Mader: Biology 8th Ed.
Classification of Modern Humans
Kingdom: Animalia Phylum: ChordataClass: MammaliaOrder: PrimatesFamily: HominidaeGenus: HomoSpecies: sapiens
IB Learning Objective
• Describe the major anatomical features that define humans as primates.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Characteristics we share with primates
• Humans retain pentadactyl limbs with five digits and marked mobility of digits
• All primates have grasping hands with long fingers and a separate opposable thumb
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Characteristics we share with primates
Hands/ Grasping Limbs – with long fingers and a separate opposable thumb
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Characteristics we share with primates
• Mobile arms with shoulder joints that allow us to move in three planes
• We are born to CLIMB!
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Limbs/ Mobile Arms
• The arrangement of bones at shoulder permits brachiation movement– the bones of the shoulder girdle allow
weight to be transferred via the arms
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Characteristics we share with primates
Developed upright walk and extensive head rotation
Our skulls are modified for an upright posture
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Characteristics we share with primates
Unique Eyes• Forward facing eyes on a flattened face
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Characteristics we share with primates
Developed unique eyes – The eyes look forward with overlapping visual giving
stereoscopic vision (depth persption
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Stereoscopic Vision
• Stereoscopic vision and resultant depth perception allows primates to make accurate judgments about distance and position of adjoining tree limbs.
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Characteristics we share with primates
Reduction in nose and teeth – Flattened noses – decrease ability to smell– Reduced in number of teeth
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Other Primate Characteristics
• Skull modified for upright posture• Nails instead of claws.• Single births• Expanded, complex brain.• Emphasis on learned behavior.
The unavoidable conclusion
• Humans evolved from other primate species.
• That is we share a common ancestor with other primates, i.e. chimpanzee.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
From Apes to Humanity in 35 million years
• Anthropoids – Apes– Earliest fossil 35 million years ago in
Africa.
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From Apes to Humanity in 35 million years
• Anthropoids – Apes– Early anthropods
were agile tree dwellers
– Important feature was brachiation of limbs that allowed them to swing between trees
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From Apes to Humanity in 35 million years
• Anthropoids – Apes– At the time of human and ape evolution
the climate had periods of extreme environmental change.
– Environmental change was partially due to movements in the tectonic plates and thus the continents.
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From Apes to Humanity in 35 million years
• Climate Change– About 15 million years ago Africa collide
with Eurasia.
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From Apes to Humanity in 35 million years
• Climate Change– As a consequence, the climate in Africa became drier
and colder.– Rainforest were the apes lived were reduced to isolated
pockets.
– Large Savannahs spread over Africa
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From Apes to Humanity in 35 million years
• Climate Change– Many scientists believe that bipedalism
(ability to walk upright) developed in the savanna about 5 Mya;
Discuss the anatomical features that enable bipedalism in humans.
• arches on feet;• stronger bones in legs / stronger legs;• longer legs;• shorter arms;• non-opposable big toe;• foramen magnum further forward;• knees closer together;• wide pelvis;• lumbar spine curved;• larger muscles on legs;
Evidence of Bipedalism
• fossil footprints found (at Laetoli) 3.6 Mya;anatomy of hominids suggests bipedality at 4.4 Mya;
• bipedality possibly associated with a change in habitat and climate
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Advantages of bipedalism
• Advantages of walking upright– Freed hands up to obtain or carry food– Hands are free to carry offspring.
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Advantages of bipedalism
• Advantages of walking upright
bipedality provides greater field of view for foraging / detecting predators;
More advantages of being bipedal
• Thermoregulation:– Smaller surface area presented to the sun
at midday (60%)– Greater air flow across body when it is lift
off the ground
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Trends in Hominid Fossils
• Hominids are members of the family Hominidae.– A notable feature of this family is the
ability to walk on two legs, called bipedalism.
– Homo sapiens is only surviving member of the Hominidae family, but in the past several species co-existed,
example Homo neaderthalensis.
Mader: Biology 8th Ed.
IB Learning Objectives
• Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including afarensis and A. africanus.
Mader: Biology 8th Ed.
Trends in Hominid Fossils
• Many hominid fossils have bee found, dated and assigned to species.
• These fossils show the following evolutionary trends– Increasing adaptation to bipedalism– Increasing brain size relative to body
size
Mader: Biology 8th Ed.
Location of hominid fossils
• Hominids genus/ species fossil location– Ardipithecus – Ethiopia– Australopithecus and Homo Habilis –
Southern or Eastern Africa– Homo Erectus – Eastern Africa & Asia– Homo neanderthalensis found in
Western Asia & Europe– Homo sapiens many parts of the World.
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Ardipithecus ramidus
Ardipithecus ramidus–4.4 Million years ago–Only fragments of skulls and other bones have been found –They show intermediate characteristics between chimpanzees & Australopithecus
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Ardipithecus ramidusArdipithecus ramidus characteristics–Teeth
1. Small number of larger molars like a chimps
2. Incisors slightly smaller than those of a chimp
3. Canines blunt & projecting less that those of a chimp
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Ardipithecus ramidusArdipithecus ramidus characteristics–Skull & Bipedalism
Foraman magnum (hole through which the spinal cord enters the skull) further forward than in chimps suggesting partially Bipedalism
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Australopithecines
• It is possible that one of the australopithecines that evolved and diversified in Africa 4 mya is a direct ancestor of humans.
– Southern Africa Australopithecus
africanus– Eastern Africa
Australopithecus afarensis
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Australopithecines – Southern Apes
• Existed 5 to 1.5 mya• Lucy – Australipithecus afarensis - 3 mya
– Lucy walked upright ( bipedalism)– Evidence to support the above idea
footsteps in volcanic ash – known as the Laetoli Ash.
– The Laetoli Ash was dated using the radioactive method….
Australopithecus afarensis
Australopithecus afarensis
1.4- 2.5 million years ago.
2.Tall lower jaw
3.Fairly large molars
4.Projecting face.
5.Brain size 380- 430 cc
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Autralopithecus africanus
Autralopithecus africanus
1.3-2.5 million years ago
2.Tall thick lower jaw
3.Large molars
4.Projecting face
5.Bony strut
6. Brain Size 435 – 530 cc
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Outline the trends illustrated by the fossils of Australopithecus afarensis. (3 points)
• A. afarensis had traits that indicated bipedality such as a non opposable big toe, a broad pelvis , a more vertical posture and a skull on top of vertebrae;
• A. afarensis also had short legs indicating bipedality;• A. afarensis curved finger bones; which indicated it was
still arboreal (living in trees);• A. afarensis had conical thorax; indicating vegetarian diet;• A. afarensis dentition (teeth) more like a chimp than
modern humans for example they had larger canines and parallel molars;
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Homo habilis
• Homo habilis –– 2.4 to 1.5 mya– Different from
Australopithecines by having light cranial bones and enhanced cranial capacity.
– First hominids to use tools
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Homo habilis –1.Flatter face 2.Large molars3.Bigger brain size relative to body size4. Brain Size was 600cc
Explain why the approximate date and distribution of H. habilis are uncertain.(3 pts)
• Homo habilis existed about 2 (±0.5) million years ago in (sub-Saharan) Africa;
• Dates have high uncertainty because:• fossils lacking or not in good form;• soft parts do not fossilize;• interbreeding of between H. habilis and other hominid
species species may have lead to a mixture of traits and thus miss identification by scientist;
• H. habilis might have migrated to other areas ;• Scientists have different views about when and where H.
habilis lived;• Fossil dating method not totally accurate;
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Homo erectus
• Homo erectus –– 1.7 t0 1.8 mya– First hominid to migrate to
other places and use fire– Large body and brain.– Because of brain size and
shape probably developed language.
– Brain size 1000cc
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Homo erectus
• Homo erectus –1. Smaller molars2. Receding forehead3. A large brow-ridge 4. Smaller jaw5. Bigger brain size relative
to body size
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Homo erectus
– Larger brain and flatter face than Homo habilis.
– Much taller than previous hominids.
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Early Humans Had large brains and busy hands
• Homo erectus –– Fossils have been found all over Europe,
Asia, and Africa.Steinheim Germany (0.25 mya) Sale, Morocco (0.25 mya) Petralona, Greece (0.3 mya) Choukoutein, China (Peking Man) (0.5 mya) Swartkans, South Africa (1 mya)
Homo neanderthalensis1. 200,000- 30,000
years ago
2. Existed at the same time as Homo sapiens
3. Lower forehead
4. Smaller brow ridge
5. Smaller molars
6. Smaller jaw
7. Brain Size 1600 cc
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
State that, at various stages in hominid evolution, several species may have coexisted.
– An example of this is H. neanderthalensis and H. sapiens.
Mader: Biology 8th Ed.
Homo Sapiens
1. 140,000 years ago
2. High forehead
3. Very small jaw
4. Small molars
5. Flat face
6. No brow ridges
7. High forehead
8. Brain size 1300 cc
Mader: Biology 8th Ed.
IB Learning Objective
• Outline the trends illustrated by the fossils of including H. habilis, H. erectus, H. neanderthalensis and H. sapiens.
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
• Knowledge of approximate dates and distribution of the named species is expected
– Ardipithecus ramidus, – Australopithecus afarensis – A. africanus.– H. habilis, – H. erectus, – H. neanderthalensis – H. sapiens.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
The Origin of Modern Humans
• Homo sapiens –– Arose in Africa about 140,000 ya– Evidence from Mitochondrial DNA indicate
that today’s population are related to an African human ancestor.
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–More evidence analysis of Y-chromosome suggest modern humans –are descendents of African-inhabiting ancestors at least 150,000 ya.
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The Origin of Modern Humans
• Homo neanderthalensis–– Arose in Central and Western Europe
about 250,000 ya– Went extinct between 45,000 and 32,000ya
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The Origin of Modern Humans
• Homo neanderthalensis–– Brain size was bigger than modern
humans– Heavier & more muscular than modern
humans– Existed at the same time and place as
modern humans.– Why did they go extinct?
Evolution of the modern human brain
• The brains of early hominids (Australopithecus) were only slightly larger relative to body size than modern apes.
• The teeth and jaws of early hominids suggest a mainly vegetarian diet.
Mader: Biology 8th Ed.
Human Evolution Tutorials/ Animations
• https://www.23andme.com/gen101/prehistory/prologue/
• http://www.becominghuman.org/• http://www.smithsonianmag.com/ist/?next=/
science-nature/The-Top-Ten-Daily-Consequences-of-Having-Evolved.html
Mader: Biology 8th Ed.
IB LEARINING OBJECTIVE
• Discuss the correlation between the change in diet and increase in brain size during hominid evolution.
Mader: Biology 8th Ed.
Evolution of the modern human brain
• About 2.5 million years ago Africa became cooler and drier.
• Savannah and grassland replaced the forest.
• This change in climate is thought to have prompted the evolution of the first Homo .
Mader: Biology 8th Ed.
Evolution of the modern human brain
• The Homo population could no longer hide in tree and there was less vegetation to feed on.
• Homo could make and use tools to hunt other animals and defend themselves from predation survived.
• This change in diet from a vegetarian based diet to a meat based diet corresponds to a rapid change in brain size. WHY?
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Diet and Brain Size
• Brains are metabolically expensive.• Brains make up 2% of our body mass, but
respire 20% of our energy budget.• Human brain is 3X the size of apes’.• This means a requirement for human
evolution was a reliable diet of protein and fat.
• Scientists believe that early humans ate a lot of bone marrow discarded from larger predators.
Mader: Biology 8th Ed.
Diet and Brain Size
• The correlation between brain size and diet are explained in two ways:
1. Eating meat increases the supply of protein, fat, and energy in the diet, making it possible for the growth of larger brains.
2. Catching and killing prey on the savannas is more difficult that gathering plants, so natural selection favoured hominids with larger brains and greater intelligence.
Outline consequences of an increase in brain size for the Homo lineage.
• large brain size correlates with language;• large brain correlates with improvements in
tool-making;• improved tools allow more nutritious diets for• further brain development;• increased brain size leads to rituals / burying
the dead;• excellent eye-hand coordination;• increased brain size leads to written history / • cave art / symbolic thought;
Genetic Evolution
• Changes in allele frequency are due two main factors:
– Genetic Variation in phenotypes
– Some phenotypes are better able to survive and reproduce than others
IB LEARNING OBJECTIVE
• Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans.
Mader: Biology 8th Ed.
Important Developments in cultural Evolution
• Extension of the Period of parental care
• The Development of Language
• The development of tool technology
Important Developments in cultural Evolution
• Extension of the Period of parental care
– Delayed onset of puberty
– Resulting long childhood, when the next generation of a population are trained and schooled as they develop essential survival skills.
• The Development of Language
– Structures necessary for elaborate vocal communication was found in early hominids:
Fossilized braincase show that areas of the brain where language is constructed was enlarged.
Positions of Vocal folds in the neck
high positioned larynx
Important Developments in cultural Evolution
• The Development of Language– Verbal communication advantages:
Passing on new ideasWhat else can you think of that would
be an advantage of having a language?
Important Developments in cultural Evolution
The development of tool technology– About 35000 years ago modern humans
had spectacular advances: bones, antlers and stones were
modified to make blades, chisels, drills, arrowheads, and barbs
Important Developments in cultural Evolution
The development of tool technology– Artistic skills developed. – Drawing dating to 25000 to 10000 years
ago showing contemporary animals in scientific detail.
Relative importance of genetic and cultural evolution
Human cultural evolution– human agricultural and other
technologies has allowed humans to significantly change their environment.
Relative importance of genetic and cultural evolution
Human cultural evolution– Enlarged populations– Rules & laws succeeded basic customs.– individuals have acquired rights and
responsibilities
Relative importance of genetic and cultural evolution
Human cultural evolution– Occurring at a very fast rate– Neolithic revolution to industrial
revolution– Silicon revolution/ information
revolution of today.
Outline the difference between genetic and cultural evolution (2 Pt).
• genetic evolution occurs through variation and reproduction / inheritance of genes;
• cultural evolution occurs through customs / languages, etc. taught / learned;
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Discuss how cultural evolution in humans depended on increases in brain size. (3 pts)
• large brain size correlates with language;large brain correlates with improvements in tool-making;
• improved tools allow more nutritious diets for further brain development;
• increased brain size leads to rituals / burying the dead;
• excellent eye-hand coordination;• increased brain size leads to written history / cave
art / symbolic thought;
Mader: Biology 8th Ed.