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A probable disease model for hominid evolution and site location
ABSTRACTS
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the interparietal as an individualized bone in inferior animals, even in Tupaia (one case) are cited. O n the other hand~ the strong incidence of vestigial forms of interparietal bone, expressed by a partial or reduced transverse biasteric suture, have been noted. Finally, the authors discuss the possibility of phylogenetic origin of the interparietaI bone, its eventual atavistic position and tile possibility to be in connection with the development of ~,he posterior pole of the h u m a n brain and its visual activity.
Models for European Pleistocene Hominid Evolution by C. B. Stringer (Department of Paleontology, British M u s e u m (Natural History), London U.K.) It is only possible to test properly the competing models of punctuated equilibria and phyletic gradualism in the fossil hominid record, if that record is relatively complete and well-dated. This is certainly not the case for the middle and upper Pleistocene, although for the later Pleistocene, the European record is arguably the most satisfactory. But dating difficulties surrounding some of the most important fossil hominid specimens (e.g. those from Petralona, Arago and Bilzingsleben) are compounded by disagreement about how many species of Homo are recognized in the European record. This paper reviews some of the problem areas and discuss which evolutionary models and classification appear to be most appropriate.
A Probable Disease Model for Hominid Evolution and Site Location, by J. Sperber (Monroe, Lousiana, U.S.A.) It is well documented that during the nineteenth and early twentieth centuries the geographic range of the tsetse fly, vector of sleeping sickness (trypanosomiosis), served as a disease barrier that obstructed the exploration and development of Africa. Working with a general disease model first proposed by Frank L. Lambrecht (1967), the full effect of the tsetse fly and its possible impact upon Australopithecine site location and evolution during the Plio-Pleistocene is explored. First the ecology of the fly is examined. It is shown that the geographic range of the fly is subject to the temperature of its environment. Both favorable and unfavorable climatic periods can affect whether the fly spreads out or recedes into another environment which will sustain its needs. Next, Australopithecine phylogenic views, site location information, and climatic data are correlated with the ecology of the fly. In light of these data the following propositions concerning Australopithecine site location and evolution are discussed: (1) Prior to 3 m.y.a the environment of Africa was similar to todays thus producing "fly belts" which cut off East Africa from the South, thereby isolating A. africanus populations in the east. (2) Around 3 m.y.a. a climatic change occurred which lowered the montane forest limits and shifted the "fly belts" to the coastal regions of Africa. This shift produced "fly free" corridors through which A. africanus could traverse the continent to the south. (3) At around 2 m.y.a, the climate changed again to a more savanna-like environment which reinstated the "fly belts", thereby isolating A. @icanus populations in the south and to the east. (4) The production of a disease barrier which inhibited population flow from the east to the south may have created reproductive isolates which prompted ethological and ecological specializations that resulted in the Australopithecine groups known a A. robustus (A. boisei) in South and East Africa. It is also suggested that such isolation may have led to specializations such as K N M - E R 1470 and H. habilis.
Family Economics in the Pliocene, by Duane Quiatt & Jack Kelso (University of Colorado, U.S.A.) Separate but overlapping subsistence needs and activities of male and female great apes are associated with sexual dimorphism of body size and behavior (e.g. day ranges), which in turn are associated with different strategies of parental investment. Forest- or savanna-dwelling primates forage independently and sex-related differences in foraging and diet are not great; they involve primarily different relative proportions of the same foods. A forest-edge setting, the ecotone in which the hominids emerged in the Pliocene, has a greater diversity of potential food resources than either savanna or forest and the early hominids could "take advantage" of existing tendencies in between-sex differences in foraging as a means of broadening and diversifying their subsistence base. However functional sexual division of labor, co-operation, food sharing, and a dual subsistence system may have been for the group, the fitness advantages to participating individuals has also to be specified precisely to meet minimal requirements of current evolutionary theory. Fitness advantages to males and females of co-operative food-sharing are reviewed and it is noted that these depend on consistent, systematic relations (the regularity of which must themselves be accounted for in terms of advantages to individual fitness) between individuals in a monogamous or, more likely, polygynous family system. AnthropologicaI discussions of family economics, even at the level ofeco-energetics, often focus narrowly on the economic and reproductive concerns of the adult male/adult female mating pair. However, apparently features crucial to the hominid family as an adaptive unit relate to: (1) an increase in the number of partly dependent offspring per mating pair, and (2) the provision for alloparental care giving on a regular basis. Therefore,
695
the interparietal as an individualized bone in inferior animals, even in Tupaia (one case) are cited. O n the other hand~ the strong incidence of vestigial forms of interparietal bone, expressed by a partial or reduced transverse biasteric suture, have been noted. Finally, the authors discuss the possibility of phylogenetic origin of the interparietaI bone, its eventual atavistic position and tile possibility to be in connection with the development of ~,he posterior pole of the h u m a n brain and its visual activity.
Models for European Pleistocene Hominid Evolution by C. B. Stringer (Department of Paleontology, British M u s e u m (Natural History), London U.K.) It is only possible to test properly the competing models of punctuated equilibria and phyletic gradualism in the fossil hominid record, if that record is relatively complete and well-dated. This is certainly not the case for the middle and upper Pleistocene, although for the later Pleistocene, the European record is arguably the most satisfactory. But dating difficulties surrounding some of the most important fossil hominid specimens (e.g. those from Petralona, Arago and Bilzingsleben) are compounded by disagreement about how many species of Homo are recognized in the European record. This paper reviews some of the problem areas and discuss which evolutionary models and classification appear to be most appropriate.
A Probable Disease Model for Hominid Evolution and Site Location, by J. Sperber (Monroe, Lousiana, U.S.A.) It is well documented that during the nineteenth and early twentieth centuries the geographic range of the tsetse fly, vector of sleeping sickness (trypanosomiosis), served as a disease barrier that obstructed the exploration and development of Africa. Working with a general disease model first proposed by Frank L. Lambrecht (1967), the full effect of the tsetse fly and its possible impact upon Australopithecine site location and evolution during the Plio-Pleistocene is explored. First the ecology of the fly is examined. It is shown that the geographic range of the fly is subject to the temperature of its environment. Both favorable and unfavorable climatic periods can affect whether the fly spreads out or recedes into another environment which will sustain its needs. Next, Australopithecine phylogenic views, site location information, and climatic data are correlated with the ecology of the fly. In light of these data the following propositions concerning Australopithecine site location and evolution are discussed: (1) Prior to 3 m.y.a the environment of Africa was similar to todays thus producing "fly belts" which cut off East Africa from the South, thereby isolating A. africanus populations in the east. (2) Around 3 m.y.a. a climatic change occurred which lowered the montane forest limits and shifted the "fly belts" to the coastal regions of Africa. This shift produced "fly free" corridors through which A. africanus could traverse the continent to the south. (3) At around 2 m.y.a, the climate changed again to a more savanna-like environment which reinstated the "fly belts", thereby isolating A. @icanus populations in the south and to the east. (4) The production of a disease barrier which inhibited population flow from the east to the south may have created reproductive isolates which prompted ethological and ecological specializations that resulted in the Australopithecine groups known a A. robustus (A. boisei) in South and East Africa. It is also suggested that such isolation may have led to specializations such as K N M - E R 1470 and H. habilis.
Family Economics in the Pliocene, by Duane Quiatt & Jack Kelso (University of Colorado, U.S.A.) Separate but overlapping subsistence needs and activities of male and female great apes are associated with sexual dimorphism of body size and behavior (e.g. day ranges), which in turn are associated with different strategies of parental investment. Forest- or savanna-dwelling primates forage independently and sex-related differences in foraging and diet are not great; they involve primarily different relative proportions of the same foods. A forest-edge setting, the ecotone in which the hominids emerged in the Pliocene, has a greater diversity of potential food resources than either savanna or forest and the early hominids could "take advantage" of existing tendencies in between-sex differences in foraging as a means of broadening and diversifying their subsistence base. However functional sexual division of labor, co-operation, food sharing, and a dual subsistence system may have been for the group, the fitness advantages to participating individuals has also to be specified precisely to meet minimal requirements of current evolutionary theory. Fitness advantages to males and females of co-operative food-sharing are reviewed and it is noted that these depend on consistent, systematic relations (the regularity of which must themselves be accounted for in terms of advantages to individual fitness) between individuals in a monogamous or, more likely, polygynous family system. AnthropologicaI discussions of family economics, even at the level ofeco-energetics, often focus narrowly on the economic and reproductive concerns of the adult male/adult female mating pair. However, apparently features crucial to the hominid family as an adaptive unit relate to: (1) an increase in the number of partly dependent offspring per mating pair, and (2) the provision for alloparental care giving on a regular basis. Therefore,