Human intelligence
The evolution of human intelligence is closely tied to the evolution of the human brain and to the origin of language. The timeline of human evolution spans approximately 7 million years from the separation of the Pan genus until the emergence of behavioral modernity by 50,000 years ago. The first 3 million years of this timeline concern Sahelanthropus, the following 2 million concern Australopithecus and the final 2 million span the history of actual human genus in the Paleolithic era. Many traits of human intelligence, such as empathy, theory of mind, mourning, ritual, and the use of symbols and tools, are apparent in great apes although in less sophisticated forms than found in humans, such as great ape language. A 2008 study argues that human cleverness is simply selected within the context of sexual selection as an honest signal of genetic resistance against parasites and pathogens. The number of people with severe cognitive impairment caused by childhood viral infections like meningitis, protists like Toxoplasma and Plasmodium, and animal parasites like intestinal worms and schistosomes is estimated to be in the hundreds of millions. Even more people live with moderate mental damages, such as inability to complete difficult tasks, that are not classified as ‘diseases’ by medical standards, may still be considered as inferior mates by potential sexual partners. Thus, widespread, virulent, and archaic infections are greatly involved in natural selection for cognitive abilities. People infected with parasites may have brain damage and obvious maladaptive behavior in addition to visible signs of disease. Smarter people can more skillfully learn to distinguish safe non-polluted water and food from unsafe kinds and learn to distinguish mosquito infested areas from safe areas. Smarter people can more skillfully find and develop safe food sources and living environments. Given this situation, preference for smarter child-bearing/rearing partners increases the chance that their descendants will inherit the best resistance alleles, not only for immune system resistance to disease, but also smarter brains for learning skills in avoiding disease and selecting nutritious food. When people search for mates based on their success, wealth, reputation, disease-free body appearance, or psychological traits such as benevolence or confidence; the effect is to select for superior intelligence that results in superior disease resistance.
Human evolution is the evolutionary process that led to the emergence of anatomically modern humans. The topic typically focuses on the evolutionary history of the primates—in particular the genus Homo, and the emergence of Homo sapiens as a distinct species of the hominids (or great apes) rather than studying the earlier history that led to the primates. The study of human evolution involves many scientific disciplines, including physical anthropology, primatology, archaeology, paleontology, neurobiology, ethology, linguistics, evolutionary psychology, embryology and genetics. Genetic studies show that primates diverged from other mammals about 85 million years ago, in the Late Cretaceous period, and the earliest fossils appear in the Paleocene, around 55 million years ago. Within the Hominoidea (apes) superfamily, the Hominidae family diverged from the Hylobatidae (gibbon) family some 15–20 million years ago; African great apes (subfamily Homininae) diverged from orangutans (Ponginae) about 14 million years ago; the Hominini tribe (humans, Australopithecines and other extinct biped genera, and chimpanzees) parted from the Gorillini tribe (gorillas) between 9 million years ago and 8 million years ago; and, in turn, the subtribes Hominina (humans and biped ancestors) and Panina (chimps) separated about 7.5 million years ago to 5.6 million years ago.
The basic adaptation of the hominin line is bipedalism. The earliest bipedal hominin is considered to be either Sahelanthropus or Orrorin; alternatively, either Sahelanthropus or Orrorin may instead be the last shared ancestor between chimps and humans. Ardipithecus, a full biped, arose somewhat later, and the early bipeds eventually evolved into the australopithecines, and later into the genus Homo.
The earliest documented representative of the genus Homo is Homo habilis, which evolved around 2.8 million years ago, and is arguably the earliest species for which there is positive evidence of the use of stone tools. The brains of these early hominins were about the same size as that of a chimpanzee, although it has been suggested that this was the time in which the human SRGAP2 gene doubled, producing a more rapid wiring of the frontal cortex. During the next million years a process of rapid encephalization occurred, and with the arrival of Homo erectus and Homo ergaster in the fossil record, cranial capacity had doubled to 850 cm3. (Such an increase in human brain size is equivalent to each generation having 125,000 more neurons than their parents.) It is believed that Homo erectus and Homo ergaster were the first to use fire and complex tools, and were the first of the hominin line to leave Africa, spreading throughout Africa, Asia, and Europe between 1.3 to 1.8 million years ago.
According to the recent African origin of modern humans theory, modern humans evolved in Africa possibly from Homo heidelbergensis, Homo rhodesiensis or Homo antecessor and migrated out of the continent some 50,000 to 100,000 years ago, gradually replacing local populations of Homo erectus, Denisova hominins, Homo floresiensis and Homo neanderthalensis. Archaic Homo sapiens, the forerunner of anatomically modern humans, evolved in the Middle Paleolithic between 400,000 and 250,000 years ago. Recent DNA evidence suggests that several haplotypes of Neanderthal origin are present among all non-African populations, and Neanderthals and other hominins, such as Denisovans, may have contributed up to 6% of their genome to present-day humans, suggestive of a limited inter-breeding between these species. The transition to behavioral modernity with the development of symbolic culture, language, and specialized lithic technology happened around 50,000 years ago according to some anthropologists although others point to evidence that suggests that a gradual change in behavior took place over a longer time span.
Human consciousness
Humans are born with a rudimentary consciousness that matures with age. The baseline for what most humans consider consciousness includes the ability to think abstractly in words and form strong memories. Humans begin to think in words and abstract concepts around age 3, and are forming strong memories by that time. Somewhere between age 2 and 3 humans start using words to form logical connections, this is where the fundamentals of adult human consciousness begin.
All in the Mind
The key to this alternative view is the fact that all our experiences—all our perceptions, sensations, dreams, thoughts and feelings—are forms appearing in consciousness. It doesn't always seem that way. When I see a tree it seems as if I am seeing the tree directly. But science tells us something completely different is happening. Light entering the eye triggers chemical reactions in the retina, these produce electro-chemical impulses which travel along nerve fibers to the brain. The brain analyses the data it receives, and then creates its own picture of what is out there. I then have the experience of seeing a tree. But what I am actually experiencing is not the tree itself, only the image that appears in the mind. This is true of everything I experience. Everything we know, perceive, and imagine, every color, sound, sensation, every thought and every feeling, is a form appearing in the mind. It is all an in-forming of consciousness.
The idea that we never experience the physical world directly has intrigued many philosophers. Most notable was the eighteenth-century German philosopher Immanual Kant, who drew a clear distinction between the form appearing in the mind—what he called the phenomenon (a Greek word meaning "that which appears to be")—and the world that gives rise to this perception, which he called the noumenon (meaning “that which is apprehended"). All we know, Kant insisted, is the phenomenon. The noumenon, the “thing-in-itself,” remains forever beyond our knowing.
