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History's Hinge - 'Ain Jalut

[Administration]

Christophe Boesch holding a freshly excavated stone from the Noulo site

MAX PLANCK SOCIETY
The Chimpanzee Stone Age


A typical stone hammer used by chimpanzees in the Tai forest to crack Panda nuts showing a deep wear

Researchers have found evidence that chimpanzees from West Africa were cracking nuts with stone tools before the advent of agriculture, thousands of years ago. The result suggests chimpanzees developed this behaviour on their own, or even that stone tool use was a trait inherited from our common ancestor. Julio Mercader, Christophe Boesch and colleagues found the stones at the Noulo site in C?te d?Ivoire, the only known prehistoric chimpanzee settlement. The stones they excavated show the hallmarks of use as tools for smashing nuts when compared to ancient human or modern chimpanzee stone tools. Also, they found several types of starch grains on the stones; part of the residue derived from cracking local nuts. The tools are 4300 years old, which, in human terms, corresponds to the Later Stone Age (PNAS, February 2007).

Before this study, chimpanzees were first observed using stone tools in the 19th century. Now, thanks to this new archaeological find, tool use by chimpanzees has been pushed back thousands of years. The authors suggest this type of tool use could have originated with our common ancestor, instead of arising independently among hominins and chimpanzees or through imitation of humans by chimpanzees.

This study confirmed that chimpanzees and human ancestors share for thousands of years several cultural attributes once thought exclusive of humanity, including transport of raw materials across the landscape; selection and curation of raw materials for a specific type of work and projected usage; habitual reoccupation of sites where garbage and debris accumulate; and the use of locally available resources. Nut cracking behaviour in chimpanzees is transmitted socially, and the new discoveries presented in this study shows that such behaviour has been transmitted over the course of many chimpanzee generations. Chimpanzee prehistory has deep roots!

The study of our living closest relative, the chimpanzee, constantly highlights new aspects of human evolution, and a better protection of this endangered species will guarantee that we can continue uncovering new facets of our past. Relevant finds come from all parts of the African continent, including the  rainforest, and not just the classical east African homeland.

[Solomon]

A chimpanzee in Senegal eats a type of primate called a lesser bush baby (also shown inset) after hunting it with a rudimentary spear?one of the first known instances of great apes using tools to hunt mammals.
Video still courtesy National Geographic/NOVA, inset photograph by P.J. Wagner/Photo Access/Getty Images

Chimps Use "Spears" to Hunt Mammals, Study Says
John Roach
for National Geographic News
February 22, 2007

For the first time, great apes have been observed making and using tools to hunt mammals, according to a new study. The discovery offers insight into the evolution of hunting behavior in early humans.

No fewer than 22 times, researchers documented wild chimpanzees on an African savanna fashioning sticks into "spears" to hunt small primates called lesser bush babies.

In each case a chimpanzee modified a branch by breaking off one or two ends and, frequently, using its teeth to sharpen the stick. The ape then jabbed the spear into hollows in tree trunks where bush babies sleep.

Video of a chimp retrieving a bush baby hunted with a "spear.")


Chimpanzees 'hunt using spears'
Chimpanzees in Senegal have been observed making and using wooden spears to hunt other primates, according to a study in the journal Current Biology.

Researchers documented 22 cases of chimps fashioning tools to jab at smaller primates sheltering in cavities of hollow branches or tree trunks.

The report's authors, Jill Pruetz and Paco Bertolani, said the finding could have implications for human evolution.

Chimps had not been previously observed hunting other animals with tools.

Pruetz and Bertolani made the discovery at their research site in Fongoli, Senegal, between March 2005 and July 2006.

"There were hints that this behavior might occur, but it was one time at a different site," said Jill Pruetz, assistant professor of anthropology at Iowa State University, US.

"While in Senegal for the spring semester, I saw about 13 different hunting bouts. So it really is habitual."

Jabbing weapon
Chimpanzees were observed jabbing the spears into hollow trunks or branches, over and over again. After the chimp removed the tool, it would frequently smell or lick it.

In the vast majority of cases, the chimps used the tools in the manner of a spear, not as probes. The researchers say they were using enough force to injure an animal that may have been hiding inside.

[Baja Bush Pilot]

Savannah chimpanzees, which can make weapons to hunt other primates for meat, can also seek refuge in caves, much like our earliest human ancestors.

New findings suggest the chimps apparently shelter themselves in caves to hide from the extreme African heat. The cave use was documented by visual observations and photographs.

Primatologist Jill Pruetz at Iowa State University in Ames and her colleagues research savannah chimpanzees (Pan troglodytes verus). These dwell in environs much like those from which humanity's ancestors are believed to have emerged.

Cool discovery

Specifically, the researchers investigated the Fongoli community of 35 savannah chimpanzees in southeastern Senegal, one of the hottest and driest habitats chimps live in today. Pruetz and her colleagues recently found that Fongoli chimps apparently could manufacture spears to hunt other primates, such as bushbabies.

Just finding the chimpanzees in their large, roughly 7,400-acre home range was very challenging at first, Pruetz recalled.

"Going for a week or 10 long days without seeing chimpanzees was normal at the beginning and, as you might imagine, very frustrating at times, especially during the dry season, when heat is such an issue for chimps and humans alike!" she told LiveScience.

The research into chimpanzees' possible use of caves began when Pruetz's field assistant Mboule Camara saw the apes coming from Sakoto cave, the largest cavern within the chimp's home range. The cave is more than 15 feet deep and located at the head of a shallow ravine that was formed through water runoff from a plateau.

To determine why they might use the cave, Pruetz recorded temperature data within the cave as well as at the different habitats the chimpanzees used, such as the woodlands and grasslands. She discovered that chimps most often use the stone cave as shelter during the hottest and driest times of the year, from October to May, findings detailed in an upcoming issue of the journal Primates. It is the first study to document regular cave use by chimps.

Up to 10 degrees cooler

Between 2001 and 2004, average annual daily temperature within the cave was 75.5 degrees Fahrenheit, compared with 85.2 degrees in the woodland locales and 76.2 degrees in grassland areas, both located at the edge of the Sakoto ravine and roughly 100 feet from the cave. The grasslands were probably cooler due to wind, Pruetz said.

"They'll bring food in and eat it in there and groom. They sort of just hang out and relax," Pruetz said. The chimps apparently used the caves during the day and not at night.

Pruetz recalled talking at a meeting in Japan about chimps using caves.

"Everyone was amazed," she said. "They thought it was great and no one had ever heard of anything like it, except that Jane Goodall actually came up to me after the talk?I was very excited of course?and she said that she heard of an incident in Mali where someone was doing a chimp survey and they surprised a bunch of chimps coming out of a cave."

"But that was the only other instance that anyone, as far as I know, has ever heard of (chimps in caves)," Pruetz said. "And if Jane Goodall hasn't heard of it, then I assume it it's not known to science."

Chimp culture

Paleoanthropologist Adrienne Zihlman at the University of California at Santa Cruz told LiveScience:  "These chimpanzees are dealing with conditions most chimpanzees don't have to deal with. They are giving a little window to some of the problems that have to be solved if you want to survive in the savannah, and are confronting the kinds of problems that our early human ancestors had to face."

Biologist Rob Shumaker at the Great Ape Trust of Iowa in Des Moines added, "These findings really point out the range of behavioral and cognitive flexibility that exists for chimpanzees."

"These results aren't seen at any other chimpanzee field site, stressing the idea that there's cultural variation between chimpanzees across sites. They continue to surprise us and teach use new things."

http://www.livescience.com/animalworld/070411_chimps_cave.html

[Solomon]

Here are some academic links on Chimpanzee awareness:

Chimpanzees: Our sister species
How can we assess chimp intelligence?

>they make tools and use them to acquire foods, for social displays, etc
>they have sophisticated hunting strategies that require cooperation, and allow animals to achieve influence and rank by sharing meat
>they are highly status conscious and manipulative, capable of deception
>they are analytical and problem-solvers, clearly capable of insight and complex "cognitive performance" in both the wild and in captivity, and particularly adept at analyzing relative relationships
>language experiments have shown that chimps are creative, can learn to use symbols (and teach them to others) and understand aspects of human language including some relational syntax, concepts of number and numerical sequence
Do chimps have language? That's the wrong question -- what do chimps want to say?

Chimpanzee Communication: Insight Into the Origin of Language
Only recently has it been realized how well chimpanzees can communicate. Most of the observations have come from a troop of wild chimps at the Gombe Stream Reserve on the shores of Lake Tanganyika and from a captive group in Holland's Arnhem Zoo (McCrone 147). Chimps make use of simple gestures, waving their hand in the direction they want another chimp to look or holding out a begging hand for support then relying on the intelligence of the other animal to sum up the situation and react (McCrone 149). Some chimps even develop their own special signals. These observations indicate that chimps are the most intelligent communicators in the animal world, even compared to other highly social species such as lions, wolves and monkeys. This level of communication comes from chimps' deep understanding of the social world around them, which means that each chimp must be able mentally to model the impact of its own actions on the group as well as being able to guess the intentions of others (McCrone 150).

The Mind of the Chimpanzee
An international multidisciplinary conference on chimpanzee cognition
March 22?25, 2007
In light of recent advances made in studies of chimpanzee cognition, the publication of the fully sequenced chimpanzee genome and the catastrophic destruction of chimpanzee populations around the world, the time is right to convene an international conference focusing on the mind of our closest living relative.

In the tradition of the ?Understanding Chimpanzees? conferences, which started 20 years ago, ?The Mind of the Chimpanzee? conference will bring together the top experts in the fields of chimpanzee cognition and conservation as well as the ?next generation? of chimpanzee researchers in order share new research findings, generate new collaborative research partnerships and examine how studying chimpanzee cognition impacts chimpanzee conservation.

In discussing intelligence with a number of scientists over the years, I have never heard quite so much claptrap, as they try to deny the obvious: that other species exhibit intelligence.

Anyone who has a dog knows that they dream. By my book, that demonstrates a degree of intelligence.

For me, the big questions are: What is intelligence? How can degrees and types of intelligence be measured? What does intelligence signify, if anything? How does intelligence relate to creativity (whatever that is) and self-awareness?

Intelligence seems to me to be a natural function of living organisms and the difference between species (and individuals) is merely degree.

The world is full of life, possibly all of it intelligent to some degree, yet we as a species are alone. The universe may be teeming with life, but are we not still alone?

Solomon

[Bart]

Scientists map DNA of research monkeys

LAURAN NEERGAARD, AP Medical Writer

Fri Apr 13, 2007

WASHINGTON - Scientists have unraveled the DNA of another of our primate relatives, this time a monkey named the rhesus macaque ? and the work has far more immediate impact than just to study evolution.

   These fuzzy animals are key to testing the safety of many medicines, and understanding such diseases as  AIDS, and the new research will help scientists finally be sure when they're a good stand-in for humans.

   "The thing we're all fascinated with is what makes us different from these animals who are so close to us," said Dr. Richard Gibbs of the Baylor College of Medicine, who led a team of more than 170 scientists that collaborated on the project.

   In Friday's edition of the journal Science, the researchers report deciphering the macaque's DNA and comparing it to the genetic blueprints of humans and chimpanzees, our closest living relatives.

   Among the most intriguing discoveries so far: a list of diseases where the same genetic mutation that makes people ill seems normal for the macaques.

   "That is really quite a stunner," said Dr. Francis Collins, genetics chief at the        National Institutes of Health, which funded the research. "It gives you a glimmer of how subtle changes in DNA cause big trouble."

   The mapping of the human genome in 2001 sparked an explosion of work to similarly decipher the DNA of other animals, so scientists could compare species in the effort to understand the functions of various genes.

   The rhesus macaque is the third primate genome to be completed, work that promises to greatly enhance understanding of primate evolution, perhaps even to help explain what makes us human.

   Not surprisingly, the DNA of humans, chimps and macaques are highly similar. Humans and chimps have evolved separately since splitting from a common ancestor about 6 million years ago, but still have almost 99 percent of their gene sequences in common.

   Macaques branched off from the ape family tree far earlier, about 25 million years ago ? yet still share about 93 percent of their DNA with humans, the new work shows.

   Here's the key: Six million years isn't long in evolutionary history. So if a particular gene is different in the human and the chimp, it's impossible to know which version came first. Add these more ancient Old World monkeys into the mix, however, and it may be possible to tease out genetic changes that were important for key traits of modern humans, such as higher brain power and walking upright.

   "That does point us, in a much more powerful way, to answering the question, 'What does humanness mean?' at the DNA level," said Collins, director of NIH's National Human Genome Research Institute.

   But right away, the work raises some important biomedical questions, because rhesus macaques are ubiquitous in medical research. Most vaccines and many drugs are tested in the monkeys before ever reaching people. And they're used as models of many human diseases, most notably the AIDS virus.

   "As models, we expect them to behave like us," noted Baylor's Gibbs. Yet consider some of the differences found so far: About one in 14,000 babies is born with PKU, or phenylketonuria, meaning their bodies can't process a protein found in most foods called phenylalanine. Without treatment, PKU causes mental retardation. But in macaques, the gene defect that causes PKU seems to cause no harm, suggesting they may somehow compensate in a way people can't.

   The researchers found a list of such mutations, from ones linked with cystic fibrosis to blood diseases, that are bad news for people but seem normal in the monkeys. Most involved metabolic disorders that in turn can harm the brain, a link Gibbs found particularly compelling.

   The monkeys had triple the number of genes as people to do run one arm of the immune system. That raises immediate questions about how they react in vaccine or AIDS research. "It would make sense that a comprehensive knowledge of their immune machinery should be a part of those studies," Gibbs said.

   On the other hand, macaques had far fewer of a family of cancer-related genes than either humans or chimps.

   Gibbs said the work has importance for the animals, too ? because knowing their genetic makeup should cut the number of monkeys needed in many biomedical experiments.

   "It's really about experimenting less and being able to learn more," he said.

   Stay tuned: More primate gene maps are on the way, including blueprints for orangutans, gorillas and gibbons.

[Solomon]

The ability to learn gestures separates apes from most species

Ape Gestures Offer Clues to Evolution of Human Communication

Media Contacts:
Emily Rios, 404-727-7732,
Lisa Newbern, 404-727-7709,

ATLANTA ? Researchers at the Yerkes National Primate Research Center, Emory University, have found bonobos and chimpanzees use manual gestures of their hands, feet and limbs more flexibly than they do facial expressions and vocalizations, further supporting the evolution of human language began with gestures as the gestural origin hypothesis of language suggests. This study appears in the current issue of the Proceedings of the National Academy of Sciences.

    Working with two groups of bonobos (13 individuals) and two groups of chimpanzees (34 individuals), Yerkes researchers Amy Pollick, PhD, and Frans de Waal, PhD, distinguished 31 manual gestures and 18 facial/vocal signals. They found both species used facial/vocal signals similarly, but the same did not hold true for the manual gestures. Rather, the researchers found both within and between species the manual gestures were less closely tied to a particular emotion and, thereby, serve a more adaptable function. For example, a single gesture may communicate an entirely different message depending upon the social context in which it is used.

    ?A chimpanzee may stretch out an open hand to another as a signal for support, whereas the same gesture toward a possessor of food signals a desire to share,? said Pollick. ?A scream, however, is a typical response for victims of intimidation, threat or attack. This is so for both bonobos and chimpanzees, and suggests the vocalization is relatively invariant,? Pollick continued.

    By studying similar types of communication in closely related species, researchers are able to determine shared ancestry. We know gestures are evolutionarily younger than facial expressions and vocalizations, as shown by their presence in apes and humans but not in monkeys. ?A gesture that occurs in bonobos and chimpanzees as well as humans likely was present in the last common ancestor,? said Pollick. ?A good example of a shared gesture is the open-hand begging gesture, used by both apes and humans. This gesture can be used for food, if there is food around, but it also can be used to beg for help, for support, for money and so on. Its meaning is context-dependent,? added de Waal.

     Looking for further distinctions between species, the researchers found bonobos use gestures more flexibly than do chimpanzees. ?Different groups of bonobos used gestures in specific contexts less consistently than did different groups of chimpanzees,? said Pollick. The researchers' findings also suggest bonobos and chimpanzees engage in multi-modal communication, combining their gestures with facial expressions and vocalizations to communicate a message. ?While chimpanzees produce more of these combinations, bonobos respond to them more often. This finding suggests the bonobo is a better model of symbolic communication in our early ancestors,? concluded Pollick.

    For more than seven decades, the Yerkes National Primate Research Center, Emory University, has been dedicated to advancing science and to improving human health and well-being. Today, the center, as one of only eight National Institutes of Health?funded national primate research centers, provides specialized scientific resources, expertise and training opportunities. Recognized as a multidisci?plinary research institute, the Yerkes Research Center is making landmark discoveries in the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems. Research programs are seeking ways to: develop vaccines for infectious and noninfectious diseases, such as AIDS and Alzheimer?s disease; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progres?sive illnesses such as Parkinson?s and Alzheimer?s; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary links between biology and behavior.

Ape gestures and language evolution

Amy S. Pollick and Frans B. M. de Waal *

Living Links, Yerkes National Primate Research Center, Emory University, 954 North Gatewood Road, Atlanta, GA 30329

Contributed by Frans B. M. de Waal, March 20, 2007 (sent for review January 28, 2007)

The natural communication of apes may hold clues about language origins, especially because apes frequently gesture with limbs and hands, a mode of communication thought to have been the starting point of human language evolution. The present study aimed to contrast brachiomanual gestures with orofacial movements and vocalizations in the natural communication of our closest primate relatives, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We tested whether gesture is the more flexible form of communication by measuring the strength of association between signals and specific behavioral contexts, comparing groups of both the same and different ape species. Subjects were two captive bonobo groups, a total of 13 individuals, and two captive chimpanzee groups, a total of 34 individuals. The study distinguished 31 manual gestures and 18 facial/vocal signals. It was found that homologous facial/vocal displays were used very similarly by both ape species, yet the same did not apply to gestures. Both within and between species gesture usage varied enormously. Moreover, bonobos showed greater flexibility in this regard than chimpanzees and were also the only species in which multimodal communication (i.e., combinations of gestures and facial/vocal signals) added to behavioral impact on the recipient.

Author contributions: A.S.P. and F.B.M.d.W. designed research, performed research, analyzed data, and wrote the paper.

The authors declare no conflict of interest.

*To whom correspondence should be addressed.
Frans B. M. de Waal, E-mail:

[Baja Bush Pilot]

WASHINGTON ? Maybe walking upright on two legs isn't such a defining human feature after all.
 
Scientists who spent a year photographing orangutans in the rain forest say the trait probably evolved in ancient apes navigating the treetops long before ancestors of humans climbed to the ground ? a hypothesis that contradicts science museums the world over. 
 
But it's more in tune with fossil evidence, contends Robin Crompton of the University of Liverpool, who co-authored the report in Friday's edition of the journal Science. ?An increasing number of people have been questioning this old 'up from the apes' idea? of how bipedalism evolved, Crompton said.

The popular explanation: Some chimpanzee-like creature that dragged its knuckles on the ground descended from trees into grasslands, and gradually straightened up to walk like modern humans. Yet climate data and fossils of such creatures as the famed Lucy suggest that early ancestors of humans lived in forests for far longer, and could move on two or four legs.

Think orangutans just swing around? Maybe in zoos. Actually, it is orangutans ? not the chimps who genetically are humans' closest relatives ? that can walk most like people, Crompton said. Recording orangutans in Sumatra, Susannah Thorpe of Britain's University of Birmingham measured something counterintuitive: When they move to the skinniest branches, where the tastiest fruit grows, they stand stiffly straight-legged, like a person. Why? They've got great long toes to wrap around skinny branches and hang on, balancing with one arm overhead while the other reaches for food.

Evolution requires a reason for such a special skill. Thorpe compares the orangutans' walking-in-treetops to the straight-legged gait of athletes running on springy tracks. Bending knees makes leg muscles work harder, she explains. Squatting makes more sense for chimps and gorillas, who developed stronger forearms as they climbed up and down big trees, than for smaller orangs, who spend all day in trees to avoid tigers. ?It's energetically quite economical for orangutans to feed and move on these bendy branches using bipedalism,? she concludes.

Other evolution experts praised the work, but aren't convinced. Why would chimps lose that bipedal ability while whatever became human retained it, asked Will Harcourt-Smith of the American Museum of Natural History in New York.

?Another view of this might be that actually, our ancestor was rather good at doing a number of things,? said Harcourt-Smith, who believes there were several gradual shifts to walking upright instead of one big leap.

Evolution aside, the new insight into how orangutans reach their food may help efforts to conserve the dwindling habitat of these endangered apes, Crompton said.

[Baja Bush Pilot]

Scientists sounding out how baboons think

Royal is a cantankerous old male baboon whose troop of some 80 members lives in the Moremi Game Reserve in Botswana. A perplexing event is about to disturb his day.

From the bushes to his right, he hears a staccato whoop, the distinctive call that female baboons always make after mating. He recognizes the voice as that of Jackalberry, the current consort of Cassius, a male who outranks Royal in the strict hierarchy of male baboons. No hope of sex today.

But then, surprisingly, he hears Cassius's signature greeting grunt to his left. His puzzlement is plain on the video made of his reaction. You can almost see the wheels turn slowly in his head:

"Jackalberry here, but Cassius over there. Hmm, Jackalberry must be hooking up with some one else. But that means Cassius has left her unguarded. Say what � this is my big chance!"

The video shows him loping off in the direction of Jackalberry's whoop. But all that he will find is the loudspeaker from which researchers have played Jackalberry's recorded call.

The purpose of the experiment is not to ruin Royal's day but to understand what goes on in a baboon's mind, in this case how carefully the animals keep track of transient relationships.

Dorothy Cheney and Robert Seyfarth, a husband-and-wife team of biologists at the University of Pennsylvania, have spent 14 years observing the Moremi baboons. Through ingenious playback experiments performed by themselves and colleagues, the researchers say they have worked out many aspects of what baboons use their minds for, along with their limitations.

Reading a baboon's mind affords an excellent grasp of the dynamics of baboon society. But more than that, it bears on the evolution of the human mind and the nature of human existence. As Darwin jotted down in a notebook of 1838, "He who understands baboon would do more towards metaphysics than Locke."

Cheney and Seyfarth are well known for a 1990 book on vervet monkeys, "How Monkeys See the World," in which they showed how much about the animals' mental processes could be deduced from careful experiments.

When a baby vervet's call is played to three females, for instance, the mother looks to the source of the sound. The two others look to the mother, evidence that vervets know whose baby is whose.

An experiment like this � recording the sounds, waiting until the animals are in the right place and performing numerous controls � can take months to complete, but the results are widely admired by other biologists. "Any work of Dorothy and Robert's is going to be as good as you get in the field," said Robert Sapolsky, a Stanford biologist and an author who has studied baboons in the wild for many years.

"There is no one else in the area of animal behavior who does such incredibly interesting experiments in the field," said Marc Hauser, a biologist at Harvard who was their first student.

Cheney and Seyfarth have summed up their new cycle of research in a book titled, after Darwin's comment, "Baboon Metaphysics." Their conclusion, based on many painstaking experiments, is that baboons' minds are specialized for social interaction, for understanding the structure of their complex society and for navigating their way within it.

The shaper of a baboon's mind is natural selection. Those with the best social skills leave the most offspring.

"Monkey society is governed by the same two general rules that governed the behavior of women in so many 19th-century novels," Cheney and Seyfarth write. "Stay loyal to your relatives (though perhaps at a distance, if they are an impediment), but also try to ingratiate yourself with the members of high-ranking families."

Baboon society revolves around mother-daughter lines of descent. Eight or nine matrilines are in a troop, each with a rank order. This hierarchy can remain stable for generations.

By contrast, the male hierarchy, which consists mostly of baboons born in other troops, is always changing as males fight among themselves and with new arrivals.

Rank among female baboons is hereditary, with a daughter assuming her mother's rank.

News of that fact gave great satisfaction to a member of the British royal family, Princess Michael of Kent. She visited Cheney and Seyfarth in Botswana, remarking to them, they report: "I always knew that when people who aren't like us claim that hereditary rank is not part of human nature, they must be wrong. Now you've given me evolutionary proof!"

Baboons live with danger on every side. Many fall prey to lions, leopards, pythons and the crocodiles that in the wet season stalk the fords where baboons cross from one island to another. Baboon watchers are subject to the same hazards. Cheney and Seyfarth say their rules are not to work alone or to wade into water deeper than knee high. They often find themselves sitting in a tree with baboons waiting out a lion below. But going into New York is more petrifying, they contend, than dodging Botswana's predators.


A Moremi baboon gingerly crossing a ford in Botswana as it watches for crocodiles. Baboons bark to warn others of danger.


The baboons will bark to warn of lions and leopards, but pay no attention to some other species dangerous to humans like buffalo and elephant. On two occasions, baboons have attacked animals, a leopard and a honey badger, that threatened their human companions. "We haven't lost any post-docs," Seyfarth said.

For female baboons, another constant worry besides predation is infanticide. Their babies are put in peril at each of the frequent upheavals in the male hierarchy. The reason is that new alpha males enjoy brief reigns, seven to eight months on average, and find at first that the droits de seigneur they had anticipated are distinctly unpromising. Most of the females are not sexually receptive because they are pregnant or nurturing unweaned children.

An unpleasant fact of baboon life is that the alpha male can make mothers re-enter their reproductive cycles, and boost his prospects of fatherhood, by killing their infants. The mothers can secure some protection for their babies by forming close bonds with other females and with male friends, particularly those who were alpha when their children were conceived and who may be the father. Still, more than half of all deaths among baby baboons are from infanticide.

So important are these social skills that it is females with the best social networks, not those most senior in the hierarchy, who leave the most offspring.

Although the baboon and human lines of descent split apart some 30 million years ago, the species have much in common. Both are primates whose ancestors came down from the trees and learned to survive on the ground in large social groups. The baboon mind may therefore shed considerable light on the early stages of the evolution of the human mind.

In some of their playback experiments, Cheney and Seyfarth have tested baboons' knowledge of where everyone stands in the hierarchy. In a typical interaction, a dominant baboon gives a threat grunt, and its inferior screams. From their library of recorded baboon sounds, the researchers can fabricate a sequence in which an inferior baboon's threat grunt is followed by a superior's scream.

Baboons pay little attention when a normal interaction is played to them but show surprise when they hear the fabricated sequence implying their social world has been turned upside down.

This simple reaction says a lot about what is going in the baboon's mind. That the animal can construe "A dominates B," and distinguish it from "B dominates A," means it must be able to break a stream of sounds down into separate elements, recognize the meaning of each, and combine the meanings into a sentence-like thought.

"That's what we do when we parse a sentence," Seyfarth said. Human language seems unique because no other species is capable of anything like speech. But when it comes to perceiving and deconstructing sounds, as opposed to making them, baboons' ability seems much more language-like.

Assuming that early humans inherited the same ability from their joint ancestor with baboons, then when humans first started to combine sounds in the beginning of spoken language, "their listeners were all ready to perceive them," Seyfarth said.

Baboons may be good at perceiving and thinking in a combinative way, but their vocal output consists of single sounds that are never combined, like greeting grunts, the females' sexual whoop and the males' competitive "wahoo!" cry. Why did language, expressed in combinations of sounds, evolve in humans but not in baboons?

A possible key to the puzzle lies in what animal psychologists call theory of mind, the ability to infer what another animal does or does not know. Baboons seem to have a very feeble theory of mind. When they cross from one island to another, ever fearful of crocodiles, the adults will often go first, leaving the juveniles fretting at the water's edge. However much the young baboons call, their mothers never come back to help, as if unable to divine their children's predicament.

But people have a very strong ability to recognize the mental states of others, and this could have prompted a desire to communicate that drove the evolution of language. "If I know you don't know something, I am highly motivated to communicate it," Seyfarth said.

It is far from clear why humans acquired a strong theory of mind faculty and baboons did not. Another difference between the two species is brain size. Some biologists have suggested that the demands of social living were the evolutionary pressure that enhanced the size of the brain. But the largest brains occur in chimpanzees and humans, who live in smaller groups than baboons.

But both chimps and humans use tools. Possibly social life drove the evolution of the primate brain to a certain point, and the stimulus of tool use then took over. Use of tools would have spurred communication, as the owner of a tool explained to others how to use it. But that requires a theory of mind, and Cheney and Seyfarth are skeptical of claims that chimpanzees have a theory of mind, in part because the experiments supporting that position have been conducted on captive chimps. "It's bewildering to us that none of the people who study ape cognition have been motivated to study wild chimpanzees," Cheney said.

"Baboons provide you with an example of what sort of social and cognitive complexity is possible in the absence of language and a theory of mind," she said. "The selective forces that gave rise to our large brains and our full-blown theory of mind remain mysterious, at least to us."

http://iht.com/articles/2007/10/09/healthscience/snbaboon.php