crushed...
Ardipithecus Group: 7 to 4.4. mya
human-like features: flattened face reduced canine teeth
enlarged cheek teeth More upright posture
Ororrin tugenensis 5.72-5.59 mya, found in Kenya,
fossils include fragmentary arm and thigh bones, lower jaws, and
teeth
lived near the time DNA data suggest our oldest hominin ancestor
split from the oldest ancestor of the great apes
Key hominin features: Teeth have thick enamel Muscle &
ligament attachment sites
indicate erect gait
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Ardipithecus ramidus - 4.4 mya
partial skeleton and indirect evidence from skeletal fragments
indicate that this species may have walked upright
Structures marking the articulation of the spine with the skull
are more forwardly located in humans rather than in apes, while the
base is shorter front to back.
Hominid-like A. ramidus cranial base
A. kadabba subspecies of A. ramidus? Mandibular fragments date
back 5.5 mya and appear to be distinct.
Australopithecus Group: A. anamensis - 3.9-4.2mya (knee
joint
suggest stress from walking upright) A. afarensis (clearly
bipedal) -
3.0-3.9mya; Lucy A. bahrelghazali - 3.4 mya A. garhi - 2.5 mya,
larger teeth A. africanus - 2.4-2.8mya (curve of lower
spine similar to modern humans, thus walked similarly; larger
molars)
A. africanus skull Lucy
Paranthropus aethiopicus 2.7-2.3 mya (known from 1 specimen;
baffling mixture of primitive and advanced traits)
P. robustus - 1.5-2 mya P. boisei - 1.4-2.3 mya;
largest teeth & jaws
Nutcracker man
P. robustus
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Homo Group larger brain size, flatter face, no skull crest,
reduced brow ridges, smaller cheek teeth, reduced canine
teeth
H. rudolfensis - 1.8-2.4 mya H. habilis - 1.6 - 1.9 mya (680 cc
brain;
handy-man - precision grip) H. erectus - 1.5 - 1.8 mya (1,000 cc
brain size; pelvis and thigh bones allow for long strides)
hand axe 1.5 mya
GAME OF THRONES!!! A Complete Skull from Dmanisi, Georgia, and
the Evolutionary Biology of Early Homo
first completely preserved adult hominid skull from the early
Pleistocenecombines a small braincase (546 cubic centimeters) with
a large prognathic face and exhibits close morphological affinities
with the earliest known Homo fossils from Africa
This implies the existence of a single evolving lineage of early
Homo, with phylogeographic continuity across continents
NATURE PAPER (Oct. 2013), Lordkipanidze et al.
1.77 - 1.85 mya
Specimens commonly deemed H. erectus (Schwartz et al., 2014)
H. heidelbergensis - 200 - 700 Ka The first truly cosmopolitan
species of Homo, is
first known from Africa at ca. 600 Ka , before appearing at
sites in Europe and eastern Asia from ca. 500 Ka onward. (stone
tools similar to H. erectus)
H. neanderthalensis - 28,000 - 200 Ka H. sapiens - 200 Ka to
present uniquely derived among hominids in the
structure of its skull and postcranial skeleton
La Chapelle-aux-Saints
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H. floresiensis? Remains of the most recently discovered
early human species, (nicknamed Hobbit), have been found between
95,000 and 17,000 years ago on the Island of Flores, Indonesia
individuals stood approximately 3 feet 6 inches tall, had tiny
brains, large teeth for their small size, shrugged-forward
shoulders, no chins, receding foreheads, and relatively large feet
due to their short legs.
Downs syndrome? Strong words over Hobbit
out of Africa hypothesis supported by genetic data the earliest
fossils that resembled members of our species came from southern
and eastern Africa. 650,000 genetic markers in nearly 1,000
individuals from 51 populations around the globe
mtDNA tree
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Y chromosome tree relationships among humans and extant apes
genomic phylogeny aligns Gorilla as nearest relative
phylogeny of COX I (mtDNA) aligns Pan as sister taxa to Homo
Gene trees dont always line up with species trees-If the
ancestral species was genetically variable for the region under
study, then the gene tree estimated from sequence data may differ
from the true species tree
MRCA = most recent common ancestor T1 and T2 denote the
speciation events of humans and chimpanzees, and of
gorillas, respectively. 23,210 alignments of human, chimpanzee,
gorilla, orangutan, and rhesus DNA
sequences from randomly chosen regions of the human genome using
maximum likelihood. We infer that for about 23% of our data set
chimpanzees are not the closest genetic relatives to humans...
(Ebersberger et al. 2007)
If the ancestral species was genetically variable for the region
under study, then the gene tree estimated from sequence data may
differ from the true species tree
selective sweeps in the humanchimp ancestral species would
remove any ancestral polymorphisms and, thus, result in islands in
our genome, where incongruent sequence trees are depleted