As far as everyone is concerned, only humans can perform intellectual feats, presumably because we are smarter than all other animal species-at least by our own definition of intelligence. It is quite obvious that intelligence must emerge from the workings of the three-pound mass of wetware packed inside our skulls. Thus, researchers have tried to identify unique features of the human brain that could account for our superior intellectual abilities. But, anatomically, the human brain is very similar to that of other primates because humans and chimpanzees share an ancestor that walked the earth less than seven million years ago. Accordingly, the human brain contains no highly conspicuous characteristics that might account for the species' cleverness. For instance, scientists have failed to find a correlation between absolute or relative brain size and acumen among humans and other animal species. Neither have they been able to discern a parallel between wits and the size or existence of specific regions of the brain, excepting perhaps Broca's area, which governs speech in people. The lack of an obvious structural correlate to human intellect jibes with the idea that our intelligence may not be wholly unique: studies are revealing that chimps, among various other species, possess a diversity of humanlike social and cognitive skills (Daney, 2006, Â¶1-4).
Nevertheless, researchers have found some microscopic clues to humanity's aptitude. We have more neurons in our brain's cerebral cortex (its outermost layer) than other mammals do. The insulation around nerves in the human brain is also thicker than that of other species, enabling the nerves to conduct signals more rapidly. Such biological subtleties, along with behavioral ones, suggest that human intelligence is best likened to an upgrade of the cognitive capacities of nonhuman primates rather than an exceptionally advanced form of cognition. Daney further argues that over years, geneticists considered complete sequencing of the genomes of a variety of species so important. One reason for this is what we learn by comparing these other genomes with the human genome. Considering the genome of a close relative of humans, such as our closest relatives, chimpanzees, the comparison can be enlightening. Researchers believe that dynamic regions of the human genome -in terms of duplications and deletions - are potentially involved in the rapid evolution of morphological and behavioral characteristics that are genetically determined. Researchers are finding similar characteristics in chimpanzees, which has implications for the understanding of genomic evolution in all species. As interesting as it is, it still does not tell us much about what accounts for the difference between human and chimp brains. Scientists believe they have found a key gene that helped the human brain evolve from our chimp-like ancestors. One area of the human genome seems to have evolved about 70 times faster than the rest of our genetic code, in just a few million years. It appears to have a role in a rapid tripling of the size of the brain's crucial cerebral cortex. Humans are believed to have gained about 200cc of brain capacity over the last few million years (Â¶5-6).
Since chimpanzees cannot read or speak, their aptitude is difficult to discern. Thus, comparative psychologists have invented behavior-based tests to assess mammals' abilities to learn and remember, to comprehend numbers and to solve practical problems. Animals of various stripes-but especially nonhuman primates-often earn high marks on such action-oriented IQ tests. Researchers now show that great apes have a sophisticated understanding of tool use and construction. For instance, during World War I, German psychologist Wolfgang Köhler showed that chimpanzees, when confronted with fruit hanging from a high ceiling, devised an ingenious way to get it by piling boxes to stand on to reach the fruit. They also constructed long sticks to reach food outside their enclosure. Scientists have strong but still circumstantial evidence that a certain gene, called HAR1F, may provide an important answer to the question: "What makes humans brainier than other primates?" Human brains are triple the size of chimp brains. This evidence is very suggestive that this gene is important in the development of the cerebral cortex, and that's exciting because the human cortex is three times as large as it was in our predecessors. According to David Haussler of the University of California, something caused our brains to evolve to be much larger and have more function than the brains of other mammals. The human brain may have evolved beyond that of our primate predecessors because our brain cells are better at sticking in place. A study comparing the genomes of humans, chimps, monkeys and mice found an unexpectedly high degree of genetic difference in the human DNA regions that influence nerve cell adhesion, compared with the DNA of the other animals. Increased evolution allowed human brain cell connections to form with greater complexity, enabling us to grow bigger brains (Ravindran, 2008, Â¶2-4).
Enhanced adhesion between neurons facilitates bigger brains but more interestingly, it's not only specific genes that play a role in this, but certain noncoding DNA regions between genes do also. The best evidence for accelerated evolution on the human line was found in noncoding sequences next to genes involved in helping neurons adhere to each other. Such sequences suggest that changes in these regulatory elements may have contributed to the evolution of uniquely human cognitive talents. Neuronal adhesion molecules play a major role in wiring the brain like the formation of connective synapses between nerve cells. These processes are important in early brain development and also crucial for learning, memory, and cognition in adults. For instance, one of the noncoding sequences is next to a gene called CNTN4, which appears to be involved in the development of both verbal and nonverbal communication abilities in humans, while another is adjacent to CHL1, which is linked to cognition in both humans and mice. Psychologists have used behavioral tests to illuminate similar cognitive feats in other mammals. Behavioral ecologists judge animals based on their ability to solve problems, relevant to survival in their natural habitats, rather than on their test-taking talents. For that matter, intelligence is a cluster of capabilities that evolved in response to particular environments. Some scientists have further projected that mental or behavioral flexibility, the ability to come up with novel solutions to problems, is another good measure of animal intellect (Â¶5-6).
According to Dicke and Roth, chimpanzees can also display humanlike social intelligence. They can engage in deception and mimic other human bahaviour including the display of emotion. Due to such findings, scientists have constructed evolutionary hierarchies of intelligence. Primates are considered the smartest mammals. Among primates, humans and apes are considered cleverer than monkeys, and monkeys more so than prosimians. Of the apes, chimpanzees and bonobos rank above gibbons, orangutans and gorillas as well. The degree of encephalization, measured by the encephalization quotient (EQ) is another cerebral yardstick that scientists have tried to tie to intelligence. The EQ expresses the extent to which a species' relative brain weight deviates from the average in its animal class. The size of the cerebral cortex- the brain's outermost layer- which is also the brain's most highly evolved region , and the seat of many of our cognitive capacities might be the is the key to our answers. Scientists have discovered that genes don't operate in isolation. Each functions within a system of related genes. They do not examine the genes individually but instead use a systems biology approach to study each gene within its context. The scientists identified networks of genes that correspond to specific brain regions. When they compared these networks between humans and chimps, they found that the gene networks differed the most widely in the cerebral cortex, which is three times larger in humans than chimps. Apart from that, the researchers discovered that many of the genes that play a central role in cerebral cortex networks in humans, but not in the chimpanzee, also show significant changes at the DNA level. Therefore there are probably scores of genes implicated in human-chimp brain differences, organized in different networks. Changes, especially in the front part of our brains, are mostly responsible for humans' high intelligence (2008, Â¶3-5).
Humans and chimpanzees shared a common ancestor 6-8 million years ago. Over that time, one group evolved into humans and another into chimps. The obvious difference between the two species is the size of their brains. Modern human brains are about three times larger than chimpanzee brains. Changes like this happen at the gene level. A gene is a part of our DNA that can control a trait. Genes control things like hair and eye color, or even height. And of course, brain size. Given the difference in brain size, these genes are bound to be different between humans and chimps. So scientists have started to compare these genes in people and chimps to find the differences responsible for making human brains so big (Â¶6-8).
It turns out that the dimensions of the cerebral cortex depend on those of the entire brain and that the size of the cortex constitutes no better arbiter of a superior mind. The same is true for the prefrontal cortex, the hub of reason and action planning. Recent studies have shown that the size of this structure in humans relatively small as compared with that of other primates. Brains consist of nerve cells, or neurons, and supporting cells called glia. The more neurons, the more extensive and more productive the neuronal networks can be-and those networks determine varied brain functions, including perception, memory, planning and thinking. Large brains do not automatically have more neurons; in fact, neuronal density generally decreases with increasing brain size because of the additional glial cells and blood vessels needed to support a big brain. Chimpanzees understand cause and effect, make and use tools, produce and comprehend language, and lie to and imitate others. It is said that these primates may even possess a theory of mind like the ability to understand another animal's mental state and use it to guide their own behavior. Chimpanzees can even understand and use human speech, gestures or symbols in constructions of up to about three words. Surprisingly, even after years of training, none of these creatures develops verbal skills more advanced than those of a three-year-old child, since humans' grammar and vocabulary skills start at age three. This timing corresponds with the development of Broca's speech area in the left frontal lobe, which may be unique to humans' .However, scientists are yet to discover whether a direct precursor to this speech region exists in the nonhuman primate brain like the Chimpanzee (Â¶9-10).
Of all animals, humans alone have a language that contains complex grammar. The absence of an intricately wired language region in the brains of other species may explain why this is so. The development of human grammar and syntax is dated by researchers to between 80,000 and 100,000 years ago. This makes it a relatively recent evolutionary advance. It is also said to be one that probably greatly enhanced human intellect. A bigger brain could have made humans smarter. This is definitely an advantage for a social animal like us. The human brain comes with control of the involuntary and voluntary functions, the sensory perceptions, memory, emotions, consciousness, and intelligence. Human hearing differs from that of chimpanzees and most other apes in maintaining a relatively high sensitivity. Even human eyes are designed for communication. The uniqueness of human eye morphology among primates illustrates the remarkable difference between human and other primates in the ability to communicate using gaze signals (Ravindran, 2008, Â¶7-8).
Although many propose that chimpanzees and humans have a common ancestor whose populations were isolated from each other, and evolved into different species, over time, through "natural selection" of individuals. Nothing is known about this elusive theorized "common ancestor". The fossil record of the living great apes is poor. The orangutan is actually the only great ape that has a fossil record. No African fossil has ever been found that is related to chimpanzees or gorillas. While humans are said to have greatly evolved, the "advancement" of chimpanzees seemed to have been relatively retarded. Svante Paabo, a renowned evolutionary geneticist says that in the end, it's a political and social and cultural thing about how we see our differences while for the evolutionist, it appears to be a political, social, and cultural bias that leads them to establish a close relationship between humans and chimps that may in fact not exist. For years, chimpanzees were considered to be only 1% genetically dissimilar to humans. A recent gene splicing study revealed a 6-8% difference, while a 2003 study revealed a 13% difference in our respective immune systems, and another study revealed a 17% difference in gene expression in our cerebral cortexes (Dicke & Roth, 2008, Â¶11-13).
The major differences between humans and chimps narrow to ones of degree, not of kind. Humans may share many profound likenesses with our closest animal relations who have been shown to possess remarkable language capacities, and have the ability to make and use tools and even to learn behaviors from other members of their community, all traits once thought to be the hallmarks of humanity. As the biblical creation model predicts, humans and chimpanzees are qualitatively different in their intellectual, linguistic, and moral capacities hence getting back to good, honest science. Nevertheless, the observational evidence seems to indicate a significant number of critical differences between chimpanzees and humans. While we are very different from chimpanzees, perhaps it is chimpanzees that are not all that different from other animals (Dicke & Roth, 2008, Â¶14-15).