Human evolution

the human evolution indicates the various stages which led to the modern man, Homo sapiens , starting from the common ancestors which it has with the others Primate S. It is not limited to the study of the kind Homo but more generally includes all the members of the family of the Homininé S (including thus the Australopithèque S which are not, strictly speaking, our ancestors). Its study especially amounts describing the history of the human line. This scientific work corresponds to what is called the Paléoanthropologie.

Beginning of the Life with the first biped

Appearance of the life at the exit of water

The broad outlines of the human origin are the following ones: ; Bacterial ancestors then fish There is 3,5 billion years, the life appears on Earth. Follow simple forms, probably rather close to some Bactérie S current primitives. Then the life took certain more complex forms, all watery, of which the most advanced expressions resembled the Poisson S osseous current. It is of this branch (ostéichtyen S) that the first terrestrial animals would come, plants being already well installed out of water.

The first known animals with four legs or Tétrapode S are Amphibians such Ichthyostega . The radiation of species resulting from this stock was enormous, the Reptile S are an alternative. A relatively primitive line of reptiles, the reptiles mammaliens was at the base of the Mammifère S.

The evolutionary Radiation of the Mammalian S

The mammals undergo a evolutionary Radiation at the beginning of the tertiary era: many different species appear and occupy of the varied mediums: airs, aquatic environments… It occurs the appearance of the mammals Arboricole S: the Primate S. Among them, a great number are Frugivore S and it is besides parallel to the acquisition of this frugivorous mode that the vision color becomes possible, for the location of the ripe fruits (the dogs or the Ruminant S have a quite lower perception of the Couleurs). Among them the monkeys (Simien S) then the large monkeys, would have diversified, the prehensile latter not having a tail.

The oldest Biped primate

With the Miocène, between -10 and -7 My, there is separation of the human line and the line of the Chimpanzé S, species nearest to us. The oldest fossil of biped primate, gone back to - 7 My, was discovered with the Chad. One gave him the name of Toumaï . Only the cranium could be studied, but it shows the characteristics of a station upright, and thus of a walk on two legs. The bipédie is thus the first human character to appear in the human line. This appearance would be the event founder having allowed thereafter the evolutions which led to the various species of Homininé S of which the Homme forms part.

This recent evolution, since our common ancestor most recent with the chimpanzees, is relatively well documented thanks to the fossils, although important gaps remain.

Evolution of the human line

The human line gathers the mankind and all other fossil species, having a closer relationship with the human ones, than with the Chimpanzé S, current species nearest to us. A Fossile can be classified in the human line only if it presents at least one of the clean derived characters to the current species human.

An evolution more “buissonnante” that linear

Since the Eighties, the discoveries of layers of fossils multiplied, and with them, the number of species or subspecies of the kind Homo .

At the same time, the history évolutionnaire of the man passed from a linear tree to a tree to several branches, and species which we thought of being our ancestors there is still little abruptly became our late cousins.

This article thus proposes to present the state of the currently allowed theories, like some alternative theories.

Evolution of the hominines

Until the beginning of the year 1980, the state of research allowed to represent the evolution of the men to the Pliocène and the Pléistocène as follows: Seen linear old of the evolution of the Hominine S

Knowledge of the time made it possible to think that the evolutionary tree of the kinds Australopithecus and Homo was linear and that the species followed one another in a continuous and regular process, each species being the ancestor of the other. This assumption knew its apogee in the years 1960-1970, time of strong influence of the synthetic Theory of the evolution (TSE) in the various disciplines of the paleoanthropology. Certain researchers defended even with force the theory of the single species: at a given time could exist only one species of hominidé. The evolutionary tree of the man was then perceived like “a large trunk with very few branches”.
This simplistic theory sometimes is still taught nowadays although it does not integrate the discoveries of these last years. One knows for example that towards 2 million years lived in the same areas of East Africa of the Paranthropus , of the Homo rudolfensis and of the Homo habilis .

Nowadays, the many fossils discovered on all the continents completely transformed our evolutionary tree into a very provided “bush”. Several models of filiation can be proposed starting from the various species of Hominides who followed one another:

Succession of the various species of Hominidé S in time:

This table proposes only filiations for the representatives of the kind Homo (milked vertical). It takes into account the following assumptions:

Homo rudolfensis would be a species with whole share and not a subspecies of Homo habilis .
Homo antecessor would be the common ancestor of Homo heidelbergensis and of Homo rhodesiensis . Its dates of appearance and extinction are for the moment indicative because this species was defined only starting from one only layer and is not recognized by the whole of the paleoanthropologists.
Homo floresiensis would go down directly from Homo erectus , and its ancestors would have arrived on the island of Flora approximately 800.000 years ago, but would have constituted a new species with whole share only well later.
the men of Néandertal would belong to the species Homo neanderthalensis , distinct from Homo sapiens .

Moreover, there exist two tendencies among paleoanthropologists. Some are in favor to gather the fossil specimens within more the small number of species and others prefer to classify these individuals among the greatest number of fossil species.

Fossils

Characteristics of the human line

These characters can be classified in three categories:

Bipédie

Four curves on the level of the spinal column;
a advanced foramen occipital at the base of cranium, which is in relation to a biped locomotion;
broad and widened Bassin which allows a better stability during walk;
Fémur S obliques compared to the vertical, which makes it possible the feet to be plumb with the center of gravity;
an inch parallel with the other toes and the existence of an arch of the foot;
Of the shortened forelimbs.

Cranial evolution

Great cranial capacity (between 500 and 1600 cm ³);
District of cranium;
flattened Face (not of Prognathisme);
know-orbital Absence of Pad.

Cultural activities

Production of tools and control of the size of the stone, realization of tools diversified (Double-side S, Scraper S…) ;
Control of fire ( Homo heidelbergensis or Homo erectus )
funerary Rites (starting from Homo neanderthalensis )
Art (paintings, sculptures…) (starting from Homo sapiens )

Technical and social evolution

See also: Paleolithic Prehistory, , Mesolithic, Neolithic, prehistoric Art, lithic Industry

See too

Bipédie
A.A.T. (Aquatic Ape Theory) or " Theory of the Aquatique" Primate;
Theory of the evolution

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