I have integrated this web page on human evolution into an electronic text, " Nature's Holism - Holism. Evolution & Ecology " (see its HOME PAGE .) The result is that some areas, such as the glossary are shared.
INTRODUCTION TO EVOLUTION:
For an overview of evolution other than human evolution, see:
- A BRIEF HISTORY OF LIFE AS "THE BOOK OF TIME";
- TABLE OF THE GEOLOGICAL TIME SCALE;
- TIME and
NEO-DARWINISM, THE MODERN SYNTHESIS:
Human evolution from an ancestral primate species is not a vague hypothesis, but a historical fact. Archaeological geology as a science had to precede the proposal of evolution, as an understanding of the immense age of the earth is necessary to understand evolution. Cuvier established amongst the scientific community the fact of extinction. Evolution only gained significant momentum after the theory of evolution, published by Charles Darwin in November 1859, implied that man was merely another product of life on earth, with origins shared by the other creatures and not its ultimate purpose. In 1858, Charles Darwin and Alfred R. Wallace proposed the same theory at a joint presentation to the Linnaean Society in London . Without the universal acceptance of the principle of evolution, there is no chance for the serious proposal of holism.
Scientists now have accurate methods (see below ) for dating fossils. Absolute dating methods such as the potassium/argon and argon-argon methods of dating fossils provide a precise measure of the date of fossil remains or associated minerals. Relative dating methods rely on characteristic faunal and geological patterns to bracket the period when the fossil existed.
At the onset of the 20th century, most scientists had accepted the great antiquity of the earth, the theory of evolution and that humanity had evolved from an ape ancestor, but by 1908 the fossil evidence of early man was scarce. Biologists included principles from genetics in evolutionary theory during the 1920s and 1930s. Between the mid-1930s and mid 1940s geneticists, systematists and palaeontologists collaborated to create a united approach to evolution, the "Modern Synthesis". Ernst Mayr reduced all the hominid (human ancestor: (see hominid books)) fossil records to three species, A. africanus (Dart, 1925) (including small brained australopithecines) (see books), H. erectus (including the Java and Peking hominids - the archetypal Missing Link) and H. sapiens (including Neanderthals and Cro-Magnon) (see the modern taxonomic classification of humans). This formed the foundation of the neo-Darwinian evolutionary theory. Very simply, there are five basic principles to this theory:
 Variation has a genetic origin (i.e. is heritable) and arises through processes such as mutation and recombination.
 Adaptation is genetically based and so leads to phenotypic changes that accumulate over time;
 Speciation (species formation) evolves through reproductive isolation and (genetic) divergence of populations;
The evolution of a species is linked to the environment.
Adaptation is a continuous response to the environment by changeable
species. This environment has a living (other animals) and non-living
component (e.g. weather).
A unique adaptation usually precedes the entry into a new niche . Tool use by our early ancestors is one such adaptation. Once multicellular organisation became possible as atmospheric oxygen levels rose, the early multicellular organisms rapidly diverged into many adaptive forms. Mass extinction events and an organism's unique adaptations mark the history of evolution, both of which may lead to adaptive radiation. ( Adaptive radiation is the evolution from an unspecialised ancestral stock of many different species that adapt to a variety of ecological roles (see books)). Mammals and subsequently humanity may not have become dominant on earth had it not been for the global catastrophe that led to the extinction of the dinosaurs 65 million years ago. Living orders of placental mammals , be it bats, humanity, whales or camels, have as their common ancestor a small insectivore creature that went through a major phase of adaptive radiation during the Early Cenozoic Era . We humans are first animals, then mammals, then primates.
In our modern view, the creation of Adam must conform with the evolutionary creation of humanity. God first completed the physical and biological constitution of humanity. Only after this, did God breathe his Spirit into Adam. There are thus two aspects of the human personality, the physical constitution and the spiritual constitution. Social forces appear to have directed much of the evolution of humanity but we are still subject to natural selection.
Primate taxonomy (see books: phylogeny, taxonomy,
systematics) is in a state of flux due to the discoveries made
in primate genetics. Our hominoid line, humans, gorillas,
chimpanzees and lesser apes, is one among the superfamily Hominoidea. See the taxonomic table
primates for two comparative classification shcemes. Extinct
Hominoidea lineages, including Proconsul (24-16Mya),
Oreopithecus , Afropithecus , Dryopithecus
(16-10 Mya), Kenyapithecus and Oreopithecus, all
existed before our hominin (hominid in older texts) line split from the
great apes. One other lineage, Sivapithecus , has a living
representative, the orangutan .
The exact relationship between the many species is uncertain.
Ramapithecus is now thought to be the male morph of the female
Sivapithecus . Hominins
(hominids in old terminology) diverged from the pongids (chimpanzees and gorillas) in
Africa, no more than nine million years ago. Palaeontological and genetic evidence indicates a divergence
time between humans and chimpanzees about 5 Myr. ago. The term " hominin " (Tribe hominini) refers to
creatures characterised by an upright posture and bipedal locomotion.
books) are the most ancient species of the hominin
(hominid in older texts) lineage that we can clearly distinguish and
humans are the only living representatives. In October 2009, in a
special issue of Science,
a multidisciplinary international team presented Ardipithecus ramidus from Aramis,
Ethiopia as the oldest known skeleton of a potential human ancestor.
Subfamiliy: Homininae, Pongidae, Dryopithecinae
Subtribus: Panina (Chimpanzee),
Hominina (Humans) (ref)
Overview of genera
Gorilla, Homo, Pan, Pongo, Ankarapithecus, Anoiapithecus, Ardipithecus, Australopithecus, Chororapithecus, Dryopithecus, Gigantopithecus, Graecopithecus, Hispanopithecus, Ouranopithecus, Pierolapithecus, Praeanthropus, Sahelanthropus, Sivapithecus
Our human lineage (Subtribe
hominina), the genus Homo , is called hominans (hominines in
older documents). It includes modern humans and our evolutionary
ancestors back to the point where we diverged from the line leading to
the living apes. Together with the chimpanzees we are now grouped
within the Subfamily Homininae ('hominines'). (Living apes and
their ancestors are called pongids in older texts). Hominoids
(Superfamily Hominoidea) include lesser apes (Family Hylobatidae),
greater apes (Pongidae), prehumans and humans ( Tribe Hominini
). The older term, (Family) Pongidae, has been dropped from scientific
terminology. The "greater apes" included the orangutan, gorilla and
1989). They are now regrouped as subfamilies of the Family
Hominidae (' hominids ') together with
humans! There is still some disagreement on the final groupings (see taxonomy table of primates ).
FOSSIL HOMINOID IMAGES:
View images by clicking on link or reduced image: (Each image opens into a new window.)
|©1 This is a reconstruction of Proconsul africanus (cast), found at Rusinga Island, Victoria Lake, Uganda. These primitive, medium sized apes lived in rain forests between 18 and 22 million years ago. This species and others such as Dryopithecus existed before the hominid line diverged on the path to humans.|
©1 A Hylobatid skull (lesser ape). This lineage (ancestral gibbons) is believed to have diverged from the great ape and human lineages between 17 and 25 Mya (Avers, 1989).
|©1 This is a 10 million year old skeleton of Oreopithecus bambolii , found in Italy. Oreopithecus 's hand closely matches the pattern of early hominids, with a grasping capability including firm pad-to-pad precision gripping that apes are unable to perform (presumably as a response to similar functional demands to hominids) (Moya-Sola et al, 1999). Bipedal activities made up a significant part of the positional behavior of this primate (Kohler and Moya-Sola, 1977).|
|©1 A gorilla skull ( Gorilla gorilla ), (greater ape). Gorilla and human DNA only differs by 2.3%. Gorillas diverged from our ancestral hominid line about 8 million years ago (Johanson & Edgar, 1996) .|
|©1 A chimpanzee skull ( Pan troglodytes ), (greater ape). Our DNA differs by only 1.6% from Chimpanzees. The two species of Pan, the chimpanzee, P. troglodytes and the bonobo, P. paniscus diverged about 2.5 million years ago. The human ancestral line must have arisen between 5 and 8 million years ago.|
|©1 Australopithecus africanus is one of the many species of this genus that is believed to be ancestral to humanity. However, with the many species to be found, the exact sequence of species leading to humanity, has not yet been established.|
|©1 Homo erectus , a tool and fire user that spread (from about 1.6 million years to 230,000 years ago) as far as China and Java in the east and the Atlantic Coast in the West.|
|©1 An early human skull, Homo sapiens neanderthalensis. Morphological differences, such as in the pelvis, supports making Neanderthals a separate species, Homo neanderthalensis .|
|©1 A human skull, Homo sapiens sapiens . Anatomically modern humans can be traced back at least 100,000 years. The oldest known human fossil, Omo I, is at least 130,000 years old. Early human fossils, classified as Homo heidelbergensis are dated at up to 400,000 years old.|
Based on fundamental research on the influence of diet on primate evolution, scientists propose that adaptations to a specific diet in our ancestors paved the way for the development of modern humans. Our dentition, with reduced canines and incisors and large molars and premolars reflect dietary modifications. Our closest living relative, the chimpanzee, has long canines, so in some way our evolutionary histories are very different. Part of human radiation is an adaptation to life on the ground . Ground living forms need to range farther to find food and survive and form fewer varieties than tree-living forms. For our human ancestor, survival as a ground living form required that the creature become wide ranging. This reduced the likelihood of geographical isolation and many species forming. Ground-living is a very ancient adaptation on the evolutionary line leading to humanity as the oldest hominid fossils yet discovered walked upright on adapted feet. Australopithecines had brain volumes similar to chimpanzees and were no more than small brained wild animals. Our upright stance evolved at least 3.6 million years ago, before any significant brain enlargement evolved.
Australopithecus was a bipedal ape with a small brain
(450 cubic centimetres) and had massive molar teeth adapted to a diet
largely of tough plant material. This ape did not use fire or tools.
There are three main species of Australopithecines. A. robustus ,
is a heavily built creature, represented by specimens from southern and
east Africa, that existed 2.2 to 1.2 million years ago (1.5 to 1.9 mya
by other estimates (Lemonick &
Dorfman, 1999) ). A. africanus , (click to see image) ©1 the 'gracile' species represented by the
Taung specimen, lived 2.3 to 3 million years ago. A. afarensis ,
also a fine boned species, existed about 4 to 3 million years ago (2.9
to 3.6 mya by other estimates (Lemonick
& Dorfman, 1999) ) and is represented by fossils found in
Tanzania and Ethiopia ( A. aethiopicus ). Sometimes they
include another species, A. boisei , (click to see image) ©1 in the classification, of which fossils
dated at 2.5 million years old have been found ((2.3 to 1.4 mya by
other estimates (Lemonick & Dorfman, 1999)
), but others say A. boisei is the same species as A.
robustus . Older fossil finds, called
Ardipithecus kadabba (at 5.8 million years old (was called A. ramidus kadabba, but is now seen
as a separate species) are presumed
ancestral to all the other species. Anatomists group A. robustus ,
A. aethiopicus and A. boisei together as the genus
Paranthropus . As palaeontologists refine the study of these
fossils, they are creating new species. Some now see Paranthropus
walkeri as the link between australopithecines and P. boisei
and P. crassidens from Swartkrans. A. afarensis
(view jaw of Australopithecus afarensis )
©1 is probably the
forerunner of all later hominid fossil records as its oldest fossil
remains precede A africanus by at least 500000 years. This
species is most likely the ancestor to two divergent lines, A.
africanus leading to A. robustus , and then culminating
in A. boisei and a route to humanity via H. habilis
and H. erectus .
Australopithecines share a common ancestor with the lineage that evolved to become H. habilis . (click to see image) ©1 A. afarensis , which became extinct about 2.9 Mya ago, is believed to be the direct ancestor of H. habilis (Avers, 1993). A. africanus became extinct about the time of the appearance of H. habilis , not allowing enough time for the evolution of the one into the other. Paranthropus robustus and P. boisei existed when the first hominine, Homo habilis lived in East Africa 1.8 to 2 million years ago (1.9 to 1.6 mya by other estimates (Lemonick & Dorfman, 1999) ). Australopithecines coexisted with the first hominines (genus Homo) for up to two million years so there must have been distinct separations of their ecological niches during this time. All Australopithecines were extinct by less than one million years ago.
Homo habilis , a maker and user of crude stone tools, (click to see image of tools) ©1 appeared no earlier than 2.5 million years ago ( the earliest evidence of tool use). Fossils of this species span 750,000 years (at least 500,000 years)! Little physical change took place during this period, suggesting a successful and enduring species. The main features of the transition from Australopithecines to H. habilis are the use of tools and an enlarged braincase (700 cc). Physical features of H. habilis are almost identical to those of A. afarensis , showing that the primitive apelike characteristics served well for the role of this creature in nature for a very long time. H. habilis shows a sulcal pattern in the left frontal lobe, so H. habilis had at least the beginnings of speech.
Homo erectus (click to see side view of skull) (click to see front view of skull) (click to see H. erectus jaw) ©1 arose in Africa about 1.6 to 1.8 and maybe even 2 million years ago. Fossil remains of H. erectus found in Bed II of the Olduvian Gorge are about 1.2 million years old. With the evolution of H. erectus , their tools became more standardised indicating improved communication and cognition between individuals. Changes in tool design were remarkably slow. This technology reached southwestern Asia by 1.2 million years ago and East Asia by 0.7 to 1 million years ago. By 500,000 years ago the Acheulean technology (click to see image of Acheulean tools. These are hand axes used by H. erectus) ©1 had spread throughout Europe. This technology was never used in Eastern Asia, where other materials, such as bamboo may have been more popular. By 500,000 years ago brain volumes and dentition of Old World H. erectus populations had attained modern levels and by 250,000 years ago the species had disappeared. The earliest Australian stone industries of perhaps 40,000 years ago, are similar to the Southeast Asian technology of the late Pleistocene. Homo erectus heidelbergensis appears to provide the transition between more primitive Homo erectus and Neanderthals and modern humans. The evolution of the former occurred well before that of modern humans from this ancestral species.
All hominid remains of the last 100,000 years belong to either H. sapiens neanderthalensis or H. sapiens sapiens (click to see image early human skull, 120,000 years old) ©1 . Neanderthals (front view of Neanderthal skull) (side view of Neanderthal skull) ©1 were hunter-gatherers who moved across Europe with the advance and retreat of the Ice Age glaciers. They were adapted to the cold northern climate and flourished during a warmer interglacial period between 200,000 and 30,000 years ago. Fossil remains provide evidence that they moved in small groups possibly occupying areas seasonally and subsisted by hunting big-game such as reindeer. Animal bones found with Neanderthal remains are mostly cold adapted species such as reindeer, arctic fox, lemming and mammoth.
Anthropologists classify Neanderthal tools as Mousterian (Neanderthal stone tool) ©1 . Early humans also used these tools, such as hand-axes, scrapers, borers, knives and points of stone. They are found beyond the Neanderthal range and associated with non-Neanderthal fossils. Neanderthal tools, evolved little during their history, and they did not use bone, antler or ivory. They may have used wood and regularly used fire. Why they did not make tools from their prey is unexplained.
The oldest modern human remains outside Africa, from Qafzeh in the Middle East may be as old as 100,000 years and those from Mount Carmel in Israel, 80,000 years old, but humans only flourished at the time of the extinction of the Neanderthals around 35,000 years ago. Migrants, which colonised the rest of the world, left Africa between 90,000 and 180,000 years ago, and reached China by 68,000 years ago, Australia by at least 50,000 years ago, and Europe by 36,000 years ago. Evidence from Human remains of the Upper Paleolithic (40,000 y.a.) shows that, by this time, humans were skilful hunters. They hunted horses, bison and reindeer.
For 99% of our history, we have lived as hunter gatherers , living a nomadic way of life. Over the period called the Middle Paleolithic (called the Middle Stone Age in Africa), 200,000 to 40,000 years ago, stone tools found are quite similar, representing a uniform technology world-wide.
Eventually there was a full transition to and dependence upon agriculture to survive. Technologically, these societies are more complex. Domestic crops and animals become more important as food than wild animals and plants. Agriculture is relatively new, only emerging between 10,000 and 6,000 B.C. and has often caused environmental damage, but has led to the social changes that have allowed the formation of our modern civilisation. This seems to have followed the end of the last Ice Age between 15,000 and 8,000 years ago. Before this, the hunter-gatherer lifestyle depended upon what was available. Over such spans of time, the social and cultural changes were largely imperceptible to the individual. With the introduction of agriculture, villages and cities became possible, as people did not have to travel in search of food.
Civilisation's advance was very slow initially. Humanities' earliest civilisation developed in Mesopotamia, the area enclosed by the Tigris and Euphrates rivers. Between 1200 B.C. and A.D. 500, many powerful empires emerged. Agriculture and animal domestication allowed humanity enough free time and energy to create empires and pursue wars. This history is a story of wars and conquerors.
Energy requirements increased as civilisations emerged, a trend that needs to be reversed in the future. Hunter gatherer societies require only 2,000 to 5,000 kilocalories per person. Early agricultural societies need 20,000 kilocalories, early industrial societies need 60,000 kilcalories and modern industrial societies need 120,000 kilocalories per person!
By the sixteenth century, machinery such as the printing press, windmill, lever, pulley, pump, clock and wheelbarrow were common features of daily life in Europe. Technology was beginning to ease human life. By 1850 machines did 35% of the work in an industrial country and animals another 52%. By 1986, machines did 98% of the work, with animals and people each doing 1% of the work.
Agricultural societies cause more harm to the environment than hunter gatherers, but the most damaging is the industrial society that evolved and prevails today. Industrial technology emerged with the steam engine, factories and mass production, only 200 years ago.
Technological innovation must reduce our impact upon the
environment to 1/16 of its present level by the year 2050 to
effectively counter the current growth trends. Clearly, we cannot
return to hunter gatherer type lifestyles, so a control of population
growth and technological innovations are the main tools at our
disposal. Reducing consumption can also be very effective. To do so
would require some major changes in our lifestyles. By necessity, we
will depend upon technological innovations to create a more benign
existence with nature. The "environmental intensity of consumption
" (T) is not equivalent to the energy consumption of an
individual. Energy consumption can be high while T is still low. This
would require that energy consumption be environmentally benign. T is
equivalent to the interactive factor (
i-factor ) discussed with the modified energetic
Lotka-Volterra model ( MELV model).
The basic conclusion here is the same as deduced from the model. We
need to reduce our interactive effect upon the environment. Our impact
upon the environment has to be drastically reduced if we wish to
maintain the present quality of life of the West. This is the essence
of compatibility and its expression can take many forms.
(see map of fossil sites from migration article )
Human evolution from a primate species is not a vague hypothesis, but a historical fact. Our distinct evolutionary line begins in the Pliocene period (started 14 Mya) of the Tertiary era, during which our physical development took definite shape (Watcher, 1990) . Much of our cultural evolution took place during the Pleistocene period covering 10,000 to two million years ago. This was a period of varying conditions, with periods of cold "Glacial" periods followed by warmer "interglacial" periods that must have affected our ancestor's way of life. The Holocene, the modern period of the last 10,000, includes the introduction of agriculture, modern religions and technology .
Modern evolutionary studies aim at establishing the mechanisms and processes determining evolutionary patterns and reconstructing the evolutionary history (Avers, 1989). This has not been an easy task due to scant fossils. Speculations as to our antiquity have ranged from James Ussher's (the Archbishop of Armagh) guess that Creation was 4004 years old (Rachel, 1991) (Mayr, 1978), to Martens suggestion that the oldest human footprint found was probably made 40,000,000 years ago (Martens, 1924) and Huxley's estimate that humanity entered Europe around 20,000 B.C. (Huxley, 1941) . Scientologists rarely found spiritual beings (theta beings) coming to earth before 35,000 years ago (Hubbard (1988) . The earliest arrival of a spiritual being that he could record was 70,000 years ago. Locke (1632-1704) noted that the common reckoning for the duration of the world was 5639 years, while the Egyptians in the time of Alexander estimated it to be 23,000 years and the Chinese believed the world to be at least 3,269,000 years old (Benton, 1952) .
Western history is marked by periods of suppression of new ideas. During the Inquisition, astronomer and physicist, Galileo (1564-1642 ) was first instructed (1616) not to hold or defend the Copernican Theory. Then, in 1633 he was again forced to recant on these ideas by testifying in a written statement and sentenced to life imprisonment (house arrest) until his death in 1642 (Gingerich, 1982) ! Others such as Giordano Bruno (1548-1600) were burnt to death for upholding unique ideas. Evolutionary ideas have also received opposition. Even today, society does not readily accept the idea of human evolution. Many Christians, Muslims and Jews refuse to accept evolution as a fact.
Archaeological geology as a science had to precede the proposal of evolution, as an understanding of the immense age of the earth is necessary to understand evolution. William Hutton , an Edinburgh doctor and scientist recognised in 1788 that dynamic geological processes were evident in rock formations. He maintained that the processes that presently act in the formation of the surface of the earth must have been in operation through all time, an idea that threatened religious creationism (Cardwell, 1994) . Natural processes weathered older rocks, depositing sediments on the floor, and hard rocks formed again in a process that occurred continuously. This view contrasted with the prevailing Christian belief that creation started at 4000 BC.
This understanding of the great age of the earth and its geological dynamism was necessary for the progress of palaeontology and the study of fossil remains (Parker, 1992) . Leonardo da Vinci (1452-1519), for example believed fossils were the remains of organisms from different times or places. Without an idea of the age of the earth or the possibility of extinction or that species evolve, people believed that these same fossil animals still flourished in unexplored parts of the world (Avers, 1989). Geology as a science emerged at around 1800 (Bowler, 1992) . In 1802, John Playfair promoted ideas on the great age of the earth. Darwin's close friend, Charles Lyell , also promoted this belief (Parker, 1992) . Lyell promoted the theory of "gradualism" in his first volume, Principles of Geology of 1830. Hutton was the first to introduce Gradualism. It opposed the prevailing belief in catastrophes being the cause of the fossil record. The slow effects of time replaced violent events as the cause of the present geology of the earth. Lyell proposed that scientists build geological theories upon observable causes to reconstruct the past. Layers of rock, which represent their period and order of formation in time, now called the stratigraphic column, were placed in their correct (modern) sequence by the 1840's. Darwin's close contact with Lyell enabled him to appreciate the great age of the earth and geological processes and so set the stage for his discovery of evolution through natural selection.
Natural theology , as a cultural world-view dominated society in the eighteenth century. They believed that God created life for use by humanity. Scientists had not established the great age of the earth, and people thought that species, as God's creation were unchangeable and unable to become extinct. Recognition that animal species could change can be found as long ago as with Anaxiamander of Miletus (c.570 BC), Heraclitus (c.500 BC) (Parker, 1992), Empedocles (440 B.C.) and Lucretius (Wells et al., 19??). Apes were called "wild men" (Pliny, AD23-79) and chimpanzees as the "man of the woods" (Homo sylvestris) (Edward Tyson, 1699) and the "man of the forest" (Nicholaus Tulp) (Parker, 1992). Linnaeus (1707-1778) placed apes and humans together in the order of primates in his Systema Naturae but insisted that species do not change. In the 1700's, Baron Cuvier and Comte de Buffon also proposed evolutionary ideas. Buffon strongly believed that species existed in eternally fixed moulds that changed only slightly (Bowler, 1992). He suggested that the earth was 70,000 years old and proposed that the planets were formed through being struck off from the sun by a colliding comet. Cuvier saw the fossil record as evidence of sudden and violent catastrophes leading to mass extinctions. He established a relationship between fossil forms and geological strata (Cardwell, 1994). He also established amongst the scientific community the fact of extinction , but said that animals did not evolve over time (Damuth, 1992) .
Modern evolutionary ideas started a new phase in 1802 when a French
biologist and botanist, (Jean Baptiste) Chevalier de Lamarck (1744-1829) claimed that " Everything
undergoes in time the most gradual changes.
Charles Darwin's grandfather, a doctor and naturalist, also became a
proponent of evolution in the 1790's. These early evolutionary theories
are not accepted today, while much of Darwin's work is still as valid
today as when it was written. Lamarck proposed the inheritance of
acquired characteristics as the basis for evolution, so that if an
animal grows a thick coat when subject to excessive cold, its offspring
inherit the ability to produce a thick coat. Another animal that
exercised specific muscles would transmit this muscle development to
its offspring. Such confused ideas on evolution persist even today, so
that some believe that intellectual training can make one's offspring
clever. Genetics and studies of creatures such as social insects has
proved that acquired characteristics or abilities are not heritable.
Darwin did not use the term "evolution" because of its progressive
implications, but used the word transmutation. Evolution comes from a
Latin verb, evolvere, which means to unfold or disclose (Richards, 1992) .
Evolution only gained significant momentum after the theory of evolution, published by Charles Darwin in November 1859, implied that man was merely another product of life on earth, with origins shared by the other creatures and not its ultimate purpose (Reader, 1988). In 1858, Charles Darwin and Alfred R. Wallace proposed the same theory at a joint presentation to the Linnaean Society in London (Avers, 1989). Wallace, a surveyor and botanist, discovered this evolutionary mechanism independently while studying life in Borneo (Livingstone, 1987) . He believed that species changed and was on a quest to discover the laws governing this process of change and the idea of a species. In 1847 he began with a 3-year specimen collection trip to the Amazon. Next, he went to the Malay Archipelago (Borneo) to continue his studies (Rachels, 1991): "Then I at once saw, that the ever present variability of all living things would furnish the material from which, by the mere weeding out of those less adapted to the actual conditions, the fittest alone would continue the race" (Jenkins, 1978).
Darwin formulated his theory after a five-year trip on the H.M.S. Beagle (1831-1836). He was the ship's naturalist, but the purpose of the journey was to map the coast of South America. Darwin modelled his theory, using three sources:
 He observed natural life during his 5-year trip along the South American coast, and especially the animal life on the Galapagos Islands (Jenkins, 1978). Finches and tortoises found on this island clearly evolved from a common ancestor. Modern studies show small genetic "distances" among several species of Darwin's finches (1994). This provided clues to the process of evolution and the mutability of species .
 Charles Lyell provided geological proof that the earth was millions of years old in his three-volume "Principles of Geology" (1830-3).
 The final piece of the puzzle appears to have been a book by Thomas Malthus (1766-1834), "An essay on the principle of population", that Darwin read in 1838 (Rachels, 1991). Darwin refers to the Malthusian principle that unchecked population increase in a world of finite resources would lead to some limit and famine. Applied to nature, this became, the survival of the fittest or natural selection.
By putting the pieces of his observations and learning
together Darwin came up with the theory of evolution with four main
[i] Organisms adapt to their environments.
[ii] Organisms are variable in their traits.
[iii] Organisms tend to reproduce in excess and beyond the environment's capacity to support
[iv] Some organisms will be better suited to their environment and so will survive and reproduce better than others; known as natural selection ("survival of the fittest"). This leads to the higher reproductive success of the better adapted organisms.
Today we hear echoes of Malthusian warnings, such as at the 1992 UN Conference on Environment and Development (UNCED) in Rio de Janeiro. This concern emerged in the 1970s during the oil crisis, when governments realised the importance of the long-term availability of natural resources to sustain economic growth. Books such as "Limits to Growth" (1972) and its 1992 sequel, "Beyond the limits" (Meadows, et al., 1992) , expressed the same concerns, supported by much data. They showed that humanity would reach the limits to physical growth on the planet within 100 years at current growth trends. By 1992 the world had already overshot some of its limits! Rio's UNCED conference gained international recognition of the scarcity of natural resources for development Sachs, 1993).
Without the acceptance of the principle of evolution, there is no
chance for the serious proposal and development of holism.
Even in Darwin's "On the Origin of Species" published in 1859, Darwin
was still wary of speculating on human evolution . He only
"Light will be thrown on the origin of man and his
history." Thomas Henry Huxley
advanced the close relationship between humans and apes in his essays
in Man's Place in Nature (1863). Darwin's "The Descent of Man" appalled
Christian fundamentalists as he ventured that human ancestors arose in
Africa, where our closest relatives, chimps and gorillas are to be
C. DATING TOOLS:
Numerous scientific dating methods and tools are now established to
correctly place a fossil find on the geological time scale. These are
now generally classified as relative dating techniques and absolute
absolute dating techniques
The following are absolute dating techniques: Archaeomagnetism,
Astronomical Dating, Dendrochronology, Electron Spin Resonance, Fission
Track, Optically Stimulated Luminescence, Oxidizable Carbon Ratio
(OCR), Potassium- Argon Dating, Racemization, Radio-Carbon Dating
(Carbon-14), Thermoluminescence Dating and Uranium-Thorium Dating.
These methods are discussed in detail in specialist sites referred to in the
The development of potassium-argon radiometric dating in the 1950's greatly enhanced the precision of estimating the age of a fossil. This advance was as important for palaeoanthropology as the discovery of fossils (Reader, 1988) . Potassium-argon dating is based on the radioactive decay of volcanic potassium-40 into argon. Other unstable elements, such as uranium, decay very slowly into lead while emitting radioactivity. It would take 45,000,000,000 years for half the uranium to become lead. Only 1% of natural potassium is in the radioactive form called K40, half of which decays into argon over a period of 1,310,000,000 years. Over the 2-3 million years of human evolution, only about 0.1% of potassium K40 found in rocks would have become argon. Scientists use a mass spectrometer to measure these minute quantities. They can precisely and consistently measure billionths of a gram and date the deposits with which the fossils are associated. K/Ar dating has a lower limit of about 600,000 years, so a dating gap of half a million years exists over a crucial period of human evolution. Fission-track dating is the term used for a dating method based on the spontaneous fission of the uranium isotope present in a wide range of rocks and minerals. This time range it overlaps with potassium-argon dating and gives useful dates from rocks adjacent to archaeological material. Uranium series dating is a dating method based on the radioactive decay of isotopes of uranium. Scientists use thorium/uranium and protractinium/thorium dating to cover this period (Waechter, 1990) . K/Ar dating method falls within the category of radiometric dating, with carbon-14 dating, rubidium-strontium, and uranium-thorium-lead dating. The latter dating method has proved to be very accurate where crystals of a mineral called zircon are found. Zircon dating, which measures relative amounts of uranium and lead in the crystals, has been used to identify the start of the Cambrian at exactly 543 million years ago.
Radiocarbon dating is an absolute dating method that measures the decay of the radioactive isotope of carbom (14C) in organic material. Carbon dating is only reliable up to 50,000 to 70,000 year-old fossils. Some prefer to use it for dating to only 40,000 years. Only specific materials are suitable for C14 dating, such as charcoal from old fires, bone, antler and shell. Researchers have to take care to prevent contamination of samples and occasionally a sample may have accumulated C14 from the surroundings (Waechter, 1990) .
relative dating techniques
Absolute dating methods such as potassium/argon method of dating fossils are not foolproof ( see image ). A certain humanoid fossil, labelled 1470 (Leakey et al , 1964), upset most schemes as its radiometric date gave it an age of 2.9 million years old. This date conflicted with the faunal evidence and geological evidence associated with the fossil, both called relative dating methods. The large brain volume of the fossil, which suggested that it belonged with H. habilis , while the age showed that it was a large brained Australopithecine an even older human ancestor. Fossil pigs of the genus, found in the Turkana Basin where the fossil was found, eventually aided to resolve the problem. Counter-evidence provided by the evolving pig lineages and the correlating geological sequence in which the fossils were found, forced scientists to accept that the fossil 1470 was essentially the same age as H. habilis (1.8-.16 mya.). The geological and stratigraphic determination was critical to resolving the interpretation of this fossil evidence.
Other relative dating methods include floral evidence such as fossil pollen present, stratigraphy, climatic evidence, chemical changes and Archaeological evidence (Bilsborough, 1992). The relative dating methods of Cation Ratio, Cultural Affiliation, Fluorine Dating, Obsidian Hydration, Patination, Pollen Analysis, Rate of Accumulation, Seriation and Varve Analysis are linked to sites with more details through the glossary. This subject falls within the field of paleoenvironmental studies. As some animals from the fossil record, such as the reindeer and red deer have living ancestors, scientists can establish prevailing habitats and to some extent climate. Pollen analysis provides a climatic indicator as pollen grains preserve well, allowing researchers to identify trees and grasses, so giving a picture of local conditions. Pine trees, for example, prefer wetter climates, while oaks are found in dryer ones (Broecker, 1995). Agreement in the climatic change over the last 100,000 years can be found from North Atlantic marine sediments, Antarctica, Scandinavian and Icelandic glacial moraines, and northern European, ice cores from the Greenland ice cap, and maritime Canadian lakes and bogs (Broecker, 1995) . Analysis of air bubbles in ice cores show conditions up to 100,000 years ago. Ice-core isotopic analysis is used to determine past climates. Where instrumental records exist, some correlation is found between these and the ice-core results (Masson et al, 1999).
Researchers measure the relative amounts of oxygen 18 and oxygen 16 in the shells of fossilised foraminifera (Potts, 1998) . As the climate cools, less of the oxygen 18 isotope is found in the sample. Spectral analysis studies of the frequency and strength of these oscillations shows that 18 O fluctuations occur at certain periodicities (cyclicities) that match variations in Earth’s orbit around the sun. These orbital variations have a prevailing influence over global climate, one on a cycle of 100,000 years, another cycling over 41,000 years and a third on a cycle lasting about 21,000 years.
There is a link between relative and absolute dating. Coral sediments show the changes in carbon-14 over time, while uranium-thorium dating provides absolute ages to the same material.
Ocean records of dust and land detritus from continents reflect strong seasonality of rainfall and the prevailing winds that carry the dust to the ocean. These ocean sediment cores provide a record of changes in seasons and wind patterns and reflect patterns of continental vegetation cover. Studies of diatom species in lake sediments allows scientists to establish the history and to calibrate rates of environmental change of ancient lake basins inhabited by our early toolmaker ancestors. Sequences of alternating loess (windblown sand) and (often organic-rich) soil (paleosols) (found in vast regions of Asia and Europe) provides a detailed record of environmental change (Potts, 1998) . In China these sediments have revealed at least 44 major shifts from cold to warm conditions over the past 2.5 myr. The organic material is also analysed to see if C 3 or C 4 type plants predominated. These terms reflect two distinct photosynthetic pathways. C 4 plants are mostly grasses adapted to hot, dry conditions and low atmospheric CO 2 concentrations. C 3 plants include woody species, herbs, and grasses adapted to cool growing seasons and shade. The two categories produce different ratios of carbon isotopes 13C/12C. 13C in temperate zone soils reflects changes in climate or atmospheric CO 2 , while in tropical lowlands, this can be used to establish habitat vegetation changes from heavily wooded to open grassland.
Stratigraphy is based on the deposition of distinctive strata of rock layers over time. After dating a stratum of rock, the fossils within that layer of rock can be assigned to the same period. Identifiable marker beds may allow the cross-relating of two separate sites. By correlating stratigraphic sections over a wide area, paleogeographic environmental and habitat settings can be reconstructed. Comparisons of chemical changes to bones at a site may establish their relative ages. We can use some archaeological evidence that follows a temporal sequence to establish the relative ages of fossil remains.
Paleomagnetism is another valuable tool used by palaeontologists to establish the age of fossils (Coppens, 1994) . This method of dating relies upon the fluctuations and even complete reversals that have occurred in the earth's magnetic field throughout its history. Volcanic rock, formed at different periods, has magnetic minerals that align with the prevailing magnetic field during cooling to form igneous rocks. These records enable world-wide correlation of rock strata!
Another useful dating method is fluorine-dating which
relies on the natural accumulation of fluorine into the bone from
ground water around it (Parker, 1992).
Scientists have developed other dating tools for special tasks, such as
thermoluminescence for burnt materials and some sediments up
to 100,000 years old. This tool is useful for comparisons with carbon
dating and the period between 50,000 and 100,000 years ago (Groves, 1994) in Burenhult). Researchers
also use fission track dating for natural (volcanic) glasses to compare
with potassium-argon dating. Amino acid racemisation for bones and
electron spin resonance for teeth are also in use (Roe in Waechter, 1990) . Deep sea cores of
sea bed sediments mixed with the shells of oceanic creatures give very
accurate estimates of environmental temperatures at the time of their
deposition. From these scientists establish that over the last 700,000
years 19 distinct climatic changes have occurred. Local estimates such
as tree-ring analysis (dendochronology) of the annual growth rings and
annual sediment deposition in lakes also provide absolute forms of
All these methods contribute to a clearer picture of the world's history, showing a majority of hominid speciation events in eastern Africa. Ultimately, through accurate dating of fossils and sites, there can be an integration of ecological, phylogenetic, and archaeological data, as well as any relevant evidence about local habitats within regions, which should lead to a more complete understanding of hominid dispersal and speciation patterns (Strait and Wood, 1999).
A more recent dating method can be categorised under Molecular Anthropology . Instead of studying primate evolution using morphological comparisons to establish phylogenetic relationships, molecular comparisons are made of protein structures, nucleic acids and chromosomes to see how they differ in structure. This is the field of the biochemist and offers many challenges. The great challenge of this field is explaining how apparently irreducibly complex molecular systems, with several parts that contribute to its function, evolved (Behe, 1998) . The tools molecular materials of this field of study are Electrophoresis , Immunodiffusion , microcomplement fixation , DNA Hybridization , Amino Acid Sequences , DNA Fingerprinting , Mitochondrial DNA , Nuclear DNA , and .
DNA analysis of archaeological and palaeontological remains allows scientists to go back in time and study the genetic relationships of extinct organisms to their living relatives (Hofreiter et al , 2001). Due to the steady decay process, very few fossils has any DNA to analyse. Scientists can retrieve DNA sequences from human and non-human remains that are up to 50,000 to perhaps 100,000 years old. A very few fossils as old as one million years old may yield DNA, but older material has too much damage to give meaningful results. DNA studies show that Neanderthals went extinct without contributing mtDNA to contemporary humans (Hofreiter et al, 2001).
An example of how the various dating tools are used to confirm dates is seen in how the important hominid ancestor fossil, Ardipithicus kadabba , discovered in the Middle Awash region of central Ethiopia, was dated. Somewhere between 5 and 10 million years ago chimpanzees and humans diverged from a common ancestor to take separate evolutionary paths. The fossil remains are between 5.54 million and 5.77 million years old, the current oldest human-ancestor fossils discovered.
The age of these fossils, determined by the Berkeley Geochronology
Center (WoldeGabriel, 2001), was done
using an argon-argon laser heating method. This is a process that
establishes the time since volcanic ashes and lavas erupted, as the
dates of the ash layers and lava flows bracket the age of the fossil
remains. Scientists measure the argon gas trapped in the rock after it
cools. These dates were then corroborated by geomagnetic polarity data,
and further confirmed by biochronological analysis of the primitive
fossil animals found with the human ancestor remains. A study of the
bones shows a toe bone indicating that this creature walked upright and
teeth that appeared to be evolving from apes to later human ancestors
(The teeth are similar to animals that eat a mix of soft leaves and
fiber-rich fruit (or root tubers)). It lived in a lush
mountain forest habitat with ancient elephants, antelopes, horses,
monkeys and rhinoceroses.
. . . since we are here, we evolved from primates" (Dennett, 1995).
"Humans are creatures whose roots lie in the animals. Accordingly, we find ourselves at the tip of a branch of an immense tree of life, a tree that has been developing and growing ever more diverse over a period of four billion years." (Coppens, 1994) .
"Has there not been over man a long period of time when he was nothing mentioned?" (QsLXXXVIv1) (Q = Islamic Holy Quraan).
"See they not how God originates creation, then repeats it: truly that is easy for God . . . Travel through the earth and see how God did originate creation; so will God produce a later creation for God has power over all things" (QsXXIXv18-19).
"You shall surely travel from stage to stage" (QsLXXXIVv19).
"If He so pleased, He could blot you out and bring in a new creation" (QsXXXVv16).
"The emergence of individual human beings on the earth seems to have been designed to take place through a process of evolution covering countless stages of transformation and in the form of a series spread over a vast span of time, as different Quranic verses and the verdict of Muslim thinkers like Rumi affirms" (Ansari, 1973) .
"O Man! what has made you careless concerning your Lord, the Bountiful? He who created you, then fashioned you in due proportion, then wrought you in symmetry; (then) into whatever form (or figure) He willed, He constituted you" (QsLXXXIIv6-8).
"Today . . . new knowledge leads us to recognise that the theory of evolution is more than a hypothesis" (Pope John Paul) (Time, V148, No. 19, Nov. 4, 1996). For more on: the Roman Catholic response to evolution .
And Allah has brought you forth from the (dust of) earth.
"The Kansas Board of Education voted 6 to 4 to remove evolution, and the big bang theory as well, from the state's science curriculum" (Gould in Time, August 1999).
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