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Almost Human, and Sometimes Smarter

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By JOHN
NOBLE WILFORD

Published: 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 Images

Jane Goodall’s studies of chimpanzees in Gombe National Park in
Northern Tanzania, starting in the 1960s, changed primatology. Ayumu is a
six-year-old male.

Multimedia

Interactive
Feature

Chimpanzees
Using Tools

Related

With a
Founding Mother in the Field of Primatology (April 17, 2007)

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 male.

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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 Harvard
anthropologist, 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 abilities.

After one session, Frans de Waal of Emory
University said 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,” he said.

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 Philosophers.”

Other reports shortly before the symposium had elaborated on the abilities of
chimps as toolmakers. Jill Pruetz, a primatologist at Iowa
State University, 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 symposium
scientists.

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 contact 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 among
elephants.

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 and 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
palsy. 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
cultures.

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
success.”

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 next
generation.

“Socially transmitted adjustable behavior,” Dr. de Waal said, is a hallmark
of culture.

Chimp behavior sometimes turns violent, particularly in territorial clashes.
In Uganda, John Mitani of the University
of Michigan observed chimp patrols regularly policing the forest boundaries
of their communities. One patrol was seen assaulting an adult male, killing and
emasculating him.

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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