HOMO SAPIENS
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Oldest humans

"When I am here in one place, I don't know what's going on over there" said the Eskimo hunter-gatherer (Binford, 1983).


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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 (Reader, 1988) (Roe, 1990) (middle and early upper Pleistocene). Within Africa the oldest modern humans are just less than 160,000 years old and represented by Homo sapiens idaltu. Another Homo sapiens skull from Dali, China, is dated at 200,000 years old.  It has a cranial capacity of 1,120 cc. (Johanson & Edgar, 1996). In Africa, 21 sites spanning Africa from north to south (Libya, Morocco, Algeria, Sudan, Ethiopia, Kenya, and Tanzania) and dating from 500,000 years to 30,000 years ago have yielded fossils with predominantly modern anatomical characteristics. In South Africa, two sites, the Klasies River Mouth and Border Cave have yielded H. sapiens sapiens fossils dating from around 60,000 to 80,000 years ago. Others put fossils from Klasies River Mouth Cave, with modern appearance, at between 115,000 and 80,000 years old (Burenhult, 1994). Along the Langebaan Lagoon are human footprints dated at 117,000 years old (Gore & Garrett, 1997). Sites in South Africa (including Equus Cave, Florisbad, Die Kelders Cave) provide evidence that modern humans evolved over a period of 200,000 years from Homo heidelbergensis.   "Rhodesia Man" from Kabew in Zambia is now recognised as an example of H. heidelbergensis . A 300 to 400 thousand year old skull from Greece (Petralona) and a 200 thousand year old skull from the French Pyrenees are also classified as H. heidelbergensis. Three skulls in a cave site (Sima de los Huesos) in Sierra de Atapuerca, Spain have been identified as early Neanderthals and dated at over 300,000 years old. One had a cranial volume of 1,125 cm 3 and the other 1,390 cm 3 (Arsuaga, et al. 1993). Specimens that cover the period from 400 thousand to 200 thousand years ago show a change to a more modern form (Bilsborough, 1992).

Migration

Humanity's ancestors first appeared in the African Rift Valley from which they migrated, north, west (Cardwell, 1994) and south. A current hypothesis is that diverging hominid (see hominid books) stock migrated from Africa at two different periods. One lineage of 700,000 years ago led to the Neanderthals evolving in the temperate zone of Europe and the Middle East. Another, which evolved in Africa about 100,000 years ago, led to modern humans. (view of modern human skull) ©1 Around 186,000 years ago, an ice age set in, creating arid conditions in Africa (Gore & Garrett, 1997). This lasted until about 120,000 years ago and prevented the migration of this evolving human out of Africa. By 100,000 years ago the Sahara desert was lush, with lakes, streams and vegetation. Plentiful game would have encouraged a wider distribution of early humans.


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Genetic evidence derived from the amount variation of mitochondrial DNA and an estimated natural rate of evolutionary divergence of this DNA of 3% per million years, has placed the origin of all modern humans at between 140,000 and 290,000 years ago (excludes the Neanderthals). Studies of a part of the human chromosome that influences the immune response, suggests that this early population was made up of only between 500 and 10000 individuals (Klein, et al, 1993). Another study of the mitochondrial DNA of 171 people and five geographic populations showed that these people arose from a single African woman postulated to have lived about 140,000 to 280,000 years ago (Cann et al. , 1987) ("out of Africa hypothesis"). Further, anatomically modern humans arose 100,000  to 140,000 years ago, and the populations outside Africa had multiple origins (i.e. multiple colonisations). 

Three 154,000 to 160,000-year-old human skulls ( two adult males and a child) from Ethiopia (dug up near a village called Herto) are currently the oldest known and best-preserved fossils of modern humans' immediate predecessors. As the Herto skullherto Homo sapiens idaltu is slightly larger than those of modern humans ( 1 450 cubic centimetres, compared with a modern human's average of between 1 350 and 1 400 cc), they are classified it as a subspecies, Homo sapiens idaltu. (Images) Radioisotopes (argon/argon dating method) in the soil (in volcanic sediment) containing the fossils allowed them to be reliably dated. Volcanic layer chemistry was used to correlate the dated layers.The skull features are very human, giving a face that is flat with prominent cheekbones. They do not have the protruding brow ridge of pre-human ancestors or Neanderthals, while their braincase is rounded, like a soccer ball, rather than the football shape of earlier human ancestors. They had no neanderthal features. The skulls were larger than all of 6000 modern human skulls with which they were compared! This confirms the Islamic traditions (hadith) that state that early humans were very big, almost giants! Further, the fossil record now meshes with the molecular evidence. Significantly, these anatomically modern humans pre-date most neanderthals, and so could not have descended from them. More than 600 stone tools, including hand axes found in the same sediments (the same era) as the fossils, along with fossils of other animals, show that they had a sophisticated stone technology (White, 2003). They used chipped hand axes and other stone tools, to butcher large mammals like hippos and buffalo (Clark, 2003). The stone tools were transitional between the Acheulean period, characterized by a predominance of hand axes, and the later flake-dominated Middle Stone Age.  Homo sapiens idaltu lived on the shore of a shallow lake created by the dammed Awash River. This lake habitat contained abundant hippos, crocodiles and catfish. The skulls also have blade cut marks.

Migrants, that 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 60,000 years ago (Strausbaugh and Sakelarisc, 2001), the New World by 12,000 years ago (Cann et al. , 1987) and Europe by 36,000 years ago (Reader, 1988) (Groves, 1994). Cann, Stoneking and Wilson's (1987) study  of mitochondrial DNA found a lack of diversity in the Asian population that would have been expected had these migrants hybridised with the Homo erectus already in the area.  The greatest divergence in DNA of non-African populations occured 90,000 to 180,000 years ago suggesting that Homo erectus (Java Man, Peking Man) did not contribute to our gene pool (as proposed by the multi-regional hypothesis to human origins).

Modern genetic studies, published as "The History and Geography of Human Genes" (Luca Cavalli-Sforza, Paolo Menozzi and Alberto Piazza), divides humanity into four major ethnic regions, African (Khoisan), Caucasoids (Basque), Mongoloids (American Indian) and Australians (Aborigine) (Time, No. 3, 1995). With fossil evidence these recent findings confirm the African origin of humanity. Africans have the greatest genetic distance from the rest of humanity, showing that on the human family tree, the split from the Africans occurred before the other branches. Australian aborigines are genetically the most distant from the Africans.

Humans migrated into Europe about 40 000 years ago (Burenhult, 1994). They used two different tool traditions at this time. People south of the Sahara had the same Middle Stone Age tools between 200,000 and 40,000 years ago. The first migrants into Europe transmitted this tradition. In North Africa and Europe, a new tool tradition started 40,000 years ago. These are associated with early Cro-Magnon cultures, called the Aterian culture in Tunisia and Libya. (view of Cro-Magnon skull) ©1 North Africa had more rain at this time and was lush and full of large game. Tool points with tangs that allowed the attachment onto a spear or arrow first appeared at this time (Burenhult, 1994). The bow and arrow are believed to have been invented here. This North African Aterian tool culture lasted for 20,000 years. Smaller points such as those used in arrows developed. Tiny microliths (small barbs) of flint, used to mount in rows on bone or wood sickles are also found, showing that they reaped wild grasses.

Eventually this culture led to the early Egyptian Quadan people of 15,000 to 13,000 years ago. Humanity was on the brink of early civilization, these people hunting and fishing and gathering seeds from wild grasses. Grinding stones found from this period show that they ground down seeds. This dependence rapidly led to agriculture.

Farther north, in France, reindeer hunters may have become reindeer herders between 10,000 and 20,000 years ago. Stone art showing horses with halters shows that domestication had occurred  by 30,000 years ago. Part of these people's diet included cockles and mussels, showing that part of their seasonal migrations was to the coast.

The meeting and interaction of modern humans and Neanderthals occurred between 100,000 and 40,000 years ago. They differed genetically by up to 500,000 years of reproductive separation. Modern humans higher fecundity may have led  to their high populations in Europe during the Middle and Upper Palaeolithic (40,000 to recent), leading to the extinction of the Neanderthals in the Mousterian period (end of the Middle Palaeolithic). Neanderthals lived in cold climates so were in some way cold-adapted. If Neanderthals were seasonally migratory, and modern humans occupied what was traditionally the Neanderthal winter refuges extinction due to a combination of a population increase, competitive exclusion and territorially would have been rapid. Whatever the actual cause, humans persisted and Neanderthals died out.

Early technology

Early hominids (see hominid books) diverged from apes through a combination of adaptation to arid or dry open habitat and increased tool-use, and linguistic and social capacity (Gibson, 1993). Tool complexity evolved from the first sharp-edged stone tools of early hominid stone caches to essentially modern humans' construction of tools from several components and then the use of materials such as bone that demand complex processing methods (Gibson, 1993).


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Tool use by modern humans usually requires conversation for its transmission, so certain features or abilities are only found with humans. Examples from the Upper Palaeolithic are:

[1] a well developed bone, antler and ivory technology,

[2] mechanical projectiles such as the spear throwers and the bow and arrow,

[3] heat treatment to manipulate raw materials,

[4] needles for sewing,

[5] art and burials,

[6] Ceramic vessels and many other examples illustrating the human's innovative and imaginative nature,

[7] harpoons and fish spears.


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Even the Neanderthals seldom used tools made of anything but stone although antler, bone and ivory must have been readily available (Burenhult, 1994). Experimentation and discovery form an early part of human culture. One discovery was that the heat treatment of flint and siliceous materials improved their texture and flaking qualities (Toth & Schick, 1993). If we were to recognise a degree of continuity in the sophistication of behaviour from humans down to other animals, we would be accused of anthropomorphism. Scientists claim that animals and humans function using different mental mechanisms. Today researchers have witnessed tool making in wild chimpanzees, destroying the myth of "man the tool maker." Chimpanzees also display lethal intergroup conflicts, and long term bonds among genetic relatives. A form of sign language taught to chimpanzees, an orangutan, a bonobo, and a gorilla, proves their symbolic capacities. Research is underway to find whether a gorilla speaking sign language will teach its offspring the same method of communication. Animals have been shown to use syntax, emit sounds of environmental reference, recognise themselves in mirrors, exhibit cross-modal perceptions, engage in deliberate deception and use a tool to make a tool (Gibson, 1993). Communication through language must have been a very beneficial adaptation for our human ancestors. It has opened the way to the communication of ideas and technologies, planning, cultural transmission and social cohesiveness. Archaeologists have not figured out when language emerged, but language forms the basis of all that is human.

40,000 years ago, the climate was colder, with parts of northern Germany, England and Ireland covered by one kilometre thick ice sheets! Cro-Magnon people adapted to become today's whites, as a pale skin better produced vitamin D from the weak sunlight. Their closest relatives today are the Indians.

Evidence from Human remains dated as belonging to populations in the Upper Palaeolithic (40,000 years ago) shows that, by this time, humans were skilful hunters, killing horses, bison and reindeer. Large game also included deer, mammoths, rhinoceros and aurochs. Wolves, lions and leopards would have been a daily threat. People made homes from mammoth bones and tusks. Palaeolithic humans in France used carved, spoon-like oil lamps between 40,000 and 11,000 years ago. These limestone lamps burnt animal oils (de Beaune & White, 1993).

Social Evolution


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A clue to the structure and character of early humanities' evolution and social structure is found in ecological observations and principles. Wynne-Edwards (1986) established that cooperation between animals is beneficial in two vital activities: the controlled use of nutritional resources through the density regulation of populations (homeostasis), and the structuring of populations leading to the genetic management of populations. Sociality in humans provides the conditions necessary for such management. Interactive pressure drives the process of natural selection and one outcome is an economic one. Later a model will show how this process takes place. In social interactions, natural selection favours more efficient interactors. The stronger the social interaction, the more intense this force will be. In humans of the Pleistocene period we see a rapid change to smaller boned people with smaller teeth. Factors that impinge on the human social system are the longevity of humans and their tendency to polygamy, and cohesive or dispersal characteristics.

Wynne-Edwards described the social structure of early Australian Aborigine societies. These people arrived in Australia from Southeast Asia up to 60,000 years ago (Wilson & Cann, 1992) (Reader, 1988). No hominid (see hominid books) fossils but those of Homo sapiens sapiens have been found in Australia. Two groups of humans may have colonised Australia, as fossils can be separated into robust and gracile groups (White, 1994). Researchers need more fossils to establish whether these differences are sexual or racial differences. At the time of colonisation, sea levels were at their lowest levels, but at least 70 kilometres of open water still had to be crossed to reach Australia. They probably achieved this via the Island chains of Indonesia (White, 1994). By 30,000 years ago these people had colonised the whole of Australia.

Aboriginal tribes of Australia numbered about 500 people and these were territorial, the size of a tribal territory strongly, inversely correlated with mean annual rainfall. Burenhult (1994) noted that to prevent inbreeding a social group must have at least 475 people. Most recorded hunter-gatherer groups comprise between 500 and 800 people.

Limiting resources, such as water holes, rivers and lakes influenced tribal distribution. Food productivity per unit area was dependent upon mean annual rainfall. Where rainfall was low, the tribes needed larger territories. In western New South Wales (Lake Tandou and Menindee) there are remains of human habitation from between 200 and 27,000 years ago (White, 1994). Infanticide was a culturally-regulated practise that favoured the survival of males (an adult sex ratio of three males to two females).

Within this larger territory, they divided the tribe into smaller units of about 25 individuals of all ages. Wynne-Edwards called such social units "in-groups", "a set of individuals that live in everyday social contact and are more or less closely acquainted with each other. They interact as rivals, allies, consorts, parents or dependants in domestic life." The in-group formed the main social arena for the individual. Roughly 20 such bands would have the right to hunt and gather food within the communal territory. The in-groups within a tribe would have the same dialect and "culture". This system led to several language families occupying a small area in the north (but Anthropologists have not explained the single, embracing Pama-Nyungan language of the south) (Renfrew, 1994).

Wives were usually selected from another of the in-groups within the tribe and seldom from another tribe. Where tribal boundaries met, the adjacent in-groups sometimes exchanged marriageable women, these forming 10 to 40% of marriages in these cases. Tribes were friendly although their dialects differed and little intertribal marriage took place. Cultural practises delayed marriage until a male achieved a certain status, associated with age and top-ranking males could have two or more wives. This practise regulated birth rates so that mothers only ever had to carry one child while gathering food.

Successful tribes of about 1000 individuals would split into two, while adjoining tribes absorbed tribes of less than 200 individuals. Some general characteristics of this system, which favoured human cultural evolution are as follows:

[a] The "dispersal" of females is considered crucial to genetic structuring, particularly the control of gene flow and the maintenance of favourable levels of inbreeding . This must be considered with the tendency of males to remain within the in-group, termed philopatry, when evaluating the genetic structure and sustainable population structuring of the in-groups. Gene flow from the movement of wives and the degree of inbreeding in such a social system depends on how far individual members of an in-group move away from their birthplace to where they eventually mate and breed. It also depends on the degree of isolation and size of the in-groups. Sexual difference in dispersal patterns is common among mammals and birds. It allows a balance between averting incestuous mating through dispersal (in females) and ensuring philopatry (in males), so that the descendants can benefit from the habitat conservation of their ancestors. The behavioural advantage of having at least one sex that remains at home is that it learns how to survive in that specific locality. It learns the food resources, hunting methods and the cultural norms of its in-group that confer stability.

Such female dispersals also occur in chimpanzee and mountain gorilla but are not found in all primitive human tribes (e.g.. North American Iroquois). Lau people of the Solomon Islands, who live on coral islands that they construct in Pacific lagoons, traditionally required that women leave their home islands to marry men of other islands. With the introduction of Christianity this custom has been lost along with much of the original culture.

[b] Small isolated groups have a greater potential to develop different phenotypes (characteristics) through natural mutation and genetic drift. Such characteristics of coherent, stable in-groups are more often tested through natural selection and random events and so speed up the evolutionary process. Such isolated units must be small enough to facilitate genetic drift and differentiation of in-group gene pools and coherent enough for these gene pools to remain intact for generations while subject to natural selection. Genetic drift is the change in the genetic constitution of a population by chance processes alone. As drift implies, it is genetic change not subject to the forces of natural selection. Chance events may shift the frequency of genes on the chromosomes. Aboriginal social units, the in-groups, will have a unique genetic constitution that is a result of the genetic constitution of the individuals (Wilson, 1992). In-group social structure thus favours the maximisation of gene-frequency variances between social units and the evolutionary potential in terms of rate, diversity and adaptation.

[c] Territoriality is a form of self regulation subdividing a renewable resource. Ecosystem stability is maintained through the population remaining within the carrying capacity of the habitat. (If food, predators, parasites, disease and weather do not regulate population numbers, some form of population self regulation should occur.) In high-yield years or habitats, the territories tend to be smaller and population densities thus denser, while the converse is true.

[d] Within the in-group social structuring is hierarchical.

[e] Two additional factors that increase the effect of philopatry are longevity and polygamy. Frequency of dispersal is less in long-lived animals, so increasing the effective population "viscosity". Polygamy reduces the effective ratio of males to females, so increasing the inbreeding rate or the gene representation of the successful polygamous male within the in-group. In doing so, it reduces the number of breeding males. A male is usually long-lived and the most fit, so he passes these traits onto the next generation.

However, contemplating the reality of our unique form, such as that of our feet, so universally representing only humanity and no other living creature, we need to question to what extent natural selection has fashioned us and why our physical form is so stable. It is clear from the unchanging universality of human form that the above social system served a different basic function, not influencing the human form. The most serious threats or challenges to such societies would have been environmental extremes such as drought or intense UV exposure from the sun (causing cancers or extreme sunburn), the acquisition of food, parasites and disease causing pathogens. The primitive social system described has the primary effect of maximising genetic variability. Genetic variability between in-groups serves to reduce disease susceptibility. As doctors have realised, after the appearance of penicillin resistant strains of many pathogens, there is a natural or inherent ability for resistant strains to emerge through repeated subjection to a single line of defence by the host. Such parasites and pathogens thus evolve mechanisms to resist the host's line of defence. In a population of genetically diverse in-groups, there is more chance for a disease resistant in-group to emerge and less chance for resistant strains of parasite and pathogen to evolve! Also disease transmission via susceptible individuals or groups is slowed and the devastation of the whole population less likely (Soule & Piper, 1991). Among evolutionary ecologists and behaviourists there is a finding that parasites have had a far greater influence on "the workings of nature," than previously suspected (Holmes, 1993). Parasite-host interactions may influence animal movement patterns, social behaviour and mate selection.

Similarly genetic variability may favour the more rapid evolution or response to environmental challenges, such as through efficient kidney function (drought), improved eyesight (hunting and predation), darker skin colour (UV radiation) and so forth. The aborigine social system thus favours the most rapid acclimation and adaptation to prevailing conditions. A shocking example of this is a tribal ceremony photographed and recorded in Wells' "The Science of Life", where on initiation to their tribe, young Aborigine men have to lie on their back all day in the sun with no food or water. Some died during this ordeal. Any "white" man would have died the first day!

Genetics:

Why the human form varies so little, although humanity has managed to occupy every imaginable habitat and persisted within specific habitats for generations, is today answered through a study of the human genome - the genetic makeup of the human race - as compared to the chimpanzee. At the genetic level, humans are remarkably homozygous. Chimpanzees show as much as 10 times the genetic variation that humans possess, showing that humanity as a whole, be they African or Chinese, arose from a small stock of common ancestors (Wilson & Cann, 1992) and were subject to some heavy selection and specialisation while surviving. One may remark that, considering the low degree of variation in the mitochondrial DNA of humans (Reader, 1988), the differences to be found between human races is quite remarkable, suggesting quite rigorous sexual and natural selection having been exerted upon humanity! I present the modified energetic Lotka-Volterra model (MELV model) in this book, suggesting that natural selection promotes differentiation as a response to differing environments, while sexual or social selection reduces this difference. Interestingly, at the genetic level, studies of mitochondrial DNA (mtDNA) has shown that the African populations have the greatest genetic variation, providing confirming evidence that humanity originated in Africa. A small group of people must have populated the rest of the world or the migrating humans were subject to heavier selective pressures (or both). Concerning similarities between apes, the myoglobin protein, found in muscle tissue and made of 154 amino acid subunits, differs between humans, gorillas and chimps, by only one amino acid! Baboons differ by only five, so this difference is not as remarkable as it initially appears.


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Fossil evidence of humanity's entry into Europe is confirmed by studying Y-chromosome genetic  markers that are inherited only male-to-male and do not recombine. The genotype of 22 markers from 1,007 European men showed that more than 80 percent of the European population’s gene pool arose from two distinct migrations of Paleolithic ancestors, one 40,000 and the other 22,000 years ago ( www: geneletter ). More recent Neolithic farmers (arrived 10,000 years ago) only comprise 20 percent of the European gene pool. Oota et al (2001) found a similar continuity between the pre-Neolithic humans (25,000 BP) and the present Semang of the Malay Peninsula, while the Neolithic humans in this area seemed to be ancestral to the Senoi.

Return to:  Human evolution index page. Goto to next  chapter: Civilisations .

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by Laurence Evans 1998 - 2008

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