Anthropology in the News
Follow the links below for new anthropological research I mention during lecture that represent recent anthropological research relevant to the course. These links will accumulate during the semester.
Texas A&M News in Anthropology
(a very complete and up-to-date site on important news stories in anthropology)
Look around the Amazon rainforest today and it’s hard to imagine it filled with people. But in recent decades, archaeologists have started to find evidence that before Columbus’s arrival, the region was dotted with towns and perhaps even cities. Read more.
Feb 6, 2012
Monogamy reduces major social problems of polygamist cultures
In cultures that permit men to take multiple wives, the intra-sexual competition that occurs causes greater levels of crime, violence, poverty and gender inequality than in societies that institutionalize and practice monogamous marriage.
That is a key finding of a new University of British Columbia-led study that explores the global rise of monogamous marriage as a dominant cultural institution. The study suggests that institutionalized monogamous marriage is rapidly replacing polygamy because it has lower levels of inherent social problems.
?Our goal was to understand why monogamous marriage has become standard in most developed nations in recent centuries, when most recorded cultures have practiced polygyny,? says UBC Prof. Joseph Henrich, a cultural anthropologist, referring to the form of polygamy that permits multiple wives, which continues to be practiced in some parts of Africa, Asia, the Middle East and North America.
?The emergence of monogamous marriage is also puzzling for some as the very people who most benefit from polygyny ? wealthy, powerful men ? were best positioned to reject it,? says Henrich, lead author of the study that is published today in the journal Philosophical Transactions of the Royal Society. ?Our findings suggest that that institutionalized monogamous marriage provides greater net benefits for society at large by reducing social problems that are inherent in polygynous societies.?
Considered the most comprehensive study of polygamy and the institution of marriage, the study finds significantly higher levels rape, kidnapping, murder, assault, robbery and fraud in polygynous cultures. According to Henrich and his research team, which included Profs. Robert Boyd (UCLA) and Peter Richerson (UC Davis), these crimes are caused primarily by pools of unmarried men, which result when other men take multiple wives.
[My addition: You are probably wondering why North and Central Americannations
are colored medium green. This is a consequence of the presence
of fundamentalist break-away Mormon and other groups.]
?The scarcity of marriageable women in polygamous cultures increases competition among men for the remaining unmarried women,? says Henrich, adding that polygamy was outlawed in 1963 in Nepal, 1955 in India (partially), 1953 in China and 1880 in Japan. The greater competition increases the likelihood men in polygamous communities will resort to criminal behavior to gain resources and women, he says.
According to Henrich, monogamy?s main cultural evolutionary advantage over polygyny is the more egalitarian distribution of women, which reduces male competition and social problems. By shifting male efforts from seeking wives to paternal investment, institutionalized monogamy increases long-term planning, economic productivity, savings and child investment, the study finds. Monogamy?s institutionalization has been assisted by its incorporation by religions, such as Christianity.
Monogamous marriage also results in significant improvements in child welfare, including lower rates of child neglect, abuse, accidental death, homicide and intra-household conflict, the study finds. These benefits result from greater levels of parental investment, smaller households and increased direct ?blood relatedness? in monogamous family households, says Henrich, who served as an expert witness for British Columbia?s Supreme Court case involving the polygamous community of Bountiful, B.C.
Monogamous marriage has largely preceded democracy and voting rights for women in the nations where it has been institutionalized, says Henrich, the Canadian Research Chair in Culture, Cognition and Evolution in UBC?s Depts. of Psychology and Economics. By decreasing competition for younger and younger brides, monogamous marriage increases the age of first marriage for females, decreases the spousal age gap and elevates female influence in household decisions which decreases total fertility and increases gender equality.
View the study, The Puzzle of Monogamous Marriage, at: http://rstb.royalsocietypublishing.org/content/367/1589/657.full.pdf
Read a discussion of the paper in Discover Magazine at: http://blogs.discovermagazine.com/gnxp/2012/01/monogamous-societies-superior-to-polygamous-societies/
Finally, last November 2011 the Canadian Supreme Court upheld a low banning polygyny. On of the sources the judge used to explain the legality and benefits of the law was research in the article by Henrich and his colleagues above. (http://news.nationalpost.com/2011/11/23/b-c-supreme-court-rules-polygamy-law-is-constitutional/)
Python Predation on Humans: read article here.
Published February 10, 2010
A 4,000-year-old hairball found frozen in Greenland has been used to create the first ancient-human genome, says a new study that paints a picture of a dark-eyed man with dry ear wax who was prone to balding.
Well preserved in Arctic permafrost, the hair belonged to "Inuk," a relatively young member of the now extinct Saqqaq culture, the earliest known inhabitants of Greenland.
The Saqqaq have long presented a puzzle to scientists, according to study co-author Eske Willerslev, an evolutionary biologist at the University of Copenhagen in Denmark.
"Various theories have suggested that they were direct ancestors to the Inuit, or that they were actually Native Americans who penetrated into the High Arctic," Willerslev said. But little has been known about the Saqqaq's genetic history, since archaeological sites have yielded only a few small bits of preserved bone and hair.
The new DNA evidence, presented online today by the journal Nature, shows that Inuk's closest relatives are not the ancestors of today's Native Americans and Inuits, but three Arctic peoples of the Siberian Far East: the Nganasans, Koryaks, and Chukchis.
"This evidence suggests a [unique] migration happening around 5,500 years ago," Willerslev said, adding that this estimate nicely matches the earliest archaeological evidence of New World Arctic habitation.
In addition, analysis of Inuk's genome?which is comparable in quality to a modern human genome?allowed the scientists to create a DNA-based profile of the Saqqaq male.
Inuk Prone to Balding, Built for Cold
The hair sample used in the study was recovered from northern Greenland in the 1980s and had been kept since then at the National Museum of Denmark. (Related: "Museum Secrets Unmasked by 'Museomics' Technologies.")
Unlike the DNA found in ancient skin or bone, genes housed in hair can be recovered relatively free of contamination from the genes of fungi or bacteria.
This advantage has helped, for example, in making breakthroughs sequencing ancient mammoth DNA.
And, as with Inuk, the ever improving techniques being used on ancient DNA are also helping scientists decipher not only where ancient peoples came from, but what they looked like. (See a photo of the first model of a Neanderthal based in part on ancient DNA evidence.)
"In many ways this is the really exciting bit of the paper," said David Lambert, an evolutionary biologist at Australia's Griffith University, who co-authored a commentary on the study for Nature.
"People have done [DNA] studies in the past able to pinpoint the geographic origin of samples to greater or lesser degrees. I think the more unusual thing they've done is this work with single nucleotide polymorphisms," or SNPs.
A person's genes are made up of bundles of molecules called nucleotides?the "letters" with which DNA is written. Some genome sequences can differ by a single nucleotide, and these variations are called SNPs.
Work on the modern human genome has produced a large database of known SNP variations, and many have been identified with specific physical characteristics, such as eye color, that their carriers are 99 percent likely to display.
Inuk's genome reveals he most likely had brown eyes, dark skin and hair, and even dry ear wax. Although the ancient Greenlander had genes susceptible to baldness, he seems to have retained plenty of hair, leading scientists to suspect he died young.
Inuk had the shovel-graded front teeth common in both Asian and Native American populations, and his A blood type is relatively frequent in northeastern Siberia. His metabolism also appears to have been genetically fine-tuned for life in unforgiving cold climates.
Inuk Proof of Third New World Migration?
In addition to establishing this genetic portrait, the newly sequenced Saqqaq genome offers the first hard proof for a theorized third human migration from Siberia to the New World, said geneticist and National Geographic explorer-in-residence Spencer Wells.
Wells, who heads the Genographic Project, was not involved in the research. (The National Geographic Society owns National Geographic News and funds the Genographic Project.)
The first such migration is generally thought to be the journey of America's original paleo-Indian settlers, who crossed the Bering Strait via the Beringia land bridge some 15,000 years ago. These people likely became the ancestors of most South Americans and many North Americans.
"Then there was a later migration?probably by boat along the coast?some 6,000 to 8,000 years ago by the ancestors of western North Americans speaking the Na-Dene languages," Wells said. Today Na-Dene languages, including Navajo and Apache, are spoken only in western North America.
Linguistic evidence had suggested to some scholars that there must have been a third migration, although that theory is far from universal.
Still, Inuk's DNA trail links the Saqqaq more closely to Siberian cultures than Native American, leading Willerslev and colleagues to suggest his people must have made a separate, later migration.
The Bering Strait land bridge had disappeared by 5,500 years ago, so Inuk's ancestors must have crossed by kayaks, like those used by more recent Arctic peoples, or by walking the winter pack ice.
Making the Impossible Possible
Overall, the new study highlights the advances being made in genetic sequencing, the study authors and other experts say.
"It's an amazing technical achievement to get a whole genome out of a hair sample," Wells said.
And as sequencing technologies continue to improve even as expenses drop, similar projects could give new insights into past peoples such as the mummies of South America, study co-author Willerslev said.
Griffith University's Lambert agrees, although he cautions that similar results may be difficult to duplicate, because it was extraordinary to find so much ancient hair in such fine condition.
DNA degradation is related to temperature, so samples from outside the permafrost regions may be especially difficult to find and sequence, he noted, although he holds out hope that scientific advances and a bit of luck might yield unexpected finds.
"What's impossible today," he said, "is possible tomorrow."
Old stories that are still worth reading
Bushmen Squeeze Money From a Humble Cactus
April 1, 2003
By GINGER THOMPSON (NY Times)
TWEE RIVIEREN, South Africa - The educated city people - a government minister, a chief executive and several directors of the nation's most important scientific organizations - traveled at sunrise to this barren region of the Kalahari Desert to see for themselves the cactus that has been trumpeted as a natural wonder.
But when they stood before it, a puny cluster of spiny stalks that looked like wrinkled cucumbers, the magnitude of the moment escaped them.
"That's it, huh?" asked Dr. Ben Ngubane, minister of arts, culture, science and technology. "How do you know this one is safe to eat?"
A grin from Petrus Valbooi, a leader of the San people, or Bushmen, who scrape life from this barren landscape, reassured the skeptics. He cut off a stalk, shaved off its spines, and sliced into its milky center, bidding them to taste.
That's where its power lies, he told them. Indeed.
From a desert weed known as hoodia, one of the world's oldest and least developed peoples hopes to enjoy its first taste of prosperity.
The San have sucked on hoodia for generations, principally to raise their energy and fight hunger during long hunting trips.
Now, Pfizer, the international pharmaceutical giant, has begun work on an appetite suppressant from the plant, and agreed to share the profits. The deal, which includes the government, is considered a landmark in the field of international property rights.
The company, with a British-based research partner, has spent millions working to develop the drug from the active chemical in the obscure runt of a cactus, hoping to make it as profitable as Viagra.
Here among the San, the concept of wealth has begun to sink in. The first payment to the San, some $30,000, was made
last month, and there are already plans to buy land and build clinics.
But at the formal signing of the agreement in March, most of the Bushmen seemed happy just knowing that the modern world had recognized that there remained wealth in ancient knowledge, and that at least one tradition in their dying culture might be saved.
"I am very happy because it was not written that this day would happen," said Mr. Valbooi, who arrived at the
ceremony wearing traditional shorts made from deerskin and a crown made from the tail of a wild cat. "Now I know that
God has not abandoned the Bushmen."
It was a happy ending to a protracted legal conflict that began in 1996 when the Council for Scientific and
Industrial Research, a government-financed laboratory, patented the active chemical of the hoodia, called P57,
without acknowledging the San.
The government then licensed rights to develop P57 to the British pharmaceutical research company Phytopharm, which sublicensed the rights to Pfizer.
After years of legal wrangling, an agreement was reached between the San and the government. Under the agreement, some 100,000 Bushmen in four countries - South Africa, Botswana, Namibia and Angola - will receive at least three more payments during the clinical testing of the drug.
Then the South African government will pay the San some 6 percent of the royalties it receives once the drug goes on the market.
Roger Chennells, a lawyer who represented the San in their legal fight, acknowledged that the community was getting the smallest slice of what could be a multibillion-dollar pie. "If this is a cop-out," he said, "then it is a cop-out I can live with because it is going to bring these people benefits no government has ever given them."
The San trace their history back some 150,000 years, to the world's first humans. The hunter-gatherers are still considered expert trackers, with abilities to read animal movements from the sand.
But they became the prey under South Africa's colonial rulers, who shot them for sport. Under apartheid, the San were enslaved and robbed of their ancestral land. The South African military used them to find black opposition leaders living on the run.
To the marvel of anthropologists, the San have been able to cling to their traditions. After the end of white rule, South Africa's first black president, Nelson Mandela, returned them to their lands, as arid as the face of the moon.
Today, however, fewer than a dozen people speak their language, and even fewer know how to hunt. Children learn traditional dances, but prefer polyester T-shirts and tennis shoes over animal skins. Most young people abandon the desert for schools and jobs in cities.
Jan Vander Westhuitzen, 47, a Bushman tracker, said hoodia is struggling, too. "Hoodia used to cover the desert, " he said, cutting a leaf from a shriveled specimen and stuffing it in a deerskin medicine pouch. "Now the land is too dry."
He said the plant had been a center of life for the Bushmen for as long as he could remember. A sip of its bitter
liquid gave them enough energy to walk all day or make love through the night. It cured a morning hangover, or, brewed like tea, soothed an aching stomach.
He seemed to delight at the idea that its secret was out. "I do not think we are being robbed of our knowledge," he said. "I think that people who know how to live from the earth should share."
Airs Sunday, Apr 06 at 4 p.m. on the National Geographic Cable Channel, #48
Meet Brazilian adventurer Sydney Possuelo. This 'Amazon Ambassador' has trekked through a landscape in which anacondas and ambush seem to lurk around every jungle bend. He's been assailed by malaria 37 times, nearly lost an eye and broke a rib in a plane crash. Along the way, he has fought to protect the way of life some of the most isolated peoples on Earth as head of Brazil's Department of Isolated Indians (FUNAI). FUNAI itself has also withstood the hardships of its work - 50 staff members have died in the field, from both violent conflicts and the jungle itself. The fate of isolated Indians has become increasingly precarious in the more than forty years since Possuelo first made their cause his life's work. Invisible People offers a unique insight into a career spent wrestling the forces of modernity, as we follow Sydney on an emergency visit to the recently contacted Korubo tribe, known locally as the "head smashers" - a reference to their unusual method of waging battles. Traveling into Korubo territory we learn about the plethora of forces that threaten Amazonian tribes; from drug smuggling and disease, to tribal conflicts, and Sydney's struggle to protect their land and preserve their way of life.
Revenge motivates tribal warfare (return)
Probably the single most common motive mentioned by tribal warriors when asked why they go to war, is revenge, according to a Penn State anthropologist. "The impulse for revenge is far from being uniquely human," says Dr. Stephen Beckerman, associate professor of anthropology.
"Clutton-Brock and Parker show how widespread in the animal kingdom is the behavior of returning injury for injury. Animals as varied and as far from us as blue-footed boobies, elephant seals, side-striped jackals and European moorhens are called punishers; they regularly respond to injuries by attacking the culprit who has injured them."
Beckerman notes that among some primates, injured individuals may punish one of his or her attacker's relatives rather than punish the attacker or, in other primates, the punishment may be meted out not to a relative, but to a friend or ally of the victim. Presumably, they intend this behavior to be negative reinforcement; training others to act so they do not damage the fitness of the punisher.
"When we come to blood revenge among human beings, it is helpful to remember that we seem to be dealing with something that is not so different from behaviors we already see in primates," Beckerman told attendees today (Feb.
14) at the annual meeting of the American Association for the Advancement of Science in Denver.
Human revenge is concerned with dominance and status as is that of other primates, and often revenge is taken on a relative or ally. Perhaps one difference is that animal punishment as defined by Clutton-Brock and Parker disavows "a conscious decision or a moral sense on the part of the punisher."
Humans add to the widespread, angry animal impulse to punish, a conscious sense of what the reception of punishment will be and achieve, and that consciousness moves the act from animal punishment to human revenge.
"Revenge is a desire to not just punish the culprit, but to change his mind, to make him see, if only in his death throws, that he was wrong," said Beckerman.
This idea of revenge colors the methods and approaches of tribal warfare. After the psychological basis for revenge in providing negative reinforcement there are the social rules developed to carry out this revenge. The idea of blood revenge - a life for a life, an eye for an eye - is of concern to social groups because the injured party is usually already dead.
"The general rule is that you are prohibited from taking blood revenge on those who would be obliged to avenge you, if you were killed," said Beckerman.
So, among the inner circle, or within the social group, revenge is forbidden. However, at a further distance, with those groups a tribe has close contact with, reciprocal exchange and trade, revenge is acceptable, but constrained by rules. At this intermediate social distance, the groups share enough values and beliefs on what injuries need revenge and how that revenge is carried out to have rules as to who is an acceptable target of revenge. These rules, which include who can carry out revenge against whom, where it can occur and for what reason, are attempts to achieve an equal balance of injuries.
"Sometimes feud goes on for centuries, but reciprocal violence at this middle social distance can also be self-limiting," said the Penn State anthropologist.
At the greatest social distance, the people are essentially strangers and evoke the bloodiest revenge without an attempt at balance. Revenge against foreigners is often disproportionate to the initial injury and often deliberately full of atrocities. The aim is not to achieve balance, but to attain total submission or extermination.
While within group revenge episodes are unusual, tribal members cannot always prevent someone who is so angry they inflict revenge on an in-law, brother or cousin, but taking that revenge is outside the rules. On the intermediate level, the value of ritualized revenge, seems to be that any group that is not willing to retaliate blood for blood finds its resources, land and homes plundered, women carried off and men bullied.
Revenge is not always an immediate act. Sometimes a group must wait for adequate manpower, resources and opportunity. During the recent fighting in the former Yugoslavia, some leaders rallied their forces by evoking the defeat at the hands of the Moslems that occurred 900 years before they were born. Revenge has a long memory.
Beckerman notes, however, that currently we do not operate on the tribal level and that a watershed in human history occurred when the decision to go to war was no longer made by those who fight the wars.
Tribal Warfare is Not Adaptive
Waging war: The curse of human intelligence
ORONO - With America and its allies poised to attack Iraq and the U.S. and North Korea locked in a showdown over nuclear weapons, diplomats and politicians would do well to remember that humans may have nuclear technology but still only possess stone-age brains. This is often a lethal combination, says University of Maine anthropologist Paul Roscoe who will present a paper on tribal warfare in New Guinea today at the annual meeting of the American Association for the Advancement of Science in Denver.
Roscoe has extensively studied revenge as a motive for war among tribes in New Guinea and concludes that killing enemies to avenge the death of kin - something only humans do - is probably not a useful evolutionary adaptation. This is because lethal revenge most frequently fuels more killing rather than deterring it, says the professor of anthropology and cooperating professor of Quaternary and Climate Studies at UMaine.
"I argue that revenge is probably not an adaptive feature because revenge is not good for you," Roscoe says. Evolutionarily speaking, it does not make sense to engage in behavior that may not only kill yourself but also other members of your clan or tribe. Writ large in a thermonuclear exchange, revenge killing could theoretically wipe out your entire species. "It makes evolutionary sense to fight and then back off."
Humans have, in a sense, deviated from the evolutionary path by engaging in revenge killings and warfare. They do so because their technical ability to harm one another has outpaced their social and cultural abilities to deal with behavior that might not be so wise, Roscoe surmises. Only in the last 10,000 years of human existence have people evolved from hunters and gatherers with spears to glorified hunters and gatherers with thermo-nuclear weapons.
"We may have nuclear technology, but we still have stone-age brains," Roscoe says. "Our social and political systems are slow to adapt in comparison to the pace of technological development."
Previous theories on motives for revenge, based on socio-biology, have centered on an escalating tit-for-tat complex. This theory holds that humans have simply taken behavior routinely practiced by other animals to the next step. Many animal species engage in escalating aggressive behavior. Male red deer competing for territory or mates, for example, will first roar at one another. If neither backs away, the animals then walk back and forth side-by-side sizing one another up. If this fails to resolve the conflict, the two animals may fight, but the results are typically not lethal.
Humans, however, are the only animals to seek out enemies and to kill them for past actions. Roscoe argues that this is because humans have a large, highly developed neo-cortex, the region of the brain known for intellectual thought and creativity. The neo-cortex is believed to have evolved for positive purposes such as enabling humans to develop tools, to communicate through language, and to plan cooperative hunting trips. However, it has not always been used for positive purposes.
"Humans developed the ability to model actions before they happen. This means we can plan collective violence. It explains why we have warfare," he says. Research on chimps confirms that, once you can gang up and launch a surprise attack on outnumbered victims, killing becomes a dramatically more attractive option than it is in the one-on-one confrontations typical of other species.
The neo-cortex also allow humans to manipulate their emotional states. Warriors, for example, can whip themselves into an angered frenzy by recalling slain kin and engaging in repetitive, war-mongering chants.
A highly developed neo-cortex also allows people to de-humanize their enemies. Many tribes in New Guinea, for example, refer to their enemies as "our game" and world leaders have equated their enemies with mad dogs and rats. This is how humans circumvent their built-in aversion to killing members of their own species, Roscoe says.
This portion of the brain has also allowed humans to develop sophisticated weapons whereby they can kill one another without face-to-face contact. This not only can make killing more efficient, but also gets around our in-bred aversion to killing other humans.
Roscoe has focussed his research on tribes in New Guinea because surprisingly little work has been done on the wars waged by these people, many of whom did not have contact with outsiders until the 1930s. In addition, the island presents a potential treasure trove of information on warfare because, at the time of contact, there were thousands of groups that spoke more than 1,000 languages. These groups were often at war with one another. With funding from the National Science Foundation, Fulbright-Hays Area Studies Program and the American Philosophical Society, Roscoe has traveled to archives around the world to collect data about warfare in contact-era New Guinea. Since anthropologists usually arrived many years after contact, Roscoe often has had to rely on other sources, especially the writings of missionaries who visited the South Pacific island. Much of the writing Roscoe reviewed is in German and Dutch.
He found that much of the warfare in New Guinea was, in fact, precipitated by revenge and that the motive was to weaken the enemy and to forestall further aggression. Some tribes believed they must fight until the number of dead on both sides were equal. Others believed they must inflict lethal revenge to be spared from the ghosts of clansmen who were killed. However the fighting began, it often escalated, sometimes involving groups not party to the initial clash, and continued for generations. This raises problems for theories that revenge stops further aggression.
"My hope is that somewhere down the road, we will use this knowledge to get around killing one another. War is the most costly thing in the world in terms of blood and treasure. We need to figure out why we have war before it wipes us off the planet," Roscoe concludes.
Miners Killed by Cinta Larga of Brazil
THURSDAY April 22, 2004
Chief defends killing of diamond prospectors
THURSDAY April 22, 2004 Chief defends killing of diamond prospectors
A female Cinta Larga warrior aims her arrow at reporters at the Roosevelt Indian Reservation in Rondonia state, Brazil, on Wednesday. (Victor R. Caivano/The Associated Press)
The Associated Press
ON THE ROOSEVELT INDIAN RESERVATION, Brazil -- An Amazonian tribal chief said Wednesday the killing of 29 diamond prospectors on his remote Indian reservation came after they were repeatedly warned to stay away. In his first comments to the media since the April 7 killings, Chief Pio Cinta Larga told The Associated Press that Indians in the area carried out the killings, but he denied ordering the attack or taking part in it. "There are some very angry Indians and not even the leadership can control their actions," he said, adding that members of other tribes have joined the Cinta Larga on the 6.7-million-acre reservation, where prospectors frequently trespass. "We told them we didn't want them here and they kept coming back. The warriors lost patience and this is what happened," said Cinta Larga, who uses the tribe's name as his surname. Federal police have said the 29 miners were killed by the Cinta Larga Indian tribe in a dispute over diamond mining. The reservation is believed to have South American's largest diamond reserves. Investigators indicated most of the miners were lined up and killed at short range with arrows, clubs, spears and firearms. Many of the bodies appeared to have been tortured or mutilated. Though denying links to the attack, he said the Indians have a right to defend their culture. "We are warriors," said Cinta Larga. "Before the white man came, none of the tribes here were friends. We fought and killed each other, that is how we resolved things."
The Roosevelt Indian reservation in Roaondonia state, some 2,100 miles northwest of Rio de Janeiro, is cloaked within the dense Amazon rainforest, reachable only over nearly 100 miles of rutted dirt roads. Travel inside the reservation is mainly over jungle footpath or by river. The Cinta Larga Indians were first contacted by outsiders in the late 1960s, but development has been a mixed blessing. Many of the Indians are fairly well-off, dressing in western-style clothing and driving pickup trucks. About two-thirds of the 1,300-strong tribe have learned Portuguese, Brazil's national language, but the remaining Indians maintain the tribe's fierce warrior traditions. The president of Brazil's Federal Indian Bureau has said he considered the Indians to be acting in legitimate self-defense because both mining and trespassing by non-Indians are illegal on Indian reservations. Those comments only served to fuel already high tension between the heavily armed Indians and prospectors. "It's illegal to mine on Indian land, it's also illegal to kill," said Celso Antim of the prospector's union in Espigao d'Oeste, about 60 miles from the reservation. Antim said the killings would not keep prospectors off the reservation for long. "There will be a little pause, but then they'll all go back because they're all going hungry," he said. "This time, though, they'll go back armed." Clashes between Indians and prospectors have claimed at least 70 lives since diamond mining began. Cinta Larga warned that prospectors who returned should know they were taking their lives in their hands. He said the solution is to change the law so Indians can legally mine on their lands. Currently, the Indians mine the diamonds in violation of federal law and sell them on the black market in violation of the international Kimberly protocol, which governs the sale and trade of diamonds. A task force composed of hundreds of state and federal agents has been deployed in and around the reservation and is expected to remain in the region for up to six months. The unit is disarming prospectors and Indians and will try to put an end to mining and prospecting activities in the reservation. But officials here said ending the illegal prospecting will not be easy. Brazil's Mines and Energy Ministry estimated some $2 billion in diamonds have been mined in the area since prospecting began in 1999. "Prospecting isn't something that ends from one day to another. It will be reactivated there is a great desire for diamonds and the diamonds on the reservation are very good," said Amoss de Mello Oliveira, a geologist working with the police.
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Pas de Deux of Sexuality Is Written in the Genes
When it comes to the matter of desire, evolution leaves little to chance. Human sexual behavior is not a free-form performance, biologists are finding, but is guided at every turn by genetic programs.
Desire between the sexes is not a matter of choice. Straight men, it seems, have neural circuits that prompt them to seek out women; gay men have those prompting them to seek other men. Women?s brains may be organized to select men who seem likely to provide for them and their children. The deal is sealed with other neural programs that induce a burst of romantic love, followed by long-term attachment.
So much fuss, so intricate a dance, all to achieve success on the simple scale that is all evolution cares about, that of raising the greatest number of children to adulthood. Desire may seem the core of human sexual behavior, but it is just the central act in a long drama whose script is written quite substantially in the genes.
In the womb, the body of a developing fetus is female by default and becomes male if the male-determining gene known as SRY is present. This dominant gene, the Y chromosome?s proudest and almost only possession, sidetracks the reproductive tissue from its ovarian fate and switches it into becoming testes. Hormones from the testes, chiefly testosterone, mold the body into male form.
In puberty, the reproductive systems are primed for action by the brain. Amazing electrical machine that it may be, the brain can also behave like a humble gland. In the hypothalamus, at the central base of the brain, lie a cluster of about 2,000 neurons that ignite puberty when they start to secrete pulses of gonadotropin-releasing hormone, which sets off a cascade of other hormones.
The trigger that stirs these neurons is still unknown, but probably the brain monitors internal signals as to whether the body is ready to reproduce and external cues as to whether circumstances are propitious for yielding to desire.
Several advances in the last decade have underlined the bizarre fact that the brain is a full-fledged sexual organ, in that the two sexes have profoundly different versions of it. This is the handiwork of testosterone, which masculinizes the brain as thoroughly as it does the rest of the body.
It is a misconception that the differences between men?s and women?s brains are small or erratic or found only in a few extreme cases, Dr. Larry Cahill of the University of California, Irvine, wrote last year in Nature Reviews Neuroscience. Widespread regions of the cortex, the brain?s outer layer that performs much of its higher-level processing, are thicker in women. The hippocampus, where initial memories are formed, occupies a larger fraction of the female brain.
Techniques for imaging the brain have begun to show that men and women use their brains in different ways even when doing the same thing. In the case of the amygdala, a pair of organs that helps prioritize memories according to their emotional strength, women use the left amygdala for this purpose but men tend to use the right.
It is no surprise that the male and female versions of the human brain operate in distinct patterns, despite the heavy influence of culture. The male brain is sexually oriented toward women as an object of desire. The most direct evidence comes from a handful of cases, some of them circumcision accidents, in which boy babies have lost their penises and been reared as female. Despite every social inducement to the opposite, they grow up desiring women as partners, not men.
?If you can?t make a male attracted to other males by cutting off his penis, how strong could any psychosocial effect be?? said J. Michael Bailey, an expert on sexual orientation at Northwestern University.
Presumably the masculinization of the brain shapes some neural circuit that makes women desirable. If so, this circuitry is wired differently in gay men. In experiments in which subjects are shown photographs of desirable men or women, straight men are aroused by women, gay men by men.
Such experiments do not show the same clear divide with women. Whether women describe themselves as straight or lesbian, ?Their sexual arousal seems to be relatively indiscriminate ? they get aroused by both male and female images,? Dr. Bailey said. ?I?m not even sure females have a sexual orientation. But they have sexual preferences. Women are very picky, and most choose to have sex with men.?
Dr. Bailey believes that the systems for sexual orientation and arousal make men go out and find people to have sex with, whereas women are more focused on accepting or rejecting those who seek sex with them.
Similar differences between the sexes are seen by Marc Breedlove, a neuroscientist at Michigan State University. ?Most males are quite stubborn in their ideas about which sex they want to pursue, while women seem more flexible,? he said.
Sexual orientation, at least for men, seems to be settled before birth. ?I think most of the scientists working on these questions are convinced that the antecedents of sexual orientation in males are happening early in life, probably before birth,? Dr. Breedlove said, ?whereas for females, some are probably born to become gay, but clearly some get there quite late in life.?
Sexual behavior includes a lot more than sex. Helen Fisher, an anthropologist at Rutgers University, argues that three primary brain systems have evolved to direct reproductive behavior. One is the sex drive that motivates people to seek partners. A second is a program for romantic attraction that makes people fixate on specific partners. Third is a mechanism for long-term attachment that induces people to stay together long enough to complete their parental duties.
Romantic love, which in its intense early stage ?can last 12-18 months,? is a universal human phenomenon, Dr. Fisher wrote last year in The Proceedings of the Royal Society, and is likely to be a built-in feature of the brain. Brain imaging studies show that a particular area of the brain, one associated with the reward system, is activated when subjects contemplate a photo of their lover.
The best evidence for a long-term attachment process in mammals comes from studies of voles, a small mouse-like rodent. A hormone called vasopressin, which is active in the brain, leads some voles to stay pair-bonded for life. People possess the same hormone, suggesting a similar mechanism could be at work in humans, though this has yet to be proved.
Researchers have devoted considerable effort to understanding homosexuality in men and women, both for its intrinsic interest and for the light it could shed on the more usual channels of desire. Studies of twins show that homosexuality, especially among men, is quite heritable, meaning there is a genetic component to it. But since gay men have about one-fifth as many children as straight men, any gene favoring homosexuality should quickly disappear from the population.
Such genes could be retained if gay men were unusually effective protectors of their nephews and nieces, helping genes just like theirs get into future generations. But gay men make no better uncles than straight men, according to a study by Dr. Bailey. So that leaves the possibility that being gay is a byproduct of a gene that persists because it enhances fertility in other family members. Some studies have found that gay men have more relatives than straight men, particularly on their mother?s side.
But Dr. Bailey believes the effect, if real, would be more clear-cut. ?Male homosexuality is evolutionarily maladaptive,? he said, noting that the phrase means only that genes favoring homosexuality cannot be favored by evolution if fewer such genes reach the next generation.
A somewhat more straightforward clue to the origin of homosexuality is the fraternal birth order effect. Two Canadian researchers, Ray Blanchard and Anthony F. Bogaert, have shown that having older brothers substantially increases the chances that a man will be gay. Older sisters don?t count, nor does it matter whether the brothers are in the house when the boy is reared.
The finding suggests that male homosexuality in these cases is caused by some event in the womb, such as ?a maternal immune response to succeeding male pregnancies,? Dr. Bogaert wrote last year in the Proceedings of the National Academy of Sciences. Antimale antibodies could perhaps interfere with the usual masculinization of the brain that occurs before birth, though no such antibodies have yet been detected.
The fraternal birth order effect is quite substantial. Some 15 percent of gay men can attribute their homosexuality to it, based on the assumption that 1 percent to 4 percent of men are gay, and each additional older brother increases the odds of same-sex attraction by 33 percent.
The effect supports the idea that the levels of circulating testosterone before birth are critical in determining sexual orientation. But testosterone in the fetus cannot be measured, and as adults, gay and straight men have the same levels of the hormone, giving no clue to prenatal exposure. So the hypothesis, though plausible, has not been proved.
A significant recent advance in understanding the basis of sexuality and desire has been the discovery that genes may have a direct effect on the sexual differentiation of the brain. Researchers had long assumed that steroid hormones like testosterone and estrogen did all the heavy lifting of shaping the male and female brains. But Arthur Arnold of the University of California, Los Angeles, has found that male and female neurons behave somewhat differently when kept in laboratory glassware. And last year Eric Vilain, also of U.C.L.A., made the surprising finding that the SRY gene is active in certain cells of the brain, at least in mice. Its brain role is quite different from its testosterone-related activities, and women?s neurons presumably perform that role by other means.
It so happens that an unusually large number of brain-related genes are situated on the X chromosome. The sudden emergence of the X and Y chromosomes in brain function has caught the attention of evolutionary biologists. Since men have only one X chromosome, natural selection can speedily promote any advantageous mutation that arises in one of the X?s genes. So if those picky women should be looking for smartness in prospective male partners, that might explain why so many brain-related genes ended up on the X.
?It?s popular among male academics to say that females preferred smarter guys,? Dr. Arnold said. ?Such genes will be quickly selected in males because new beneficial mutations will be quickly apparent.?
Several profound consequences follow from the fact that men have only one copy of the many X-related brain genes and women two. One is that many neurological diseases are more common in men because women are unlikely to suffer mutations in both copies of a gene.
Another is that men, as a group, ?will have more variable brain phenotypes,? Dr. Arnold writes, because women?s second copy of every gene dampens the effects of mutations that arise in the other.
Greater male variance means that although average IQ is identical in men and women, there are fewer average men and more at both extremes. Women?s care in selecting mates, combined with the fast selection made possible by men?s lack of backup copies of X-related genes, may have driven the divergence between male and female brains. The same factors could explain, some researchers believe, why the human brain has tripled in volume over just the last 2.5 million years.
Who can doubt it? It is indeed desire that makes the world go round.