The evolution of race was as simple as the politics of race is complex.
- THE BIOLOGY OF SKIN COLOR
- Recent research explores the idea that human skin color is an adaptation to differing levels of ultraviolet radiation in different parts of the globe. The key, this hypothesis suggests, is the effect of sunlight on different vitamins, some of which need ultraviolet light in order to be produced in the human body, while others are destroyed by it.
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Nina Jablonski an expert in primate evolution and her husband, George Chaplin, a geographic information systems specialist, have formulated the first comprehensive theory of skin color. Their findings show a strong, somewhat predictable correlation between skin color and the strength of sunlight across the globe. But they also show a deeper, more surprising process at work: Skin color, they say, is largely a matter of vitamins.
Jablonski begins by assuming that our earliest ancestors had fair skin just like chimpanzees, our closest biological relatives. Between 4.5 million and 2 million years ago, early humans moved from the rain forest and onto the East African savanna. Once on the savanna, they not only had to cope with more exposure to the sun, but they also had to work harder to gather food. Mammalian brains are particularly vulnerable to overheating: A change of only five or six degrees can cause a heatstroke. So our ancestors had to develop a better cooling system.
The answer was sweat, which dissipates heat through evaporation. Early humans probably had few sweat glands, like chimpanzees, and those were mainly located on the palms of their hands and the bottoms of their feet. Occasionally, however, individuals were born with more glands than usual. The more they could sweat, the longer they could forage before the heat forced them back into the shade. The more they could forage, the better their chances of having healthy offspring and of passing on their sweat glands to future generations.
A million years of natural selection later, each human has about 2 million sweat glands spread across his or her body. Human skin, being less hairy than chimpanzee skin, "dries much quicker," says Adrienne Zihlman, an anthropologist at the University of California at Santa Cruz. "Just think how after a bath it takes much longer for wet hair to dry."
Hairless skin, however, is particularly vulnerable to damage from sunlight. Scientists long assumed that humans evolved melanin, the main determinant of skin color, to absorb or disperse ultraviolet light. But what is it about ultraviolet light that melanin protects against? Some researchers pointed to the threat of skin cancer. But cancer usually develops late in life, after a person has already reproduced. Others suggested that sunburned nipples would have hampered breast-feeding. But a slight tan is enough to protect mothers against that problem.
Jablonski also found a 1978 study that examined the effects of ultraviolet light on folate, a member of the vitamin B complex. An hour of intense sunlight, the study showed, is enough to cut folate levels in half if your skin is light. Jablonski made the next, crucial connection only a few weeks later. At a seminar on embryonic development, she heard that low folate levels are correlated with neural-tube defects such as spina bifida and anencephaly, in which infants are born without a full brain or spinal cord.
As far back as the 1960s, the biochemist W. Farnsworth Loomis had suggested that skin color is determined by the body's need for vitamin D. The vitamin helps the body absorb calcium and deposit it in bones, an essential function, particularly in fast-growing embryos. (The need for vitamin D during pregnancy may explain why women around the globe tend to have lighter skin than men.) Unlike folate, vitamin D depends on ultraviolet light for its production in the body.
Loomis believed that people who live in the north, where daylight is weakest, evolved fair skin to help absorb more ultraviolet light and that people in the tropics evolved dark skin to block the light, keeping the body from overdosing on vitamin D, which can be toxic at high concentrations.
Until the 1980s, researchers could only estimate how much ultraviolet radiation reaches Earth's surface. But in 1978, NASA launched the Total Ozone Mapping Spectrometer. Jablonski and Chaplin took the spectrometer's global ultraviolet measurements and compared them with published data on skin color in indigenous populations from more than 50 countries. To their delight, there was an unmistakable correlation: The weaker the ultraviolet light, the fairer the skin. Jablonski went on to show that people living above 50 degrees latitude have the highest risk of vitamin D deficiency.
"This was one of the last barriers in the history of human settlement," Jablonski says. "Only after humans learned fishing, and therefore had access to food rich in vitamin D, could they settle these regions."
Humans have spent most of their history moving around. To do that, they've had to adapt their tools, clothes, housing, and eating habits to each new climate and landscape. But Jablonski's work indicates that our adaptations go much further. People in the tropics have developed dark skin to block out the sun and protect their body's folate reserves. People far from the equator have developed fair skin to drink in the sun and produce adequate amounts of vitamin D during the long winter months.
Jablonski hopes that her research will alert people to the importance of vitamin D and folate in their diet. It's already known, for example, that dark-skinned people who move to cloudy climes can develop conditions such as rickets from vitamin D deficiencies.
<< Back to Human Evolution
- BIRTH OF LANGUAGE
- Even before the development of speech, there must have first been a desire to communicate.
Purposeful communication is very different from animal calls that signal more or less automatically to the whole group. Purposeful communication requires a coordinated transmitter and an attentive receiver. The first form of such communication may have been through hand gestures and facial expressions. Reading facial expressions may have helped individuals to anticipate the coming actions of their peers. Attention to hand movements may have allowed copying of skills requiring manual dexterity such as tool making.
Language first appeared between 30,000 and 100,000 years ago in the species Homo sapiens. But how did language evolve? Currently, there are two rival answers to this question: the first and more common explanation is that language was an adaptation of some sort; the second (chiefly espoused by Stephen Jay Gould) is that language is a spandrel, a nonadaptive element arising as a byproduct of other processes. We will consider these explanations in reverse order.
Language as a Spandrel
- Some people, Stephen Jay Gould most prominent among them, believe language to be the byproduct of other evolutionary processes, not a special adaptation that arose by ordinary natural selection acting on mutations. As Gould puts it, "Natural selection made the human brain big, but most of our mental properties and potentials may be spandrels - that is, nonadaptive side consequences of building a device with such structural complexity". In other words, our ancestors encountered environments which required the type of advanced reasoning only provided by a larger brain; however, language capability was not one of those functions for which the brain was selected. Instead, language is a result of exapting neural structures formerly used for other functions: "Many, if not most, universal behaviors [including language] are probably spandrels, often co-opted later in human history for important secondary functions".
This view has been reinforced by the famous linguist Noam Chomsky, who argues that the brain's language capability cannot be explained in terms of natural selection. He attempts to explain the brain not through biology or engineering principles, but instead through the effects of physical laws. According to Chomsky, there may be unexpected emergent physical properties associated with the specific structure of the brain that explain language.
Language as an Adaptation
- The mainstream view is that language is an adaptation, evolved in response to some selection pressure toward improved communication between humans. This explanation is associated with many speculative possibilities and proposals for the adaptive function of language, and some (such as Steven Pinker) postulate "mental modules" that compartmentalize linguistic functions.
There are many different possible "adaptationist" explanations for the evolution of language. For instance, perhaps there was a need for improved communication between hunters at some point in the history of Homo sapiens, and oral expressions were simply the optimal way to solve the problem. More plausibly (or at least more importantly), sharing information between individuals probably conferred an extremely major advantage: groups of humans with language, or even "proto-language", could share a wealth of information about local hunting conditions, food supplies, poisonous plants, or the weather. It would be extremely beneficial to the survival of all members of the tribe if only one had to encounter a poisonous plant, rather than each member having to rediscover the fact for himself!
It is also simple to imagine a series of "oral gestures", perhaps indicating the presence of an animal to another person by imitating the animal's cries. Steven Pinker suggests in his book The Language Instinct, "Perhaps a set of quasi-referential calls . . . came under the voluntary control of the cerebral cortex [which controls language], and came to be produced in combination for complicated events; the ability to analyze combinations of calls was then applied to the parts of each call".
Another possible source of selection pressure towards better linguistic abilities is the social group. Social interactions between people with widely divergent or conflicting interests "make formidable and ever-escalating demands on cognition". Increasing cognitive ability could easily have focused on the improvement of language as well, since so many social interactions depend on effective persuasion.
Language Evolution and Memes
- It is possible to imagine numerous potential scenarios by which language might have evolved as a purely biological adaptation. However, in her book The Meme Machine, Susan Blackmore reveals a different theory of language evolution: she proposes that it evolved for the sake of memes, not as an adaptation for the benefit of genes.
Blackmore explains that memes first came into existence with the advent of true imitation in humans, which allowed memes to spread through populations. Recalling that fecundity, or proudction of new copies, is essential to a replicator, she proposes that language came into existence as a mechanism for improving the fecundity of memes. Sound transmission has many advantages for the purpose - sounds can be heard by multiple listeners and can be used even at night. After sound transmission (proto-language) came into existence, the "digitalization" of language into discrete words arose as a mechanism for ensuring meme fidelity, or lack of errors in the new copies. She explains that those alterations that produce the most copies of the highest fidelity will be those that predominate, thus improving the language.
Blackmore goes on to suggest that grammar was an adaptation to improve the fecundity and fidelity of existing memes; its recursive structure then provided the framework for the development of more complex memes, which then favored the existence of more complex grammar, etc. in a self-sustaining process.
Furthermore, language then began to exert pressure on the genes, creating a selection pressure toward bigger brains that are better at language. If people prefer to mate with those possessing the best or most memes, then the genes that allowed those people to be good meme-spreaders will be differentially transmitted into the next generation. This process again leads to a self-catalytic process of brain evolution that places a strong survival and reproductive advantage on those most capable of meme transmission.
Finally, Blackmore believes that language is an unavoidable result of the existence of memes, which follow naturally from the ability to imitate (an ability that is, surprisingly, realized in very few species). She states, "verbal language is almost an inevitable result of memetic selection. First, sounds are a good candidate for high-fecundity transmission of behaviour. Second, words are an obvious way to digitise the the process and so increase its fidelity. Third, grammar is a next step for increasing fidelity and fecundity yet again, and all of these will aid memorability and hence longevity".
<< Back to Human Evolution
- Sing a Song of Evolution
- One of Charles Darwin's beautiful evolutionary speculations was that music might have preceded language.
He was interested in the way many species use song for sexual display and wondered if human vocalizations might have started out that way too. Perhaps vocalizations became varied and complex only later, when song was applied to topics other than mating and such basics of survival.
Language might not have entirely escaped its origins. Since you can be understood even when you are not well-spoken, why bother being well-spoken at all? Perhaps speaking well is still, in part, a form of sexual display. By being well-spoken I show not only that I am a clued-in member of the tribe but also that I am intelligent and likely to be a successful partner and helpful mate.
Only a handful of species, including humans and certain birds, can make a huge and ever-changing variety of sounds. Most animals, including our great-ape relatives, tend to make the same patterns of sound repeatedly. It is reasonable to suppose that an increase in variety of human sounds had to precede, or at least coincide with, the evolution of language. Which leads to another question: What makes the variety of sounds coming from a species increase?
As it happens, there is a well-documented case of song variety growing under controlled circumstances. Kazuo Okanoya of the Riken Institute in Tokyo compared songs between two populations of birds: the wild white-rump munia and its domesticated variant, the Bengalese finch. Over several centuries, bird fanciers bred Bengalese finches, selecting them for appearance only. Something odd happened during that time: Domesticated finches started singing an extreme and evolving variety of songs, quite unlike the wild munia, which has only a limited number of calls. The wild birds do not expand their vocal range even if they are raised in captivity, so the change was at least in part genetic.
The traditional explanation for such a change is that it must provide an advantage in either survival or sexual selection. In this case, though, the finches were well fed, and there were no predators. Meanwhile, mate selection was done by breeders, who were influenced only by feather coloration.
Terry Deacon is a professor of anthropology at the University of California at Berkeley and an expert on the evolution of the brain; he is also interested in the chemical origins of life and the mathematics behind the emergence of complicated structures like language.
Terry proposed an unconventional solution to the mystery of Bengalese finch musicality. What if there are certain traits, including song style, that naturally tend to become less constrained from generation to generation but are normally held in check by selection pressures? If the pressures go away, variation should increase rapidly. Terry suggested that the finches developed a wider song variety not because it provided an advantage but merely because in captivity it became possible.
In the wild, songs probably had to be rigid in order for mates to find each other. Birds born with a genetic predilection for musical innovation most likely would have had trouble mating. Once finches experienced the luxury of assured mating (provided they were visually attractive), their song variety exploded. Brian Ritchie and Simon Kirby of the University of Edinburgh worked with Terry to simulate bird evolution in a computer model, and the idea checked out.
Recent successes using computers to hunt for correlations in giant chunks of text offer a fresh hint that an explosion of variety in song might have been important in human evolution. To see why, compare two popular stories of the beginning of language.
In the first story, a protohuman says his first word for something—maybe ma for "mother" —and teaches it to the rest of the tribe. A few generations later, someone comes up with wa for "water." Eventually the tribe has enough words to have a language.
In the second story, protohumans have become successful enough that more of them are surviving, finding mates, and reproducing. They are making all kinds of weird sounds because evolution allows experimentation to run wild, so long as it doesn't have a negative effect on survival. Meanwhile, the protohumans are doing a lot of things in groups, and their brains start correlating certain distinctive social vocalizations with certain events. Gradually, a large number of approximate words come into use. There is no clear boundary at first between words, phrases, emotional inflection, or any other part of language.
The second story seems more likely to me. Protohumans would have been doing something like what big computers are starting to do now, but with the superior pattern-recognizing capabilities of a brain. While language became richer over time, it never became absolutely precise. The ambiguity continues to this day and allows language to grow and change. We are still living out the second story when we come up with new slang, like bling or LOL.
Even if the second story happened, and is still happening, language has not necessarily become more varied. Rules of speech may have eventually emerged that place restrictions on variety. Maybe those late-arriving rules help us communicate more precisely or just sound sexy and high status, or more likely a little of both. Variety doesn't always have to increase in every way.
Variety could even decrease over time. In fact, there may be a bizarre example of that happening right now in human song. We can easily explore the changing amount of variety in songs over the last hundred years because of an amazing data archive: audio recording. Since the beginning of recorded music, the sound of human song has changed with each new generation of people. There's no confusing a 1930s song with a 1940s song, or a 1950s song with a 1960s song. The pattern sticks until roughly the end of the 1980s. It's not easy to tell whether a song came from 1990 or 2000.
This might sound like an extraordinary claim, but you can test it yourself. Listen to random clips from the many sources of songs available on the Internet and don't peek at the year they were produced. You'll discover that it's harder to date songs from the last two decades than songs from previous decades.
If you accept that there has been a recent decrease in stylistic variety in human song, the next question is "Why?" There are plenty of possibilities: Maybe the Internet makes too much information available, so everyone has the same influences to absorb—and songs lose flavor and take on a generic quality. To be more cynical, it could be a sign of cultural decline.
Another explanation, which is the one I suspect, is that the change since the mid-1980s corresponds with the appearance of digital editing tools for music. Digital tools are more suggestive about results than previous tools: If you deviate from the kind of music a digital tool was designed to make, the tool becomes difficult to use. For instance, it's far more common these days for music to have a clockwork regular beat. Some of the most widely used music software becomes awkward and can even produce glitches if you vary the tempo much while editing. In predigital days, tools also influenced music, but with not nearly such a sharp edge.
So this is an ironic moment in the history of computer science. We are beginning to succeed at using computers to analyze data without the constraints of rigid grammarlike systems. But when we use computers to create, we are confined to equally rigid 1960s models of how information should be structured. The hope that language would be like a computer program has died. Instead, music has changed to become more like a computer program.
<< Back to Human Evolution
- INSTINCT AND INTELLIGENCE
- Early single-cell organisms, billions of years ago, developed sensors to detect light and an instinct to swim toward that light. Others developed poison darts and sensors to tell when another organism was near. When their sensors said that something was near, their instinct fired the darts to obtain a meal. With the development of sexual reproduction, the instinct of sexual desire provided the drive for reproduction.
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The northern pike is a fish in the lakes of northern North America. It is a predator. If one is placed in a tank of water and a smaller fish tossed into the tank, the pike will quickly eat it. If two fish of equal size are tossed into the pond, it will eat the closest one first. If the two fish are of unequal size but are placed in the tank equally far from the pike, it will eat the largest first. If the larger one is farther away, it will still eat the larger one first up to a certain distance differential. If the larger one is too far away, it will eat the small one first. It judges the relative distance of the two fish, juggles that with the size of the fish, then optimizes his chance for the most food. This is called reasoning. Yet the pike can be raised in isolation and it will still do this. This is called instinct. The parameters of the calculation are fixed in his genetic description.
The purple martin can fly beautifully, directly out of the box. Flying is not easy. It requires much skill, but the purple martin chick does it the first time. Adult martins will make sure he practices awhile, that first time out, but he knows how to do it. That is instinct. He is fix-wired to fly well, to a point. He usually falls right out of the tree, the first time he lands. If he tries to land on a pole, he will usually fall off or slide down. His genetic code prepared him for flying, those parameters are fixed, but it did not directly prepare him for every possible landing site. It gave him memory and a landing formula for that. Watch that chick a week later and see a perfect landing every time.
He has learned how to grab onto the standard surfaces. He has learned. He remembers what he has learned and uses that knowledge to control his claws when he lands. That is reasoning. Yet he does not need another martin to teach him. That is instinct.
Reasoning of this type in man is indistinguishable to him from intellectual reasoning. The reasoning mechanism is fixed and is the same one used in both cases. The only difference in the process is that intellectual reasoning follows a learned process (program) stored in a learning memory (RAM). The pike follows a process (program) stored in fixed memory (ROM). Most reasoning by man, which he considers to be intellectual, is not intellectual at all. All cultural (emotional) interactive reasoning processes are of the fixed type, embedded eons ago. Modern data may be fed into these processes from memory or senses, but the process is instinctive. Anything involving mother love or sex, for example, will be reasoned following ancient fixed processes.
It is the author's contention that there is no distinction between instinct and intelligence (which includes memory and reasoning) other than in size, relative proportions and complexity. They are dimensions of the same structure and are decreed by the coding in the DNA. Pure reasoning in the human is not only a myth but is impossible. His method of thinking, utilization of memory, and problem solving skills, are all fixed by his DNA, a DNA designed by an idiot. Man can conceive the idea of pure objective thought, but he is incapable of it. Man is a subjective organism.
Evolution took millions of years to make sure of it. He can talk about objectivity all he wants, he can foolishly believe that he is being objective, but there is no way that he can remove himself from his own instinct-reasoning programming. Ancient instincts and modern intellect are seamlessly intertwined in his brain. The idea of pure objective thought is no more than another example of man's ability to conceive the perfect bird or animal trap or the advantages of moving to another valley that he has not seen yet.
Man cannot fly to the moon. However, he could conceive the idea and then build a machine that will take him there. He is not ashamed in the least of using the machine. Still, when he considers pure objective thought in dealing with personal things, such as his culture, his arrogance forces him to believe that he can 'fly to the moon' without any outside help. He will become quite irritated with suggestions to the contrary (the irritation alone illustrates the degree of his objectivity). Similarly, there is no reason that man cannot build a machine (perhaps even an organic one) which is capable of 'pure' reason. Only a machine designed for the purpose could be completely objective. His biggest problem will be in defining 'pure' reason. Incidently, this is a machine that we should be working on now with a high priority. Think of it, intelligence without instincts. We need it badly. Elect one for president. Put a bunch more on the bench.
The long term result of evolution is bare survival. If the organism is in distress, the higher death rate removes survival impediments rapidly. An organism suffering a high mortality rate tends to become stronger to match its environment. If the organism is better than required, evolution will degrade it, again matching the organism with the environment. A comfortable organism has a lower death rate and so does not weed out detrimental characteristics as quickly. The result is a gradual degradation of function until the comfort is removed.
Now back to the pike and the martin, with that in mind:
If the pike is successful in his environment, he will not develop any further intelligence. He does not need it. It would be of no value to him. If the environment becomes harsher, he will either develop offsetting ability or perish. Still, what is the most likely change? He already knows how to hunt. He does not have a hand to hold a weapon and has no need to understand Shakespeare. Bigger teeth, a sleeker body for speed, or a quicker reaction time would solve his problem far better and quicker than a higher IQ. Look at a pike. He has been gaining those features for millions of years. Pound for pound there is not a better killing machine on earth (well, maybe with man as an exception).
The martin is in the same fix. He is born flying. It does not take long, even with a low IQ, to learn how to fly with your mouth open and scoop up insects. Only if his environment changed would he need to learn something new. Perhaps a more agile flying style, a different territory, a bigger mouth, or more broods each year would solve the problem better and quicker than a higher IQ. If he should have a mutation that gave him a higher IQ, what would be the value? What would he use it for? If the new-found intelligence is not required, it would not last long. Evolution quickly removes unused features. Most animals fit this pattern.
Why did man develop the large brain? Why did the other primates not do so? The answer, of course is in his particular environment, how well he matched it, and what the evolutionary alternatives were. His upright posture was both a blessing and a curse. He found himself standing upright on the ground. He could not outrun or out-fight his predators. It would take massive changes in his physical structure to improve the situation. Evolution usually works in an incremental fashion. Mutations occurred to his entire body and brain. Small changes to his body did bring about some physical changes. He developed stronger and better shaped eating tools. Still, his biggest problem was the predators, big fast cats and the men in the next tribe. Incremental physical changes did not help that problem one whit. Yet every time the brain grew incrementally (mutations that affected brain size), good things happened. He not only was able to handle his predator problem better, but his cultural life improved. With the free arms and hands to carry things and to handle weapons, his lot improved with each brain size increase.
Another factor in evolution may have been brought into play. It is rare but when it occurs it multiplies the effect of evolution. It works in both a negative and a positive way, and aids the organism in its balance with its environment, in either case. If mutations in a critical area in the DNA causes organism distress, natural selection will eliminate the mutation each time it happens (through death and misery). A mutation may occur which protects the organism from mutations in that critical area. This new mutation will prosper in the gene pool. This is a case where one mutation eliminates or reduces the recurrence of another unfavorable mutation before it happens. Its result is very favorable to the organism.
The reverse of that action is also beneficial. If a mutation in a particular area is favorable (say, one that causes an increase in brain size), natural selection will allow that mutation to remain in the gene pool each time it occurs, if it is needed and utilized. The brain will grow incrementally each time the mutation happens. Since mutations are rare and random, brain growth would be quite slow even if greatly needed. Nevertheless, if a mutation occurred which encouraged such mutations so that they would happen more often, the rate of brain growth would be accelerated. This could explain the more rapid brain growth starting at the juncture of africanus and habilis. Still, the coding of an accelerator mutation is itself subject to mutation. If brain-power was really making a difference then, then this new mutation would be detrimental and be quickly eliminated. Yet if the organism was comfortable, the accelerator would soon disappear from the gene pool since it would not affect survivability. The latter probably happened about 100,000 years ago when the human population started expanding rapidly (showing ability greater than needed). An expanding population is a good measure of organism comfort. Detrimental mutations will accumulate in the gene pool at such times, and favorable characteristics will be degraded.
Evolution, through the liberal application of death and hardship, had built a strong body and a sound mind by the time of the appearance of Homo sapiens sapiens. Both were designed for entirely different environments than experienced by man today. We live longer today for three reasons. One is our health care and diet. The second is that our bodies were constructed to last thirty years under brutally harsh conditions. Removal of those harsh conditions allows a longer life span. Third is our culture. We cheat evolution of the deaths that it needs to cleanse the gene pool. In the short run we will live longer. Eventually mutations will erase these benefits. Evolution seeks to have us hanging over the edge.
In modern society, survivability is no longer dependent on the condition of the mind. In fact, the more successful tend to have fewer children. Mutations that distort the function or size of the brain are no longer removed by natural selection from the gene pool. The enormous size of the population slows the spread of adverse mutations across the gene pool, but if no one dies of their adverse effects before he has his offspring, alleles from adverse mutations will accumulate.
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