mader: biology 8 th ed. human evolution. mader: biology 8 th ed. classification of modern humans...

Mader: Biology 8th Ed.

Human Evolution


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.



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



Hands/ Grasping Limbs – with long fingers and a separate opposable thumb



• Mobile arms with shoulder joints that allow us to move in three planes

• We are born to CLIMB!


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



Developed upright walk and extensive head rotation

Our skulls are modified for an upright posture



Unique Eyes• Forward facing eyes on a flattened face



Developed unique eyes – The eyes look forward with overlapping visual giving

stereoscopic vision (depth persption


Stereoscopic Vision

• Stereoscopic vision and resultant depth perception allows primates to make accurate judgments about distance and position of adjoining tree limbs.



Reduction in nose and teeth – Flattened noses – decrease ability to smell– Reduced in number of teeth


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.



From Apes to Humanity in 35 million years

• Anthropoids – Apes– Earliest fossil 35 million years ago in

Africa.



• Anthropoids – Apes– Early anthropods

were agile tree dwellers

– Important feature was brachiation of limbs that allowed them to swing between trees



• 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.



• Climate Change– About 15 million years ago Africa collide

with Eurasia.



• 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



• 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



Advantages of bipedalism

• Advantages of walking upright– Freed hands up to obtain or carry food– Hands are free to carry offspring.


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


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.


IB Learning Objectives

• Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including afarensis and A. africanus.


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


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.


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


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


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



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


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….


–Laetoli Ash.



1.4- 2.5 million years ago.

2.Tall lower jaw

3.Fairly large molars

4.Projecting face.

5.Brain size 380- 430 cc


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


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;



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


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;



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


Homo erectus

• Homo erectus –1. Smaller molars2. Receding forehead3. A large brow-ridge 4. Smaller jaw5. Bigger brain size relative

to body size


Homo erectus

– Larger brain and flatter face than Homo habilis.

– Much taller than previous hominids.


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)


Where Homo erectus fossils have been found.

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


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.


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


IB Learning Objective

• Outline the trends illustrated by the fossils of including H. habilis, H. erectus, H. neanderthalensis and H. sapiens.



• 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.



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.


–More evidence analysis of Y-chromosome suggest modern humans –are descendents of African-inhabiting ancestors at least 150,000 ya.



• Homo neanderthalensis–– Arose in Central and Western Europe

about 250,000 ya– Went extinct between 45,000 and 32,000ya



• 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?


Homo neanderthalensis


Human Evolution

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.


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


https://www.23andme.com/gen101/prehistory/prologue/

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



IB LEARINING OBJECTIVE

• Discuss the correlation between the change in diet and increase in brain size during hominid evolution.



• 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 .



• 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?



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.


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;


Large brain size lead to cultural evolution


• Distinguish between genetic and cultural evolution.


Genetic vs. Cultural Evolution

Genetic Evolution

• Refers to changes in allele frequency in a population.

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

Cultural Evolution

• Refers to the development of customs, civilization and achievements of people.


• Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans.


Important Developments in cultural Evolution

• Extension of the Period of parental care

• The Development of Language

• The development of tool technology


• 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


• 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?


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


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.


Human cultural evolution– Enlarged populations– Rules & laws succeeded basic customs.– individuals have acquired rights and

responsibilities


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;


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 8 th ed. human evolution. mader: biology 8 th ed. classification of modern humans...

Documents

arms slide

sapiens slide

upright posture slide

human evolution slide

flattened face slide

number of teeth slide

primates humans

separate opposable thumb