Hominid intelligence
Encyclopedia
The evolution of human intelligence refers to a set of theories that attempt to explain how human intelligence
has evolved
. These theories are closely tied to the evolution
of the human brain
and to the emergence of human 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
species (the Paleolithic
).
Many traits of human intelligence, such as empathy
, theory of mind
, mourning
, ritual
, and the use of symbols
and tool
s, are already apparent in great apes although in lesser sophistication than in humans.
The great apes show considerable abilities for cognition
and empathy
.
Chimpanzee
s make tools and use them to acquire foods and for social displays; they have sophisticated hunting
strategies requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception
; they can learn to use symbol
s and understand aspects of human language
including some relational syntax, concepts of number and numerical sequence.
In one study, young chimpanzees outperformed human college students in tasks requiring remembering numbers. This claim was refuted in a later study after it was noted that the chimpanzees had received extensive practice with the task while the students were evaluated on their first attempt. When human subjects were given time to practice, they substantially outperformed the young chimps. Chimpanzees are capable of empathy, having been observed to feed turtle
s in the wild, and show curiosity in wildlife (such as pythons).
Homininae
Around 10 million years ago, the Earth's climate entered a cooler and drier phase, which led eventually to the ice ages
beginning some 2.6 million years ago. One consequence of this was that the north African tropical forest began to retreat, being replaced first by open grasslands and eventually by desert
(the modern Sahara
). This forced tree-dwelling animals to adapt to their new environment or die out. As their environment changed from continuous forest to patches of forest separated by expanses of grassland, some primates adapted to a partly or fully ground-dwelling life. Here they were exposed to predators, such as the big cats, from whom they had previously been safe.
Some Hominina
(Australopithecines) adapted to this challenge by adopting bipedalism: walking on their hind legs. This gave their eyes greater elevation and the ability to see approaching danger further off. It also freed the forelimbs (arms) from the task of walking and made the hands available for tasks such as gathering food. At some point the bipedal primate
s developed handedness
, giving them the ability to pick up sticks, bone
s and stones and use them as weapon
s, or as tool
s for tasks such as killing smaller animals, cracking nut
s, or cutting up carcasses
. In other words, these primates developed the use of primitive technology
. Bipedal tool-using primates form the Hominina
subtribe, of which the earliest species, such as Sahelanthropus tchadensis
, date to about 7 to 5 million years ago.
From about 5 million years ago, the Hominin brain began to develop rapidly in both size and differentiation of function.
It has been shown that Great Ape cooperation and communication is severely impeded by their competitiveness, and thus that the apes would revolutionize their culture-bearing ability if they could just shrug off their competitiveness. It is also well known that even early hominins lacked the size and sharpness of their canine teeth that apes use as a threat signal, suggesting prehumans simply had no use for threat signals. That means they had already transcended ape competitiveness and thus developed superior cooperation and communication.
The paradox of Homo floresiensis. There has been a gradual increase in brain volume as we progressed along the Human timeline of evolution (see Homininae
), starting from about 600 cm3 in Homo habilis
up to 1500 cm3 in Homo sapiens neanderthalensis. Thus, in general there's a correlation between brain volume and intelligence. However, modern Homo sapiens have a brain volume slightly smaller (1250 cm3) than neanderthals, women have a brain volume slightly smaller than men and the Flores hominids (Homo floresiensis
), nicknamed hobbits, had a cranial capacity of about 380 cm3 (considered small for a chimpanzee) about a third of that of H. erectus
. It is proposed that they evolved from H. erectus as a case of insular dwarfism. With their three times smaller brain the Flores hominids apparently used fire and made tools as sophisticated as those of their ancestor H.erectus. In this case, it seems that for intelligence, the structure of the brain is more important than its volume.
had appeared in East Africa
: the first known human
species, and the first known to make stone tool
s.
The use of tools conferred a crucial evolutionary advantage, and required a larger and more sophisticated brain to co-ordinate the fine hand movements required for this task.
The evolution of a larger brain created a problem for early humans, however. A larger brain requires a larger skull
, and thus requires the female
to have a wider birth canal for the newborn's larger skull to pass through. But if the female's birth canal grew too wide, her pelvis
would be so wide that she would lose the ability to run: still a necessary skill in the dangerous world of 2 million years ago.
The solution to this was to give birth at an early stage of fetal development, before the skull grew too large to pass through the birth canal.
This adaptation enabled the human brain to continue to grow, but it imposed a new discipline
. The need to care for helpless infants for long periods of time forced humans to become less mobile . Human bands increasingly stayed in one place for long periods, so that females could care for infants, while males hunted food and fought with other bands that competed for food sources . As a result, humans became even more dependent on tool-making to compete with other animals and other humans, and relied less on body size and strength .
About 200,000 years ago Europe
and the Middle East
were colonized by Neanderthal man
, extinct by 20,000 following the appearance of modern humans in the region from 40,000 years ago.
Around 200,000 years ago, Homo sapiens first appears in East Africa
. It is unclear to what extent these early modern humans had developed language
, music, religion
etc. They spread throughout Africa
over the following 50,000 years or so.
According to proponents of the Toba catastrophe theory
, the climate in non-tropical regions of the earth experienced a sudden freezing about 70,000 years ago, because of a huge explosion of the Toba volcano that filled the atmosphere with volcanic ash for several years. This reduced the human population to less than 10,000 breeding pairs in equatorial Africa, from which all modern humans are descended. Being unprepared for the sudden change in climate, the survivors were those intelligent enough to invent new tools and ways of keeping warm and finding new sources of food (for example, adapting to ocean fishing based on prior fishing skills used in lakes and streams that became frozen).
Around 80–100,000 years ago, three main lines of Homo sapiens diverged, bearers of mitochondrial haplogroup L1
(mtDNA) / A
(Y-DNA) colonizing Southern Africa
(the ancestors of the Khoisan
/Capoid
peoples), bearers of haplogroup L2
(mtDNA) / B
(Y-DNA) settling Central
and West Africa
(the ancestors of Niger–Congo and Nilo-Saharan speaking peoples), while the bearers of haplogroup L3
remained in East Africa.
The "Great Leap Forward" leading to full behavioral modernity
sets in only after this separation. Rapidly increasing sophistication in tool-making and behaviour is apparent from about 80,000 years ago, and the migration out of Africa follows towards the very end of the Middle Paleolithic
, some 60,000 years ago. Fully modern behaviour, including figurative art
, music
, self-ornamentation, trade
, burial rites etc. is evident by 30,000 years ago. The oldest unequivocal examples of prehistoric art
date to this period, the Aurignacian
and the Gravettian
periods of prehistoric Europe
, such as the Venus figurines
and cave painting
(Chauvet Cave
) and the earliest musical instruments
(the bone pipe of Geissenklösterle, Germany
, dated to about 36,000 years ago).
, who argues that human intelligence did not evolve primarily as a means to solve ecological problems, but rather intelligence evolved as a means of surviving and reproducing in large and complex social groups. Some of the behaviors associated with living in large groups include reciprocal altruism, deception and coalition formation. These group dynamics relate to Theory of Mind
or the ability to understand the thoughts and emotions of others, though Dunbar himself admits in the same book that it is not the flocking itself that causes intelligence to evolve (as shown by ruminant
s).
Dunbar argues that when the size of a social group increases, the number of different relationships in the group may increase by orders of magnitude. Chimpanzees live in groups of about 50 individuals whereas humans typically have a social circle of about 150 people, which is now referred to as Dunbar's number
. According to the social brain hypothesis, when hominids started living in large groups, selection favored greater intelligence. As evidence, Dunbar cites a relationship between neocortex size and group size of various mammals. Howewer, meerkat
s have far more social relationships than their small brain capacity would suggest. Another hypothesis is that it is actually intelligence that causes social relationships to become more complex, because intelligent individuals are more difficult to learn to know.
There are also studies that show that Dunbar's number is not the upper limit of the number of social relationships in humans either.
who argues that human intelligence is unnecessarily sophisticated for the needs of hunter-gatherers to survive. He argues that the manifestations of intelligence such as language, music and art did not evolve because of their utilitarian value to the survival of ancient hominids. Rather, intelligence may have been a fitness indicator. Hominids would have been selected for greater intelligence as a proxy for healthy genes and a positive feedback loop of sexual selection would have led to the evolution of human intelligence in a relatively short period.
A sexual selection theory must explain why both sexes are intelligent. In many species, only males have impressive ornaments and show-off behavior. Sexual selection is also thought to be able to act on both males and females in species that are at least partially monogamous. With complete monogamy, there is assortative mating
for sexually selected traits. This means that less attractive individuals will find other less attractive individuals to mate with. If attractive traits are good fitness indicators, this means that sexual selection increases the genetic load of the offspring of unattractive individuals. Without sexual selection, an unattractive individual might find a superior mate with few deleterious mutations, and have healthy children that are likely to survive. With sexual selection, an unattractive individual is more likely to have access only to an inferior mate who is likely to pass on many deleterious mutations to their joint offspring, who are then less likely to survive.
Sexual selection is often thought to be a likely explanation for other female-specific human traits, for example breasts and buttocks far larger in proportion to total body size than those found in related species of ape. It is often assumed that if breasts and buttocks of such large size were necessary for functions such as suckling infants, they would be found in other species. Growing human brains require more nutrition than brains of related species of ape. Human males find human female breasts attractive, in agreement with sexual selection acting on human females.
Sexual selection for intelligence and judging ability can act on indicators of success, such as highly visible displays of wealth (cattle, farmland, servants, etc.). It is possible that for females to successfully judge male intelligence, they must be intelligent themselves. This could explain why despite the absence of clear differences in intelligence between males and females on average, there are clear differences between male and female propensities to display their intelligence in ostentatious forms.
. According to the model, human intelligence was able to evolve to significant levels because of the combination of increasing domination over habitat
and increasing importance of social interactions. As a result the primary selective pressure for increasing human intelligence shifted from learning to master the natural world
to competition for dominance among members or groups of its own species.
As advancement, survival and reproduction within an increasing complex social structure favored ever more advanced social skills, communication
of concepts through increasingly complex language patterns ensued. Since competition had shifted bit by bit from controlling "nature" to influencing other humans, it became of relevance to outmaneuver other members of the group seeking leadership
or acceptance
, by means of more advanced social skills. A more social and communicative person would be more easily selected.
Studies of chimpanzees show that they cooperate well in conflictless situations but not in situations with conflict, so human cooperativeness cannot have evolved to form coalitions against each other.
and large brains are costly in terms of nutrient
and oxygen
requirements. Thus the direct adaptive benefit of human intelligence is questionable at least in modern societies, while it is difficult to study in prehistoric societies. However, alleles coding for even larger human brains are spreading continuously even in modern societies This suggests that humans of higher intellect may gain indirect selective benefits.
A recent study argues that human cleverness is simply selected within the context of sexual selection
as an honest signal of genetic resistance against parasites
and pathogen
s. The number of people living with cognitive abilities seriously damaged by childhood infections is high; estimated in hundreds of millions. Even more people live with moderate mental damages, that are not classified as ‘diseases’ by medical standards, who may still be considered as inferior mates by potential sexual partners. Pathogens currently playing a major role in this global challenge against human cognitive capabilities include viral infections like meningitis
, protist
s like Toxoplasma and Plasmodium
, and animal parasites like intestinal worms and Schistosomes.
Thus, widespread, virulent, and archaic infections are greatly involved. Given this situation, our sexual preferences for clever partners increase the chance that our descendants will inherit the best resistance alleles. Like some people search for mates based on their bodily beauty, height, or social position (e.g. wealth or fame), or psychological traits such as benevolence or confidence; people are just searching for signals of good resistance genes. Intelligence appears to be one of these signals. But the term intelligence used for humans is ill-defined.
theory contends that organism characteristics that provide benefits to a group (clan, tribe, or larger population) can evolve despite individual disadvantages such as those cited above. The group benefits of intelligence (including language, the ability to communicate between individuals, the ability to teach others, and other cooperative aspects) have apparent utility in increasing the survival potential of a group.
, zinc
, protein
, iodine
, B vitamins
, omega 3 fatty acids, magnesium
and other nutrients can result in lower intelligence either in the mother during pregnancy or in the child during development. While these inputs did not have an effect on the evolution of intelligence they do govern its expression. A higher intelligence could be a signal that an individual comes from and lives in a physical and social environment where nutrition levels are high, whereas a lower intelligence could imply a child (and/or the child's mother) comes from a physical and social environment where nutritional levels are low. Previc emphasizes the contribution of nutritional factors, especially meat and shellfish consumption, to elevations of dopaminergic activity in the brain, which may have been responsible for the evolution of human intelligence since dopamine is crucial to working memory, cognitive shifting, abstract, distant concepts, and other hallmarks of advanced intelligence.
Intelligence
Intelligence has been defined in different ways, including the abilities for abstract thought, understanding, communication, reasoning, learning, planning, emotional intelligence and problem solving....
has evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. These theories are closely tied to the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
of the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
and to the emergence of human language
Origin of language
The origin of language is the emergence of language in the human species. This is a highly controversial topic. Empirical evidence is so limited that many regard it as unsuitable for serious scholars. In 1866, the Linguistic Society of Paris went so far as to ban debates on the subject...
.
The timeline of human evolution
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
spans approximately 7 million years, from the separation of the Pan
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
genus until the emergence of behavioral modernity
Behavioral modernity
Behavioral modernity is a term used in anthropology, archeology and sociology to refer to a set of traits that distinguish present day humans and their recent ancestors from both living primates and other extinct hominid lineages. It is the point at which Homo sapiens began to demonstrate a...
by 50,000 years ago. The first 3 million years of this timeline concern Sahelanthropus
Sahelanthropus tchadensis
Sahelanthropus tchadensis is an extinct hominid species that is dated to about . Whether it can be regarded as part of the Hominina tree is unclear; there are arguments both supporting and rejecting it...
, the following 2 million concern Australopithecus
Australopithecus
Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...
and the final 2 million span the history of actual human
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....
species (the Paleolithic
Paleolithic
The Paleolithic Age, Era or Period, is a prehistoric period of human history distinguished by the development of the most primitive stone tools discovered , and covers roughly 99% of human technological prehistory...
).
Many traits of human intelligence, such as empathy
Empathy
Empathy is the capacity to recognize and, to some extent, share feelings that are being experienced by another sapient or semi-sapient being. Someone may need to have a certain amount of empathy before they are able to feel compassion. The English word was coined in 1909 by E.B...
, theory of mind
Theory of mind
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own...
, mourning
Mourning
Mourning is, in the simplest sense, synonymous with grief over the death of someone. The word is also used to describe a cultural complex of behaviours in which the bereaved participate or are expected to participate...
, ritual
Ritual
A ritual is a set of actions, performed mainly for their symbolic value. It may be prescribed by a religion or by the traditions of a community. The term usually excludes actions which are arbitrarily chosen by the performers....
, and the use of symbols
Great Ape language
Research into non-human great ape language has involved teaching chimpanzees, bonobos, gorillas, and orangutans to communicate with human beings and with each other using sign language, physical tokens, and lexigrams; see Yerkish...
and tool
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
s, are already apparent in great apes although in lesser sophistication than in humans.
Hominidae
The great apes show considerable abilities for cognition
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...
and empathy
Empathy
Empathy is the capacity to recognize and, to some extent, share feelings that are being experienced by another sapient or semi-sapient being. Someone may need to have a certain amount of empathy before they are able to feel compassion. The English word was coined in 1909 by E.B...
.
Chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s make tools and use them to acquire foods and for social displays; they have sophisticated hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...
strategies requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception
Deception
Deception, beguilement, deceit, bluff, mystification, bad faith, and subterfuge are acts to propagate beliefs that are not true, or not the whole truth . Deception can involve dissimulation, propaganda, and sleight of hand. It can employ distraction, camouflage or concealment...
; they can learn to use symbol
Symbol
A symbol is something which represents an idea, a physical entity or a process but is distinct from it. The purpose of a symbol is to communicate meaning. For example, a red octagon may be a symbol for "STOP". On a map, a picture of a tent might represent a campsite. Numerals are symbols for...
s and understand aspects of human language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
including some relational syntax, concepts of number and numerical sequence.
In one study, young chimpanzees outperformed human college students in tasks requiring remembering numbers. This claim was refuted in a later study after it was noted that the chimpanzees had received extensive practice with the task while the students were evaluated on their first attempt. When human subjects were given time to practice, they substantially outperformed the young chimps. Chimpanzees are capable of empathy, having been observed to feed turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s in the wild, and show curiosity in wildlife (such as pythons).
HomininaeHomininaeHomininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
Around 10 million years ago, the Earth's climate entered a cooler and drier phase, which led eventually to the ice agesQuaternary glaciation
Quaternary glaciation, also known as the Pleistocene glaciation, the current ice age or simply the ice age, refers to the period of the last few million years in which permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets have occurred elsewhere...
beginning some 2.6 million years ago. One consequence of this was that the north African tropical forest began to retreat, being replaced first by open grasslands and eventually by desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
(the modern Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
). This forced tree-dwelling animals to adapt to their new environment or die out. As their environment changed from continuous forest to patches of forest separated by expanses of grassland, some primates adapted to a partly or fully ground-dwelling life. Here they were exposed to predators, such as the big cats, from whom they had previously been safe.
Some Hominina
Hominina
The more anthropomorphic primates of the Hominini tribe are placed in the Hominina subtribe. Referred to as hominans, they are characterized by the evolution of an increasingly erect bipedal locomotion. The only extant species is Homo sapiens...
(Australopithecines) adapted to this challenge by adopting bipedalism: walking on their hind legs. This gave their eyes greater elevation and the ability to see approaching danger further off. It also freed the forelimbs (arms) from the task of walking and made the hands available for tasks such as gathering food. At some point the bipedal primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s developed handedness
Handedness
Handedness is a human attribute defined by unequal distribution of fine motor skills between the left and right hands. An individual who is more dexterous with the right hand is called right-handed and one who is more skilled with the left is said to be left-handed...
, giving them the ability to pick up sticks, bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s and stones and use them as weapon
Weapon
A weapon, arm, or armament is a tool or instrument used with the aim of causing damage or harm to living beings or artificial structures or systems...
s, or as tool
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
s for tasks such as killing smaller animals, cracking nut
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...
s, or cutting up carcasses
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
. In other words, these primates developed the use of primitive technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
. Bipedal tool-using primates form the Hominina
Hominina
The more anthropomorphic primates of the Hominini tribe are placed in the Hominina subtribe. Referred to as hominans, they are characterized by the evolution of an increasingly erect bipedal locomotion. The only extant species is Homo sapiens...
subtribe, of which the earliest species, such as Sahelanthropus tchadensis
Sahelanthropus tchadensis
Sahelanthropus tchadensis is an extinct hominid species that is dated to about . Whether it can be regarded as part of the Hominina tree is unclear; there are arguments both supporting and rejecting it...
, date to about 7 to 5 million years ago.
From about 5 million years ago, the Hominin brain began to develop rapidly in both size and differentiation of function.
It has been shown that Great Ape cooperation and communication is severely impeded by their competitiveness, and thus that the apes would revolutionize their culture-bearing ability if they could just shrug off their competitiveness. It is also well known that even early hominins lacked the size and sharpness of their canine teeth that apes use as a threat signal, suggesting prehumans simply had no use for threat signals. That means they had already transcended ape competitiveness and thus developed superior cooperation and communication.
The paradox of Homo floresiensis. There has been a gradual increase in brain volume as we progressed along the Human timeline of evolution (see Homininae
Homininae
Homininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
), starting from about 600 cm3 in Homo habilis
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
up to 1500 cm3 in Homo sapiens neanderthalensis. Thus, in general there's a correlation between brain volume and intelligence. However, modern Homo sapiens have a brain volume slightly smaller (1250 cm3) than neanderthals, women have a brain volume slightly smaller than men and the Flores hominids (Homo floresiensis
Homo floresiensis
Homo floresiensis is a possible species, now extinct, in the genus Homo. The remains were discovered in 2003 on the island of Flores in Indonesia. Partial skeletons of nine individuals have been recovered, including one complete cranium...
), nicknamed hobbits, had a cranial capacity of about 380 cm3 (considered small for a chimpanzee) about a third of that of H. erectus
H. erectus
H. erectus may refer to:* Homo erectus, an extinct hominid species* Hippocampus erectus, a seahorse species from the Western Atlantic-See also:* H. erecta * Erectus...
. It is proposed that they evolved from H. erectus as a case of insular dwarfism. With their three times smaller brain the Flores hominids apparently used fire and made tools as sophisticated as those of their ancestor H.erectus. In this case, it seems that for intelligence, the structure of the brain is more important than its volume.
Homo
By 2.4 million years ago Homo habilisHomo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
had appeared in East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
: the first known human
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....
species, and the first known to make stone tool
Stone tool
A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric, particularly Stone Age cultures that have become extinct...
s.
The use of tools conferred a crucial evolutionary advantage, and required a larger and more sophisticated brain to co-ordinate the fine hand movements required for this task.
The evolution of a larger brain created a problem for early humans, however. A larger brain requires a larger skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
, and thus requires the female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
to have a wider birth canal for the newborn's larger skull to pass through. But if the female's birth canal grew too wide, her pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
would be so wide that she would lose the ability to run: still a necessary skill in the dangerous world of 2 million years ago.
The solution to this was to give birth at an early stage of fetal development, before the skull grew too large to pass through the birth canal.
This adaptation enabled the human brain to continue to grow, but it imposed a new discipline
Discipline
In its original sense, discipline is referred to systematic instruction given to disciples to train them as students in a craft or trade, or to follow a particular code of conduct or "order". Often, the phrase "to discipline" carries a negative connotation. This is because enforcement of order –...
. The need to care for helpless infants for long periods of time forced humans to become less mobile . Human bands increasingly stayed in one place for long periods, so that females could care for infants, while males hunted food and fought with other bands that competed for food sources . As a result, humans became even more dependent on tool-making to compete with other animals and other humans, and relied less on body size and strength .
About 200,000 years ago Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
were colonized by Neanderthal man
Neanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...
, extinct by 20,000 following the appearance of modern humans in the region from 40,000 years ago.
Homo sapiens
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
. It is unclear to what extent these early modern humans had developed language
Origin of language
The origin of language is the emergence of language in the human species. This is a highly controversial topic. Empirical evidence is so limited that many regard it as unsuitable for serious scholars. In 1866, the Linguistic Society of Paris went so far as to ban debates on the subject...
, music, religion
Evolutionary origin of religions
The evolutionary origin of religions theorizes about the emergence of religious behavior during the course of human evolution.- Nonhuman religious behavior :...
etc. They spread throughout Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
over the following 50,000 years or so.
According to proponents of the Toba catastrophe theory
Toba catastrophe theory
The Toba supereruption was a supervolcanic eruption that occurred some time between 69,000 and 77,000 years ago at Lake Toba . It is recognized as one of the Earth's largest known eruptions...
, the climate in non-tropical regions of the earth experienced a sudden freezing about 70,000 years ago, because of a huge explosion of the Toba volcano that filled the atmosphere with volcanic ash for several years. This reduced the human population to less than 10,000 breeding pairs in equatorial Africa, from which all modern humans are descended. Being unprepared for the sudden change in climate, the survivors were those intelligent enough to invent new tools and ways of keeping warm and finding new sources of food (for example, adapting to ocean fishing based on prior fishing skills used in lakes and streams that became frozen).
Around 80–100,000 years ago, three main lines of Homo sapiens diverged, bearers of mitochondrial haplogroup L1
Haplogroup L1 (mtDNA)
In human mitochondrial genetics, Haplogroup L1 is a human mitochondrial DNA haplogroup common in Central and West Africa.-Origin:Haplogroup L1 is believed to have appeared approximately 110,000 to 170,000 years ago...
(mtDNA) / A
Haplogroup A (Y-DNA)
In human genetics, Haplogroup A refers to a group of y-chromosome lineages that were among the first to branch off from the root of the human y-chromosome phylogeny...
(Y-DNA) colonizing Southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
(the ancestors of the Khoisan
Khoisan
Khoisan is a unifying name for two ethnic groups of Southern Africa, who share physical and putative linguistic characteristics distinct from the Bantu majority of the region. Culturally, the Khoisan are divided into the foraging San and the pastoral Khoi...
/Capoid
Capoid
The Capoid race is a historical racial category proposed in 1962 by anthropologist Carleton S. Coon and named after the Cape of Good Hope; these people had formerly been regarded as a sub-type of the historical racial category Negroid....
peoples), bearers of haplogroup L2
Haplogroup L2 (mtDNA)
In human mitochondrial genetics, Haplogroup L2 is a human mitochondrial DNA haplogroup typical of Africa. Its subclade L2a is a somewhat frequent and widespread mtDNA cluster in Africa, as well as in the African diaspora Americans . et al.-Origin:L2 is a common African lineage. It is believed to...
(mtDNA) / B
Haplogroup B (Y-DNA)
In human genetics, Haplogroup B is a Y-chromosome haplogroup.-Distribution:Haplogroup B is localized to sub-Saharan Africa, especially to tropical forests of West-Central Africa. After Y-haplogroup A, it is the second oldest and one of the most diverse human Y-haplogroups...
(Y-DNA) settling Central
Central Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
and West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
(the ancestors of Niger–Congo and Nilo-Saharan speaking peoples), while the bearers of haplogroup L3
Haplogroup L3 (mtDNA)
In human mitochondrial genetics, Haplogroup L3 is a human mitochondrial DNA haplogroup. Haplogroup L3 has played a pivotal role in the history of the human species...
remained in East Africa.
The "Great Leap Forward" leading to full behavioral modernity
Behavioral modernity
Behavioral modernity is a term used in anthropology, archeology and sociology to refer to a set of traits that distinguish present day humans and their recent ancestors from both living primates and other extinct hominid lineages. It is the point at which Homo sapiens began to demonstrate a...
sets in only after this separation. Rapidly increasing sophistication in tool-making and behaviour is apparent from about 80,000 years ago, and the migration out of Africa follows towards the very end of the Middle Paleolithic
Middle Paleolithic
The Middle Paleolithic is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle Paleolithic in African archeology. The Middle Paleolithic and the Middle Stone Age...
, some 60,000 years ago. Fully modern behaviour, including figurative art
Figurative art
Figurative art, sometimes written as figurativism, describes artwork—particularly paintings and sculptures—which are clearly derived from real object sources, and are therefore by definition representational.-Definition:...
, music
Music
Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...
, self-ornamentation, trade
Trade
Trade is the transfer of ownership of goods and services from one person or entity to another. Trade is sometimes loosely called commerce or financial transaction or barter. A network that allows trade is called a market. The original form of trade was barter, the direct exchange of goods and...
, burial rites etc. is evident by 30,000 years ago. The oldest unequivocal examples of prehistoric art
Prehistoric art
In the history of art, prehistoric art is all art produced in preliterate, prehistorical cultures beginning somewhere in very late geological history, and generally continuing until that culture either develops writing or other methods of record-keeping, or it makes significant contact with another...
date to this period, the Aurignacian
Aurignacian
The Aurignacian culture is an archaeological culture of the Upper Palaeolithic, located in Europe and southwest Asia. It lasted broadly within the period from ca. 45,000 to 35,000 years ago in terms of conventional radiocarbon dating, or between ca. 47,000 and 41,000 years ago in terms of the most...
and the Gravettian
Gravettian
thumb|right|Burins to the Gravettian culture.The Gravettian toolmaking culture was a specific archaeological industry of the European Upper Palaeolithic era prevalent before the last glacial epoch. It is named after the type site of La Gravette in the Dordogne region of France where its...
periods of prehistoric Europe
Prehistoric Europe
Prehistoric Europe refers to the prehistorical period of Europe, usually taken to refer to human prehistory since the Lower Paleolithic, but in principle also extending to geological time scale - for which see Geological history of Europe....
, such as the Venus figurines
Venus figurines
Venus figurines is an umbrella term for a number of prehistoric statuettes of women portrayed with similar physical attributes from the Upper Palaeolithic, mostly found in Europe, but with finds as far east as Irkutsk Oblast, Siberia, extending their distribution to much of Eurasia, from the...
and cave painting
Cave painting
Cave paintings are paintings on cave walls and ceilings, and the term is used especially for those dating to prehistoric times. The earliest European cave paintings date to the Aurignacian, some 32,000 years ago. The purpose of the paleolithic cave paintings is not known...
(Chauvet Cave
Chauvet Cave
The Chauvet-Pont-d'Arc Cave is a cave in the Ardèche department of southern France that contains the earliest known cave paintings, as well as other evidence of Upper Paleolithic life. It is located near the commune of Vallon-Pont-d'Arc on a limestone cliff above the former bed of the Ardèche River...
) and the earliest musical instruments
Prehistoric music
Prehistoric music is a term in the history of music for all music produced in preliterate cultures , beginning somewhere in very late geological history...
(the bone pipe of Geissenklösterle, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, dated to about 36,000 years ago).
Social brain hypothesis
The model was proposed by Robin DunbarRobin Dunbar
Robin Ian MacDonald Dunbar is a British anthropologist and evolutionary psychologist and a specialist in primate behaviour. He is currently Professor of Evolutionary Anthropology and the Director of the Institute of Cognitive and Evolutionary Anthropology of the University of Oxford and the...
, who argues that human intelligence did not evolve primarily as a means to solve ecological problems, but rather intelligence evolved as a means of surviving and reproducing in large and complex social groups. Some of the behaviors associated with living in large groups include reciprocal altruism, deception and coalition formation. These group dynamics relate to Theory of Mind
Theory of mind
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own...
or the ability to understand the thoughts and emotions of others, though Dunbar himself admits in the same book that it is not the flocking itself that causes intelligence to evolve (as shown by ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s).
Dunbar argues that when the size of a social group increases, the number of different relationships in the group may increase by orders of magnitude. Chimpanzees live in groups of about 50 individuals whereas humans typically have a social circle of about 150 people, which is now referred to as Dunbar's number
Dunbar's number
Dunbar's number is suggested to be a theoretical cognitive limit to the number of people with whom one can maintain stable social relationships. These are relationships in which an individual knows who each person is, and how each person relates to every other person...
. According to the social brain hypothesis, when hominids started living in large groups, selection favored greater intelligence. As evidence, Dunbar cites a relationship between neocortex size and group size of various mammals. Howewer, meerkat
Meerkat
The meerkat or suricate, Suricata suricatta, is a small mammal belonging to the mongoose family. Meerkats live in all parts of the Kalahari Desert in Botswana, in much of the Namib Desert in Namibia and southwestern Angola, and in South Africa. A group of meerkats is called a "mob", "gang" or "clan"...
s have far more social relationships than their small brain capacity would suggest. Another hypothesis is that it is actually intelligence that causes social relationships to become more complex, because intelligent individuals are more difficult to learn to know.
There are also studies that show that Dunbar's number is not the upper limit of the number of social relationships in humans either.
Sexual selection
This model is proposed by Geoffrey MillerGeoffrey Miller (evolutionary psychologist)
Geoffrey F. Miller , Associate Professor of Psychology at the University of New Mexico, is an American evolutionary psychologist.Miller is a 1987 graduate of Columbia University, where he earned a B.A. in biology and psychology. He received his PhD in cognitive psychology from Stanford University...
who argues that human intelligence is unnecessarily sophisticated for the needs of hunter-gatherers to survive. He argues that the manifestations of intelligence such as language, music and art did not evolve because of their utilitarian value to the survival of ancient hominids. Rather, intelligence may have been a fitness indicator. Hominids would have been selected for greater intelligence as a proxy for healthy genes and a positive feedback loop of sexual selection would have led to the evolution of human intelligence in a relatively short period.
A sexual selection theory must explain why both sexes are intelligent. In many species, only males have impressive ornaments and show-off behavior. Sexual selection is also thought to be able to act on both males and females in species that are at least partially monogamous. With complete monogamy, there is assortative mating
Assortative mating
Assortative mating , and the related concept Disassortative mating, is the phenomenon where a sexually reproducing organism chooses to mate with individuals that are similar or dissimilar to itself in some specific manner...
for sexually selected traits. This means that less attractive individuals will find other less attractive individuals to mate with. If attractive traits are good fitness indicators, this means that sexual selection increases the genetic load of the offspring of unattractive individuals. Without sexual selection, an unattractive individual might find a superior mate with few deleterious mutations, and have healthy children that are likely to survive. With sexual selection, an unattractive individual is more likely to have access only to an inferior mate who is likely to pass on many deleterious mutations to their joint offspring, who are then less likely to survive.
Sexual selection is often thought to be a likely explanation for other female-specific human traits, for example breasts and buttocks far larger in proportion to total body size than those found in related species of ape. It is often assumed that if breasts and buttocks of such large size were necessary for functions such as suckling infants, they would be found in other species. Growing human brains require more nutrition than brains of related species of ape. Human males find human female breasts attractive, in agreement with sexual selection acting on human females.
Sexual selection for intelligence and judging ability can act on indicators of success, such as highly visible displays of wealth (cattle, farmland, servants, etc.). It is possible that for females to successfully judge male intelligence, they must be intelligent themselves. This could explain why despite the absence of clear differences in intelligence between males and females on average, there are clear differences between male and female propensities to display their intelligence in ostentatious forms.
Ecological dominance-social competition model
A predominant model describing the evolution of human intelligence is ecological dominance-social competition (EDSC) explained by Mark V. Flinn, David C. Geary and Carol V. Ward based mainly on work by Richard D. AlexanderRichard D. Alexander
Richard D. Alexander is an Emeritus Professor and Emeritus Curator of Insects at the Museum of Zoology of the University of Michigan in Ann Arbor, Michigan, USA. Prof...
. According to the model, human intelligence was able to evolve to significant levels because of the combination of increasing domination over habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
and increasing importance of social interactions. As a result the primary selective pressure for increasing human intelligence shifted from learning to master the natural world
Nature
Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
to competition for dominance among members or groups of its own species.
As advancement, survival and reproduction within an increasing complex social structure favored ever more advanced social skills, communication
Communication
Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...
of concepts through increasingly complex language patterns ensued. Since competition had shifted bit by bit from controlling "nature" to influencing other humans, it became of relevance to outmaneuver other members of the group seeking leadership
Leadership
Leadership has been described as the “process of social influence in which one person can enlist the aid and support of others in the accomplishment of a common task". Other in-depth definitions of leadership have also emerged.-Theories:...
or acceptance
Acceptance
Acceptance is a person's agreement to experience a situation, to follow a process or condition without attempting to change it, protest, or exit....
, by means of more advanced social skills. A more social and communicative person would be more easily selected.
Studies of chimpanzees show that they cooperate well in conflictless situations but not in situations with conflict, so human cooperativeness cannot have evolved to form coalitions against each other.
Intelligence as a resistance signal
Human intelligence developed to an extreme level that is not necessarily adaptive in an evolutionary sense. Firstly, larger-headed babies are more difficult to give birthBirth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
and large brains are costly in terms of nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
requirements. Thus the direct adaptive benefit of human intelligence is questionable at least in modern societies, while it is difficult to study in prehistoric societies. However, alleles coding for even larger human brains are spreading continuously even in modern societies This suggests that humans of higher intellect may gain indirect selective benefits.
A recent study argues that human cleverness is simply selected within the context of sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...
as an honest signal of genetic resistance against parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
and pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s. The number of people living with cognitive abilities seriously damaged by childhood infections is high; estimated in hundreds of millions. Even more people live with moderate mental damages, that are not classified as ‘diseases’ by medical standards, who may still be considered as inferior mates by potential sexual partners. Pathogens currently playing a major role in this global challenge against human cognitive capabilities include viral infections like meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, protist
Protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
s like Toxoplasma and Plasmodium
Plasmodium
Plasmodium is a genus of parasitic protists. Infection by these organisms is known as malaria. The genus Plasmodium was described in 1885 by Ettore Marchiafava and Angelo Celli. Currently over 200 species of this genus are recognized and new species continue to be described.Of the over 200 known...
, and animal parasites like intestinal worms and Schistosomes.
Thus, widespread, virulent, and archaic infections are greatly involved. Given this situation, our sexual preferences for clever partners increase the chance that our descendants will inherit the best resistance alleles. Like some people search for mates based on their bodily beauty, height, or social position (e.g. wealth or fame), or psychological traits such as benevolence or confidence; people are just searching for signals of good resistance genes. Intelligence appears to be one of these signals. But the term intelligence used for humans is ill-defined.
Group selection
Group selectionGroup selection
In evolutionary biology, group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group....
theory contends that organism characteristics that provide benefits to a group (clan, tribe, or larger population) can evolve despite individual disadvantages such as those cited above. The group benefits of intelligence (including language, the ability to communicate between individuals, the ability to teach others, and other cooperative aspects) have apparent utility in increasing the survival potential of a group.
Nutritional status
Higher cognitive functioning develops better in an environment with adequate nutrition, and diets deficient in ironIron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
, B vitamins
B vitamins
B vitamins are a group of water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to as vitamin B . Later research showed that they are chemically distinct vitamins that often coexist in the same foods...
, omega 3 fatty acids, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and other nutrients can result in lower intelligence either in the mother during pregnancy or in the child during development. While these inputs did not have an effect on the evolution of intelligence they do govern its expression. A higher intelligence could be a signal that an individual comes from and lives in a physical and social environment where nutrition levels are high, whereas a lower intelligence could imply a child (and/or the child's mother) comes from a physical and social environment where nutritional levels are low. Previc emphasizes the contribution of nutritional factors, especially meat and shellfish consumption, to elevations of dopaminergic activity in the brain, which may have been responsible for the evolution of human intelligence since dopamine is crucial to working memory, cognitive shifting, abstract, distant concepts, and other hallmarks of advanced intelligence.
Flexible problem solving
The statement that such high intelligence "lack survival value", which is used by believers in social intelligence and sexual selection, invariably assumes a stable environment. If climate change is factored in, howewer, the evolution of human intelligence can be perfectly explained by flexible problem solving during those climate changes. However, such a theory must account for the apparent uniqueness of human levels of intelligence, which can be explained by free hands that allows for efficient manipulation of the environment, which gives intelligence a practical survival value that can be selected by evolution.See also
- Behavioral modernityBehavioral modernityBehavioral modernity is a term used in anthropology, archeology and sociology to refer to a set of traits that distinguish present day humans and their recent ancestors from both living primates and other extinct hominid lineages. It is the point at which Homo sapiens began to demonstrate a...
- Heritability of IQ
- Human evolutionHuman evolutionHuman evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
- Fisherian runawayFisherian runawayFisherian runaway is a model of sexual selection, first proposed by R.A. Fisher in 1915, and expanded upon in his 1930 book The Genetical Theory of Natural Selection, that suggests an explanation for sexual selection of traits that do not obviously increase fitness of survival, based upon a...
- Primate cognitionPrimate cognitionPrimate cognition is the study of the cognitive abilities of non-human primates. Humans are also primates but, traditionally, humans have been thought to be different from other animals...
Further reading
- Byrne, Richard W. (1995) The Thinking Ape: Evolutionary origins of intelligence Oxford University Press, Oxford, England, ISBN 0-19-852188-X
- Greenspan, Stanley I. and Shanker, Stuart (2004) The First Idea: How symbols, language, and intelligence evolved from our early primate ancestors to modern humans Da Capo Press, Cambridge, Mass., ISBN 0-7382-0680-6
- Itzkoff, Seymour W. (1983) The Form of Man: The evolutionary origins of human intelligence Paideia Publishers, Ashfield, Mass., ISBN 0-913993-00-X
- Lynch, Gary and Granger, Richard (2008) Big Brain: The Origins and Future of Human Intelligence Palgrave Macmillan, New York, ISBN 1-4039-7978-2
- Skoyles, John RJohn Skoyles (scientist)John Skoyles is a dyslexic neuroscientist and evolutionary psychologist. He initially studied philosophy of science at the London School of Economics and then did MRC funded research upon neuroscience and dyslexia at University College London....
. and Sagan, DorionDorion SaganDorion Sagan is an American science writer, essayist, and theorist. He has written and co-authored many books on culture, evolution, and the history and philosophy of science, most recently "The Sciences of Avatar: from Anthropology to Xenology" and "Death and Sex," which won first place at the...
(2002) Up from Dragons: The evolution of human intelligenceUp from DragonsUp from Dragons: The Evolution of Human Intelligence is a 2002 book on human evolution, the human brain, and the origins of human cognition by John Skoyles and Dorion Sagan. The book considers how the brain and genes evolved into their present condition over the course of thousands and millions of...
McGraw-Hill, New York, ISBN 0-07-137825-1 - Tobias, Phillip V. (1971) The Brain in Hominid Evolution Columbia University Press, New York, ISBN 0-231-03518-7