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The Human Species

 

 

Primates

 

Forerunners

The ancestor of all the animals belonging to the order of which we are members (the primates) is, probably, the Cretaceous’ mammal "Purgatorius unio", a small insectivore animal with nocturnal habits. However, like the primitive primates, it also included a significative quantity of fruits in its diet.

 

The First Primates

During the Paleocene (the most ancient epoch of the Terciary), arose the earliest true primitive primates. One of the most ancient is the Plesiadapis, with an appearance similar to the arboreal rodents and, as the Purgatorius, it was simultaneously insectivore and frugivore (it ate fruit).

 

Plesiadapis (Adrian Sington)

 

About 50 million years ago they were followed by the adapids, which were also arboreal. However, they had a more modern appearance than the plesiadapis and their diet consisted mainly on fruits and leaves. It’s thought that they were the ancestors of the lemurs.

The most ancient fossil of the ancestor of the tarsiers’ family – The Necrolemur – dates from a not much later epoch, compared with the adapids. It had a big skull, more developed than the adapids’ and it was also arboreal. The Necrolemur may also be the ancestor of the anthropoids (which include the human species).

 

The Anthropoids

The anthropoids were split, 30 million years ago, between the direct ancestors of the platyrrhines (monkeys with 36 teeth and a short visage, very agile at the arboreal life of south-american forests) and the catarrhines (monkeys with 32 teeth, which include the human species).

The oldest known platyrrhine is the Branisella and the oldest catarrhine is the Ægiptopitecus, arboreal and frugivore, with a relatively developed brain and able to distinguish between colours and reliefs. However, it still preserved ancient characteristics like a long muzzle and large ocular orbits far from each other.

 

Ægiptopitecus (Günter Radtke)

 

Catarrhines

Among the catarrhines two groups arose: the cercopithecoids (baboons, colobines, other African and Asian monkeys), which preserved the tail, and the hominoids, which lost it.

 

Hominoids

The group of the hominoids includes the gibbons, orangutans, gorillas, chimpanzees, humans and several extinct species.

The gibbons were split from the lineage that originated the humans little after the cercopithecoids had done so, or in other words, little less than 30 million years ago. They are characterized by their long arms that give them an unusual ability to move between the tree branches and lianas of the forests.

The orangutans were the 2nd hominoids to be split from our lineage, 17 million years ago and, finally, the gorillas and, later, the chimpanzees also diverged from us, between 7 and 12 million years ago. These two hominoids share a common form of locomotion (knuckle walking) and, more remarkably in the case of the chimpanzee, they share extraordinary resemblances with the humans concerning to physiognomy and behaviours. They are also extraordinarily intelligent, reaching the capabilities of a 3 or 4-year old human child.

 

Chimpanzee mother with her child

 

 

Hominids

 

Toumaï, Millenium Man, Ardipithecus and Evolution Trends

Until a few time ago the most ancient known hominid was Ardipithecus ramidus, which lived 4,4 million years ago in Ethiopia. It was possibly preceded by two species that were more recently discovered: the “Millenium Man” or Orrorin tugenensis shall have lived 1,5 million years earlier and its bones were found in 2000 in Kenya; Toumaï or Sahelanthropus tchadensis shall have lived 6 to 7 million years ago and its skull was found in Chad in 2002. However, it’s not known if those two species were ancestors of the humans, ancestors of the chimpanzees, common ancestors or if they belonged to some parallel branch, not directly linked to any of them. ). They would be, anyway, species very close to the common ancestor of humans and chimpanzees. The Ardipithecus ramidus ramidus shall have also been preceded by its relative Ardipithecus ramidus kadabba, whose fossils were found in Ethiopia. This hominid is posterior to Orrorin tugenensis and Sahelanthropus tchadensis, but it lived little later, having most of the fossils ages between 5,6 and 5,8 million years. It was a hominid with a behaviour very similar to the actual chimpanzees’, it lived in a forest environment and it’s quite probable that it walked upright, on 2 legs.

Concerning to Ardipithecus ramidus ramidus, there are also signs that it was a biped (he walked upright, on 2 legs), although it may have also lived in the forest, which doesn’t agree with the traditional idea that the bipedism developed when our ancestors were forced to start living in an open environment (the savanna). It’s probable that this characteristic, which provided advantage in such environment, had been developed prior to the transformation of the forests into savannas, to the east of the Rift Valley in Eastern Africa (where most of the ancient hominids’ fossils have been found). It would be, anyway, a species very close to the common ancestor of humans and chimpanzees.

A theory that has collected some acceptation inside the scientific community and that would explain many human characteristics (the relative absence of hair, the thick layer of visible fatness specially in babies, the capability for controlling breathing, the water-dynamic shape of the body, among others) is the Theory of the Aquatic Ape, according to which the first hominids (not living in the savanna but rather in wet environments) would have crossed through a semi-aquatic phase. During this period, the hominids would feed themselves in shallow waters of rivers, lakes or seas, where they would have developed those characteristics. There are some monkeys living in swamps that walk on 2 feet in the water, allowing them to keep the head above its surface. This seems to support this theory. It is, nevertheless, a theory still faced sceptically by many paleo-anthropologitsts.

Along with bipedism, other properties that gradually evolved on hominids were the dentition (eyeteeth increasingly smaller, a bigger amount of molar teeth, parabolic distribution of the teeth), the growth of the cranial capacity (which may have been favoured by the reduction of the volume of the jaws), among others.

However, the evolution wasn’t so linear because it is thought, for instance, the Australopithecus africanus was in some aspects less adapted to bipedism than his ancestor Australopithecus afarensis.

 

Two Australopithecus afarensis (Richard Effland Costello)

 

Australopithecines

Slightly more recent than the Ardipithecus ramidus are the Australopithecus anamensis (with an age between 4,2 and 3,9 million years) and the already mentioned Australopithecus afarensis (with an age between 3,9 and 3 million years), whose physiognomic characteristics became gradually closer to the modern humans’ but whose brain was kept small, with dimensions comparable to the chimpanzees’.

The Australopithecus africanus (with an age between 2,9 and 2,4 million years), who followed them, started to display some traces of growing brain volume, His dentition continued to evolve to modern configurations, suggesting a diet that was essentially composed by fruits and leaves. Because he lived in the hot regions of Africa, it is thought that he should have a dark skin.

Contemporaneously there were 3 other species with more robust heads faces, with similar cranial capacities – the Australopithecus æthiopicus (between 2,7 and 2,3 million years ago) and his descendants Australopithecus robustus (between 1,9 and 1 million years ago) and Australopithecus boisei (between 2,2 and 1,2 million years ago), who didn’t leave further descendants.

 

 

Ecce Homo

 

Homo habilis and Homo rudolfensis

In other branch of the evolution, the Homo habilis (between 2,2 and 1,6 million years ago) was the first species to chop tools (although there are indirect traces that make us think that the Australopithecus africanus already did it), instead of only use them in raw conditions, as their ancestors did and the actual chimpanzees do. This culture is called Olduvai, which consists on the slivering of stones so that they can display a cutting edge.

The brain volume of the Homo habilis was already considerably higher than the chimpanzees’, which along with the slivering of tools, shows that he would be a more intelligent hominid. It’s possible that he had elementary speaking skills and it’s thought that he built the first shelters (stone circles) about 2 million years ago. He would have been also one of the earliest hominids to possess an intensely carnivore diet, which could even include australopithecines.

A close “cousin” of the Homo habilis, the Homo rudolfensis (between 2,1 and 1,8 million years ago), was presumably the mother species of our closest ancestors (although that is still far from being clear) and, despite the lack of proofs, it’s thought that he was also able to sliver Olduvai tools, because his brain volume was clearly higher than the Homo habilis’.

 

Homo habilis (Washington State University)

 

Tools from the culture of Olduvai

 

 

Homo ergaster

The Homo ergaster (between 1,8 and 1,2 million years ago), which is a possible descendant of the Homo rudolfensis and possessed a larger brain, was the founder of the Acheulean culture, which consisted on the slivering of tools, in order to produce symmetric cutting edges (bifaces). These tools were often much bigger and heavier than those produced by the culture of Olduvai.

The Homo ergaster would have become specialized in the art of hunting and, through the use of these tools, he could transform the animal and vegetable products. This way of life would resemble, in part, the one that nowadays characterizes the hunting-recollecting tribes and would have forced the individuals to join in large social groups. It would have also encouraged the development of the communication and of the vocal and body language (in order to coordinate their hunting tactics and transmit knowledge about the surrounding environment, for instance).

 

Homo erectus

The Homo erectus (who lived between 1,2 million and 150 thousand years ago) probably descended from the Homo ergaster and he already had a brain capacity close (although smaller) to the modern humans’. This species may have been the first to control, use and light up the fire, which allowed its movement toward colder climates. It also allowed them to protect themselves against dangerous animals (and to attack them too) and to cook the food.

About 1 million years ago, the Homo erectus would have, finally, left Africa for the first time, in the direction of Asia and Europe. They leaded their carnivore behaviour so far that they left signals of cannibalism practices (which could, nevertheless, have only a ritual nature rather than a daily one). However, the Homo erectus probably is not the direct ancestor of the Homo sapiens.

 

A community of Homo erectus (Richard Leakey, Roger Lewin)

 

Tools used during the Acheulean culture

 

 

Homo sapiens

 

Homo antecessor and Homo heidelbergensis

It’s probable that the primitive Homo sapiens (Homo antecessor) evolved about 1 million years ago from Homo ergaster. There are also traces that, following his preys, he entered in Europe little after his appearance.

They were probably replaced, about 700 000 years ago, by the Homo sapiens heidelbergensis. Their brain volume evolved to the dimensions of the modern human brains, their jaws and skeletons became less robust and, as the Homo erectus, they would have practiced the cannibalism and manufactured tools that were typical of the Acheulean culture.

 

Hut dated from more than 400 000 years ago. It’s linked to the Acheulean culture, but it’s thought that it could have been inhabited by Neanderthals

 

 

The Neanderthals

One of the descendants of this sub-species, the Homo sapiens neanderthalensis (or the Neanderthals), which may have arisen 300 000 years ago or more, had a cranial capacity higher than the actual humans’, but it is thought that their brains were organized in a different way. They were the first humans to live under the harsh conditions of the glaciations, which may have determined the evolution of their physiognomy, particularly the prominent foreheads and noses.

The Neanderthals would have reached a much more complex culture, inside which the weakest and sick elements would have the support of their mates. The deads were buried together with tools and food, which indicates the practice of funerary rituals and the existence of religious beliefs. They possessed a form of spoken language, although their physiognomy didn’t allow them yet the production of a sounds’ set as broad as the modern human’s physiology does. They had knowledge about the medicinal plants and they created the Mousterian culture on tools’ manufacture, which appeared for the first time about 200 000 years ago. These tools were manufactured in several phases, so that bigger and, sometimes, dented (saws) cutting surfaces were carved. Among the tools that were produced, they included axes, knives, scrapers and the tips used in spears. They were used to prepare skins, to cut the meat, to hunt, to saw wood, etc. There are signs that they proceeded to the periodic maintenance of the tools, which suggests that the tools were used during long time periods. They built huts of wood, stone and animal skins, with central fireplaces. The Neanderthals were also the first artists, in spite of being accused of non-imaginative people: they made musical instruments (as flutes made out of bones) and other artifacts with symbolic meanings.

About 28 000 years ago, the Neanderthals disappeared, but is not well known why that happened. It’s possible that the Homo sapiens sapiens (a sub-species relative to the Neanderthals, to which we all belong), which presumably migrated from Africa, had in some way interbred with the Neanderthals during the long period when they co-existed in the same regions. This hypothesis is favoured by the discovery of what seems to be the skeleton of a 24 000-year old hybrid child in a rock-shelter site called Lagar Velho, in Portugal. It’s also quite possible that the competition exerted by the Homo sapiens sapiens (which, compared to the Neanderthals, held competitive advantages at diverse levels, namely the more developed imaginative capability – the Neanderthals spent terribly long periods of time using the same techniques, contrarily to the modern humans), along with the glaciation that was intensified during that time, had driven this human sub-species to the extinction (the last Neanderthal fossils were found in Gibraltar, at the very end of Europe).

 

Neanderthals: the burial of the man of Shanidar (Richard Leakey, Roger Lewin)

 

Tools from the Mousterian culture

  

 

Homo sapiens sapiens

The most ancient known fossil of the Homo sapiens sapiens dates from 130 000 years ago. Until recently it was considered a species native of Africa, but today it’s thought that it could have evolved simultaneously in Asia or could be the result of migrations from Africa that occurred much earlier than 100 000 years ago, as it was traditionally thought. Those hypotheses could, for instance, explain why some Australian fossils date from 60 000 years ago (20 000 years more than it would be expected if it was a sub-species that had come out of Africa in a single migration 100 000 years ago). The Homo sapiens sapiens is linked to the culture of the Superior Paleolithic, dominant between 40 000 and 12 000 thousand years ago. It was a culture that was originated independently in Asia and (90 000 years ago) in Africa. The appearance of this culture represented an increase in the complexity of the tools’ manufacture techniques. The clothes (sewed with needles), the dwellings (whose construction included the clay and/or mammoth bones and skins), the adornments, the medicine, the nutrition and the ritual practiced were very refined during this epoch. New forms of art emerged (sculpture – like the figures linked to fertility – and painting – scenes recreated at the walls of the caves that were cult places), different regional cultures began to become distinct and the earliest hierarchies and social and labour divisions appeared, resulting from the new industries associated to this culture.

 

Religious cult in the cave of Lascaux (Washington State University)

 

 

The Dawn of Civilization

 

Neolithic

About 12 000 years ago, at the beginning of the Neolithic, a new cultural revolution started to come, when the traditional style of life consisting in hunting and recollecting was replaced by the agriculture, cattle domestication and sedentarization of the populations in villages formed by houses built with bricks (replacing the previously prevailing nomadism).

The agricultural excesses that started to accumulate led to the construction of warehouses useful in shortage periods, to the appearance of trade (where the excesses were exchanged by other products, agricultural or not) and released work force to constitute armies, build temples and fortifications, etc. At last, they paved the way for the foundation of new social classes like the metallurgists (when the metal fusion was discovered, 8000 years ago) and other artisans, civil clerks, warriors, clergymen and rulers.

 

Neolithic scene (Conhecer Universal, Editora Abril S.A.)

 

At the end of the Neolithic big stone monuments (megaliths) were lifted in several places of Europe and they are thought to have had funerary and religious meanings (the religion was still very linked to the natural elements, particularly the astronomical objects).

 

Historic Epoch

About 5000 years ago finally started to appear (in Mesopotamia (now Iraq) and, later, in Egypt, India and China) the earliest large towns and it was invented the writing, which allowed the humans to accumulate an unprecedented quantity of knowledge. There emerged theocratic states (ruled by semi-gods and clergymen), the first legal codes, the first literary works and artistic objects made of precious metals.

From then on, the arts, the sciences and techniques, the philosophy and the spirituality tended to improve quickly across the successive civilizations. In the case of Europe the graeco-roman civilization was followed by the middle ages (more advanced than the previous one in some aspects but less advanced in others) and the renaissance. The evolution accelerated when about 400 years ago Galileo defended that the Earth orbited around the Sun (beginning a scientific revolution that lasts until today), when about 250 years ago the textile industry was mechanized by the first industrial revolution and when about 200 years ago new ideas about the structure of the society started to be endorsed by the American independence (1776) and the French revolution (1789).

 

Photography taken in Varanasi (sacred Indian city) in 1865 (Library of Congress, Washington D.C.)

 

Today, so few decades later, the humans dominate the physics of the atom, build increasingly powerful computers, prevent and cure illnesses that were lethal just a few centuries ago, explore the extraterrestrial space, study their own nature through sciences like genetics or neurology, create democratic states and international cooperation organizations and continuously found new cultural and social movements. What the future reserves for us will depend on our capability for using the technology in the benefit of the living beings that inhabit this planet or, contrarily, to use it with self-destruction purposes.

 

 

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