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Thread: Genetics of Modern Human Origins and Differentiation

  1. #11

    Post Re: Modern Human Origins: Genetic and cognitive aspects

    From Homo erectus to Modern Humans

    Now that the basic theoretical building blocks have been presented, the scenario is as follows: The first step in the sequence begins with Homo erectus, which is the first fossil hominid to exhibit basicranal morphology associated with laryngeal descent. This implies that this was the first hominid to use articulated speech as a crucial part of its adaptive strategy. (This in turn implies that H. habilis was very probably well on its way to that point, but that is beyond the scope of this discussion.)

    Linguistic potential at this point need not have been any greater than that exhibited by extant primates. Indeed, any evolutionary "just so" story should, for the sake of plausibility, begin at such a point. What is important is that the use of that potential was normal rather than extraordinary. The possible environmental (ecological or social) stimuli for the original evolution of articulated (and presumably referential) speech are again beyond the scope of this discussion. It seems quite likely, though, that they are what explain the shift from the Australopithecines to Homo.

    However, once in place, I presume that simple, referential articulated vocal communication generated drastic effects on the complexity of the social environment; effects which would have been 'evolutionarily unexpected'. This increased social complexity during the Lower and Middle Paleolithic provided the context for the continued development and expansion of unconscious, rule-governed model-building ability; one which was used for interpersonal problem-solving in increasingly complex social contexts (i.e., Alexander's (1989) 'runaway social arms race'). This would have been a conceptual cognitive ability, not necessarily a linguistic ability per se. And since it presumably functioned at an implicit level, it could fairly be described as domain-specific and modular.

    Well-developed social cognition is clearly not an evolutionarily new ability. It is this implicit capability which underlies all the greater apes' ability to model and predict their conspecific's actions and mental states. But the novel existence of a (proto-) linguistic social environment would have produced a new level of requirements for building models of others' minds; requirements driving the evolution of abilities quantitatively more sophisticated (if not qualitatively so) than those in other hominoids, probably involving increases in attention span and concentration.

    At the same time, this ability, by way of its effects on social organization and capacity for culture, would have provided for its own bioenergetic possibility. Cranial capacity during this period was undergoing slow but substantial change. That extra neural mass is extraordinarily costly in terms of caloric maintenance and parental investment. While strict ability-brain size correlations are not valid, some rough relationship between average size and ability must exist, given the expense of that tissue. Any account of human evolution must account for the point at which ecological energy-extraction efficiency ceased to be the primary determiner of neural mass. I suggest that the ecological repercussions of the social consequences of referential language account for this change.

    I suggest that the next step in the sequence, the Middle-to-Upper Paleolithic transition, consisted of the evolution of conscious access to this previously unconscious social model-building system, not (surprisingly) for its linguistic benefits, but for its value in subsistence planning and organization. If, as argued above, conscious access to the algorithms of cognitive modules permits their abstraction to new conceptual domains, then model-building could very profitably be applied to extractive activities.

    Thus the relevance of Leslie's (1987) analysis of pretense to the Middle-Upper Pleistocene transition is that building alternate models of the world can be adaptive in two ways.

    One:
    building alternate systems of belief to accurately predict the actions of conspecifics with different experiences of the real world; and
    two:
    building models of alternate subsistence strategies which can be compared along several axes of variation (effort, risks, rewards, reliability, etc.).
    The advantage to the second only accrues when the 'world is what you make of it' rather than there being a particular 'best' strategy in all situations. In other words, its usefulness depends upon the flexibility, both social and technological, to take advantage of a newly-realized opportunity for exploitation.

    Most importantly, both kinds of problems (social and extractive) encounter the same kind of difficulties with computational resources: the problem of combinatorial explosion. In social interactions, the formation of meta-level relationships such as parent-child, friend, enemy, sibling, etc. allow a great variety of dyadic relationships to be abstractly conceptualized. This process of conceptualization is inherently hierarchical and categorical. By enabling a kind of mental shorthand, the individual is freed from keeping in mind concrete examples of what is being considered. This ability, which allows large collections of entities to be considered, manipulated, and compared is plausibly powerful enough to underlie much of human ability in social cognition, subsistence strategy, syntactic processing, and perhaps a range of other uniquely human problem-solving capacities.

    Although Homo erectus was able to live in environments previously uninhabitable by primates i.e., high latitudes and sparse grasslands, they were far less ecologically efficient than modern human hunter-gatherers. At the erectus-sapiens boundary, the ability to carefully and consciously weigh multiple courses of subsistence-oriented action would have immediate and drastic effects on survivorship of any individual with the ability.

    One may reasonably ask why specifically linguistic consequences are not offered as the evolutionary driving force behind the shift. As Bickerton has noted (1990) any characteristic presumably responding to evolutionary pressure must at all times be adaptive now. Linguistic capacities rely on a community of speakers for their expression and adaptiveness. Now some improvements in linguistic capacity have plausible incremental steps by which they can develop. But rule-governed grammar appears to be an all-or-nothing phenomenon, and thus its (initial) evolutionary explanation must be sought elsewhere.

    The idea of two levels of language advocated here seems to reflect a distinction between the specificity of perception and the specificity of the integration of those perceptions. Ample evidence demonstrates that there are a host of auditory processing mechanisms which focus attention on articulated speech and increase discriminative ability with regard to speech (Lieberman 1984). In humans, the important sounds of speech are wired to be given a greater degree of attention than other sounds in the child's environment: a highly specific form of perceptual tuning. They go on to integrate those sounds linguistically. Similar mechanisms can be described for the output side of the process. These certainly have an evolutionary basis; one which I believe is quite long. These are "prepared systems" in every sense of the term, 'hard-wired' into the low levels of perceptual processing. But their evolution would not necessarily have required language as we know it to drive their development.

    Yet deaf infants exposed to ASL "babble" and begin to "speak" with their hands on exactly the same developmental timetable as hearing infants (Petitto and Marenette 1991). They learn to integrate visual patterns linguistically as well, and do so with as much ease as hearing children. This suggests that full language acquisition is an aptitude which occurs at a very high (i.e., abstract) level of cognitive processing, i.e., it presumably can occur with input from any sensory modality. It is a purely abstract pattern-recognition ability rather than a "prepared system" in the narrow sense. At the level of linguistic processing, i.e., syntactic parsing, there is no domain-specific effect. Presumably, any sensory input with sufficient signal-carrying capacity could serve as well as the others.

    This evidence, to some extent, flies in the face of psycholinguistic evidence (see Fodor 1983 and Jackendoff 1987 for fairly brief reviews) which paints a picture of (mostly) informationally encapsulated and domain-specific acoustic and phonological levels of processing. The conflict here can be resolved if one considers the possibility of Bickerton's two*step evolutionary sequence for human language; the first being the evolution of articulated speech (probably with Homo habilis ) and the second being the evolution of complex grammar and syntax (with modern Homo sapiens ). This would account for the apparently ancient origin of acoustic and phonological processing as well as the lack of input domain-specificity indicating recent origins.

    Bickerton (1981, 1990) argues for just such a division of human linguistic potential into a fairly old 'proto*linguistic' capacity and a more recent 'syntactic' capacity. Even aside from any specific inferences about the chronological order of evolution, this evidence strongly supports the idea that the different levels of what are now seemingly integrated systems probably evolved at different times and possibly for different purposes. Indeed, just such a view could characterize almost all we know about the evolution in the more obvious realms of physiology and anatomy.

    This suggests that it is evolutionarily recent, even within the timespan of hominid evolution. This difference in level, between form and content, is a crucial hint to an understanding of the evolutionary basis for the existence of the two systems. From the perspective of the sensory system, the content is not arbitrary, it is constrained. From the perspective of the cognitive system, the content is arbitrary, but the form is constrained. Thus French, Chinese and ASL (American Sign Language) use the same cognitive linguistic system while having entirely different contents.

    I thus suggest that H. erectus possessed articulated speech and referential language, but lacked grammar. Such a language would be linguistically identical to the two-word stage of language acquisition in children. However, the power and sophistication of such a system in an adult with the non-linguistic conceptual abilities plausible for erectus would be impressive relative to previous developments.

    One could have said "dog brown", or "kitty gone" or "outside play"; meaning "the dog is brown," "the kitty is gone," or "I want to go play outside"; however "the man whose daughter the boy chased was angry" would be impossible.

    There is little qualitative difference between this level of grammar and that which seems to be within the capabilities of chimpanzees and bonobos (at least after they have been intensively trained). The difference would be the ease with which the hominid could use this system; it clearly would have been spontaneous and easy to exercise for the hominoid ancestor. It is neither spontaneous nor easy for our extant primate relatives. Just how close other extant primates are to this level of language competence is demonstrated by Kanzi, a bonobo who spontaneously uses referential symbols, and responds to spoken English, after having been exposed to them during his development.

    The theoretical relevance of spontaneously used symbols vs. those acquired by training is well emphasized by Savage-Rumbaugh (1990:604). The fact that Kanzi has been observed re-presenting symbols to himself, in private, is even more provocative (Savage-Rumbaugh et al. 1986:228).

    Obviously, there are important differences between symbol use in Bonobos and humans. (1) Bonobos in the wild do not spontaneously generate referential symbols, and (2) Even under human tutelage, only bonobos exposed to language during development are able to demonstrate referential use of symbols (Kanzi's mother failed to adopt the desired skills). But this evidence shows that at least one extant ape has (potentially) all the major linguistic faculties which humans possess except grammar.

    One aspect of Jackendoff's (1987) theory may be useful here to make sense of the notion that so little, in terms of completely novel mental capacities, separates us from our closest relatives. In order to explain the observed interpenetration between bottom-up and top-down processes (e.g., in perception, where expectations and even conscious decisions can bias low-level decisions, as in the face-vase illusion), he argues that several levels of representation are maintained in 'registration' with one another in short=term memory (1989:258-9). In like manner, he supposes that linguistic representations can be held in registration with the conceptual structures which generated them (and vice versa). The interesting thing about this mechanism is that it does not result in a capacity which is an either-or question. In other words, a lack of registration would not interfere with conceptual structures or linguistic representations. However, the presence of registration, he reasons, would result in much more 'stability' in both forms of representation.

    Registration may be the phenomenon responsible for the 'explosiveness' of Upper Pleistocene human cognitive ability. It effects how easily processing can be carried out, rather than the either-or possibility of performing a given form of processing at all. Also, just such a picture of high-level human cognition may make sense of Goldstein's evidence (see below) of slight deficits in language-deprived individuals and Brother John's seemingly unhampered problem-solving ability during one of his attacks.

    These speculations greatly suggest that detailed research which can sort our subtle effects of language deprivation (either due to injury or deafness) is called for.

  2. #12

    Post Re: Modern Human Origins: Genetic and cognitive aspects

    The primacy of social cognition
    The role that social cognition plays in this scenario is a dominant one, and so it seems logical to justify that assignment, particularly when so many other driving forces have been offered for this period of human evolution, e.g., tool use, symbolism, etc. Likewise, I have argued that, in general, it was social-cognitive algorithms being accessed, resulting in such dramatic results.

    First, in general terms, primates are arguably the most (flexibly) social order, and thus the most socially sophisticated animals. They have been so for at least 20 million years. If for no other reason than this, it might be guessed that social-cognitive abilities may be the most 'advanced' we possess. Extensive tool use and (more) sophisticated subsistence activities, on the other hand, extend at most 5*7 million years (to the common ape*human ancestor) and may only be as old as the Homo line. Articulated language, as discussed , extends backwards at most to Homo habilis.

    Second, if one accepts that the improved social organizational and communicative capabilities of Homo erectus enabled a greater degree of 'insulation' from the natural environment, it would follow that for erectus, even more than any other primate, the social environment becomes the most crucial adaptive environment. Intraspecific competition becomes more relevant than environmental interactions. Alexander (1989) argues for just such a social 'arms race' at this point in human evolution. He sees sociality as the initial driving force, with other selective arenas only "kicking in" later.

    Third, a number of characteristics of both human abstract thought (conceptual processing) and language per se share interesting characteristics with what we might identify as the hallmarks of social cognition: hierarchical structure, binary categorical distinctions, and the ability to manipulate multiple mental entities simultaneously.

    Bickerton's (1990) account of syntax as described by X-bar theory suggests that the subject-predicate relationship is the fundamental relationship of language. Bickerton argues that the reason for this is that the basic element of protolanguage was entity + characteristic i.e., the noun phrase. He suggests that the verb phrase simply represents an extension of noun phrase rules.

    Bickerton argues that the basic template being used here is 'animate individual + behavior.' If this is true it would be another reason why a primate (rather than some other organism) developed syntactic language; small surprise that the most socially attentive order produced a cognitive algorithm based on relating individual entities and behavioral characteristics. And small surprise that the primate facing the greatest degree of social complexity would develop an efficient, hierarchical, meta-representational system, since some form of abstraction is the only way to sidestep computational limits in information processing systems.

    The Enigma of Homo erectus
    The scenario presented above accounts for a number of aspects of the archaeological, anatomical, and evolutionary puzzles presented by the last 2 million years of human evolution. And if the signature of a good theory is that it explains things that perhaps we hadn't even noticed needed explaining, then recall that the adaptation of erectus to high latitudes should be a bit of an enigma, insofar as their adaptation proved inferior to that represented by the modern condition. In other words, while erectus was far more successful than any previous primate, it was ultimately inferior to modern humans (whether viewed as a species or as a phyletic suite of characteristics). In discussing erectus' cognitive capacities, most discussion focuses either on their superiority or their deficits; care must be taken to account simultaneously for their long success and subsequent failure.

    The theory presented here would attribute erectus' success as the first inter-continental hominid to its social precocity, and view its adaptation as a primarily social one. That this kind of adaptation did not include adequate technology to completely buffer the organism from the hostile environment is illustrated by the continuing robusticity of the erectus musculo-skeletal system. It then attributes H. sapiens' subsequent success (i.e., the success of sapiens genetic attributes) in the same environments to its technological precocity (technology in this case encompassing technique); and views its adaptation as a technological one. The technology in this case is that relying on characteristically human culture. This analysis accounts for erectus' apparent success, albeit accompanied by the persistence of its physical robusticity; as well as modern humans' rapid shift to skeletal gracility.

    It makes sense of some of the bizarre deficiencies of late Middle Paleolithic peoples, i.e., fairly sophisticated tools, but little long-term planning or large-scale social organization. (Tool-making is partially an unconscious, implicit procedure, but subsistence scheduling and decision-making is a necessarily explicit thought process.) It accounts for the presence of articulatory anatomy from 2 million years ago but the lack of modern "culture as we know it" until 50 thousand years ago. It also would account for the 'explosiveness' of the Middle to Upper Paleolithic transition since this shift consists of the conscious integration of two well-developed, but previously unconnected cognitive domains (social cognition and referential language/articulated speech) rather than the fresh evolution of basic cognitive algorithms.

    Archaeological Perspectives on Cognitive evolution
    So how consistent is the evolutionary scenario presented above with the body of archaeological evidence from the Middle and Upper Paleolithic? Ironically, it seems that the constraints embodied in the linguistic and cognitive data serve better to eliminate alternate possibilities than any particular item of archaeological evidence. However, the archaeological data do serve well to provide plausible temporal milestones to which various steps in the cognitive theory can be assigned. Beyond that, they serve to broadly constrain the kinds of explanation that will remain consistent with what we know of Middle and Upper Pleistocene subsistence patterns.

    Interestingly enough, in the first section of this thesis I endeavored to minimize the distinctions made between the Middle and Upper Pleistocene under the belief that there is a phyletic relationship between Homo erectus and modern Homo sapiens. In this section, the theory presented here suggests that there should be a rather clear shift, reflected in evidence of cognitive capacity for complex predictive reasoning, both in the social and subsistence spheres.

    Isaac (1972:54-56) describes the pattern of change between the Middle Pleistocene and the Upper Pleistocene as one of a shift from a low-density "walking pattern" to one of fine-grained differentiation with more evidence of complex structure in human subsistence activity. Arguments over the best way to characterize the comparison of Middle Paleolithic technology and subsistence to that in the Upper Paleolithic often hinge on the degree to which evidence from within the chronological units is 'averaged.' In other words if one compares the Middle Paleolithic overall to the Upper Paleolithic overall, then there is indeed significant disparity in complexity and sophistication.

    On the other hand, several more chronologically restricted studies (e.g., Marks 1990:74 for the Near East and Nile valley, Reynolds 1990:273 for Southwestern France) have shown that differences between late Middle Paleolithic sites and early Upper Paleolithic sites are much less striking. Reynolds' conclusion is especially interesting since Western Europe is typically offered as the most unambiguous example of Middle-Upper Paleolithic discontinuity. However, he attributes this impression more to the typologies traditionally used for the periods than to differences inherent to the industries: "The Middle-Upper Paleolithic transition as it is pictured through a 'before and after' approach highlights differences in the two typological systems in the treatment of compound forms and also the technological move towards increased use of regular blank forms with additional types being size-based. As such, this approach presents an image of increased typological complexity and innovation that is not, in fact, substantiable when the final Mousterian (MAT) and first Upper Paleolithic industries are taken alone" (Reynolds 1990:273). This has also been the conclusion of other more general reviews of Paleolithic change (Rolland 1990:377).

    Binford (1989), on the other hand, emphasizes the disjunctive nature of the transition when viewed in archaeological terms. Contrary to what had been thought before, Binford finds no evidence of significant time depth to planning of any activities by Middle Paleolithic (or earlier) peoples. Most significantly, Binford (1987:52) reassesses the evidence of large-scale game drives at Torralba. He concludes that the presence of language explains the abrupt transition while noting that Wolpoff (in conference) maintained that language and culture were present in the Lower Paleolithic.

    In archaeological terms a picture has begun to emerge of some gradual improvements of a panspecific adaptation throughout the Lower and Middle Paleolithic with an abrupt shift to longer-range planning, artifact curation, and cultural adaptation to environments. This way of looking at the problem, one where linguistic ability, social organization, and cognitive potential become relevant as more than simply advantageous alleles, is one which draws on a much wider range of fields than paleoanthropology has so far embraced.

    However, contrary to Binford, there is evidence for extensive foresight and planning in the Middle Pleistocene. Raw material for tools was often selected well prior to use. For example, raw material for tools at Terra Amata came from at least 30 miles from the site (de Lumley 1969). This indicates that Binford's simple division of cognitive potential into planning/non-planning is inadequate. Binford discusses the advantages of tactical thinking as if it involved only a simple unitary ability to 'think ahead'. Clearly what humans typically do is similar but by no means identical to what chimpanzees do when they select a hammerstone before they reach where they will use it. His conclusions elsewhere have simply been that, for instance,

    "It is most unlikely that we are seeing structured assemblages derived from organizationally integrated tool*assisted actions centered in camps. Early humans were probably not very much like us"
    (Binford 1987:29).

    Binford rightfully concludes that earlier humans "were ... not very much like us", but he then goes on to deprive them of far more than is justified by his analysis. At issue here is what Binford considers to be 'human', and all that 'humanness' connotes in terms of cognitive potential. The issue is not whether Middle Paleolithic hominids could 'plan ahead', it is how structured, and thus how powerful, that planning was. One way of approaching the question might be to ask how much planning is possible, or probable, by individuals solving problems largely on their own, and if greater amounts of planning involve more sophisticated forms of social organization and cultural codification for their persistence.

    Complicating the issue, of course, is the argument presented in this thesis that the cognitive capacity underlying social cognition, complex planning, and problem-solving, is the same capacity which underlies language.

    Ambrose and Lorenz 1990
    This paper is very important for this exploration for two reasons. First, at a very detailed level, its conclusions are significant for the assessment of MSA (Middle Stone Age) vs. LSA (Late Stone Age) technology and subsistence in Southern Africa. Second, and more important, it represents precisely the kind of approach needed to distinguish in the archaeological record between evolved biological potential and non-biological socio-cultural evolution. Ambrose and Lorenz (1990) find that at one particular time (between MSA 1 and MSA 3/4), approximately 70,000 years ago, the response of human hunter-gatherers to environmental change itself changed: ecological cycles encountered many times before over the previous two million years elicited a novel response. By asking certain questions from within a well-developed theoretical framework of resource structure and optimal subsistence strategies, they are able to address the precise causes of that change.

    The strength of their strategy comes from the breadth and generality of resource structure theory: it is a theory about human adaptation in general, not merely this or that group. As a means of assessing the organization of human adaptation in general, it is able to look past the presence, or absence, of technological complexity and address the cognitive capacity behind that technology. Put simply, MSA peoples were unable to adapt (as LSA peoples did) not because they lacked any particular technology, but because they lacked (presumably because of neurobiology) modern human social organizational potential, itself enabled by the requisite cognitive capacities. Once this is said, it is important, as they note, not to start seeing 'MSA peoples as unskilled mental midgets.' But it does force further analysis of 1) what underlies modern potential and 2) what form did pre*modern potential take and what changes to archaeological theory must be made to make it suitable for the analysis of pre*modern human technology.

    At the least this evidence suggests that the shift in underlying cognitive capacity, i.e., that involved in complex subsistence-oriented problem-solving, occurred (at least in Southern Africa) approximately 70,000 years ago. Most importantly, this shift is reflected in adaptive subsistence strategies rather than improved technology or obvious changes in social organization. This observation suggests that archaeological studies which focus specifically on technology or gross indicators of social organization, e.g., group size, are likely to miss the subtle structural changes which signal underlying cognitive developments.

    Thus, to a large degree, the utility of archaeological data to the study of cognitive evolution may depend on first mapping human resource structure theory onto particular cognitive capacities. Of course, this cannot occur until some unambiguous characteristics of the relevant cognitive capacities can be defined in accordance with experimental data. The theory presented here at least points to some aspects of those capacities: hierarchical structure, binary categorical distinctions, and the ability to manipulate multiple mental entities simultaneously; all of which bear suspicious resemblance to the characteristics of social cognition and syntactic linguistic processing.

    PROBLEMS THAT REMAIN
    In the spirit of intellectual honesty, I shall spell out several outstanding dilemmas which remain in my mind concerning the theory presented here. The first is theoretical, the second evidentiary, the third a suggested subject for research.

    If, as I have argued, the syntactic parsing mechanism is the product of evolved access to a social modeling mechanism (by way of an explicitly conscious analytical capacity), then why is it not accessible to conscious awareness? Other than admitting it is a good question, I will offer two possibilities. One, that syntactic parsing was plausibly once a conscious type of problem solving which, because of computational strains placed upon it, became informationally re-encapsulated for the sake of speed. Another approach may be to point out that Rozin's notion of the cognitive conscious and unconscious is not necessarily the same as a distinction between availability and non-availability to introspection. In other words, not all of the 'cognitive consciousness' need actually be available to consciousness in the normal sense, i.e., cognitive abilities may result from access but still be implicit.

    Goldstein, an aphasiologist, found that linguistic aphasia is commonly accompanied by more subtle non-linguistic deficits, and that these deficits are best defined by a loss of what he called the "abstract attitude". The 'abstract' (also categorical or conceptual) attitude is basic for the following potentialities:

    "1. Assuming a mental set voluntarily, taking initiative, even beginning a performance on demand. 2. Shifting voluntarily from one aspect of a situation to another, making a choice. 3. Keeping in mind simultaneously various aspects of a situation; reacting to two stimuli which do not belong intrinsically together. 4. Grasping the essential of a given whole, breaking up a given whole into parts, isolating them voluntarily, and combining them in wholes. 5. Abstracting common properties, planning ahead ideationally, assuming an attitude toward the 'merely possible', and thinking or performing symbolically. 6. Detaching the ego from the outer world."(Goldstein, 1948:6)
    Lieberman (1991:92) notes that many recent studies have confirmed this view. "Although standard tests of intelligence may show no decrement in overall intelligence, more specialized tests demonstrate that aphasic patients have considerable difficulty in performing tasks that involve keeping track of and applying different abstract concepts, translating specific facts into appropriate action, handling simultaneous sources of information, relating isolated details, and failing to grasp the key element of a problem (Stuss and Benson, 1986:194-203)."

    This is interesting because it suggests that an extreme form of modularity (i.e., that implied by Brother John's ability to reason clearly and handle social situations appropriately during a period of global aphasia) may not be supported by a closer look at the cognitive concomitants of language. More to the point, it challenges (to some degree) my description of the separability of human analytic ability and human linguistic ability.

    One question which seems to divide the several scholars at work on this subject is whether or not complex problem solving, e.g., the kind that humans alone appear to excel at, is or is not specifically enabled by the presence of language. Brother John and deaf-mutes appear to argue against such an identification. Much other evidence and theory appears to support the notion, i.e., that such problem solving is language-based whether communicative language is present or not. While it is obvious that experimental research concerning symbolic problem-solving might be made rather difficult by the inability of a subject to use language or writing, it seems that many of those problems have been overcome with non-human cognitive psychology. In any case, it seems something which is clearly open to elucidation by experimentation.

  3. #13

    Post Re: Modern Human Origins: Genetic and cognitive aspects

    Archaeological Perspectives on Cognitive evolution
    So how consistent is the evolutionary scenario presented above with the body of archaeological evidence from the Middle and Upper Paleolithic? Ironically, it seems that the constraints embodied in the linguistic and cognitive data serve better to eliminate alternate possibilities than any particular item of archaeological evidence. However, the archaeological data do serve well to provide plausible temporal milestones to which various steps in the cognitive theory can be assigned. Beyond that, they serve to broadly constrain the kinds of explanation that will remain consistent with what we know of Middle and Upper Pleistocene subsistence patterns.

    Interestingly enough, in the first section of this thesis I endeavored to minimize the distinctions made between the Middle and Upper Pleistocene under the belief that there is a phyletic relationship between Homo erectus and modern Homo sapiens. In this section, the theory presented here suggests that there should be a rather clear shift, reflected in evidence of cognitive capacity for complex predictive reasoning, both in the social and subsistence spheres.

    Isaac (1972:54-56) describes the pattern of change between the Middle Pleistocene and the Upper Pleistocene as one of a shift from a low-density "walking pattern" to one of fine-grained differentiation with more evidence of complex structure in human subsistence activity. Arguments over the best way to characterize the comparison of Middle Paleolithic technology and subsistence to that in the Upper Paleolithic often hinge on the degree to which evidence from within the chronological units is 'averaged.' In other words if one compares the Middle Paleolithic overall to the Upper Paleolithic overall, then there is indeed significant disparity in complexity and sophistication.

    On the other hand, several more chronologically restricted studies (e.g., Marks 1990:74 for the Near East and Nile valley, Reynolds 1990:273 for Southwestern France) have shown that differences between late Middle Paleolithic sites and early Upper Paleolithic sites are much less striking. Reynolds' conclusion is especially interesting since Western Europe is typically offered as the most unambiguous example of Middle-Upper Paleolithic discontinuity. However, he attributes this impression more to the typologies traditionally used for the periods than to differences inherent to the industries: "The Middle-Upper Paleolithic transition as it is pictured through a 'before and after' approach highlights differences in the two typological systems in the treatment of compound forms and also the technological move towards increased use of regular blank forms with additional types being size-based. As such, this approach presents an image of increased typological complexity and innovation that is not, in fact, substantiable when the final Mousterian (MAT) and first Upper Paleolithic industries are taken alone" (Reynolds 1990:273). This has also been the conclusion of other more general reviews of Paleolithic change (Rolland 1990:377).

    Binford (1989), on the other hand, emphasizes the disjunctive nature of the transition when viewed in archaeological terms. Contrary to what had been thought before, Binford finds no evidence of significant time depth to planning of any activities by Middle Paleolithic (or earlier) peoples. Most significantly, Binford (1987:52) reassesses the evidence of large-scale game drives at Torralba. He concludes that the presence of language explains the abrupt transition while noting that Wolpoff (in conference) maintained that language and culture were present in the Lower Paleolithic.

    In archaeological terms a picture has begun to emerge of some gradual improvements of a panspecific adaptation throughout the Lower and Middle Paleolithic with an abrupt shift to longer-range planning, artifact curation, and cultural adaptation to environments. This way of looking at the problem, one where linguistic ability, social organization, and cognitive potential become relevant as more than simply advantageous alleles, is one which draws on a much wider range of fields than paleoanthropology has so far embraced.

    However, contrary to Binford, there is evidence for extensive foresight and planning in the Middle Pleistocene. Raw material for tools was often selected well prior to use. For example, raw material for tools at Terra Amata came from at least 30 miles from the site (de Lumley 1969). This indicates that Binford's simple division of cognitive potential into planning/non-planning is inadequate. Binford discusses the advantages of tactical thinking as if it involved only a simple unitary ability to 'think ahead'. Clearly what humans typically do is similar but by no means identical to what chimpanzees do when they select a hammerstone before they reach where they will use it. His conclusions elsewhere have simply been that, for instance,

    "It is most unlikely that we are seeing structured assemblages derived from organizationally integrated tool*assisted actions centered in camps. Early humans were probably not very much like us"
    (Binford 1987:29).

    Binford rightfully concludes that earlier humans "were ... not very much like us", but he then goes on to deprive them of far more than is justified by his analysis. At issue here is what Binford considers to be 'human', and all that 'humanness' connotes in terms of cognitive potential. The issue is not whether Middle Paleolithic hominids could 'plan ahead', it is how structured, and thus how powerful, that planning was. One way of approaching the question might be to ask how much planning is possible, or probable, by individuals solving problems largely on their own, and if greater amounts of planning involve more sophisticated forms of social organization and cultural codification for their persistence.

    Complicating the issue, of course, is the argument presented in this thesis that the cognitive capacity underlying social cognition, complex planning, and problem-solving, is the same capacity which underlies language.

    Ambrose and Lorenz 1990
    This paper is very important for this exploration for two reasons. First, at a very detailed level, its conclusions are significant for the assessment of MSA (Middle Stone Age) vs. LSA (Late Stone Age) technology and subsistence in Southern Africa. Second, and more important, it represents precisely the kind of approach needed to distinguish in the archaeological record between evolved biological potential and non-biological socio-cultural evolution. Ambrose and Lorenz (1990) find that at one particular time (between MSA 1 and MSA 3/4), approximately 70,000 years ago, the response of human hunter-gatherers to environmental change itself changed: ecological cycles encountered many times before over the previous two million years elicited a novel response. By asking certain questions from within a well-developed theoretical framework of resource structure and optimal subsistence strategies, they are able to address the precise causes of that change.

    The strength of their strategy comes from the breadth and generality of resource structure theory: it is a theory about human adaptation in general, not merely this or that group. As a means of assessing the organization of human adaptation in general, it is able to look past the presence, or absence, of technological complexity and address the cognitive capacity behind that technology. Put simply, MSA peoples were unable to adapt (as LSA peoples did) not because they lacked any particular technology, but because they lacked (presumably because of neurobiology) modern human social organizational potential, itself enabled by the requisite cognitive capacities. Once this is said, it is important, as they note, not to start seeing 'MSA peoples as unskilled mental midgets.' But it does force further analysis of 1) what underlies modern potential and 2) what form did pre*modern potential take and what changes to archaeological theory must be made to make it suitable for the analysis of pre*modern human technology.

    At the least this evidence suggests that the shift in underlying cognitive capacity, i.e., that involved in complex subsistence-oriented problem-solving, occurred (at least in Southern Africa) approximately 70,000 years ago. Most importantly, this shift is reflected in adaptive subsistence strategies rather than improved technology or obvious changes in social organization. This observation suggests that archaeological studies which focus specifically on technology or gross indicators of social organization, e.g., group size, are likely to miss the subtle structural changes which signal underlying cognitive developments.

    Thus, to a large degree, the utility of archaeological data to the study of cognitive evolution may depend on first mapping human resource structure theory onto particular cognitive capacities. Of course, this cannot occur until some unambiguous characteristics of the relevant cognitive capacities can be defined in accordance with experimental data. The theory presented here at least points to some aspects of those capacities: hierarchical structure, binary categorical distinctions, and the ability to manipulate multiple mental entities simultaneously; all of which bear suspicious resemblance to the characteristics of social cognition and syntactic linguistic processing.

    PROBLEMS THAT REMAIN
    In the spirit of intellectual honesty, I shall spell out several outstanding dilemmas which remain in my mind concerning the theory presented here. The first is theoretical, the second evidentiary, the third a suggested subject for research.

    If, as I have argued, the syntactic parsing mechanism is the product of evolved access to a social modeling mechanism (by way of an explicitly conscious analytical capacity), then why is it not accessible to conscious awareness? Other than admitting it is a good question, I will offer two possibilities. One, that syntactic parsing was plausibly once a conscious type of problem solving which, because of computational strains placed upon it, became informationally re-encapsulated for the sake of speed. Another approach may be to point out that Rozin's notion of the cognitive conscious and unconscious is not necessarily the same as a distinction between availability and non-availability to introspection. In other words, not all of the 'cognitive consciousness' need actually be available to consciousness in the normal sense, i.e., cognitive abilities may result from access but still be implicit.

    Goldstein, an aphasiologist, found that linguistic aphasia is commonly accompanied by more subtle non-linguistic deficits, and that these deficits are best defined by a loss of what he called the "abstract attitude". The 'abstract' (also categorical or conceptual) attitude is basic for the following potentialities:

    "1. Assuming a mental set voluntarily, taking initiative, even beginning a performance on demand. 2. Shifting voluntarily from one aspect of a situation to another, making a choice. 3. Keeping in mind simultaneously various aspects of a situation; reacting to two stimuli which do not belong intrinsically together. 4. Grasping the essential of a given whole, breaking up a given whole into parts, isolating them voluntarily, and combining them in wholes. 5. Abstracting common properties, planning ahead ideationally, assuming an attitude toward the 'merely possible', and thinking or performing symbolically. 6. Detaching the ego from the outer world."(Goldstein, 1948:6)
    Lieberman (1991:92) notes that many recent studies have confirmed this view. "Although standard tests of intelligence may show no decrement in overall intelligence, more specialized tests demonstrate that aphasic patients have considerable difficulty in performing tasks that involve keeping track of and applying different abstract concepts, translating specific facts into appropriate action, handling simultaneous sources of information, relating isolated details, and failing to grasp the key element of a problem (Stuss and Benson, 1986:194-203)."

    This is interesting because it suggests that an extreme form of modularity (i.e., that implied by Brother John's ability to reason clearly and handle social situations appropriately during a period of global aphasia) may not be supported by a closer look at the cognitive concomitants of language. More to the point, it challenges (to some degree) my description of the separability of human analytic ability and human linguistic ability.

    One question which seems to divide the several scholars at work on this subject is whether or not complex problem solving, e.g., the kind that humans alone appear to excel at, is or is not specifically enabled by the presence of language. Brother John and deaf-mutes appear to argue against such an identification. Much other evidence and theory appears to support the notion, i.e., that such problem solving is language-based whether communicative language is present or not. While it is obvious that experimental research concerning symbolic problem-solving might be made rather difficult by the inability of a subject to use language or writing, it seems that many of those problems have been overcome with non-human cognitive psychology. In any case, it seems something which is clearly open to elucidation by experimentation.

  4. #14

    Post Re: Modern Human Origins: Genetic and cognitive aspects

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  5. #15
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    Haplotype trees and modern human origins.

    AKA rossi, rusman

    If you adhere to the truth, and have a good grounding in logic and the scientific method, then, you might, just might, know something sometime.

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    Re: Haplotype trees and modern human origins.

    Quote Originally Posted by Dr. Solar Wolff
    If this is true, then the idea that modern humans originated from one group of H. erectus in Africa is as dead as disco. Multiregionalism instantly becomes a better model for humanity although it can still be claimed that humans originated in Africa, through multiple morphospecies (unless one or more morphospecies can be shown to have evolved in Asia). Also, reproductive isolation within the genus Homo should now be considered a myth.
    Yup, and disco is pretty dead. This also puts much pressure on an discrete racial classification.
    AKA rossi, rusman

    If you adhere to the truth, and have a good grounding in logic and the scientific method, then, you might, just might, know something sometime.

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