[monkeywire] Almost Human and Sometimes Smarter
cdstar at gmail.com
Tue Apr 17 10:57:12 EDT 2007
Almost Human, and Sometimes SmarterBy JOHN NOBLE WILFORD
April 17, 2007
CHICAGO — Observed in the wild and tested in captivity, chimpanzees invite
comparison with humans, their close relatives. They bear a family
resemblance that fascinates people, and scientists see increasing evidence
of similarities in chimp behavior and skills, making some of them think on
the vagaries of evolution.
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Left, Bettmann/CORBIS; right, Michael K. Nichols/National Geographic— Getty
Jane Goodall's studies of chimpanzees in Gombe National Park in Northern
Tanzania, starting in the 1960s, changed primatology. Ayumu is a
Multimedia [image: Chimpanzees Using Tools]Interactive Feature Chimpanzees
Related With a Founding Mother in the Field of
From top, Estuko Nogami/Kyoto University; Tetsuro Matsuzawa; Michael K.
Nichols/National Geographic; Estuko Nogami/Kyoto University
>From the top, Ayumu, a 6-year-old male, shows foresight in stacking blocks;
chimps can outperform humans at some memory tasks; they use simple tools
like twigs to dig out ants and termites, and rocks to crack open nuts.
Enlarge This Image
Etsuko Nogami/Kyoto University
Chimpanzees defend territories and patrol boundaries, as this group is doing
in Uganda, where one patrol was seen to kill and mutilate a trespassing
Enlarge This Image
Yerkes National Primate Research Center/Emory University
*QUICK STUDIES* Chimpanzees pass on what they have learned. Here a group
watches and learns while Georgia, trained separately, puts a token in a
bucket to obtain food.
Center for Great Apes
Knuckles, top, has cerebral palsy. Although Knuckles' disability made him an
easy target, chimps in his community never took advantage of him.
For some time, paleontologists and evolutionary biologists have known that
chimp ancestors were the last line of today's apes to diverge from the
branch that led to humans, probably six million, maybe four million years
ago. More recent examination shows that despite profound differences in the
two species, just a 1.23 percent difference in their genes separates Homo
sapiens from chimpanzees, Pan troglodytes.
And certain similarities between the two species, scientists say, go beyond
expressive faces and opposable thumbs.
Chimps display a remarkable range of behavior and talent. They make and use
simple tools, hunt in groups and engage in aggressive, violent acts. They
are social creatures that appear to be capable of empathy, altruism,
self-awareness, cooperation in problem solving and learning through example
and experience. Chimps even outperform humans in some memory tasks.
"Fifty years ago, we knew next to nothing about chimpanzees," said Andrew
Whiten, an evolutionary psychologist at the University of St. Andrews in
Scotland. "You could not have predicted the richness and complexity of chimp
culture that we know now."
Jane Goodall, a young English woman working in Africa in the 1960s, began
changing perceptions. At first, experts disputed her reports of chimps'
using tools and social behavior. The experts especially objected to her
references to chimp culture. Just humans, they insisted, had "culture."
"Jane suffered early rejection by the establishment," Richard Wrangham, a
said. "Now, the people who say chimpanzees don't have
emotions and culture are the ones rejected."
The new consensus framed discussions in March at a symposium, "The Mind of
the Chimpanzee," at the Lincoln Park Zoo here. More than 300 primatologists
and other scientists reviewed accumulating knowledge of chimps' cognitive
After one session, Frans de Waal of Emory
that as recently as a decade ago there was still no firm consensus on
many of the social relationships of chimps. "You don't hear any debate now,"
In his own studies at the Yerkes Primate Research Center at Emory, Dr. de
Waal found that chimps as social animals have had to constrain and alter
their behavior in various ways, as have humans. It is a part of ape
inheritance, he said, and in the case of humans, the basis for morality. The
provocative interpretation was advanced in his recent book, "Primates and
Other reports shortly before the symposium had elaborated on the abilities
of chimps as toolmakers. Jill Pruetz, a primatologist at Iowa State
described 22 examples of chimps in Senegal making stick spears to hunt
smaller primates for their meat. Dr. Goodall was the first to call attention
to chimps as hunting carnivores, not strictly vegetarians
Dr. Pruetz observed several chimps jabbing the spears into hollow tree
trunks where bush babies often dwell. Just one attempt was successful.
Previously, chimps had been seen using sticks mainly to extract termites
from their nests.
A team of archaeologists led by Julio Mercader of the University of Calgary
reported finding stones in Ivory Coast that chimps used 4,300 years ago to
crack nuts. Today's chimps have often been videotaped using rocks as a
hammer to open nuts. The old stones with starch residues from nuts, the
researchers said, were the earliest strong evidence of chimp tool use, and
the finding suggested that chimps had learned the skill on their own, rather
than copying humans.
Other researchers combine field work showing chimp behavior in natural
habitats with laboratory experiments that are created to disclose their
underlying intelligence — what scientists call their "cognitive reserve."
For example, chimps on their own would not sit at a computer responding with
rapid touches on the screen as a test of their immediate memory. Videos of
their doing just that at Kyoto University in Japan especially impressed the
Tetsuro Matsuzawa, a Kyoto primatologist, described a young chimp watching
as numbers 1 through 9 flashed on the computer screen at random positions.
Then the numbers disappeared in no more than a second. White squares
remained where the numbers had been. The chimp casually but swiftly pressed
the squares, calling back the numbers in ascending order — 1, 2, 3, etc.
The test was repeated several times, with the numbers and squares in
different places. The chimp, which had months of training accompanied by
promised food rewards, almost never failed to remember where the numbers had
been. The video included scenes of a human failing the test, seldom
recalling more than one or two numbers, if any.
"Humans can't do it," Dr. Matsuzawa said. "Chimpanzees are superior to
humans in this task."
Dr. Matsuzawa suggested that early human species "lost the immediate memory
and, in return, learned symbolization, the language skills."
"I call this the trade-off theory," he continued. "If you want a capability
like better immediate memory, you have to lose some other capability."
Other experiments at Kyoto's primate center demonstrated the ability of
chimps to recognize themselves and focus attention on others. Masaki
Tomonaga, who conducted the tests, said that an infant made eye with its
mother at about 2 months and that sometime after the first year was able to
maintain a gaze as the mother moved about.
Dr. Tomonaga said such "gaze following" developed in humans about the same
age, "though infant humans generally have more complex interactions."
Misato Hayashi, also from Kyoto, described experiments with infant chimps'
manipulating nesting cups and square and cylindrical blocks. They were
slower to learn than humans, but the manual dexterity was there. A human
starts stacking blocks shortly after age 1, he said; chimps are almost 3
before getting the hang of it.
In experiments with mirrors, researchers showed that chimps had an awareness
of themselves that is absent in monkeys but present in dolphins and all the
great apes. Similar tests by Emory scientists showed some self-recognition
These behaviors were reported by Dr. de Waal and his associate J. M.
Plotnik, who said that they "may suggest convergent cognitive evolution
probably related to complex sociality and cooperation well documented in
both chimpanzees and elephants."
Other researchers said that when confronted with problems obtaining food
from the other side of a fence, chimps were not only clever on their own and
often competitive with a fellow chimp, but they also showed a willingness to
cooperate with one another to get the job done.
Brian Hare of Duke University
the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany,
said bonobos outperformed their chimp relatives in cooperative tasks and
shared food more readily.
The emotions of caring and mourning have been observed, as in the case of
the chimp mother that carried on her back the corpse of her 2-year-old
daughter for days after she had died. After fights between two chimps,
scientists said, others in the group were seen consoling the loser and
acting as mediators to restore peace.
Devyn Carter of Emory described the sympathetic response to a chimp named
Knuckles, who was afflicted with cerebral
No fellow chimp was seen to take advantage of his disability. Even the alpha
male gently groomed Knuckles.
Dr. Wrangham of Harvard said the challenge to primatologists working in the
field was to learn how much of the behavior and "surplus cognitive capacity"
observed in captivity applied in the wild.
The answer seems to vary from one isolated chimp community to another.
Scientists said that indicated the role of social learning — picking up
skills by emulation — and responses to different opportunities in separate
At Gombe, the site in Tanzania where Dr. Goodall made a name for herself,
the chimps with stick tools are accomplished extractors of termites from
their nests. But termite fishing is rare in Bossou, Guinea. At Bossou, and
not Gombe, chimps have learned to make use of many other tools, including
stones for cracking nuts.
Dora Biro of the University of Oxford in England has studied tool use by
chimps at the Bossou site. They fold leaves in a mat to sponge water out of
tree hollows and scoop algae off stream surfaces. They collect edible ants
with sticks. They take stouter tree branches and pound the juicy palm fiber
to a pulp, preparing another favorite food.
Videos of Bossou nutcrackers show adult chimps, often female, placing a nut
on a flat stone anvil and slamming down on it with a smaller rock. Two or
three youngsters sit around watching. The adults do not appear to be giving
instructions, except by example.
"What we've learned is that manipulation of objects begins around 1 year of
age," Dr. Biro said. "If it involves two or three objects, as in cracking
nuts, that happens at 3 ½ to 5 years. If it is not learned by 6 or 7, it
will never be acquired."
At a dense forest in the Congo Republic, Crickette M. Sanz of the Max Planck
institute said the chimps seemed as curious about her as she was about them.
Groups came forward, calling others to join them. Sometimes, they sat with
her for hours, eating fruit, grooming and even mating.
For a more detached study, Dr. Sanz deployed 18 video cameras at remote
locations and recorded 84 hours of chimp tool use. Leaf sponging was the
simplest, she concluded, and collecting honey with a long stick required the
most effort and risk, with termite fishing having "the highest element of
Dr. Sanz, who has worked with her husband, David B. Morgan, on some of the
research, described mother chimps' carefully withdrawing from a hole sticks
swarming with black termites while their infants looked on. These social
interactions, she said, passed on essential techniques and behaviors to the
"Socially transmitted adjustable behavior," Dr. de Waal said, is a hallmark
Chimp behavior sometimes turns violent, particularly in territorial clashes.
In Uganda, John Mitani of the University of
chimp patrols regularly policing the forest boundaries of their
communities. One patrol was seen assaulting an adult male, killing and
Kristin Bonnie, another Emory primatologist, said the transmission of
behavior could be benign and spontaneous, with the prospect of reward being
secondary. "It is the desire to act like others, an identification with
certain others," she explained, citing as an example the way chimps usually
clasp hands while grooming each other.
At the symposium, researchers said the interest in learning more about
chimps was not just a case of knowledge for the sake of knowledge. Their
behavior and intelligence, scientists say, may offer insights into the
abilities of early human ancestors like Australopithecus afarensis, the
apelike "Lucy" species that thrived more than three million years ago. A
more urgent motivation for the research, primatologists say, is that these
are sentient beings and the closest living relatives of humans, and their
survival is threatened.
Elizabeth V. Lonsdorf, a primatologist at the Lincoln Park Zoo and a
symposium organizer, said researchers needed "to keep their eyes out for
ways to improve the care of chimpanzees."
Diseases like ebola and anthrax are taking their toll. Hunting chimps for
"bush meat" is increasing. Many of the forest habitats of chimps in central
Africa are being cut by loggers and land developers. As a result, Dr.
Lonsdorf said, "Groups of the animals are getting closer together, which
increased the threat of chimp violence and territorial disputes."
Dr. Goodall recalled that when she went to Africa nearly a half-century ago,
at least a million chimps lived in the continent, and "now there are perhaps
only 150,000." In that time, they have impressed scientists with physical
and emotional reminders of their kinship to humans and their occasional
triumphs over them at a computer screen.
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