(Reconstructed skull of Peking Man, a representative of the extinct species believed to be the nearest ancestor of Homo sapiens, Homo erectus.
Reconstructed skull of Peking Man, a representative of the extinct species believed to be the nearest ancestor of Homo sapiens, Homo Erectus )
Reconstructed skull of Peking Man, a representative of the extinct species believed to be the nearest ancestor of Homo sapiens, Homo Erectus )
The scientific study of human evolution encompasses the development of the genus Homo, but usually involves studying other hominids and hominines as well, such as Australopithecus. "Modern humans" are defined as the Homo sapiens species, of which the only extant subspecies is Homo sapiens sapiens; Homo sapiens idaltu (roughly translated as "elder wise man"), the other known subspecies, is extinct.[3] Anatomically modern humans appear in the fossil record in Africa about 130,000 years ago.[4][5]
The closest living relatives of Homo sapiens are the two species of chimpanzee: the Bonobo (Pan paniscus) and the Common Chimpanzee (Pan troglodytes). The two species are equally close (they share the same common ancestor), the main difference between them is the social organization: matriarchal for the Bonobo and patriarchal for the Common Chimpanzee.[6] Full genome sequencing resulted in the conclusion that "after 6.5 [million] years of separate evolution, the differences between bonobo/chimpanzee and human are just 10 times greater than those between two unrelated people and 10 times less than those between rats and mice". In fact, 98.4% of the DNA sequence is identical between the two Pan species and human.[6][7][8][9] It has been estimated that the human lineage diverged from that of chimpanzees about five million years ago, and from gorillas about eight million years ago. However, a hominid skull discovered in Chad in 2001, classified as Sahelanthropus tchadensis, is approximately seven million years old, which may indicate an earlier divergence.[10]
There are two prominent scientific theories of the origins of contemporary humans. They concern the relationship between modern humans and other hominids. The single-origin, or "out-of-Africa", hypothesis proposes that modern humans evolved in Africa and later migrated outwards to replace hominids in other parts of the world. The multiregional hypothesis, on the other hand, proposes that modern humans evolved, at least in part, from independent hominid populations.[11]
Geneticists Lynn Jorde and Henry Harpending of the University of Utah proposed that the variation in human DNA is minute compared to that of other species, and that during the Late Pleistocene, the human population was reduced to a small number of breeding pairs — no more than 10,000 and possibly as few as 1,000 — resulting in a very small residual gene pool. Various reasons for this hypothetical bottleneck have been postulated, the most popular being the Toba catastrophe theory.
Human evolution is characterized by a number of important physiological trends, including the expansion of the brain cavity and brain itself, which is typically 1,400 cm³ in volume, over twice that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differs from that of other apes (heterochrony), allowing for an extended period of social learning and language acquisition in juvenile humans. Physical anthropologists argue that a reorganization of the structure of the brain is more important than cranial expansion itself. Other significant evolutionary changes included a reduction of the canine tooth, development of bipedal locomotion, and the descent of the larynx and hyoid bone, making speech possible. How these trends are related and what their role is in the evolution of complex social organization and culture are matters of ongoing debate.[12][13]
Rise of civilization
The rise of agriculture led to the foundation of stable human settlements.The rise of agriculture led to the foundation of stable human settlements.
The most widely accepted view among current anthropologists is that Homo sapiens originated in the African savanna around 200,000 BP (Before Present), descending from Homo erectus, had colonized Eurasia and Oceania by 40,000 BP, and finally colonized the Americas approximately 10,000 years ago.[14] They displaced Homo neanderthalensis and other species descended from Homo erectus (which had colonized Eurasia as early as 2 million years ago) through more successful reproduction and competition for resources.
The earliest humans were hunter-gatherers, a lifestyle well-suited to the savanna. They generally lived in small, nomadic groups. Around 10,000 years ago, the advent of agriculture prompted the Neolithic Revolution. Access to a stable food source led to the formation of permanent human settlements, the domestication of animals, and the use of metal tools. Agriculture also encouraged trade and cooperation, leading to complex societies. Villages developed into thriving civilizations in regions such as the Middle East's Fertile Crescent.
Around 6,000 years ago, the first proto-states developed in Mesopotamia, Egypt and the Indus Valley. Military forces were formed for protection, and government bureaucracies for administration. States cooperated and competed for resources, in some cases waging wars. Around 2,000 – 3,000 years ago, some states, such as Persia, China, and Rome, developed through conquest into the first expansive empires. Influential religions, such as the Abrahamic and Dharmic religions, also rose to prominence at this time.
The late Middle Ages saw the rise of revolutionary ideas and technologies. In China, an advanced and urbanized economy promoted innovations such as printing and the compass, while the Islamic Golden Age saw major scientific advancements in Muslim empires. In Europe, the rediscovery of classical learning and inventions such as the printing press led to the Renaissance in the 14th century. Over the next 500 years, exploration and imperialistic conquest brought much of the Americas, Asia, and Africa under European control, leading to later struggles for independence. The Scientific Revolution in the 17th century and the Industrial Revolution in the 18th – 19th centuries promoted major innovations in transport, such as the railway and automobile; energy development, such as coal and electricity; and government, such as representative democracy and Communism.
As a result of such changes, modern humans live in a world that has become increasingly globalized and interconnected. Although this has encouraged the growth of science, art, and technology, it has also led to culture clashes, the development and use of weapons of mass destruction, and increased environmental destruction and pollution.
Map of early human migrations according to mitochondrial population genetics (The arctic is at the centre of the map and the numbers are millennia before present).
