Chapter 19 Human Evolution. On the Origin of The Species Sold out in 1 day, had only a small section...
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Transcript of Chapter 19 Human Evolution. On the Origin of The Species Sold out in 1 day, had only a small section...
Chapter 19Chapter 19
Human EvolutionHuman Evolution
On the Origin of On the Origin of TheThe Species SpeciesOn the Origin of On the Origin of TheThe Species Species
Sold out in 1 day, had only a small section on the origin of man.
12 years later The descent of Man, and Selection in Relation to Sex.
The last chapter concerns the origin and evolution of our species
Sold out in 1 day, had only a small section on the origin of man.
12 years later The descent of Man, and Selection in Relation to Sex.
The last chapter concerns the origin and evolution of our species
On the Origin of On the Origin of TheThe Species SpeciesOn the Origin of On the Origin of TheThe Species Species
It is a much debated topic with different camps of researchers drawing different conclusions
Scopes Monkey Trial 1925 in TN– Prohibited teaching evolution– 1995 AL state board of education ruled
all textbooks must state Evolution is a theory not fact.
It is a much debated topic with different camps of researchers drawing different conclusions
Scopes Monkey Trial 1925 in TN– Prohibited teaching evolution– 1995 AL state board of education ruled
all textbooks must state Evolution is a theory not fact.
On the Origin of On the Origin of TheThe Species SpeciesOn the Origin of On the Origin of TheThe Species Species
I have taught you that evolution is a process, and this process is occurring around us.
Utilizing evolutionary theory we will examine physical, morphological, molecular, and behavioral evidence to test hypotheses about human origins
I have taught you that evolution is a process, and this process is occurring around us.
Utilizing evolutionary theory we will examine physical, morphological, molecular, and behavioral evidence to test hypotheses about human origins
Relationships of Humans and Relationships of Humans and Extant ApesExtant ApesRelationships of Humans and Relationships of Humans and Extant ApesExtant Apes Order Primates– Suborder Catarrhini = Old World monkeys
and apes• Superfamily Hominoidea = great and lesser apes
– Family Hominidae = great apes and humans • Homo sapiens
Our closest relatives are Pongo pygmaeus, Gorilla gorilla, Pan troglodytes, and Pan paniscus– Orangutan, gorilla, standard chimpanzee,
bonobo
Order Primates– Suborder Catarrhini = Old World monkeys
and apes• Superfamily Hominoidea = great and lesser apes
– Family Hominidae = great apes and humans • Homo sapiens
Our closest relatives are Pongo pygmaeus, Gorilla gorilla, Pan troglodytes, and Pan paniscus– Orangutan, gorilla, standard chimpanzee,
bonobo
Relationships of Humans and Relationships of Humans and Extant ApesExtant ApesRelationships of Humans and Relationships of Humans and Extant ApesExtant ApesThese taxonomic classifications are not
universally acceptedIt is accepted that humans belong to the
same clade as African great apes– Synapomorphies
• Relatively large brain, elongated skulls, enlarged brow ridges, shortened canines, wrist bone fusion, reduced hair, absence of a tail, great flexibility of hips and ankles
Which is our closest relative?– Chimpanzees or gorilla?
These taxonomic classifications are not universally accepted
It is accepted that humans belong to the same clade as African great apes– Synapomorphies
• Relatively large brain, elongated skulls, enlarged brow ridges, shortened canines, wrist bone fusion, reduced hair, absence of a tail, great flexibility of hips and ankles
Which is our closest relative?– Chimpanzees or gorilla?
Relationships of Humans and Relationships of Humans and Extant ApesExtant ApesRelationships of Humans and Relationships of Humans and Extant ApesExtant Apes
Molecular phylogeny of Sarich and Wilson had polytomy of chimpanzees, gorilla, and man
Timeline showed that split between apes and Old World monkeys was 30 Mya
Split between African great apes and humans 5 Mya
Molecular phylogeny of Sarich and Wilson had polytomy of chimpanzees, gorilla, and man
Timeline showed that split between apes and Old World monkeys was 30 Mya
Split between African great apes and humans 5 Mya
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican Apes Gorillas and chimpanzees share
knucklewalking which humans lack Humans and two chimpanzees share
features of skull, teeth, limbs, and delayed sexual maturity
Some molecular analyses place humans and gorillas as sister taxa
Conflicting evidence makes interpretation of correct branching order difficult
Gorillas and chimpanzees share knucklewalking which humans lack
Humans and two chimpanzees share features of skull, teeth, limbs, and delayed sexual maturity
Some molecular analyses place humans and gorillas as sister taxa
Conflicting evidence makes interpretation of correct branching order difficult
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican Apes Difficult to identify which characters are
ancestral or derived Dryopithecus is an extinct European ape 10 My
old Shares many traits with gorillas that humans
and chimps lack If these characters are ancestral and humans
and chimps don’t have them, it is most parsimonious for humans and chimps to be sisters
Difficult to identify which characters are ancestral or derived
Dryopithecus is an extinct European ape 10 My old
Shares many traits with gorillas that humans and chimps lack
If these characters are ancestral and humans and chimps don’t have them, it is most parsimonious for humans and chimps to be sisters
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican Apes
Using DNA sequences, researchers attempt to answer human/chimp/ gorilla question
Three different genes gave different tree topologies–mtDNA, Y chromosome, nuclear gene– All trees support humans as sister to
chimpanzees
Using DNA sequences, researchers attempt to answer human/chimp/ gorilla question
Three different genes gave different tree topologies–mtDNA, Y chromosome, nuclear gene– All trees support humans as sister to
chimpanzees
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican ApesCriticism of these reconstructions
because they are gene trees and not species trees
If ancestor was genetically variable for a particular locus, the gene tree may not accurately represent the species tree– Ancestor may pass on a subset of its alleles
for a gene to each descendent species • That gene will not give an accurate estimate of
phylogeny
Criticism of these reconstructions because they are gene trees and not species trees
If ancestor was genetically variable for a particular locus, the gene tree may not accurately represent the species tree– Ancestor may pass on a subset of its alleles
for a gene to each descendent species • That gene will not give an accurate estimate of
phylogeny
Gene Tree vs Species TreeGene Tree vs Species TreeGene Tree vs Species TreeGene Tree vs Species Tree
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican ApesRuvolo wanted to address this issue
directly– She exhaustively sampled human and ape
individuals
– If the gene tree and species tree is incongruent, individuals of a species would not group together
– They always did group together in her study so it was not a problem for that gene
Ruvolo wanted to address this issue directly– She exhaustively sampled human and ape
individuals
– If the gene tree and species tree is incongruent, individuals of a species would not group together
– They always did group together in her study so it was not a problem for that gene
Relationships of Humans and Relationships of Humans and African ApesAfrican ApesRelationships of Humans and Relationships of Humans and African ApesAfrican ApesAnother way to test this issue is use as
many genes as possible and see which ones are congruent
In 14 independent genes – 11 showed humans and chimps together– 2 showed gorillas and chimps– 1 showed humans and gorillas
Human/chimp relationship most likely
Another way to test this issue is use as many genes as possible and see which ones are congruent
In 14 independent genes – 11 showed humans and chimps together– 2 showed gorillas and chimps– 1 showed humans and gorillas
Human/chimp relationship most likely
Genome ProjectsGenome ProjectsGenome ProjectsGenome Projects
Humans 23 prs of chromosomes while chimps and gorillas have 24
Humans 23 prs of chromosomes while chimps and gorillas have 24
Timing the Split (by an undergrad)Timing the Split (by an undergrad)Timing the Split (by an undergrad)Timing the Split (by an undergrad)
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Humans and chimps last shared a common ancestor 5.4 Mya
Most recent ancestor was a knucklewalker, ate mostly fruit, lived in many habitats, had complex social groups, and made tools
What intermediate ancestors lived between chimp/human ancestor and modern Homo and Pan?
Humans and chimps last shared a common ancestor 5.4 Mya
Most recent ancestor was a knucklewalker, ate mostly fruit, lived in many habitats, had complex social groups, and made tools
What intermediate ancestors lived between chimp/human ancestor and modern Homo and Pan?
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Fossils provide some answers– Fossil record is incomplete– Scientists disagree on placement of fossils
on hominid tree Sahelanthropus tchadensis
Fossils provide some answers– Fossil record is incomplete– Scientists disagree on placement of fossils
on hominid tree Sahelanthropus tchadensis
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Sahelanthropus older end of window for split. Looks like chip due to brain case but from front looks like Australopithecine.
Australopithecines are one of the earliest humans– Two main body forms• Robust and gracile
– Bipedal like modern humans• Known from limb structure and footprints
Sahelanthropus older end of window for split. Looks like chip due to brain case but from front looks like Australopithecine.
Australopithecines are one of the earliest humans– Two main body forms• Robust and gracile
– Bipedal like modern humans• Known from limb structure and footprints
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Australopithecines were short with small brain cases
Modern human structure more similar to gracile australopithecines
Robust australopithecines had enormous teeth and very strong jaw muscles for biting tree branches (like gorillas do today)
Australopithecines were short with small brain cases
Modern human structure more similar to gracile australopithecines
Robust australopithecines had enormous teeth and very strong jaw muscles for biting tree branches (like gorillas do today)
Gracile australopithecines
Fossil TimelineFossil TimelineFossil TimelineFossil Timeline
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
First Homo was H. habilisHomo had larger brain cases and smaller
teeth than AustralopithecusHomo was also taller with less sexual
dimorphism in sizeHomo rudolfensis may be the same species
as H. habilis but have some skeletal differences
H. ergaster is more recent ancestor from Africa
First Homo was H. habilisHomo had larger brain cases and smaller
teeth than AustralopithecusHomo was also taller with less sexual
dimorphism in sizeHomo rudolfensis may be the same species
as H. habilis but have some skeletal differences
H. ergaster is more recent ancestor from Africa
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
H. erectus was first human to leave Africa
H. heidelbergenesis is its descendentH. neanderthalensis may be our
ancestor or may have been a sister species that died out
Modern Homo sapiens appeared approximately 100,000 ya
H. erectus was first human to leave Africa
H. heidelbergenesis is its descendentH. neanderthalensis may be our
ancestor or may have been a sister species that died out
Modern Homo sapiens appeared approximately 100,000 ya
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Strait reconstructed a cladogram based on fossils– Such a cladogram is difficult to read
because ancestor-descendent relationships are not adequately depicted
– All species appear as terminal taxa
Strait reconstructed a cladogram based on fossils– Such a cladogram is difficult to read
because ancestor-descendent relationships are not adequately depicted
– All species appear as terminal taxa
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Strait also constructed hypothesis of descendent relationships– Time scale allows testing by fossil
record• New fossils should be found from ages
depicted in correct hypothesis
Strait also constructed hypothesis of descendent relationships– Time scale allows testing by fossil
record• New fossils should be found from ages
depicted in correct hypothesis
Recent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of HumansRecent Ancestry of Humans
Determining trait polarities is difficult so that deciding on which hypothesis is more likely is difficult
In the past as many as five human species coexisted
We are the sole surviving species of a much larger human radiation
Determining trait polarities is difficult so that deciding on which hypothesis is more likely is difficult
In the past as many as five human species coexisted
We are the sole surviving species of a much larger human radiation