Sharon N. Solomon xerexes@yahoo.com
Dept. of Anthropology
University of Toronto Dec. 2000
Paleoenvironment
Research on Greenland and Antarctic ice cores (Hewitt 1999, 2000; Allen et. al. 2000) indicates that the Arctic ice cap became established approx. 2.4 mya (the beginning of the Quaternary). From then until approx. 900 kya, the ice sheets advanced and receded with a roughly 41 ky cycle. After that period, they have followed a 100 ky cycle (ibid.). The Croll-Milankovitch theory proposes that the regular variations in the Earth’s orbit around the sun are the controlling factors of the ice age cycles.
The main orbital eccentricity has a 100 ky cycle, variation in the Earth’s axial tilt has a 41 ky cycle and precession due to the Earth’s axial wobble has a 19-23 ky cycle. These factors, in conjunction with the energy transported by the oceanic circulation system, leads to significant climate changes (Hewitt 2000:907). There were 24 interstadials through the last ice age, with average temperatures rising rapidly by approx. 7?C over just decades (ibid.).
From approx. 130 to 71 kya, during and following the last interglacial, the climate was fairly warm, with some reversals (Hewitt 2000:912). This period is characterized with a predominance of temperate deciduous forests alternating with steppe conditions, in rapid succession (Allen et. al. 2000:740). During the forested periods, the mean temperatures were similar to modern values. However, during the steppe periods, they were approx. 12?C lower.
These severe climatic changes produced dramatic changes in species distributions. Species went extinct over large parts of their range: some dispersed to new locations, and some survived in biotic refugia and then expanded again (ibid.). Identified areas of biotic refugia include the southern peninsulas of Iberia, Italy, the Balkans, Greece and much of Turkey (Hewitt 1999:104). These refugia contributed to the post-glacial biotic colonization of Europe.
The Ice Ages lead to changes in vegetation patterns with forests disappearing and steppes and tundra opening up in their place. The colder climate, changing vegetation, and resulting migration of the animals had a great impact on the way in which our hominid ancestors evolved. Pleistocene vegetation displays a markedly lower degree of specific growth zones than is found today (ibid.). Prior to the end of the last ice age (approx. 10 kya), vegetation types, and their associated faunal species, appear to have been intermingled with each other (i.e. woodland, tundra and grassland) (Mithen 1996:244).
However, it is important to remember that the Ice Ages were not simply periods of extreme cold, characterized by windy steppes and tundra, and 2 km thick ice sheets. Within each 100 ky period, environmental conditions varied, dependent upon local geographic conditions such as latitude, elevation and topography (Tattersall and Schwartz 2000:205).
Multiregional Theory
The Multiregional hypothesis states that there is no one single origin for modern humans. It attempts to explain not only the origin of Homo sapiens sapiens, but also the existence of anatomical diversity in modern geographical populations. According to the Multiregional hypothesis, this diversity resulted from the evolution of distinctive traits, through adaptation and genetic drift, in different geographical regions that became established in early populations of Homo erectus (Thorne and Wolpoff 1992:28-29; Wolpoff and Caspari 1997). This persistence is known as regional continuity.
Multiregionalism traces all modern populations back to when humans first left Africa approx. 1 mya, through an interconnected web of ancient lineages in which the genetic contributions of all living peoples varied regionally and temporally. The analogy used is that of several individuals paddling in separate corners of a swimming pool; although they maintain their individuality over time, they influence one another with the spreading ripples (which are equivalent to genes flowing between populations) (Wolpoff and Caspari 1997).
Proponents of this hypothesis believe that the fossil record provides the real evidence for human evolution. Unlike genetic data, fossils can be matched to the predictions and theories about the past without relying on a long list of assumptions. The mtEve theory makes five predictions that the fossil evidence should prove (Ambrose 1998:624-625; Thorne and Wolpoff 1992:28): 1) modern humans from Africa completely replaced all other human groups; 2) the earliest modern humans appeared in Africa; 3) the earliest modern humans in other areas should have African features; 4) modern humans and the people they replaced should never have mixed or interbred; and 5) an anatomic discontinuity should be evident between the human fossils before and after the replacement.
mtDNA and mtEve
The main premise behind the mtDNA research was based on the assumption that genes mutate at a constant rate. If the rate of gene mutation was known, then evolutionary changes can be dated. Human body cells contain not only the DNA that resides in their nuclei, they also carry a small quantity of DNA in their mitochondria. Mitochondria are structures in the outer part of the cell that functions as the ‘powerhouse’ behind cell operations. Mitochondral DNA is a small circle of DNA in the mitochondria. It is present in several copies per mitochondrion so that the overall there are hundreds of copies per cell. mtDNA has several important properties that make it suitable as a molecular marker (Cann 1987:31-33; Stoneking 1993:607-608; Tattersal and Schwartz 2000; Thorne and Wolpoff 1992:28-29; Holliday 1997:426): 1) It lacks the elaborate self repairing mechanisms of nDNA and thus accumulates mutations at a high rate. (Roughly 10 times that of nuclear DNA, which allows the main branches in the genealogy to be sequenced more easily); 2) It is largely free of noncoding DNA; 3) mtDNA consists of about 16,500 nucleotides as opposed to nDNA which has more than 3 billion, so it makes comparisons easier; and 4) It is maternally inherited so the gene tree is an estimate of maternal genealogy. The paternal contribution is apparently destroyed or subsequently lost. However, some allele positions in the DNA may undergo parallel or back mutation, as a result there are many different methods to gene tree construction.
mtDNA evidence for Out of Africa
In 1978 Cann, Wilson and Stoneking removed DNA samples from the placentas of 147 women of 5 different ethnic groups (African American, East Asian, Caucasian, aboriginal Australian and New Guinean). They then ran the data through a maximum parsimony program to produce a gene tree in which the geographic origins of the sample were indicated (Tattersal and Schwartz 2000; Thorne and Wolpoff 1992:28-29). The tree was divided into two main branches: one including only Africans and the other containing members of all five populations. This suggested that non Africans had an African origin. By calibrating the molecular clock against the archaeological date for the colonization of New Guinea, they estimated that the common ancestor in the tree lived 140-290 kya. The Out of Africa migration could have occurred at anytime between 13-180 kya (Cann 1987:31-33; Stoneking 1993:607-608). Africa seemed to be the source for human lineages not only because Africans contained the root, but because they were the most diverse region.
Early Modern Homo sapiens
Roughly 100 kya a new form of hominid appeared. It has been proposed that during this interglacial period, hominids belonging to an East African biotic community, expanded northward out of Africa, across the Sinai Peninsula and into the southern Levant (Holliday 1997:426; Ambrose 1998:625). This date is important because it suggests that modern humans left Africa during the generally warm, humid last interglacial period and it provides support for the Out of Africa hypothesis (ibid.).
The earliest anatomically modern humans are found in the Near East, in the caves of Qafzeh and Skhul (dating between 100 and 80 kya), Omo-Kibish, Ethiopia (approx. 130 kya), and in South Africa at Border Cave (approx. 100 kya) and Klasies River Mouth (140 to 20 kya). Questionable fossil specimens are found in Jebel Irhoud, North Africa; Dar es Soltan Cave, Morocco (approx. 40 kya); Singa, Sudan (approx. 133 kya); Laetoli, Tanzania (approx. 120 kya); Guomde, Kenya (approx. 180 kya); and Florisbad, South Africa (approx. 180 kya) (Mithen 1996:25; Tattersall and Schwartz 2000:225-227). Stature estimation ranges between 1.2 and 2 m, and cranial capacity ranges between 1370 cc and 2000 cc.
These hominids were robust (skeletally) but shared more derived features with modern Homo sapiens than with Neanderthals or other hominid species. These features consist of (Tattersall and Schwartz 200:203-204) :
1) a small face and a protruding chin: there is no clear consensus for the functional significance of the chin. It may be due to a reduction in face size, to reduce chewing stress of the mandible, or it may be an adaptation to speech production;
2) smaller teeth and jaws than other hominids: it has been proposed that anatomically modern humans did not use their teeth as tools to the same degree as earlier hominids, hence the reduction in size;
3) a rounded skull with high forehead and reduced brow ridges: the raising of the cranial vault has been associated with more complex cognitive functions and changes in brain structure, which seems highly unlikely since overall brain size was reduced;
4) a bipartite brow, or two component brow; and
5) Less robust post cranial skeleton characterized by long limbs with thinner walled bones, lightly built hands, short, thick pubic bones and distinctive shoulder blades. These features are said to reflect a greater dependency on tool usage instead of muscular strength.
This early group, with their derived features and mtDNA supported dates, are assumed to be the founding group for modern Homo sapiens, even though there is no archaeological evidence which indicates that they were intellectually different from the contemporary Neanderthals.
Diet
Both Neanderthals and archaic Homo sapiens appeared to have hunted similar fauna. These include eland, gazelle, several species of deer, rhino, horses, bovids, as well as small mammals and birds (Mithen 1996:246; Albert and Weiner 2000:933; Albert et. al. 1999:1249: Hockett 2000:715). There has been some evidence of seal and tortoise hunting, and shellfish collection in some coastal sites (Mithen 1996:246; Klien and Cruz-Uribe 2000:171-172).
However, even in modern human populations, meat rarely forms the bulk of the diet. Plant derived proteins and carbohydrates provide most of the dietary requirements. Additionally, the lack of fish bones found at these sites may have more to do with excavation techniques and parameters than the full dietary range of both Neanderthals and archaic Homo sapiens.
The Kebara Cave site (Israel) contains abundant visible hearths which range in size from 30 cm to more than 1 meter in diameter (Albert and Weiner 2000:934). Phytolith studies of hearth sediments indicate that a wide variety of plant materials, other than those used as fuel, were brought into the cave (ibid.). Occupants at the Tabun Cave site in Israel apparently used a natural opening in the ceiling as both an animal trap and a chimney for large hearths (Albert et. al. 1999:1250).
Technologies
Discussions of hominid technologies focus on lithics and bone tools, simply because these tend to preserve archaeologically. However, ethnographic studies of modern hunter gatherers, as well as logical deduction, clearly indicate that the majority of ‘tools’ are either fabricated from perishable materials such as plants and animal skins, or are items which are not modified in any way to indicate its usage.
Another bias in the literature is the assumption that archaic Homo sapiens, by their very taxonomic identification, were superior to their contemporaries, the Neanderthals (and any other, as yet unidentified, hominid species). This is confidently stated throughout the literature, even though both employed the same technologies, lived in the same regions, ate a similar diet, had similar group sizes and practiced similar methods of burial (Boyd and Silk 1997:467).
Tool cultures did not remain static throughout human evolution. The change from one tool culture to another was gradual, with much overlap existing during the period of transition. Neanderthals and archaic Homo sapiens both used and manufactured Mousterian tools. This tool technology dates to 250 kya in Europe (Tattersall and Schwartz 2000:207). Also known as the prepared core technique, this method allowed the tool maker to produce an instrument with a larger cutting edge in less time and from less raw material than before. A stone core was carefully shaped, to the point where a single blow would detach a semifinished tool or series of tools, of predefined form. This process has been proposed as a factor in developing cognitive complexity (ibid.).
There is no certainty that we can fully understand what function these flakes served. During the middle of the 20th century, an elaborate typology of Mousterian stone tool types was devised. More than 60 separate sorts of flakes were identified as well as a large number of handaxe types (Tattersall and Schwartz 2000:207). However, further research suggested that some of these flakes were the result of retouching, wear from usage and geographic variations in tool making and resource availability.
During this time period small stone blades and ground bone tools first appear. While pieces of bone and antler appear at Neanderthal sites, they are assumed to have been used as opportunistic, not intentional, tools (Tattersall and Schwartz 2000: 208). The small flakes found at archaic Homo sapiens sites, have been interpreted as being designed for multicomponent tools, and the ground bones employed as fish hooks or harpoons (Mithen 1996:183). Both Neanderthals and archaic Homo sapiens may to have used short thrusting spears, with either fire hardened tips or attached stone points (Mithen 1996:180). Studies of wear patterns on Mousterian flakes have shown that some were used to ‘work wood’. This could encompass wiping the flake on a tree trunk, cutting wood or sharpening a stick or spear (Tattersall and Schwartz 2000:208).
Behaviour
Social
It has been proposed that sociability developed in several evolutionary steps: bonding and partner proximity, parental care, affection and friendliness (Eibl-Eibesfeldt 1989:167-169). Bonding and partner proximity may have developed as a means of predator avoidance and as a means to facilitate mating (i.e. schooling fish, flocking birds). Parental care is defined as individualized bonding between the mother and offspring, which developed in mammals whose young could move about shortly after birth (ibid.). The mother offspring relationship is reciprocal. Mothers understand the distress calls of their species’ young, and can recognize their individual young. Oxytocin production during the birth process has been proposed as a factor in the initial mother offspring bond (ibid.). The behavioural patterns of affection and infant appeals evident in the mother offspring bond, may have been a preadaptation for adult bonding and friendliness (ibid.).
Xenophobia
Fear of strangers, xenophobia, is present cross-culturally amongst all modern human groups. It has been proposed that xenophobia is a phylogenetic adaptation which is mitigated through learning. It first appears in modern human infants around five to six months after birth (Eibl-Eibesfeldt 1989:170-175). After this time, they are able to distinguish between individuals they know and strangers. When confronted with a stranger, the child will first smile but then turn away and hide its face, after which the child will reinitiate visual contact (ibid.). Eye contact is used to signal that the channels of communication are open, but if eye contact is maintained too long, it becomes threatening.
Even children who are blind and deaf from birth display a fear of strangers (ibid.). If the stranger maintains a distance, the child can make friends. However, if the stranger approaches, the child’s behaviour turns to fear and panic. This reaction is stronger if the stranger deviates from the ethnic appearance of the child’s parents (ibid.). However, in the absence of the mother, the child will actively seek contact with the stranger.
Group size
During much of the Pleistocene, early hominids would have lived in small, mobile groups. Females and their children would be distributed in relation to food resources, and males would congregate near the females (Miller 2000:190). Group size estimates range from 20 to 200 individuals (Mithen 1996:248:). Group membership would have been variable, according the the availability of local resources (Miller 2000:181). The most basic model of group size divides environmental conditions into ‘good’ and ‘bad’ years (Klien and Cruz-Uribe 2000:172). During good years, higher birth rates, while innately risky, will tend to be favoured while the lower birth rates are favored during bad years (Madsen et. al. 1999:260).
Mathematical models predict that throughout their lifetimes, ancestral hominids would have come into contact with anywhere from several hundred to a thousand members of the same local population, from which sexual partners would have been selected (Miller 2000:181). Due to social pressures, the larger the group size, the higher the incidents of aggressive behaviours (Schaffner and French 1997:177).
Sexual selection and Mate choice
In an ethnographic survey of 849 modern societies, 708 (83.5%) were deemed polygynous, 137 (16%) monogamous and 4 were polyandrous (Eibl-Eibesfeldt 1989:235). While this gives the impression that polygyny is typical of modern human societies, only leaders and wealthy males within polygynous societies had more than one wife, with monogamous marriages being 2.5 times as frequent as polygynous ones (ibid.). Even in a polygynous marriage, males seldom have more than two wives (ibid.).
In monogamous societies, polygyny is expressed in the form of extramarital relationships or concealed by a pattern of serial monogamy (divorce, remarriage) (Eibl-Eibesfeldt 1989:235: Mace 2000:5). The polygynous inclination has been explained by the fact that males have a higher reproductive potential in comparison to females, since there is a restriction upon the number of children a woman can bear and raise (ibid.; Ihara and Aoki 1999:77-78; Cunningham and Birkhead 1998:1314; Low 2000:102). It has been proposed that the matrilineal family was the initial family group, with females bonded to children who were no longer physiologically dependent upon them (Tyrell 1978 cited in Eibl-Eibesfeldt 1989:237). It has been suggested that the extended period of childhood and adolescence has evolved in response to social pressures associated with learning (ibid.; Joffe 1997:594).
However, early hominids would not have been as constrained by social pressures or cultural norms. Nonanthropological evolutionary models propose that these hominids would have had sexual experiences before puberty, and engaged in both short and long-term partnerships (Miller 2000:186). It would seem highly unlikely that there would be a desire for a ‘life’ mate when mortality rates were so high and group sizes were so small.
Based upon cross-cultural studies, the following female physical traits have been suggested to be preferred by males: lighter skin colour, lower waist to hip ratio, neotenous face, large breasts, full lips, and clear skin (ibid.; Mace 2000:5; Low 2000:80). Most studies equate these traits with youth. However, there is no reason to assume that ancestral hominids were so picky. As long as the female was still fertile there is no real hindrance, other than personal preference, to forming a sexual liaison (Miller 2000:212).
Ironically, when these same studies report what females desire in a mate, the responses tend to reflect economic rather than evolutionary adaptations (Low 2000:78-90). Studies which do attempt to look for evidence of phylogenetic sexual selection in males, they tend to focus on penis size and its connection to the female orgasm (Miller 2000:226-241).
Modern human females and males reach sexual maturity (puberty) at a much later date than other primates (i.e. 13 years instead of 9 years of age) before that time, they are infertile (Low 2000:94: Miller 2000:211). However, since modern humans have a longer life span, and the average interbirth intervals are shorter than that of the great apes, and the reproduction rate is much higher (ibid.). Reproductive scheduling in modern human females ranges from 2.5 to 3.5 year interbirth intervals, compared to 4-5 years for chimpanzees (Mace 2000:5). Birth intervals tend to increase with age even before menopause is reached. It has been proposed that this may be an evolved response, as well as part of the aging process, derived from sibling competition as well as the cost of parental investment in response to environmental conditions (ibid.; Low 2000:97). One rarely sees the acknowledgment that engaging in sexual activity does not automatically result in conception, and even then it is used to support the ‘long-term’ partnership hypothesis (Miller 2000:186; Eibl-Eibesfeldt 1989:239).
Reproduction terminates with the programmed senescence of the reproductive organs, menopause, roughly 20 years before the rest of the body (ibid.). Other female mammals spend approx. 10% of their lives as postreproductive adults, while modern human females spend roughly 30% (Low 2000:94). The grandmothering hypothesis proposes that menopause may have evolved in order for older females to assist their children to reproduce, rather than to continue to do so themselves (Mace 2000:6).
Land use strategies
The dwelling sites of Neanderthals and archaic Homo sapiens were often located in rock shelters, the mouths of caves or open air sites (Tattersall and Schwartz 2000:209). Rock shelters and near the entrance of caves were desirable places to live since they are light and airy, as well as sheltered (ibid.). These particular locations are more well studied, simply do to factors of preservation.
While it is accepted that Homo erectus was capable of building a simple brush covered dwellings, Neanderthals are assumed not to have the ability to build a shelter. However, at the site of Combe-Grenal, France, a natural cast of a ‘tent peg’, closely laid cobble ‘floors’ and shallow ‘storage pits’ have been found (Tattersall and Schwartz 2000:209). At the Southern French beach site of Terra Amata, excavations revealed evidence of what might have been 21 separate oval living floors within branch and brush huts, attributed to archaic Homo sapiens (Galanidou 2000:274). These structures apparently were up to 22 m long and 10 m wide. Among modern foragers and horticulturists who employ rock shelters and caves as campsites, there appears to be no consensus as to the use of space (Galanidou 2000:274). Differences in the number, size, usage and location of hearths, sleeping arrangements, refuse disposal, activity areas, usage of open air sites and ‘furnishings’ were all deemed to be subject to individual group preferences (ibid.).
It has been proposed that archaic Homo sapiens occupied seasonal habitation sites based upon a ‘herd following’ adaptation (Kusimba 1999:167). This is based upon the assumption that hunters would have been able to easily kill sick animals as the grazing herd migrated (ibid.). However, ethnographic data suggest that modern hunter-gatherers rarely move their settlements since they rely on accessible plant foods for their dietary needs more so than upon grazing animals (ibid.).
Rituals
The oldest grave sites have been associated with archaic Homo sapiens or Neanderthals. Almost all of these individuals have been found buried with something, for example flowers or jewelry. However, the appearance of burials in the archaeological record should not be used as an indication of cognitive advance or something uniquely human. There are millions of modern humans who do not bury their dead but still hold complex cognitive beliefs.
Secondly, these burials may simply have been a method of protecting the dead from scavengers or they may be taphonomic illusions (Tattersall and Schwartz 2000:213). The conventional bias is to assume that if these were intentional burials, those assigned to archaic Homo sapiens are granted symbolic meaning while Neanderthal burials contain items which were just lying around the cave floor (i.e. animal bones and stone tools) and then “kicked or shoveled into the grave as part of the filling process” (Tattersall and Schwartz 2000:214).
In the cave of Qafzeh, a child was found buried with the skull and antlers of a deer (Mithen 1996:180). At Skhul, one of the burials contained a body which had been laid on its back, with the jaws of a wild boar placed within its hands (ibid.). The placing of animal parts within the burials has been interpreted as evidence of some form of totemic thought. There is also a significant increase in the amount of red ochre found at sites associated with early modern humans. Although it is not certain how the ochre was employed, some researchers have hypothesized it use in rituals as a body paint (Mithen 1996:182; Powers and Aiello 1997:153-154).
The European cave art seems to have been associated with ceremonies, which may have been accompanied by music. Drum sticks, flutes, and bull roarers were found near the paintings in Lascaux Cave. Some researchers have suggested that they were, in part, depicting their spirit world (Mithen 1996:182). The fact that footprints of both adults and children have been found in some of the caves near the paintings has also suggested that the art was connected with initiation ceremonies (ibid.). Some evolutionary psychologists view early ‘art’ as an expression of cognitive expansion and diversity while others propose that it serves as a sexual ornamentation for males (since only males would be producing art to attract females) (Miller 2000:258-275). It is important to remember that Europe was not the only part of the world in archaic Homo sapiens produced art. Depictions of animals were being painted in southern African, Siberia and Australia
Some cave walls and bone artifacts have sequences of incised marks or ticks, and have been interpreted as being calendrical systems. Such marks appear on bone artifacts made by late Neanderthals, but they did not become common until the Upper Paleolithic. If calendars were being made, it implies that some people were recognizing the cyclical nature of the seasons. To people dependent on seasonally available foods and migrating herds, a calendar would have allowed accurate predictions that would make the food quest more efficient. Also of great value to Upper Paleolithic hunter and gatherers would have been maps. A 16 ky old bone found at Mezhirich in Ukraine, apparently shows the countryside around an anatomically modern human settlement (Mithen 1996:182).
While the above examples fall within the Upper Paleolithic period, the precursors to these behaviours must have been laid during the preceding millennia. For example, rock art and carvings may have been placed on the outside of rock shelters and caves and eroded due to environmental forces. Similarly, if symbolic representations were created using perishable materials such as hides or wood, or were temporary creations, such as Tibetan sand paintings, there would be no trace of the actions or intent. The same would be true of body ornamentation in the form of tattoos and piercings. We are lulled into a false belief that all material objects will stand the test of time and taphonomy. However, even in our current material obsessed western culture, few items survive several decades without deliberate conservation intervention.
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