Human Evolution

Sources: Miller, Living in the Environment, Ch. 4 J. Diamond, The Worst Mistake in the History of the Human Race Bronowski, J. The Ascent of ManHuman Evolution: The Current State of Affairs and So Near Yet So Far - S.J. GouldNew York Review of BooksScientific American, Jan. 2003 – An Ancestor to Call Our Own.The Greening of the World - Clive PontingThe Great Leap Forward by Jared Diamond in text Technology and Society

GENERAL FACTORS AFFECTING HUMAN HISTORY

Large scale geological and astronomical forces over long periods of time have had effects on human life:

Plate tectonics - movement of land masses caused by convection currents in the molten core of the earth.

Where the plates meet there is disruption in the form of earthquakes and volcanoes. Many natural disasters have essentially devasted human civilizations/settlements. Thera may have destroyed the Minoan culture in Crete and Vesuvius destroyed Herculaneum and Pompeii. An earthquake in Shensi province in China in 1556 killedover 800,000 people. More recently, Lisbon in 1755 and Tokyo in 1923 that killed tens of thousands.

Continental drift - (dates vary greatly)

Pangaea - somewhere around 225 million years ago (Permian period), various land masses had collided forming a large continent surrounded by the Panthalassa ocean. The Appalachian mountains in the US were formed by the collision between north america and Europe. Ten different orders of reptiles, from cro-codiles to dinosaurs dominated primitive mammals. Appearance of birds.

200 million years ago (Triassic period) earth had two supercontinents: Laurasia (north America, Europe and Asia) and Gondwanaland (south America, Africa, India, Australia and Antarctica) divided by the Tethys Sea. Separates species on the two continents, flowering plants appear. Southern continents situated over south pole, causing glaciers in what is now Brazil and South Africa, while Laurasia was in the tropics. North American broke from Europe about 80 million years ago, the last 80 million years has seen the creation of the Atlantic ocean.

65 million years ago - further separation of continents. South America and Africa separates during last 100 million years, although Africa was still touching Euroasia until 40 million years ago. Northern animals could spread south, and African mastodon and elephant expand range, even to New World. India as island moves upward. Break between Australia and Antarctica occurred in last 60 million

years. Expansion of mid-ocean ridge floods continental margins. Mammals diversify and come to dominate reptiles.

Today - India moving into Asia, uplifts the Himalayas and Tibetan plateau (rise a meter every century). The Mediterranean Sea is the remnant of Tethys Sea (plate boundary between Europe and Africa). rifts inch open in East Africa. Coastal California moves northwest and 40 million years from now will be an island. Arabia and Africa are separating, creating new sea bed in the Red Sea. Stress of converging plates causes volcanoes, like in the Pacific Rim.

Continental drift has had a profound effect on human history. Determined distribution of resources and distribution of flora and fauna on the continents.

Coal, oil and natural gas come from the decomposition of the vast tropical forests present about 250-300 million years ago.

Some animals have evolved in isolation and some have been driven to extinction by competitors when suddenly brought into contact with other parts of the world.

e.g. marsupials had a worldwide distribution about 80 million years ago. Replaced in Europe by mammals when continents drifted apart. Survived in South American until it joined with North America about 30 million years ago. Still live only in isolated Australia.

e.g. Isolation of Americas from the Eurasian landmass meant that animals domesticated in Europe and Asia such as sheep, goats, cattle and horses were not present. Influenced both agriculture and transport. Americans knew the concept of the wheel, but could not use it effectively with drought animals.

 Climate: a fundamental force in shaping human history. Climate variations affects crop yields, and in the long term have influenced the ability of humans to settle in certain areas of the world, have influenced the way plants and animals are distributed and have placed limits on the types of crops that can be grown. The ice ages were created due the concentration of land masses down from the north pole, which allowed glaciers to creep down from the north. The south pole is basically isolated by water, and so glaciers could not form down there. The ice ages have dominated the earth's climate for the last 2 and a half million years.

Causes:

1. Position of the continents (see above)2. Steadily increasing solar output3. Carbon dioxide and methane in atmosphere4. Three astonomical cycles affecting the earth and its orbit round the sun.

Earth's orbit varies from an elipse to a nearly perfect circle every 90-100,000 years. At present orbit is becoming more circular, thereby decreasing the difference between the times when the heat from the sun falling on the earth is at its maximum and minimum.

The timing of the earth's closest approach to the sun is completed every 21,000 years. At the moment the earth is nearest to the sun during the northern hemisphere winter. Reduces the impact of seasonal climatic change in the north whilst increasing it in the southern hemisphere.

The third cycle affects the tilt of the earth, which varies over a period of about 40,000 years. At the moment the tilt is decreasing which again reduces the difference between the seasons.

These cycles affect the distribution of the sun's energy falling on the earth. The current closeness of the continents in the northern hemisphere to the pole is of crucial importance because only a 2 per cent drop in heat from the sun during the northern summer can initiate glaciation. Cool summers allow winter snow and ice to survive to the next winter and the growing snow cover causes further cooling by increasing the reflectivity of the earth's surface. Further reduces the temperature in the northern hemisphere leading to a rapid increase in the extent of ice sheets and glaciers. This does not work in southern hemisphere, because of insufficient land mass.

The series of ice-ages has dominated the earth's climate for the last 2 and a half million years. There has only been about 250,000 years between glaciers.

 What Makes Us Human?

Humans are characterized by a particular morphology, or structure. We use the word “morphology” to refer to our form at any given moment, since our present form is the result of a life of development involving biological structure taking on form via couplings with the environment. We are dependent for our survival on complex and interrelated physical, chemical and biological processes.

Our species form is the product of at least 5-8 million years of evolution along a distinctive track, this being the estimated length of time we have been evolving separately from other primate species.

All species are unique, and are defined by a pattern of variables. There is not just one characteristic that makes us human, but a number of combined characteristics - upright posture, large brain, opposable thumb, a flat face, a unique vocal apparatus, etc. We cannot also forget the physico-chemical aspects that make us unique, etc.

What we are today is the result of multiple adaptations to certain environments throughout our evolutionary history. We have carved out a niche for ourselves - a place within all the physical, chemical, and biological processes and we hold certain interrelationships with other organisms. We belong to communities of organisms, and our place in these communities is something that must be continually maintained.

The environment to which we have adapted provides the essential foundation for our viability as organisms. It influences our behavior by providing constraints on our development as individuals and patterns of interaction with each other, or our social structure.

The particular way in which we live in the world is the result of several interdependent factors:

1. Our morphology - determines what we need to survive as biological organisms; nutrients, air, water, etc. We also require social stimulation for the proper functioning of our nervous system.Our physical shape determines how we walk through and touch the world - upright posture, manipulating hands, eyes in front, flat face, face to face communication. A large brain has made it possible for us to attend to the world in more complex ways, allowing for more complex behaviors such as planning and controlling our actions.

2. Social organization - our morphology necessitates development within a social context. In the absence of any particular physical skills, our primary means of adapting has been the development of group cooperation. This includes all the mechanisms by which we get what we need from the world - our economics.

3. Ecology - in this context, environment. We live in a structured environment, first "natural" characteristics and then "human", "artificial" characteristics. The need to survive in the world has given us the morphology that characterizes us today. We now live in a human, artificially constructed world - structured in time, physically organized, objects of daily use.

Continuities Between Humans and other Living Organisms(Source: S.J. Gould; A matter of degree. In Ever Since Darwin)

From the beginning of recorded history, we find a concern with what makes humans distinct from other living organisms. This is really a search for human nature, for our essence. We have had a hard time accepting that we are part of the living world. A great many suggestions have been made over the centuries. Some popular ones have been the soul, a mind, the use of tools, language, and our intelligence.

One favorite approach to this question during the last 150 years has been to compare ourselves to our closest relatives, the chimpanzees and gorillas. Strange as it may first seem, the differences between ourselves and our closest evolutionary relatives are minimal. We share every brain and bone structure with a chimpanzee. In fact, a bit over 98% of our genes are the same, and yet they look quite different.

A debate raged in England in 1861 about possible differences in brain structure between chimps and humans between T. Huxley and R. Owen. Owen claimed that there was a small convolution in the hippocampus minor - a small structure in the limbic system of the brain. Huxley claimed that such a structure did not really exist. Huxley won.

Possible criteria for asserting our uniqueness.

Popular distinctions:

1. Functional or behavioral differences When asked what the differences are between ourselves and chimpanzees most people come up with examples of functional or behavioral differences. These include such things as intelligence, tool use, rationality or logical abilities, language, morality, a mind, or self-awareness.

In every one of these areas differences exist but these differences are not differences in kind, they are differences in degree. Chimps show elementary aspects of all these characteristics, if raised under the appropriate conditions.

2. Structural or Morphological (form) differencesAgain, differences between ourselves and chimpanzees exist but they are not qualitative differences (of kind) but are qualitative (degree) differences. A chimp has every brain structure we have – but our brain in larger. We share every single bone, but their shape differs.

We can point to a number of characteristics which mark a difference between the two species and which seem to have played a very important role in human evolution – e.g. an upright posture, an opposable thumb, a round, bulbous cranium (allowing for a larger brain), a vocal apparatus which makes speech possible.

3. Genetics There are very few genetic differences as mentioned above. We share over 98% of our genes with chimpanzees. If we thought that each organic trait (like an upright posture) is caused by a single gene we could reconcile the paradox; many differences in form and function would reflect many differences in genes. But then there should be many more gene differences than there are, given the differences in form and function.

In biology we can define Sibling species, which are similar in morphology but separately reproduce. We also define Congeneric species - pairs of species placed in same genus but different morphologically.

Chimps and humans are much closer than either category.

Question: what do those genes that make up the 1 or 2% difference do?

Answer: certain genes must have big effects on entire organism. These few genes must be creating a great divergence. The biggest effects could come from genes that control the regulation of timing of when things happen in the developing organism. Humans may have had mutations of the regulatory system.

All cells in our body have the same genes in their nucleus. Liver and skin have the same genes – so what makes them different? The difference is in their alternate paths of development. Genes are turned on and off at different times during development depending on their location in the embryo and fetus.

perhaps it is the timing of when events occur and the changing sensitivities of the organism at different points in development, that makes the differences between us and a chimpanzee. The turning off and on of genes is a complex process involving all sorts of chemical, genetic, and more general higher level factors. The effect of a single gene or chemical early on can have a great effect when the developing system is simple. Are the differences then due to the timing of gene expression during development?

Could regulatory genes be the difference between ourselves and chimpanzees? If so, they would have to account for the major important human characteristics:

1. a large brain2. an upright posture3. speech4. the technological means to adapt to hostile environments

Delayed Development

One thing we might note about humans is that there appears to have been a retardation in developmental rate. Compared to other primates, we are physically less developed at birth, we mature later, and live longer.

For example, compare the state of brain development at birth for different primates:

Rhesus monkey - 65% of final sizeChimpanzee - 40.5% of final size, 70% in first year.Man - 23% of final size, 70% at third year.

30% of the human's total life span is spent growing.

One consequence of this is that learning is enhanced by our delayed maturation. This is important for an animal that is not particularly strong, swift or well designed. Nor do we reproduce rapidly. Learning is enhanced by extending childhood and delaying sexual maturation which leads to a desire for independence. We are tied for a longer time to our parents which makes for greater learning and the strengthening family/social ties.

A lot of our advantage is related to the size of our brain. It also must have to do with the way it functions. Over 70% of the final growth of our brain occurs outside the womb in a human world. This is absolutely necessary for normal brain functioning. We would not be human if we were not raised in a human social context.

(Note that there have been unfortunate cases of children who are normal physically but who have been raised by ill parents in closets or attics. These children, without social and physical stimulation, do not grow up to be what we call human. They lack language, are of low intelligence, and have little self-awareness. Being human requires a human developmental context, it is not “given” in our biology. Our biology, while a necessary condition for being human, is not sufficient.)

Let’s take a closer look at the human state at birth….(Source: S.J.Gould; Human Babies as Embryos. In Ever Since Darwin)

Newborn animals may be characterized as falling into two general types (work of Adolf Portmann):

1. altricial species – these species have a brief gestation period (gestation means the time the female is pregnant) and large litters of poorly developed young (tiny, hairless, helpless, unopened eyes and ears), short life spans, small brains (relative to body size), and low level of social behavior.

Altricial species may correlate with marginal, fluctuating and unstable environments in which animals do best by high reproductive rates.

2. precocial species – these species have long gestation periods, long life spans, large brains, complex social behavior, give birth to a few well developed babies that are partially capable of defending themselves at birth.

Precocial species may correlate with stable, tropical environments. Predictable resources and so invest energy in a few will developed individuals.

How would you characterize humans? We seem to be a mix of these two types. Our young are relatively helpless at birth compared to other primates, and yet we seem to fall in the precocial catetegory in other respects.

The answer seems to lie in the fact that human development has been retarded but our gestation period has not. If we examine the relationship between primate gestation period and the total life span of an individual species we find a ratio that is the same for all primates. The longer the life span the longer the gestation period. However, this relationship does not hold for humans. Our gestation period is slightly longer than other primates but quite short in relation to our life span.

Total Life Span Gestation Period

Apes _________/__________________

Humans _________/___________________________________________________

Chimpanzees for example have a life span of roughly 65 years and the females have a gestation period of about 8.5 - 9 months and usually have a single baby at a time; twins are rare. They are fully grown and able to reproduce at 12-13 years old.

If we had a gestation period of the same life span proportion as other primates, our females would be pregnant for 18 months.

Consequently, we are born too early. This explains why we are both altricial and precocial. We are born as fetuses, and still have a lot of growing to do after we are born.

Why has gestation stayed short? A likely reason is that the female birth canal is too small, restricted in size by our upright posture. As it is, the birthing process in humans is not too easy, our babies are large compared to size of the female. As it is, an infant’s head has to be compressed so that it can pass through the birth canal. If development occurred later, after the skull plates had become fused, the baby could not pass through the birth canal. (the “tight squeeze” hypothesis). Fetal size is near its limit in our species.

Neoteny (“holding youth”)(Source: Gould; The child as man's real father. In Ever Since Darwin)

The idea of neoteny is that because our development has been delayed, we spend more of our time in the world as infants, and because of this longer development time, juvenile primate characteristics could have been selected for in evolution. Those characteristics would have been retained that make human adults more adaptive. "Juvenile features are a storehouse of potential adaptations for descendants, and they can be utilized easily if development is strongly retarded in time...In our case, the "availability" of juvenile features clearly controlled the pathway to many of our distinctive adaptations.” The slowdown or retardation of development does not guarantee the retention of juvenile characteristics. But it makes them available for selection.

If we compare ourselves to primates, especially the gorilla or chimpanzee, we find that we share certain characteristics with infant apes. The apes lose these characteristics as they grow up – we retain them. We can identify at least 20 such characteristics, 6 of which are listed below.

Characteristics we share with juvenile stages of other pri mates

1. Rounded, bulbous cranium – Infant apes have a round head, but the brain grows much more slowly than rest of the body so the skull is lower and relatively smaller in adults. We have retained our rapid fetal growth rate and the brain grows faster.

2. Juvenile face – Infant apes and humans have a straight facial profile, with small jaws and teeth, a weak brow ridge. Jaws of juvenile apes grow more rapidly than the rest of the face, forming a pronounced muzzle in adults.

3. Position of foramen magnum - the foramen magnum is the hole at base of skull where the spinal column enters the head. In humans this hole is pointing downward, with the skull on top of the backbone and the eyes directed forward. Infant apes share this characteristics, but as they grow this hole moves toward the back of the skull so their natural posture is one of walking more or less on all fours.

4. Skull sutures – In humans there is late closure of the skull sutures and delayed cal-cification of the skeleton. This is noticed in the soft spot in the head of newborn humans, where the bones are not yet closed over the brain. It allows for postnatal expansion of the brain. Fingers are cartilaginous at birth.

5. Vaginal canal – In humans the ventral position (facing forward) makes face-to-face copulation possible. In other primates it rotates towards the back as the animal grows up, so that their natural posture for sex is from the rear.

6. Big toe - Our big toe is strong and unopposable. In most primates the toe begins as ours and later rotates to the side and opposes others for efficient grasping. For us a strong toe creates a stronger foot for walking upright.

These are retarded characteristics (neoteny) but there are more advanced characteristics as well – such as our long legs and large brain.

To some extent our organs evolve separately in response to different adaptive requirements. This is called mosaic evolution.

Does this mean that if we lived longer we would grow into apes?

No. But the idea has had its defenders. A satirical story was written on this theme by Aldous Huxley (author of Brave New World). The story was called After Many a Summer Dies the Swan:

An American millionaire, Jo Stoyte, sets out to purchase his immortality. His hired scientist, Dr. Obispo, discovers that the fifth Earl of Gonister has, by daily ingestion of carp guts, prolonged his life well beyond 200 years. They rush to England, break into the earl's well guarded estate, only to discover that the Earl and his lover have grown into apes.

The truth about our evolution is out - we evolved by retaining the youthful features of our ancestors (neoteny - "holding youth")

"A foetal ape that's had time to grow up," Dr. Obispo managed at last to say. "It's too good!" Laughter overtook him again....Mr. Stoyte seized him by the shoulder and violently shook him..."What's happened to them?" "Just time," said Dr. Obispo airily...the foetal anthropoid was able to come to maturi-ty...without moving from where he was sitting, the Fifth Earl urinated on the floor.

The Emergence of Humanity

(See Ch. 1 "Lower Than the Angels" in The Ascent of Man by Jacob Bronowski)

Origins in Africa - from Ethiopia to South AfricaSome 3,000,000 years ago.

The earliest fossils are found in the savannah country that stretches out across Northern Kenya and South West Ethiopia near Lake Rudolph. The Great Rift Valley along the river Omo. 4 million years of thick sediments.

The fossils of animals are similar to those of animals today. Humans have changed more than animals - why? Not because they were better hunters - the hunting animals are basically the same.

Because humans were not well adapted to their environment. Being well adapted traps a species - change does not occur. Human evolution began when Africa's climate changed to drought - lakes shrank, forests changed to savannah.

Walking upright - man's foot two million years ago was basically the same as today. Standing upright occurred when we moved from the forest to the savannah - looking out over the tops of bushes. This freed the hands for other tasks than walking, like carrying things.

Walking upright brought about systemic changes in the human morphology. The head has changed a great deal - probably a by-product of an upright posture.

The following timeline summarizes most of the fossils we have discovered that related to human evolution. There are various interpretations of how these fossils fit together. For a discussion of this issue, you may visit the following websites:Becoming Human Documentary Origins of Humankind Website

HUMAN EVOLUTION – THE FOSSILS

There have been about 20 human and hominid (human-like) fossils found thus far. Every find leads us to reconceptualize possible lineages leading to humans. The following list includes most of these fossils by their estimated date as well as primate precursors to the hominid line.

50 million years ago - the lemur

Flat face, short snout, large eyes set wide apart. Selection against sense of smell for sense of vision, possibly because early primates were tree dwellers (stereoscopic vision).

Next 20 million years sees the branching off of the present day monkey line from that of the great apes and man.

30 million years ago - Aegyptopithecus

Found in the Fayum, in Egypt. Shorter snout than the lemur, teeth are ape-like, larger but still lives in trees, spending part of the time on the ground.

20 million years ago - Proconsul and Dryopithecus.

Brain markedly larger, eyes now fully forward in stereoscopic vision. Could be on a branch line moving toward apes, not man. Teeth demonstrate that he is an ape, since the jaw is locked by the big canines.

14 million years ago - Ramapithecus

Found in Kenya and India, indicating movement and dispersal. Jaw fragments only showing teeth that are level and more human. Great canines are gone, face much flatter. Man or ape?

Gap of 5 to 10 million years - hiding the time when the ape and human lines separated. Now we have begun to find interesting fossils from this period, but it is still too difficult to draw conclusions

Human - Chimp/Gorilla Separation6-8 million years ago

7 million years ago - Sahelanthropus tchadensis (Toumaí)

Found in Chad, some 2,500 miles from the normal sites in East Africa, suggesting a new site of origin for humanity. Not clear whether this was an ape or human, or really the common ancestor of both. Brow ridges, teeth that look like on a line to humans (larger molars and smaller cannines). No evidence regarding upright posture.

The next two are recent finds that are controversial. Ape or human?

6 million years ago – Orrorin tugenensis (Kenya)

Appears to have walked upright (long femur neck), arms and fingers retain adaptations for climbing, sharp canine teeth.

5.2-5.8 million years ago – Ardipithecus ramidus kadabba

Considered to be a subspecies of ardipithecus ramidus. We have found a toe, teeth, an adult mandible, pieces of a skull, several arm bones, lower-jaw of a child. Could be chimpanzee. May have walked upright.

5 million years agoArdipithecus ramidus

(Ethiopia)4.4 million years ago

Australopithecus anamensis(Kenya)

4.2-3.9 million years ago

Australopithecus afarensis (Lucy - Ethiopia)

3.0-3.9 million years

Two branches now appear (speciation). The second, Genus homo, appears somewhat later than the first, the Australopithecines (“Southern Ape from Afar”):

1. Genus Australopithecines - two forms: one lighter, and one a more robust form. Erect but small-brained. [ Modern feet ]

The lighter "gracile" forms, composed of 3-5 speciesAustralopithecus africanus (Raymond Dart, 1920's)

3.0-2.3 million years ago.In the Taung baby found by Raymond Dart, foramen magnum is under skull indicating upright posture. Teeth are small and square - indicates an animal foraging with hands, not its mouth. Teeth may also show it was eating raw meat. To get raw meat the

animal was probably making tools, pebble-tools, stone choppers, to carve it and hunt.

Australopithecus aethiopicus – 2.6 million years ago.Australopithecus garhi – 2.5 million years ago. Found with

earliest stone tools.

The heavier, more robust forms, which are sometimes placed in a different genus called Paranthropus.

Australopithecus robustus (S. Africa) – 2.0-1.0 million years ago. Generally nuts and tubors, but perhaps eating some meat.Australopithecus boisei (Leakey, East Africa) – 2.3-1.2 million

years ago.

The Australopithecines lived and died entirely in Africa, with 1 or 2 species surviving until perhaps 1 million years ago.

2. Genus Homo

Homo habilis (Leakey, Olduvai Gorge, Tanzania) 1.9-1.8 million years ago.Homo rudolfensis - a possible variation of homo habilis.

Homo erectus - 1.8 million – 300,000 years ago. The earliest fossil, of "Turkana boy" (Leakey, 1985), is 1.6 million years.

Large brain size - 1,100 c.c. (three quarters of modern human capacity), showing increase in species over time. Upright posture (as early as 3.5 million years ago)

Populations of this species left Africa for Europe, China (Peking Man) and Indonesia (Java Man). Earliest fossil in Indonesia is 1.8 or 1.9 million years old, leading to the idea that humans originated in Indonesia. Appears to be an older line than previously thought (less archeological work has been carried out in south-east Asia than in Africa). The oldest known African Homo erectus is 1.8 million years old - perhaps Homo erectus is more than 2 million years old?

One million years ago Homo erectus lived on the 3 continents of Africa (homo ergaster), Europe (homo antecessor) and Asia (home erectus). Spread out of Africa

730,000 b.p. - first signs of humans in Europe

Homo heidelbergensis – 600,000 – 100,000 years ago. Generalized diet, lived in Africa, Asia, and Europe.

Homo sapiens - 100 thousand years ago

Then between 500,000 and 100,000 years ago we begin finding a highly confusing group of specimens called "archaic Homo sapiens" who lived on all 3 continents, presumably descendants of Homo erectus. In morphology seem to be intermediate between Homo erectus and modern humans. It would seem that Neanderthal is a direct descendent of these archaic Homo sapiens in Europe.

500,000 b.p. evidence that fire was being used.

400,000 b.p. wooden spears

350,000 b.p. most areas of Europe settled.

The debate over Neanderthal Man. Discovered first in 1856 and has been found all over Europe. Lived from 270,000 to 30,000 years ago. Was Neanderthal our direct ancestor or a separate dead-end line competitively replaced by our true ancestors?

Two theories have arisen to explain what happened - the "multiregional view" and the "out of Africa" view.

Multi-regionalist view (Franz Weidenreich - 1940's)

Homo erectus populations on all three continents evolved in parallel - some migration provided gene flow and prevented all three from differentiating into different species. Changes primarily involved increased brain size and decreased jaws and teeth. Neanderthal therefore represents the European version of a late stage in the global trend.

Out of Africa view

Modern humans arose out of one isolated group of Homo erectus in Africa, and then spread. The evidence for this view consists of:

The best and oldest remains of fully modern humans are from 100,000 to 125,000 year ago in Africa.

Genetic variability among modern Africans is larger than all other humans, indicating long presence of modern humans there.

Neanderthal therefore represents one among several non-African descendents of Homo erectus that did not transform to modern humans, but died out.

Homo sapiens sapiens - 50 thousand years ago

40-30,000 b.p. - By 30,000 years ago fully modern human types were widespread through out the world. The earliest humans appear to have inhabited a variety of habitats within a belt of tropical and semi-tropical country stretching from Ethiopia to southern Africa. The population was small, thinly spread, living in groups which probably depended mainly on the gathering of nuts, seeds and plants, which they would have supplemented by scavenging dead animals killed by other predators and perhaps the hunting of a few small mammals. This form of subsistence - gathering and hunting - lasted as the human way of life until the development of agriculture about 10,000 years ago.

During this period we see an expansion in the types of tools being used from a previous 6 to over 80 types. Large hand axes, which required minimum time and effort in production are replaced by very thin, parallel-sided blades from the core of the stone. 20,000 b.p. small projectile points being made. Bone, antler and ivory tools.

New tools - required more complicated manufacturing techniques such as heat treatment and pressure flaking from

core of stone. This implies higher motor abilities and greater mental skills that could handle a several stage fabrication process.

Humans in Nature: Hunter-Gatherers

Some 90% of all humans that ever lived have been hunter-gatherers, only 6% agriculturalists, and a small % industrialists.

Gathering nuts, seeds, plants and supplementing this with scavenging dead animals and perhaps hunting a few small mammals. Living in small groups, low population and thinly spread.

Today's hunter-gatherers have been pushed into marginal areas - the Bushmen of south Africa, the Hadza of east Africa, pygmies in equatorial forests of Africa, a few groups in India and east Asia, some Aborigines in Australia, Inuit in the Arctic and native inhabitants in tropical forests of South America.

We now believe that this life-style was relatively easy - gathering requires few hours a day, with plenty of leisure time. Very few tools and instruments, which would be hard to carry with their mobile life. Pattern of life varies throughout the year depending on seasonal availability of foods. Hunting is a periodic activity, lasting intensively for a week and then not at all for 2 or 3. Hunting is difficult, hazardous and has only intermittent rewards. Very low rate of success. Easier to scavenge for dead food when spears are poor.

Near the equator hunting is less frequent than in cooler climates where plants are not as available.

Apparently hunter-gatherer groups have always had means of controlling their population - infanticide, leaving the old to die, killing twins, the handicapped or females.

Development of human societies and settlement across the globe was probably due to 4 evolutionary changes that occurred during 2 million years:

1. Upright posture2. Increase in brain size3. Speech4. Technology (making of tools)

2,000,000 b.p. stone tools - chopper made from pebbles and a hand axe with a working edge round most of the perimeter. Easy to make and found in large quantities.

500,000 b.p. evidence that fire was being used.400,000 b.p. wooden spears 80,000 b.p. bolas stones for entangling animals

Delayed maturation of the nervous system, ability to handle fine detail, control over state and ability to make plans for the future.

Settlement Across the Globe

Original home: from Ethiopia to South AfricaMove to frost-free zones of middle east, India, south China and parts of

Indonesia. Clothing would have been necessary in addition to tools. Homo erectus had spread out of Africa by 1 and a half million years ago.

Hunter-Gatherer Effects on Environment

Possibly caused animal extinctions, plant extinctions.Should be considered "affluent societies" - rich variety of foods, less

disease, more leisure time.

History of Agriculture

The way we make a living has changed during our evolution – from hunter-gatherer groups, to herding nomads, to agriculture

Agriculture developed separately over the course of a few thousand years in south-west Asia, China and Mesoamerica. The most important transition in human history. Capable of providing larger quantities of food and therefore settled communities. Once started it couldn't be stopped, because the increase in population it created couldn't be supported by the old methods of hunting and gathering.

Bronowski (The Ascent of Man) calls the agricultural revolution a “biological revolution” because it involved not only the cultivation of plants but also the domestication of animals. These in turn led to a social revolution.

The transition represents a shift in the spectrum of activities engaged in by "hunters and gatherers". They did practice certain forms of cultivation. The move has been from foraging of wild plants, tending wild plants through cultivation, domestication of genetically distinct crops some of which can only propagate through human intervention, (breeding), and finally genetically engineered plants.

Cultivation of animals goes through a similar sequence: random hunting of a herd, controlled predation, heard following, loose herding, close herding and finally modern intensive factory farming.

Neither of these required the development of radically different techniques from what they were doing before.

Why adopt agriculture? It was probably necessary because of population pressure. The population of 4 million (10,000 years ago) was probably the maximum size possible given the hunting and gathering way of life. As movement became less possible, groups were forced into less favourable areas for subsistence, and eventually would have been forced to exploit what were seen at the time as less favourable resources.

In a nomadic life, there was no room for innovation. If you had to pack up and move on frequently, you could not carry a lot of extras with you. Culture therefore could not take off in a big way.

Domestication of both plants and animals.

Dogs probably first. Sheep and goats (which have no natural migratory patterns to follow) about 10,000 years ago. Draught animals – ox, onager, ass, the horse (about 2000 b.c.)In the nomadic life, everything has to be carried. No time for skill or specialization. No room for innovation.

Every stage in the domestication of plants and animals requires new inventions.The sickle – flint set in gazelle horn or bone – flat edge. A serrated edge is necessary for cutting wheat.The plough – a lever – a wedge to divide the soil.The wheel – 3000 B.C. in the southern Russian steppes – grinding wheat, the cart, the pulley, the bow lathe.

The plough and the wheel were not invented in the Americas because both needed draught animals, and there were none. Planting was done with a digging stick and pack for carrying seeds.

Humans against Nature: Agricultural Societies(Handouts: "Noble Savages" and "The Worst Mistake in the History of the Human Race"

Has human history over the past million years been a long tale of progress?

Archeologists are discovering that the adoptation of agriculture was in many ways a catastrophe from which we never recovered. With agriculture came the gross social and sexual inequality, disease and despotism, that curse our existence.

10,000 -12,000 years ago became food producers via domestication of animals and cultivators of plants.

Horticulture - growing plants close to home.Slash-and-burn or swidden - cutting forest for planting crops, ash works as fertilizer, a variety of roots, tubers, and seeds and tree-crops planted.

Development of a food surplus had 6 major consequences:

1. Population increase.2. Landscape slowly changes from forest to open habitats.

Desertification. Irrigation without proper drainage.3. Urbanization around fields.4. Health decline.5. Social classes. Land and water rights. Encourages open conflict.

Concentration of power in few. Much individual freedom given up for group living.

6. Encouraged inequality between sexes.

Humans against Nature: Industrial Societies

Initiated by change from animal, wind, water power to fossil fuels - coal, oil, gas. Makes large scale mining possible.

Introduces various types of pollution and work monotony.

Humans and Nature: A Sustainable-Earth Society