Human Evolution

Part II

Evolution of the Human Brain

• Intelligence is not just a function of brain size – it appears that what is more important is the brain size compared to body size.

• Modern humans have brain volume three times larger than that predicted for an average monkey or ape with our body size.

• Another important factor is the way the brain is organised – evident in the development of the areas concerned with spoken language.

• Two areas of the brain have become highly developed in modern humans – Broca’s area concerned with speech and Wernicke’s area concerned with comprehension of language.

• Selection pressures for increased brain size must have been considerable given the increasing brain volume evidenced throughout hominin evolution.

• Coupled with the brain’s evolutionary development is the increasingly complex behaviour exhibited by hominins

Brain volume for hominins

Hominin Species Millions of Years Ago Average Brain Volume (mL)

Australopithecus afarensis

3.5 440

Australopithecus africanus

2.5 450

Paranthropus robustus 2.0 520

Paranthropus bosei 1.5 515

Homo rudolfensis 2.0 700

Homo habilis 1.8 575

Homo ergaster 1.8 800

Homo erectus 0.5 1,100

Homo heidelbergensis 0.2 1,250

Homo neanderthalensis 0.05 1,550

Early Homo sapiens 0.08 1,450

Changes in Brain Size

Evolution of Behaviour

• Coupled with the brain’s evolutionary development is the increasingly complex behaviour exhibited by hominins

• Enhancing the natural protection of rock shelter

• Caring for the elderly

• Toolmaking using bone and antler

• Toolmaking using flint

• Making clothes from animal skins

• Prolonged infant dependency

The Modern Human MindCreating artifacts and images with symbolic meanings as a means

of communicationUsing knowledge of animal habits, tools, advanced planning

communication to coordinate the hunting of large game

Natural History Intelligence

Predict the future by understanding:•The habits of game•The rhythms of the seasons•The geography of the landscape

Technical IntelligenceProducing and using artifacts required an understanding of abstract ideas and physical processes:•The fracturing behaviour of stone•Best angles of striking stone•How hard to strike a stone•Trajectory of a thrown projectile

Social IntelligenceGroup bonding behaviour improves survival opportunities for members. Language allowed early humans to:•Communicate ideas•Plan survival strategies•Coordinate hunting and gatherings

Paleolithic Tools

• The term paleolithic refers to a time period in the development of human culture that means Old Stone Age

• It spans the emergence of the first recognisable stone tools until the development of sophisticated tool kits in the mesolithic period (Middle Stone Age) about 10,000 years ago

• The earliest human tool cultures date from about 2.6 million years ago in eastern Africa and are known mostly by their stone implements

• This does not mean that the associated hominins did not use other , biodegradable materials (such as wood) – they just did not preserve well,

Timeline of Stone Tool Technologies

Paleolithic Tool Use

• It is impossible to tell with certainty what a tool recovered from an archaeological site was used for

• By studying how similar tools have been used by ‘recent’ stone age societies, it is possible to guess at their likely function

• People using only stone-based technology were still in existence well into the first half of the 20th century

• Anthropologists studying these primitive cultures gathered valuable insights into how our ancestors may have lived

Paleolithic Tool Use

Tool Making Methods

• A variety of stone tool manufacturing methods have been used through the history of tool making

• Some of these methods (particularly hard hammer and soft hammer percussion) were probably combined with other methods in the manufacturing process

Oldowan Tool Culture

First appeared: 2.5 MyaAssociated hominin: Homo

habilis• These tools were simple

river-worn pebbles that were crudely fashioned with a minimum of flakes being removed

• These tools typically had flakes knocked from several angles to produce a core with a cutting edge

• Although the cores may have been used as tools, it is known that the sharp flakes were also useful in cutting

Acheulian Tool Culture

First appeared: 1.5 MyaAssociated hominin: Homo

erectus• These tools were typically ‘tear

drop’ in shape and were carefully crafted with a slight bulge on each broad surface (called a bi-face)

• They ranged greatly in their size and are often referred to as ‘hand axes’ although it is not clearly understood how they were used

• They differ markedly from the earlier pebble tools in that there appears to be a standard “design” and each tool is manufactured using a great many more blows to remove flakes

Mousterian Tool Culture

First appeared: 150,000 years agoAssociated hominin: homo

neanderthalensis• More refined tool culture than the earlier Acheulian tool culture

• Flint became a preferred material to produce stone tools because the very predictable way in which it would chip when struck with another hard object (much finer workmanship was possible)

• The Levallois tool making method involved preparing a core and striking off a large oval flake which is then retouched on one surface only

Neanderthal Culture

• The Neanderthals of Europe and southwest Asia buried their dead in a way that suggests they practiced ritualised burial:– The grave is usually

characterised by certain items found buried with body (burnt animal bones, stone tools and flowers)

– The position and orientation of the body are also found consistently the same (aligned east-west with legs curled up)

• A flute-like piece of cave bear bone has been found at a Neanderthal hunting camp Slovenia (dated at between 43,000 and 82,000 years ago) suggesting that Neanderthals may have made music

Upper Paleolithic Tool Culture

First appeared: 40,000 years agoAssociated hominin: Homo sapiens• There was a rather sudden increase in the

sophistication of tool making about 35,000 to 40,000 years ago

• Both the modern homo sapiens and the last of the Neanderthals produced flint tools of much finer workmanship using a technique called punch blade, in which long, thin flakes are removed and shaped into a large number of different tool types

• European sub-cultures (traditions) include the Magelanian, Solutrean and Aurignacian.

• Other material such as bone, ivory and antler became increasing utilised to produce very fine tools such as needles

Upper Paleolithic Tool Culture

Hunting Big Game

• The ability to hunt and kill large game (such as woolly mammoth and woolly rhinoceros) was a triumph of human innovation requiring:

– Well developed technology to make effective weapons

– Cooperative behaviour plans and coordination of hunts

– Understanding of the habits and behaviour of prey animals

– A knowledge of the local landscape to effect an ambush

– An understanding of the physical laws in order to use weapons (e.g. gravity on the trajectory of a thrown spear)

Paleolithic Art

• Modern humans underwent a cultural explosion about 35,000 years ago giving rise to prehistoric art and new kinds of tools

• The stimulus was probably the need to represent, in some lasting way, ideas concerned with the unknown: death, hunting success and fertility

Mesolithic Cultures

Mesolithic Period: Middle Stone Age

First appeared: 12-10,000 years ago

• Foraging and fishing economy• Characterised by the use of small stone

tools (called microliths) and by a broad-based hunting and gathering economy (including foraging for seeds from wild cereal grasses).

Neolithic Cultures

Neolithic Period: New Stone AgeFirst appeared: 10,000 ya in Middle East• Plant cultivation and animal domestication• The Neolithic culture is usually associated with

the beginnings of agriculture, pottery and permanent settlements in the Old World

• This shift away from a hunter-gather economy, to one which could provide surplus food, meant greater population densities could be achieved and allowed for the development of artisans.

Tools ofMesolithic and Neolithic Cultures

The Beginning of Agriculture

• Farming began in parts of western Asia, the so-called “Fertile Crescent” running from Egypt to the Persian Gulf about 10,000 years ago

• By about 7,000 years ago, agriculture became established in China, followed by Mesoamerica (Guatemala, Honduras and southern Mexico) about 5,000 years ago

Summary of CropsFertile Crescent (10,000 years ago)• Plants - barley, wheat, emmer, einkorn, lentils• Animals - sheep, goats, cattle

Southeast Asia (>4,000 years ago)• Plants - rice, bananas, sugar can, citrus fruits, coconuts, soya beans,

yams, millet, tea, taro• Animals – pigs

Northern China (7,000 years ago)• Plants – rice and millet

Mesoamerica (8,000 years ago)• Plants – beans, maize, peppers, squash, gourds, cotton• Animals – guinea pigs, llamas

South America (8,000 years ago)• Plants – lima beans, potatoes, squash, beans, pumpkin

Africa (>4,000 years ago)• Plants – millets, sorghum, groundnuts, yams, dates, coffee, melons

Domestication of AnimalsDomesticated

AnimalWild Ancestor Region of

OriginDate

(Years ago)

Dog Wolf Many places? 13,000

Goat Bezoar goat Iraq 10,000

Sheep Asiatic mouflon Iran, Iraq, Levant 11,000

Cattle Aurochs Southwest Asia 8,500

Pig Boar Anatolia 9,000

Domestic fowl Red jungle fowl Indus Valley 4,000

Horse Wild horse Southern Ukraine 6,000

Arabian camel (one hump)

Wild camel Southern Arabia 5,000

Bactrian camel(two humps)

Wild camel Iran 4,500

Llama Guanaco Andean plateau 6,000

Water buffalo Indian wild buffalo

Indus Valley 4,500

Ass Wild ass Northeast Africa 5,500

Bronze Age Cultures

Copper Usage• 9,000 years ago in South-east Turkey native copper was

worked by cold-hammering• 6,600 years ago saw the first smelting of copper

Bronze Age• 5,000 years ago saw the

first bronze created by smelting an alloy of tin and copper

• Bronze was used to make implements, vessels and weapons, although stone implements continued in use

• Pottery (beakers) made from fired clay pots became valuable storage vessels

Evolutionary Trendsin Modern Humans

• Modern humans have to withstand selection pressures that are quite different to those experienced by our ‘cave-dwelling’ ancestors

• New natural selection pressures resulting from our modern culture and technology may be affecting our evolution

• Modern humans have:– Larger, more complex brain– Reduced face projection– Less broad nose– Reduced jaw robusticity– Reduced tooth size– Human pelvis has enlarged birth canal– Human femur better adapted for walking– Coarseness of body hair reduced

Anatomical Problems ofModern Humans

• Hypothermia may occur in cooler climates if no clothing is worn (caused by heat loss due to the lack of insulating hair covering the body)

• Teeth are overcrowded as a result of a general reduction in jaw size• Slipped disks and other lower back troubles are compounded by the

load carried by two limbs instead of four• Hernias occur because the gut is no longer hung from the spine and

the intestines may bulge out through a weakened abdominal wall• Childbirth problems are caused by changes in the shape of the

pelvis (a response to bipedalism), together with babies born with larger skulls

• Skin cancer is more prevalent because a reduction of protective body hair means the skin is exposed to more radiation from the sun

• Varicose veins are caused by an upright posture that allows blood to collect in the veins of the thigh and leg (blood must overcome about 1.2 metres of gravitational pressure to return to the heart).

• Feet may suffer strain because the body rests on just two limbs (the arches of the feet collapse producing flat footedness, distorted bones, even hammer toes and bunions)

Biological and Culture Evolution

• Phrases such as ‘biological evolution’ and ‘cultural evolution’ may suggest that the two processes are similar.

• In reality, there are major differences between the two. The term ‘cultural change’ is preferable to the term ‘cultural evolution’.

• In contrast to biological evolution, cultural evolution or change, often based on technological evolution, occurs very quickly in human populations.

• For example, which of the following would occur more rapidly in a human population immigrating to a cold climate: 1. evolving a stocky body shape through the processes of biological

evolution, or 2. learning how to control fire and make fur clothing from the pelts

of mammals through the processes of cultural evolution?• Cultural evolution can occur in other primates. For example, a

female macaque monkey from a troop of monkeys living on a Japanese island began to carry her food to a nearby stream and washed the sand off it prior to eating. Eventually other monkeys copied this behaviour until it spread through the entire troop.

Biological and Cultural Evolution

Biological evolution Cultural evolution•Traits can be transmitted to a person only from parents.•Transmission can occur only from one generation to the next.•Slow pace, with many generations required to spread a trait widely in a population•Traits acquired during a person’s lifetime cannot be transmitted through genetic inheritance.•People cannot choose which genetic traits they will inherit.•Data transmitted are encoded in the genetic material.•Biological evolution is unplanned and results from random processes.

•Cultural traits can be transmitted to a person by many unrelated persons.•Transmission can be within or between generations and can occur between people widely separated in time and space.•Fast pace, as the spread can be by immediate learning and does not depend on inheritance•Cultural traits acquired during a person’s lifetime can be transmitted through processes such as teaching or imitation.•People can choose to accept or reject some cultural traits.•Data transmitted are commonly in the form of written, spoken or signed language.•Cultural change can be conscious and the result of deliberate processes.

Technological Evolution• Technology is the application of science by human beings in order to

gain better control of the material environment. • Technology is expressed through objects, such as tools, machines

and automatons (self-controlled machines), and through complex processes, such as medical procedures.

• Technological evolution refers to changes over time in technology that give humans increased control over their environment, such as the change from stone tools to metal tools, from steam power to electric power, from copper to fibre-optic cables for data transmission, and from typewriters to word processors.

• Historic examples of technological evolution include: – the invention in 1456 of the printing press that enabled mass production

of written material to replace handwritten documents produced in small numbers

– the invention in 1895 of radio that enabled transmission of spoken language across geographic space

– the invention in the 1930s of television that enabled images to be transmitted across space

• In the second half of the twentieth century, technological evolution led to many developments including fibre-optics, lasers and space travel.

Interaction betweendifferent types of evolution

• Many of the cultural changes seen in human societies are based on technological evolution. If we look at human pre-history, we can also see an example of a profound cultural change that was based on technological evolution and on biological evolution.

• This cultural change in early human species was tool making and it first appeared in the habilines (Homo habilis).

• Initially, tool making developed through a technology that used stone tools to create new tools that were also made of stone; for example, using a hammer stone to make stone flakes to be used as cutting tools.

• The significance of this cultural change is in the fact that tools, such as axes, enable the power of the body to be concentrated on a small area of an object so that it can be cut or otherwise manipulated and tools, such as levers, provide a mechanical advantage.

• The development of a tool-making culture by early human species depended on both technological evolution and biological evolution.

• Why? Tool making was possible only because, much earlier, biological evolution in hominins had resulted in two important developments:1. bipedal (two-footed) locomotion that freed the hands for other

purposes2. increased brain size that gave the capacity for greater problem-

solving skills.• So, biological evolution provided the physical and cognitive framework in

which cultural change based on technology could take place in human species.

Interaction betweendifferent types of evolution

Key Points:• Biological evolution, cultural change and technological

evolution interact.• Cultural change in many cases has been based on

technological evolution.• Cultural change refers to changes in human societies

transmitted by social agents, such as imitation and teaching.

• Technological evolution refers to changes over time in technology that give humans increased control over their environment.

• Biological evolution and cultural evolution differ in many ways.

• Technology extends human capabilities.