Human Evolution CLASS NOTES

Page 1

05.30.18 - Introduction to Human Evolution

Question structure:

1. Cranial differences between us and other homogenous species, bipedalism

2. Dispersal - how we evolved, where did we evolve,

3. Cultural evolution - brain development leading to agriculture techniques, utilisation of better diets, domestication of wolves for dogs

Cranial Differences between Apes and Humans

1. Foramen Magnum

- Humans: centre of the underside of the skull, better balance for bipedalism

- Apes:

2. Nuchal Muscles

- Humans: reduced, centre of gravity behind the vertebral column

- Apes: large, centre of gravity in front of the vertebral column

4. Shape of skull

- Humans: rounded, enlarged, reduced sites for muscle attachment

- Apes: flatter, smaller brain, (all for aggressive facial features to get their food), allows for greater muscle attachment, cranial capacity reduced (can't process information at high depths like humans)

5. Cranial Capacity

- Humans: enlarged frontal lobes, 1350 cranial capacity

7. Sagittal Crest

Humans

Page 2

06.6.18 - Post Cranial differences between Apes and Humans: Anatomical Adaptations for habitual bipedalism

Main Cranial Differences I need to know:

Sagittal Crest

Zygomatic Arch

Nuchal Crest

Teeth Structure

Jaw Shape

Foramen Magnum

Main Post-Cranial Differences I need to know:

Spine

Rib Cage (Chest)

Pelvis

Femur length linked to Valgus Angle

Opposable Thumb

1. Chest

- Humans: Ribcage flattened from front to back, chest centre of gravity little far forward of the spine - minimises the tendency to fall forward

- Apes: Chest flattened from the sides, have a deeper chest

2. Scapula

- Humans: Shoulder allows the arms to hang freely - enables flexing of the arm at the elbow, the arm is great for throwing and performing tasks

- Apes: Shoulder blade is more suited for hanging from trees, should have three main bones - scapula, clavicle, humerus

3. Spine

- Humans: S-shaped curve to provide support (even distribution of mass leading to bipedalism), balances for the upright biped - centre of mass aligns centrally above the joint

- Apes: C-shaped spine, less strength but promotes quadrupedal locomotion, centre of mass in the middle

4. Neural Spines

- Humans: Short, little muscle attachment required to hold the head upright

- Apes: Long, need for a large surface area for muscle attachment to support massive head held horizontally

5. Pelvis

- Humans: Broader, shorter, supports an upright torso (gives greater stability), the weight of trunk transmitted to the legs

- Apes: Longer, narrower, provides greater attachment area for gluteus medius muscle facilitating the pelvic tilting in quadrupedal motion, greater support for abdominal muscles

6. Legs Structure

- Humans: Longer than arms for walking, the femur is longer to increase stride, straighter to centre body weight down the length of bone, thinner to make light structure so weight is distributed better

- Apes: Shorter than arms for not walking, required for support of the parts of the body attached to lower part of the curved spine, the femur is short and broader, promotes quadrupedal movement

7. Knee Valgus Angle

- Humans: Femur slants downwards and inwards and angles in at the knee joint, knee joints closer together, legs and weight of the body centrally under the spinal cord, increased valgus angle to better balance when walking

- Apes: Femur descends vertically from pelvis with no slant, no weight distribution (balance) for balance

8. Feet

- Humans: Feet placed under the spine, walking is carried out without swaying, feet shape has convex arch under the foot to act like a spring under tension, allows for the transfer of weight down onto the foot to the big toe

- Apes: Feet has no arch (flat-footed),

9. Big toe in Foot

- Humans: Aligned with the other toes, provides the final thrust against the ground to propel the body forward

- Apes: Divergent (slightly opposed), allows for grasping action and anchorage in toes

10. Hand Structure

- Humans: Thumb is long and fully opposable enabling precision grip,

- Apes:

Page 3

06.8.18 - Adaptations for Bipedalism

The position of Foramen Magnum

Femur

Spine Shape

Knee Joint

Pelvis Shape

Shape of Foot

These support the movement away from quadrupedalism to bipedalism

The position of Foramen Magnum

Located more centrally under the skull

Skull is balanced on the spine

Femur

Longer and angled inwards from the hips so that the knees nearly touch

Assists in positioning the upper body over the centre of gravity

Spine Shape

Short and broad

Knee Joint

Bottom of the femur has a buttress of bone (lateral condyle)

Lateral condyle stops the sideways deflection of thigh muscles during walking

Page 4

0.6.8.18 - Advantages of Bipedalism

Efficient Locomotion

Sustenance over long distances

Seeing over the grass

Menacing

Mating

Efficient Locomotion:

Bipedalism provides an energy efficient method that favours low speed, long-distance walking

Sustenance over long distance:

Seeing over the grass

Look over a larger distance and find food sources that over a long distance away

Bipedalism raised hominids' bodies

Quadrapeds had a small surface area - overheated regularly, less thermoregulation

Bipeds big surface area - thermoregulate with convection

Freeing of hands

Tool developments

Diet changes, brain capacity, sourcing food

Disadvantages of Bipedalism

Feet

Flexibility

Back Pain

Morphed Pelvis Shape

The gut is no longer hung from the spine by a broad ligament

Varicose Veins - enlarged veins due to gravity and being bipedal a lot of force and energy required to push blood upwards into the heart

Page 5

06.8.18 - Selection Pressures for Bipedalism

Climate and habitat changed

Pre-hominins may have been forced to move across open ground to exploit their dwindling food resources amongst trees

Near-continuous feet changed to wooded savannah which

drove the pre-hominins (quadrupeds) into bipeds

Shade and Brain Cooling (Radiator Theory)

Seashore Foraging (Wading)

The significance of the emerging of the SAVANNAH and how that led to BIPEDALISM

Selection For Nakedness:

Parasite control

Reduced body hair improves control of ectoparasites

Retention of head hair

The hair on head reflects and radiates solar radiation (heat) before it reaches the skin

Thermoregulation

Shorter, finer hair allows greater heat loss by increasing radiation from the skin surfaces

Well developed sweat glands allowed to lose heat quickly

Hominid - all of the primate species

Hominin - strictly related to the homo-genus which diverged from the great Ape millions of years ago e.g homo recuts, homo sapiens (bipeds)

Page 6

06.12.18 - Human Dispersal

Two theories surrounding the origin of anatomically modern humans (Homo sapiens)

Multi-regional Hypothesis

Replacement Hypothesis (Out of Africa Hypothesis) - talked about the most and is most supported

Multi-regional Hypothesis:

Gene flow between Homo erectus population distributed largely out of Africa

All distributed populations evolved at the same rate

Archaic Homo sapiens evolved into

Out of Africa Hypothesis:

Small population, no contact with other Homo erectus populations in Africa, trapped by mainland barrier distrubuted out of Africa

Genetic Variation reduced - migration out of Africa led to an independent evolution

Sub-species evolved to the rest in Mainland Africa and were displaced by all other human populations in existence at the time

Page 7

06.14.18 - Modern Human Origins

Key Points:

Roughly 100,00 years ago, the Old World was occupied by a morphologically diverse group of hominids. (There was co-existence.) In Africa and the Middle East, there were Homo sapiens, in Asia, Homo erectus and in Europe, Homo neanderthals.

30,000 years ago this taxonomic diversity vanished and humans everywhere had evolved into the anatomically and behaviourally modern form. (Only humans existed, no co-existence). This could be stressed multiregional continuity or a single origin for modern humans (OOA).

OOA hypothesis is more supported by NCEA --> so it would be best to use it for

Multiregional Continuity Model:

Contends after Homo erectus left Africa (as a result of selection pressure, climatic change that affected food availability) and disperse in small population groups, regional populations slowly evolved into modern humans.

Some level of gene flow between geographically separated populations

All living humans derive from the species Homo erectus that left Africa nearly 2 million years ago

Natural Selection in regional populations, ever since their original dispersal, is responsible for the regional variants

The emergence of Homo sapiens throughout the entire geographic range where humans lived

Out of Africa Model:

Modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo erectus (140,000 years ago Homo erectus started to migrate OOA)

Homo erectus (small population size e.g 500) migrated out of Africa, the different populations became reproductively isolated (founder effect), evolving independently

Homo sapiens arose in one place, probably Africa (geographically this includes the Middle East)

Homo sapiens ultimately migrated out of Africa and replaced all other human populations without/minimal interbreeding

Modern human variation is a relatively recent phenomenon

Page 8

06.14.18 - Evidence to support OOA and Multiregional

Out Of Africa: most likely dispersal method

Non-African males share a common ancestor about 140,000 years ago

Africans are more genetically diverse than other races

Low amount of genetic variation in modern human populations (outside of Africa)

There is no Neanderthal DNA in sub-Saharan African populations

Non-African males share a common ancestor about 140,000 years ago

140,000 years is too early to support the multiregional hypothesis

The date coincides with the time Homo sapiens migrated out of Africa

Y CHROMOSOME DNA can be used to trace paternal ancestry to approx. 140,000 years ago

Low amount of genetic variation in modern human populations (outside of Africa)

Origins reflect a small founding population of Homo sapiens

mtDNA supports the view that a small population of Homo sapiens migrated out of Africa between 50,000 and 100,000 years ago

Migrating populations only took a portion of the gene pool with them from their ancestral Africa population (display a lot less variation due to the founder effect in play)

There is no Neanderthal DNA in sub-Saharan African populations

Homo sapiens did not encounter the Neanderthals as they didn't migrate out of Africa - no interbreeding to trace back DNA back to the Neanderthals

Multiregional Hypothesis: look over HYBRIDISATION!!

Fossils (such as "Peking Man" dated at about 750,000 years ago in Asia) seem to show a combination of H. sapiens and H. erectus type features

Fossils (such as "Peking Man" dated at about 750,000 years ago in Asia) seem to show a combination of H. sapiens and H. erectus type features

H. erectus evolving gradually to become H. sapiens

The fossil is a transitional fossil as it is an intermediate between the two genus species

Didn't independently evolved, they dependently evolved at the same rate due to gene flow between each other

Non-Africans include small (1-4%) traces of ancient hominin DNA (Neanderthal)

As modern human moved out of Africa - encountered the Denisovans in Asia and interbred with modern humans (as well as Neanderthal)

Page 9

06.20.18 - Evolution: Tool Development

Biological Evolution: changes in genetic information as it is passed on from one generation to the next

Cultural Evolution: development of learned behaviour as it is passed on from one generation to the next

Tool Cultures:

Oldowan

Acheulian

Mousterian

Diverse shapes and materials

Diverse

Relate it to lifestyles:

H. habilis were scavengers, their lifestyle was scavenging, they didn't actively hunt and kill food, they took rotting carcasses and utilised fleshy remains as a source of protein

Use of tools was limited, simplistic, allowed them to access bone marrow, craniums, scrape remaining tissues of bones for protein source - leant itself for their lifestyles

H. erectus were hunter/gatherers

Use of tools allowed them to hunt for others, therefore, processing meat and protecting themselves against predators - allowed them to go from scavengers to hunters

H. neanderthals didn't have enough food and land-based mammals to get food

Tools gave them the ability to capture mammals and protein from across a distance, increased cranial development overall, brought along division of labour (using tools to make new tools - divided labour between populations for manufacturing and labouring got them great thinking processes, increased the success of reproduction, increased cranial capacity)

H. sapiens

Allowed them to capture and utilise fish, increased protein intake and cranial capacity, allowed to tailor clothing (needles piecing together animal hide and fur to keep them warm as they migrated around the land), allowed them to manufacture farming tools

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06.22.18 - Cultural Evolution Implications

Fire:

First controlled by H. erectus

Couldn't produce fire as they didn't know - knew how to control fire

Their cranial capacity wasn't enough to produce fire

Their ecological niche being dry caused fires - this allowed them to control and regulate fires (used it to their advantage by softening their food, which evidently, reduced their zygomatic arch, brow ridges and sagittal crest, jaw, teeth structure reduced heavily in size)

Selective Advantages: successful alleles can be passed onto next generations

Night activity: see in the dark - spot oncoming predators

cooking: softened food - less energy required to process food, increases reproductive success with the conserved energy, preventing a disease from being spread by toxin-producing bacteria within the meats they consumed, preserves food from rotting

weapons and tools: charring wood and sharpening wood allowed to make a spear which H. erectus utilised

predators: large land-based animals deterred by the fire

communal fire: populations gathered over a fire and passed on knowledge for tool productions

prey herding: helped herd potential prey, or prevented prey from dispersing

warmth:

Selective Disadvantages:

Burning:

Competition: increases - fire highlights their presence in a certain area, potential rival populations will be made aware of homo populations and be found

Ecological Destruction:

More fuel required: less energy is available for reproductive success as greater work input needed

Page 11

06.25.18 - The Implications of Cultural Evolution

Jaw Size

Wide for grinding raw materials for eating

Use of fire makes food softer, easier to chew and grind down

Selection pressures saw these jaw developments

Link to zygomatic arch - there to able the muscle tissue to attach to the jaw to the cranium, larger in earlier species as muscle tissue attached was larger for more forceful movements as food was not pressed/tougher/harder, homo sapiens and neanderthals have small zygomatic arch, less need for muscles attached and the fire makes food processed (positive feedback loop)

Link to sagittal crest - homo sapiens and Neanderthals none crest as less muscle tissue required for the food is more palatable

Brain development - food brings more energy expenditure, cranial capacity gets larger, so cranium got larger in the skull to meet the larger requirement

Clothing

Made from animal skins/hides to keep them warm when migrating from Europe to Asia (experienced a very harsh Ice Age)

The utilisation of fire and animal hide kept them warm during the Ice Age

Clothing wasn't tailored so it didn't keep much warm (due to lack of tool developments)

Animal hide was tough, so it was stuffed inside the jaw to soften (by the females) -

Neanderthals had lack of sophisticated clothing - their reduced thoughts meant communication abilities weren't good and couldn't finess clothing

"The fact that all humans feel

Implications of clothing: migration, wealth, tribe identification/innate role

Communication

Earlier hominin species couldn't communicate properly due to smaller cranial capacity

Broca's area - speech,

Wernicke's area - processing noises

Selective Advantages: tool making, communication, teaching, cooking (preservation, palatable, inedible plants, parasites and toxins gone), predation (protection), social interaction, prey herding, hunting preparation

Spirituality

Made possible by the development of speech, language and technologies - provided a relatively adequate and regular food supply and freed up leisure time

Care for elderly and injured,

The dead were orientated in a particular way - orientated toward East-West direction, head resting on a stone facing south, decorated with black potassium stuff, prevented carnivores organisms from utilising the dead for a food supply

Burial selective advantages: contagious tissue, care for deceased, social bonding (overcoming hardships), social interaction (cohesion), reduce attraction to carnivores

Evidence shows Nandy was cared for despite his extensive injuries

Page 12

06.27.18 - Agriculture - MAY BE PRESENT IN THE MOCKS AND ACTUAL NCEA EXAMS MORE SO

Domestication: bringing in an animal or plant under human control

Causes of Industrial Revolution: (driving forces behind the Agricultural Revolution)

Climate change - End of Ice Age

Fewer animals available - Many large animals became extinct

Selective Advantages of Animal Domestication:

Source of milk or hair: hair for clothing,

Providing a steady income (upper palaeolithic):

Organisms were killed or harvested at their optimum age

When cattle were domesticated, they could be used to lift and carry

Selective breeding occurred - domestication of bees, use of yeast for bread and beer making, use of bacteria for cheese making

Saves/Preserves energy for finding terrestrial mammals - preserves warmth and raising cattle and energy can be utilised to aid successful reproduction

Disadvantages of Animal Domestication:

Many breeds could not survive without human intervention

Selective breeding led to a decrease in gene pools of domesticated species - more prone to many human diseases

Human diseases have evolved from animal diseases - e.g cowpox --> smallpox and influenza probably originated in ducks and chickens

Selective Advantages of Plant Domestication:

Crops became a source of wealth and could be traded

Populations became settled and towns and cities developed

Occupations developed to support food production - e.g carpentry, clothing, art, medicine

Opened up new technological opportunities - e.g pottery (to store food and carry water), smelting

Disadvantages of Plant Domestication:

Potato famine - monoculture in farming (one crop being susceptible to disease as it was the only crop farmed)

Pollution - burning food and the gas emissions as a result, into the atmosphere

Reliance on small number of plant species - which may fail due to disease, flood or drought

Stored food can be eaten by rodents/weevils, or destroyed/rotted by diseases

There were existing hunter-gatherers (H. erectus) during the H. sapiens co-existence with H. neanderthals and Denisovans.