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“To the problem of Australopithecus Origin”


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“To the problem of Australopithecus Origin”


(Some illustrations of allopatric differentiation and genetic isolation of population)

Sergey V.Vyrski




FOREWORD

The paper presented gives an account of the conception of allopatric origin of Australopithecus.

At the basis of this work is accepted the fact of simultaneous co-existence of two morpho-physiological types of Australopithecus on the African continent that were genetically isolated from each other.

Assuming that the development and formation of Australopithecus had taken place in two successive stages - first, the transition of a certain parent hominid species to bipedia and, second, thereafter, its divergence into two species: the author, while adhered to the classical theory of speciation, arrived at the conclusion of impossibility of their origin in Africa.

Careful examination and study of paleoclimatic and paleobotanical maps of Eurasia timed by the end of Miocene - middle of Pliocene allows the author to suggest a hypothesis of the onset of bipedia with Australopithecus as the result of habitat conditions change on the Loess plateau in the Central China some 7-8 million years ago during the cooling off period.

Supposing, that the Tibet area in Asia could be served as the geographic isolate for the Australopithecus, the author believes that the geographic population area of the initial species, well adapted to the environmental habitat of steppe and prairie to the North from Tibet, might have spread as far as the territory of Russia.

The author highly appreciates and wishes to express his sheer gratitude to professor V.G.Ochev for his indispensable help and advice in the process of preparation and editing this work for publication.

1.

During the last few decades the African continent has given a considerable evidence in the form of a large number of Pliocene hominid fossils which are essentially belonged to the Australopithecus. The bipedia of the Australopithecus puts them at the very beginning of the Hominoidea branch of the phyletic tree of man’s descent which makes it of a special importance in the study of phylogenesis. The multiplicity and great diversity of the fossils obtained enables us to build up the conception that not only describes their phylogenesis but also helps to localize and identify the geographic place and the time of the Hominoidea transition to bipedia which, in turn, makes for a more constructive approach while solving the problems of anthropogenesis.

However, it should be noted here that the bipedia was also typical for the Ramapithecus, the relative position of which in the earlier systematic history will be discussed at the last Part of the present paper.

While proceeding to analyze the Australopithecus, it is, first of all, necessary to make a note of the two generally accepted principal features, recognized by the majority of the researches: that is developed bipedia and segregation of Australopithecus into two morphophysiologic types - specifically herbivorous (robustus type) and non-specific omnivorous (gracilis type).

The bipedia of the Australopithecus was, at long last, confirmed by the discovery of the famous skeleton “Lucy” (Al-228-1) in Hadar, Ethiopia, aged approximately 3.5-4.0 million years (D.Johanson, 1974), as well as by the discovery of the hominid fossilized foot-prints of the same age in petrified volcanic ash in Laetolil, Tanzania (M.Leakey, 1974).The discovery of a distal fragment of the shoulder bone at Kanapoi (the lake of Turkana) and lower jaw bone (mandible) fragments from the hollow of Baringo and Lothagam (the lake of Turkana) is of special significance, since the phenomenon of bipedia could now be dated back as far as 4.5, 5.0 and 5.5 million years, respectively [2, 6, 11].

Isolating from the family of Hominidae the subfamily Australopithecinae, it was professor Robinson J.T. [6, 12, 15, 19] who first subdivided Australopithecinae into two genera - the proper Australopithecus (gracilis) and Paranthropus (robustus). The most cogent proof of necessitating this subdivision and classification was presented in papers written by A.A.Zubov [17, 18, 19] in which he analyzed the peculiarities of the dental system structure of the species. The analysis of the fossils discovered by the International expedition in Hadar allowed D.Johanson and T.White to generalize the two types of nourishment(diet) and the two respective types of dental system for all Australopithecinae taxons ever discovered on the African continent [5,6].

At present, the two above mentioned genera are attributed to one - the genus of Australopithecus, differentiated into two groups of species - gracilis and robustus. Among those of gracilis it is assumed to specify two taxons - the one more primitive Australopithecus Afarensis dated back to 4.0 - 3.0 million years (found in Hadar, Ethiopia and in Laetolil, Tanzania) and the other - classical A.A.Afrikanus aged 3.0 - 2.0 million years (found in Sterkfontein, Makapansgat, South Africa; Omo, Koobi-Fora on the bank of the Turkana lake) [2, 6]. The robustus are represented by A.robustus (the “Paranthropus” of Swartkrans, Kromdraai, Taung in South Africa) dated back to 3.0 - 2.0 million years and A.boisei (Ileret, Omo, Afar) - aged 3,3 - 2.0 million years. It being known that of special interest are the fossil remains of A.boisei “Zinjanthropus” found in Olduvai, aged 1.8 -1.0 million years, and analogous forms found in Peninge, aged 1.5 million years and those found in Koobi-Fora, aged 2.0 - 1.0 million years, distinguished by gigantism and maximum for the given morphotype herbivorous characteristics [2].

The location sites of Australopithecus fossils, with the exception of the only one fossil remains found in the Central Africa in the vicinity of the Chad-lake, lake, could be provisionally divided into 4 groups:




  • North-East Africa (the desert of Afar, Hadar and Maka sites);

  • The shores of the Turkana-lake (Omo, Koobi Fora, Lothagam, Kanapoi, Kanam, Chemeron);

  • The Eastern shore of the Victoria-lake (Fort Ternan, Olduvai, Laetolil, Peninge, Garusi);

  • South Africa (Makapansgat, Sterkfontein, Kromdraai, Swartkrans, Taung).



The comparison of gracilis and robustus fossil remains ages (Fig. 1) shows their co-existence on the continent from 3.3 to 2.0 million years back [19]. If we take into consideration that some researches attribute A.Africanus and the earliest Homo to one and the same species [4, 6, 11], then this time period could be extended from 3.3 to 1.0 million years.

The difference of evolutionary patterns change of gracilis and robustus types, on provision of their co-existence, gives an evidence of their genetic isolation. Their morphological affinity, bipedia in particular, allows us to suppose their divergence from some protomorphic species, already distinguished by bipedal locomotion.

The foregoing shows that the origin of Australopithecus should be considered to have been taken place in two consequent stages:


  • the transition of hominoids to biped locomotion;

  • their divergence into the two species, irreversibly adapted to different types of diet (food).



Fig. 1. Australopithecus’ remains age distribution relative to their location sites

(Constructed according to [2] with correction according [6, 11].)


million years

5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0

S.E.Africa

Gracilis 




Robustus 

Turkana-Lake

 Gracilis 




Robustus 

Victoria-Lake

Gracilis 




Robustus 

S.Africa

Gracilis 




Robustus 



While adhering to the allopatric conception [7], according to which the most probable reason for mammal’s populations differentiation and genetic isolation is the area breaking - up caused by various geographic and geological factors, it is necessary, first of all, to put such a question: at what time and where the area of protomorphic species of the bipedal hominids was broken up to such an extent, that the populations could develop for a rather long period of time in conditions of isolation and adaptation to different habitats?

It is apparent, that the area of Australopithecus on the African continent is an uninterrupted and common for the both morphotypes, hence, there is all the reason to believe that their divergence took place outside the African continent.
The extrapolation of this very area onto the territory of Eurasia is the starting point in the research attempt of this problem solution.

2.

In order to determine the northern area temperature boundary of Australopithecus in Eurasia, let us consider paleoclimatic habitat conditions of the Miocene hominoid driopithecus and Ramapithecus, who are regarded to be the most probable hominid ancestors or, at any way, represented a certain developmental stage preceding erect locomotion, i.e. four-footed, terraneouslocomotion with semi-vertical body position.

There are only three known locations of Ramapithecus: Sivalik region, Lu-fen and Le-juan in the South of China [2, 6], therefore we would rather analyze more numerous remains of driopithecus, there is no reason to presume any considerable difference in the climatic habitat conditions.

The earliest remains of driopithecus have been found in the low Miocene strata, near Victoria-lake (Honwood, 1933). Many driopithecus fossil remains have been also found in medial Miocene strata on the territory of Central Europe, Eastern Europe, Caucasus, Asia Minor, Northern part of Hindustan and Southern China. The upper Pliocene driopithecus remains are also known, but they are scarce [2, 11].

Habitat area of driopithecus in Europe, Caucasus and in Northern Hindustan at the end of Miocene coincides with the typical paleoclimatic period with an average July temperature of + 20 - 25 C and average January temperature + 3-5C. It being also known that “ the area was covered by coniferous and broad-leaved forest intermixed with heat-loving broad-leaved bush and evergreen plants at the undergrowth” [14]. The fossil remains found in the South China are located in the zone with the warmer January temperature of +5...10 C; however, there is no reason to exclude the feasibility of spreading the area farther to the North of coniferous-broad-leaved forest, analogous to the European forest with an average January temperature of +3...5 C, the zone that extends in China upto 40 degrees N.L. [14].

Geobotanical maps of Africa dated to lower and medial Pliocene show that the biotope for the both groups of Australopithecus species was savanna with thin xerophilous open forest in the vicinity of water supply basin, which is confirmed by the description of flora and fauna remnants near the fossils discovered [2, 6].

Spreading of driopithecus, able of four-footed terraneous locomotion, in forest points to one particular way of life also typical for their anthropoidal counterparts - i.e. getting food from the ground and securing breeding sites up in the trees. At the same time it should be noted that they differ from Australopithecus who pick up food and secure breeding sites on the ground only. If we exclude the possibility of securing breeding sites by Australopithecus in the open and their ability to construct the sites on their own, then we may suppose that they organized their dwellings by widening the natural hollows or burrows in soft, alluvial deposits along the shores of reservoirs, which seems to be quite probable because the majority of their fossil remains were located near Pliocene rivers and lakes (Hadar, Omo, Olduvai, Laetolil, etc.)[5].

Presuming 40 degrees N.L. as being the Northern border of Australopithecus area, let us consider the expansion of savanna and forest steppe on the territory of Eurasia. In conformity with the Geobotanical maps of the Middle Pliocene, the zone of savanna intermixed with thin xerophilous forest starts expanding from the territory of Africa, extended through Arabia, Desht-Kevir plateau and forked around the Tibet.

The Northern part of the Tibet circle extending by a wide expanse of steppe up to 45 degrees N.L. reached the river-Hwang Ho - the upper board of Miocene hominoid dissemination area.

The Southern and narrower part of the Tibet semicircle, along Himalayan foothills, approached the Loess plateau in the South, completing the circle around the Tibet.

While observing the Northern and Southern areas dismembered by the Tibet, one their would notice their ecological heterogeneity.

Thus, the Northern area was a vast expanse of savanna and steppe of prairie type inhabited by the typically hipparion fauna species; while flora was represented by a wide variety of cereals, buckwheat, ephedra. That ecological environment was good to Australopithecus gracilis. Microstructural analysis of dental system of one of the gracilis types (Australopithecus Afar, Laetolil, Hadar, 3.6 - 3.7 million years) allowed to restore an exemplary list of foodstuff that included fruits, seeds, plant stems, rootstock, insects, lizards, small mammals [8].

To the South from the Tibet, the area was represented by a relatively narrower savanna region at the Himalayan foothills with nearby tropical evergreen forests and meridionally flown rivers and valleys. The population existence at those places was dependent on adaptation to planteating.

Thus, the conception of allopatric divergence for the reconstructed area is considered to be as follows: some hominoid species, already adapted to erect locomotion while being in Asia, due to centrifugal force started to spread around the Tibet. The Northern and Southern populations adapt to different kinds of food and dietary regimes and slowly getting isolated from each other genetically. Some time later, after having penetrated onto the African continent, they co-exist, though in different ecological niche, and evolutionize in synchronism but in different ways and directions.

Indirect confirmation of correctness of the Australopithecus geographic isolate reconstruction is shown by the fact of hipparions segregation (the most typical fauna Mc3 - PL1 representatives) into two ecologically differentiated types. Thus, one of them was adapted to habitats with more afforestation and soft, succulent vegetation, while the other adapted to more xerophilous habitats; and what is more important, their areas correspond to the areas of hypothetical emerged populations of Australopithecus, adapted to different types of food [3].

3.

When analyzing geobotanical habitat conditions of Australopithecus on the territory around the Tibet we would note drastic vegetation changes in the region of the Loess plateau, that took place during the cooling off period which had started some 8.0 - 7.0 million years ago [6, 9]. At the end of Miocene the plateau was covered by coniferous-broad-leaved forests and heat-loving, evergreen undergrowth vegetation of taxodium family, which is typical to the area inhabited by hominoids of driopithecus type.

At the onset of Pliocene the forests were slowly replaced by steppe of prairietype that suited perfectly as the habitat environment for Australopithecus [14].

The cooling off period was associated with general climate continentalization - the average January temperature on the plateau came down from 3 - 5 C to 0 - 3 C and average July temperature remained unchanged (20 - 25 C), but it should be noted, on the whole, this July isotherm moved farther to the North, reaching 65 degrees N.L. [14].

Still another vegetation change feature that was peculiar for the Loess plateau should be specifically noted here. In spite of the fact that climatic cooling off was rather slow in tempo (during 0.5 million years the average January temperature was reduced by 3 degrees C only), forest migration to the South warmer region did not happen. That was purely geographic reason and actual cause of forest elimination were the mountain ranges in the South, which were not high enough at the beginning of Pliocene because orogenesis in Asia developed to the full only during the second half of Pliocene. Climatically, the peculiarity of the cooling off phenomenon was essentially in reduction of winter night temperatures, therefore, one of the most probable reasons was that the animal world and vegetable kingdom were entrapped geoclimatically.

The analogous case was described at the time of Pleistocene glaciers advance in Western Europe, when the Alps situated latitudinally did not allow the animal world and vegetable kingdom migrate, thus dooming all of them to mass extinction. Meanwhile in the North America, where the mountain ranges situated longitudinally, even such heat-loving plants as magnolia were able to survive [9].

On the whole, if we take into consideration that cooling off maximum occurred mainly in the Central China and Mongolia while the territory of Europe was not practically subjected to cooling off at all, we have the right to suppose that some 7.0 - 6.0 million years ago a unique historic event took place on the Loess plateau. Here, we mean the most favorable, if not singular, situation in the history of anthropoids, which allows us to suggest the feasibility of hominoids, so far able of semi-vertical, four-footed locomotion, to come over to erect locomotion (bipedia).

The Loess plateau is situated in the midstream of the Hwang Ho-river with the total area of 430,000 sq.km. and confined by the mountain ranges of Taikhan-shan, Tsin-lin and eastern branches of Nan-shan. The depth of loess ranges from 100 to 250 m. with the rivers flown along deep canyons taking out immense quantities of alluvium.

While considering the feasibility of hominoids transition to erect locomotion, let us take as the basis of evolutionary transformation of the species the natural selection of the population phenotypes in conformity with their fitness to the habitat conditions. Such an approach implies “fluctuation” of speciation characters within a population; however, the scope of this work does not allow to dwell upon the reasons of “ fluctuation” and the species distribution law according to the characters. It will be enough for the purpose to consider the action of natural selection from the qualitative point of view [10].

In case of stable outside ecological conditions the majority of species will be distinguished by the most conformed to the environment character and the natural selection activities will be focused on speciation stabilization.

In case of minor environmental changes the natural selection mechanism will trigger one of the most conformed to these changes fluctuation characters.

As this takes place and the environment changes are considerably slower than the time needed for self-copying of reproductive volume, then the number of species nonconformed to the new character will be steadily reducing, while the number of those conformed to this character will be steadily increasing, thus transforming the phenotype of the population.

In our case, the initiation of bipedia with four-footed, land-based hominoids could be imagined as a successive series of induced adaptations, while a complete morpho-physiological reconstruction could be assumed as a sequence of the so-called phase portraits of the population corresponding to these adaptations.

a. In conditions of land-based subsistence “the fluctuation” character of breeding site making up in the tree branches is a sporadic making the same by some of the hominoids, only this time on the ground - in natural caves and hollows, which are plentiful on the Loess plateau. In the result of climatecontinentalization with subsequent lowering winter night temperatures, the firstclimatic adaptation should take place and, and thus, hominoids have to get adapted to completely land-based way of life.

b. Making breeding sites up in the tree branches was performed by hominoids by making use of the materials at hand (branches, sticks, etc.) and arranging them with the aid of upper limbs. The natural “fluctuation” of grasping movements in the process of making “bed-recess” in caves, hollows and burrows was the grasp of handy objects nearby (sticks, stones, etc.) for indenting and expanding the hollows in soft loess ground. Thus, at that stage of evolution the hominoids should have acquired the instinctive habits of handling primitive implements in the process of “bed-recess” making.

c. Cessation of brachiate and tree-climbing activities during the land-based way of life as well as instinctive upper limbs motion activities, naturally, brought about still one more adaptation of the population - modification of upper limbs structure - the thumbs of the hands changed their position and contrapositioned other fingers so, that now the hand could perform two types of handling and holding objects:

- powerful grasping grip (“fist clench”);

- more sophisticated gripping and holding manipulation performed by means of the thumb aided by the second or third finger.

d. In line with the hand modification as an organ actively engaged in manipulation with handy implements and with minimizing its function as an organ of support, the whole locomotion complex should have had changed with the bias to erect locomotion followed by pedalis modification, pelvic girdle strengthening, spinal column lordosis, shift of posterior occipital foramen towards the middle base of the skull, etc.

Now, let us try to gestimate the time necessary for prehominides origin.

The territory of the Loess plateau, similarly to the nowadays anthropoids, could accommodate the population of hominoids of approximately 400,000 species. Let us assume that the fluctuation character of one of the species was more conforming to the changed environments and in the process of reproduction that progressive character would double during the lifetime of one generation. Then, during 20 generations (20 years each - the total of 400 years) the population would completely replace the former phenotype.

This period would be ample for the hominoids to learn to make breeding sites on the ground and acquire instincts of handling the implements in the process of accommodating caves and burrows for living. However, the advent of human-like hand was not at all the fluctuation of a simian character as well as the whole morphophysiological complex of erect locomotion, therefore the time necessary for such reconstructional developments would be extended considerably. If we assume, that the human being hand genom differs from that of hominoid by more than 1000 micromutations (essentially the mutations concern the change and counter-position of a thumb), then a period of 400,000 years would suffice for the purpose. Besides, if we take into consideration that in the process of forest replacement by savanna the population was reduced considerably and species replacement by progressive character criterion proceeded faster, we may conclude that the period of forest replacement (approximately 2.0 - 1.0 million years) would be sufficient for hominoid evolution into erect locomotive species.

Assuming that the origin of the initial erect locomotive type of Australopithecus took place in the Central China, we may estimate the time necessary for spreading the population around the Tibet, i.e. the time period of their geographic isolation from each other.

Let us make use of rate gene computation formula which is based on the population growth increase value in the process of single self-copying in proportion to the area increase inhabited by this population and to the reproduction period (i.e. lifetime of one generation)[1].

Let us suppose that a group of 7-10 species occupies the territory of 10x10 km., then with 5% growth increase during one generation (approximately 20 years) [1] without any demographic pressure exerted by the population, the territory occupied by this group would increase upto 10.5 x 10 km. during 20 years. The value of 0.5 km during 20 years may be accepted as the approximate rate of population propagation. Then the distance of 10,000 km from the Loess plateau in the North Tibet to the Desht-Kevir plateau could be inhabited during 400,000 years approximately.

It is more difficult to estimate the population propagation rate in the South of Tibet because the smaller savanna area and a great many of water and forest obstacles would slower population propagation, making it adapt to planteating and expand the habitat area at the expense of tropical forests. In this particular case the area inhabited by the population group would decrease, so would the rate of propagation. If the rate of propagation decreases four times as less, then the time necessary for the population to reach the Desht-Kevir plateau would equal to 2 million years.

The period of time the Northern and Southern initial erect locomotive types of Australopithecus were in geographic isolation and adaptation to different types of food was comparable with duration of evolutionary transformations, typical for the mammals of hipparion fauna, and was confirmed by genetic separation of Australopithecus into omnivorous and herbivorous types.

Completing specific patterns as implied by the conception of non-African origin of Australopithecus, let us represent space and time model of phylogenesis in its accomplished form.

Thus, in consequence of cooling off period commenced on Asian continent 8.0 - 7.0 million years ago the population of hominoids, inhabited the territory of the Loess plateau, came over from four-footed to bipedal locomotion. In some 0.5 - 1.0 million years, as required for a morphological type formation, the initial species started spreading around the Tibet, forming two geographically isolated populations in two ecologically different habitats. During the time necessary for spreading the populations around the Tibet (0.5 - 2.0 million years), these populations adapted to different types of food, acquiring genetically isolating factors and thus forming two new species:


  • robustus (herbivorous) to the South from the Tibet;

  • gracilis (omnivorous) to the North from the Tibet;

Penetrating onto the African continent (herbivorous species 1.0 - 2.0 million later) they continue evolutionize - one population towards hominization, the other population towards strengthening and stabilizing planteating forms.

Continued cooling off forced the omnivorous forms out from the North of the Tibet, while the planteating forms continue developing as the four populations: in China, India, Indonesia and Africa, megagnatic forms of which survived to the middle of Pleistocene.

Map.1 Reconstruction of Australopithecus area.

4.

The conception of non-African origin of Australopithecus is confirmed by identification of fossil remains attributed to the proposed area.

For this purpose it is, first of all, necessary explicate the characters that discriminate herbivorous forms from omnivorous ones as well as common for both forms characters that are also inherent to the mentioned earlier initial erect locomotive species.

The key morphological characteristic of Australopithecus, recognized by the majority of researches, is the availability of the human like hand disengaged from support function combined with the complex of erect locomotion. As an additional important character of highly practical significance is the structure of dental system, closely associated with the change of way of life and nutrition. The latter is expressed in shortening of alveolar arch and anterior section reduction, decreasing of canine tooth, elimination of diastemata and development of posterocanine part nonparallelism.

Masticatory and crushing functions of maxillodental system of herbivorous form is expressed by peculiar proportion of anterior and posterior sections: small incisors and canines with big molars and molarized lower premolars [5, 9, 19]. In addition to that, their condyles structured specifically in such a way that allows lower maxilla masticatory motions in horizontal plane [2, 4].

The peculiar structure of massive skull is distinguished by availability of sagittal crest, served for fastening chewier muscles. Sagittal crest in combination with occipital one is typical for land-based, four-footed locomotive anthropoids.

Gracilis species lack the crest. Being not a narrowly specialized form, the gracilis form is distinguished by a large number of primitive features, that could be generalized to the initial species - dental arch is narrower, behind canine rows look almost parallel, upper molars are not rhombiform but of square (anthropoid) form [9, 19]. The earlier gracilis forms have the incisors of clearly expressed spadeform: enamel tori are on the mesial and distal sides of lingual surface.

Omnivorousity of gracilis forms of Australopithecus is expressed by alveolar prognathism (different form of lower and upper arch with some protrusion of the latter), that provides for “paring” function.

Some of the species are observed to have an increased canine and supraorbital torus, that implies a considerable amount of meat in their diet.

Asia is incomparably richer by the fossil remains attributed to Miocene-Pliocene history of hominoids than Africa: only one site Lu Fen in the province Youn-Nan gave as many fossil remains as the whole Africa [6].

On the whole, the fossil remains of Asian hominoids are characterized by extraordinary variability and mosaic of characters; sexual dimorphism or allotropism are not convincing enough explanations, therefore it does not seem possible at present to make any differentiation even on the generic level [6].

Unfortunately, it is not feasible to conduct a revision of the fossil material, based on the non-African conception, although some descriptions of fossil remains can be identified with the taxons of the given phylogenesis model.

If we start analyzing the fossil remains found in regions located nearest to the Loess plateau then the best choice will be the description of the teeth of a giant “anthropoid” Gigantopithecus blacki, discovered by professor Koenigswald and identical maxilla described by professor Pei Ven-June. The lower molars are of driopithecus pattern, diastemata are non-available, the canin is relatively small and its form reminds man’s one, although its wear indicates about its functional role as a premolar or molar, rather than canine as with a human being. On the whole the maxilla is a clear evidence of masticatory and crushing specificity typical for planteating animals which use seeds, tubers, rigid sprouts of bamboo, etc.

Professor Weidenreich came to the conclusion that the above mentioned teeth belonged to primitive hominid - Pithecanthropus robustus ancestor and gave him the name Giganthropus blacke [2]. In our opinion this species belongs to the planteating form of Australopithecus, whose extraordinary size and the time dating to Pleistocene implies the concluding phase of development.

Analogous complex of characters is displayed by Gigantopithecus bilaspurensis (Simons, Chopra), discovered in Pliocene strata in the Sivalic Hills, India and Meganthropus paleojavanicus (Von Koenigswald) discovered in Lower Quaternary deposits Sangirana, the island of Java, that was renamed later as Australopithecus paleojavanicus (Robinson). Similarly to the Chinese Gigantopithecus, these fossil remains should be attributed to the concluding phases of geographically isolated populations of planteating form, represented on the African continent by Australopithecus (Zinjanthropus) boisei (L.Leakey).

To the initial phase of development of planteating form, very close morphologically to the initial species, belongs pliocenic Ramapithecus brevirostris (Lewis), which has the dental arch of more or less parabolic form, with no diastemata, small man-like canine, weakly expressed prognathism and molarization of the second premolar (availability of two tubercles in vestibulo-lingual direction).

In general, the situation of Ramapithecus in the hominide system is complex enough. The general character of fossil remains of anthropoids that allows to classify them as Ramapithecus is the structure of teeth, which is similar to hominids: the form of crowns of “P” and “M” type, correlation of their vestibulo-lingual and mesiodistal diameters; the location of tubercles and crests on the occlusion surface. These characters allowed us to refer the two separate molars discovered at the Chinese site Le Juan, as belonged to Ramapithecus.

Based on the fact that pliocene Ramapithecus, as in case of above-mentioned Ramapithecus brevirostris have, in addition to nearly parabolic dental arch, a hominid-like structure of maxilla and, particularly, Gothic palate, which is considered to be a true sign of bipedia, some of the researchers attribute all Ramapithecus, including miocenic, to the bipedal ones. Thus, E.Simons refers Ramapithecus hariensis (Lewis) and Dryopithecus punjabicus (Pilgrim) 14 millions years of age to one common erect locomotive species - Ramapithecus punjabicus.

Many researchers also attribute to erect locomotive miocenic Ramapithecus wickeri (Leakey) from Africa on the basis of its belonging to the genus only; completely ignoring an ordinary anthropoid form of dental arch [12].

For some time past many researchers keep to the opinion about existence of two independent branches of hominoids - african “dryomorphus” and asian “ramamorphus”, which are essentially ecological equivalents, prohibiting any considerable interpenetrating [6]. For instance, the above-mentioned african ramapithecus was proposed to be given the initial name - keniapithecus [2, 11].

In this case, we are coming to still one more conclusion: only ramapithecus could adapt to erect locomotion in the Central China, which is confirmed by australopithecoid tendencies of dental-maxilla apparatus of miocenic species [6].

5.

The above-stated hypothesis of non-African origin of Australopithecus, allows to answer some specific questions concerning anthropogenesis, in particular, it allows to reconstruct a continuous taxonomic line that reflects their origin and evolution from the middle of Miocene to the end of Pliocene (Fig.2).



On the basis of the conception reported we have arrived to the following conclusions as to the direction of paleoanthropological investigations. It is apparent that African continent cannot give us any principally new fossil remains of miocene-pliocene hominids. There is no doubt that the center of the research should be transferred to Asia. It is also important to note that the area of the initial population, adapted to omnivorousity could include the territory of Russia. In this respect the region of the Southern part of the Turan depression surround is considered to be promising for the search of Pliocene hominide fossil remains.

The paramount significance of the conception proposed by the author is that it allows to unite chronologically and evolutionally the whole afro-asian paleoanthropological miocene-pliocene material, the revision of which on the basis of unified methodology is essential.

In conclusion, the author would like to express his confidence in that, that the new investigations and discovery of subsequent hominide fossil remains would confirm the hypothesis suggested and contribute to the solution of the main problem of anthropogenesis.

REFERENCES:

1. Alexeyev, V. P., Human Being: Evolution and Taxonomy (Some Theoretical Aspects). Moscow, “Nauka” Publishing House, (1985).

2. Big Illustrated Atlas of Primitive Man. Artia Prague, (1982).

3. Gromova, V.I. Hipparions. The Works of Paleontological Institute, Academy of Science of the USSR, Vol.36, (1952).

4. Harrison, G.A., Weiker, J.S., Tanner J.M., etc. Human Biology. Oxford Univ. press, (1977).

5. Johanson, D.C., Edey, A.E. Lucy. The Beginnings of Human Kind. Warner Books

6. Khrisanfova, E.N. The Earliest Stages of Hominization//Results of Science and Technology. Anthropology Series. Moscow, VINITI,1987,Vol.2,pp 5-92.

7. Mayr, E. Populations, species and evolution. The Belknap Press of Harvard University Press. Cambridge, Massachusetts (1970).

8. Nature. (Reference to the American Journal of Anthropology) #1, p.118 (1986).

9. Our Planet Winters. Edited by B.John, Moscow, “Mir”, (1982).

10. Philippov, A.E. Discrete Speciation and the Willis Law. Journal of General Biology, #3. (1984).

11. Reshetov, V.J. Tertiary History of Higher Primates/Results of Science and Technology. Stratigraphy series. Paleontology. Moscow, VINITI, Vol.13, p.p. 1-148. (1968).

12. Roginsky, J.J. Anthropogenesis Problems. Moscow, Higher School, (1977).

13. Roginsky, J.J., Levin, M.G. Anthropology. Moscow, Higher School, (1978).

14. Sinitsin, V.M. Relict Climates of Eurasia. Leningrad University Press, Part 1. (1965).

15. Yakimov, V.P. Australopithecus. /Fossil Hominids and Origin of Man/. Edited by V.V.Bunak. The Works of the Institute of Ethnography. Vol.92. (1966).

16. Zhedenov, V.N. Comparative Anatomy of Primates (including Human Being). Edited by M.F.Nesturkh, Moscow, Higher School, (1969).

17. Zubov, A.A. Dental System. (Fossil hominids and origin of man) The works of the Institute of Ethnography. Edited by Bunak V.V., Vol.92, (1966).

18. Zubov A.A. Odontology. Anthropological Research Methodology, Moscow, “Nauka”, (1968).

19. Zubov, A.A. On Taxonomy of Australopithecus. The Problems of Anthropology. #17, 99-105. (1964).



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