by DK
Key works
1952 King Solomon’s Ring: New Light on Animal Ways
1949 Man Meets Dog
1963 On Aggression
1981 The Foundations for Ethology
See also: The selfish gene • Field experiments • Keystone species • Animal ecology • Clutch control • Using animal models to understand human behavior • Thermoregulation in insects
IN CONTEXT
KEY FIGURE
Jane Goodall (1934–)
BEFORE
1758 Carl Linnaeus, the father of taxonomy, dares to classify humans within the rest of nature, calling us Homo sapiens (“wise man”).
1859 Charles Darwin’s theory of evolution further challenges the established view that man is different from the animal kingdom.
AFTER
1963 Konrad Lorenz publishes On Aggression, proposing that warlike behavior in humans is innate.
1967 Desmond Morris, a British zoologist and ethologist, publishes The Naked Ape: A Zoologist’s Study of the Human Animal, a major study that describes human behavior in the context of the animal kingdom.
Modern molecular studies mapping the genomes of humans and other animals have confirmed a theory that was first suggested by Charles Darwin in the mid-19th century—that we share a common ancestor with the great apes. Today, few scientists would dispute that the common chimpanzee (Pan troglodytes) and the bonobo or pygmy chimpanzee (Pan paniscus) are our closest living relatives. The study of these animals therefore offers us a unique chance to learn about ourselves and the origins of our behavior. Yet for many years the scientific community remained convinced that humankind was different from the rest of nature.
It was largely the work of British primatologist Jane Goodall that opened our eyes to the similarities between chimps and man. In 1961, in an excited communication to her mentor, Louis Leakey, Goodall announced an observation that would shake the scientific establishment: she had seen a chimp using a tool. It was the first time this behavior had been documented and it would challenge perceived ideas of what it means to be human.
Goodall’s knowledge of natural history had impressed Leakey on their first meeting in 1957 and he offered her a job studying the behavior of chimpanzees. As an anthropologist and paleontologist, Leakey believed in evolutionary theory, which proposed that humans and the great apes—chimpanzees, bonobos, gorillas, and orangutans—in the family Hominidae (Great Apes), share a common ancestor.
Humans and their closest relatives, chimpanzees, are both primates. This shows how primates have evolved over the last 66 million years.
“In reality, we are Pan narrans, the storytelling chimpanzee.”
Terry Pratchett
British fantasy author
Making connections
Leakey’s fieldwork focused on looking for the “missing link”—fossils of transitional forms between that common ancestor and humans. Chimpanzees had not been studied seriously in the wild and such a study, he reasoned, could throw light on the evolution of early humans. Goodall, a keen observer and free of academic ties, was the ideal choice for the work. As Leakey had hoped, she provided a fresh perspective on the theory and was brave enough to say that chimps and humans were more alike than had been imagined.
Until this point, the scientific and popular consensus was that the ability to devise and make tools marked humans out as superior to the rest of the animal kingdom. Goodall’s findings forced scientists to think again.
Goodall’s camp was in Gombe Stream National Park, Tanzania, where she studied a chimp community on the eastern shore of Lake Tanganyika. In choosing to live among chimps to witness their true unfettered behavior, Goodall was one of the first people to work in the field of ethology, whereby biologists monitor animals in their natural environments and try to understand their natural behaviors. In her first few months at the camp, the chimps fled from her, but they then began to forget she was there.
Goodall sat for many hours observing the chimps, keeping her distance and quietly making field notes. One morning in November 1961, she noticed a chimpanzee she called David Greybeard sitting over a termite mound. He was poking blades of grass into the mound, pulling them out, and then putting them into his mouth. She watched for some time before the chimp moved off. On reaching the spot where the chimp had been sitting, Goodall saw discarded grass stems lying on the ground. Picking one up and poking it into the mound, she found that the agitated termites bit onto the stem. She realized the chimp had been “fishing” for termites with the grass stems, and transferring them into his mouth.
From talks with Leakey, Goodall knew this was a major discovery. She also saw chimps modifying thin twigs by stripping them of leaves and then using them in termite mounds; the chimps were not only using tools but making them.
A chimp uses a twig stripped of its leaves—a modified “tool”—to catch termites for consumption. Goodall first recorded the ability of chimpanzees to invent simple technologies in Gombe.
JANE GOODALL
Born in London in 1934, Jane Goodall’s first meeting with a chimp was a stuffed animal that her father named Jubilee. She was interested in animal behavior from an early age—once, she hid in a henhouse for hours so that she could watch a chicken lay an egg. She left school at 18 and worked in various jobs, before going to Kenya in 1957 and meeting paleoanthropologist Louis Leakey. With his support, in 1960 Goodall set up a research base in Gombe, Tanzania, where she was to study chimpanzees until 1975. Her work radically transformed our understanding of chimpanzees and challenged perceived ideas of our own place in the natural world. In 1965, she earned a Ph.D. in ethology from Cambridge University. Her many awards include France’s Legion of Honor, given to her in 2006.
Key works
1969 My Friends the Wild Chimpanzees
1986 The Chimpanzees of Gombe: Patterns of Behavior
2009 Hope for Animals and Their World
Chimp technology
Goodall went on to witness nine different tools being used by chimps in the Gombe community. At the time, scientists questioned Goodall’s methods and ridiculed her for giving the chimps names instead of numbers, suggesting that her fieldwork was less than rigorous. Since then, however, many other studies around the world have corroborated her findings: chimps in the Congo have been observed stripping twigs to use in termite mounds; chimps in Gabon have been seen heading into the forest with a five-piece “toolkit” that included a heavy stick for opening bee hives and pieces of bark for scooping up the honey. In Senegal, hunting parties of chimps have been observed traveling with sticks that they chew to a sharp point and use like spears to kill bush babies.
Jane Goodall working, notebook in hand, at Gombe National Park in 2006. The pioneering primatologist continues her lifelong commitment to protect endangered chimpanzees.
“I viewed my fellow man not as a fallen angel, but as a risen ape.”
Desmond Morris
British Zoologist
More alike than different
Ethologists take behaviors studied across several species to formulate generalizations that apply to many species. The idea that animal behavior could be a model for human behavior took root in the work of ethologists in the 1950s and ’60s, such as Konrad Lorenz, Nikolaas Tinbergen, and Karl von Frisch. Studying animals in their natural habitats, they saw how complex the lives of animals were. They began to understand social interactions arising from instinct as well as learned behaviors. The animal studies held a mirror up to human behaviors.
The persistent belief that humans are totally different from other species was firmly rebutted with the advent of gene mapping. When the chimpanzee genome was mapped in 2005—followed by the other great apes—and compared with the human genome, the results were clear. Humans share 98.8 percent of their DNA with chimps, 98.4 percent with gorillas, and 97 percent with orangutans. Humans and great apes are more alike than they are different. Yet it is worth noting that these percentages are based on genes that instruct the body how to
make proteins, which make up a very small part of the human genome (about 2 percent). It is likely that the things that make humans different from chimpanzees can be found in the regions of DNA called “junk DNA” because they were previously thought to be redundant. It is now understood that this junk DNA holds vital information about how and when genes are expressed. Still, the similarities between the DNA of humans and the great apes are striking.
“We admit that we are like apes, but we seldom realize that we are apes.”
Richard Dawkins
British evolutionary biologist
Meat-eating hunters
During her studies, Goodall also witnessed chimps eating meat and hunting. As with tool-making, the idea that chimpanzees were carnivorous predators went against all received knowledge. At first, scientists claimed it was aberrant behavior, but as the research continued and more sightings were made, it became established fact. Meat-eating has been reported in just about every area where chimps have been studied, from Gombe and Mahale Mountains National Park, Tanzania, to Tai National Park, in Côte d’Ivoire.
Such behavior has implications for human evolution. Science has long questioned why and when humans first began eating meat. From prehistoric stone tools and marks on bones, paleontologists know that the early hominids were using stone tools to cut meat from animals bones 2.5 million years ago, but it is not known what they were eating between then and 7 million years ago, when the common ancestor of chimpanzees and humans is thought to have lived.
It is likely that these early hominids hunted prey. Although they did not have large canine teeth like chimpanzees, these are not necessary for hunting and killing small prey. Biologists have observed that chimps hunting colobus monkeys grab them from the trees and then kill them by repeatedly thumping the bodies on the ground; early hominids could have hunted and killed in a similar fashion long before the earliest known tools.
An alpha male’s body language says “keep away” to begging chimps wanting a share of his prey in Gombe National Park. The main source of prey for chimps is the colobus monkey.
Chromosomal evidence
A strong piece of evidence in favor of a shared common ancestor is seen by comparing chromosomes. Chimpanzees (and gorillas) have 24 pairs of chromosomes. Humans have only 23. Evolutionary scientists believe that when we diverged from a common ancestor, two chromosomes in humans fused and this is why we have one less pair than other apes.
On the ends of every chromosome, there are genetic markers—or sequences of DNA—called telomeres. In the middle of each chromosome there is a different sequence, known as a centromere. If two chromosomes have fused, it should be possible to see telomere-like regions in the middle of the chromosome as well as at each end. Also, the fused chromosome would have two centromeres. Scientists looked and found just this. Human chromosome 2 appears to be the fusion of chimp chromosomes 2a and 2b. It is almost beyond doubt that we share a common ancestor with chimps, bonobos, and gorillas.
Cooperative behavior
Another aspect of chimps’ hunting behavior that is similar to that of humans is the social element. Although chimps sometimes hunt alone, hunting tends to be a group activity. Chimps rampage through the forest, coordinating their positions and surrounding their prey. After the hunt, the food is shared. This shows how early ancestors of humans may have developed cooperative behavior, a factor that may have contributed to their evolutionary success.
Chimp warfare
A shocking revelation that came out of the Gombe camp was that chimps are capable of violence, murder, and in particular warfare—once believed to be the preserve of humans. Between 1974 and 1978, Jane Goodall watched as her peaceful community of chimps fractured into two rival groups that then waged savage war on each other. Goodall was deeply upset about the chimps’ activity, which included ambushes, kidnappings, and bloody murder. The trigger for the war was unclear; some researchers blamed the feeding stations Goodall had set up in the area, which may have encouraged unnatural congregations of chimps. The answer to the mystery came in March 2018, when a research team at Duke and Arizona State Universities, US, digitized Goodall’s meticulous check sheets and field notes from 1967 to 1972 and fed them into a computer in order to analyze the social networks and alliances of all the male chimps. Their findings revealed that the fracture in the community occurred two years before the war broke out, when an alpha male Goodall called Humphrey took over the troupe, alienating two other high-ranking males called Charlie and Hugh and causing them to split off with some other chimps to the south. The two groups became more and more separate, feeding in different parts of the forest. At first there was the odd aggressive skirmish and then war broke out. Over four years, Humphrey and his cohorts killed every male in the southern group and took over their territory, as well as three surviving females. It is thought that the full-blown war may have been due to a lack of mature females in the northern group. Power struggles and fighting over a female all sound very human.
Chimps may fight over territory in order to acquire more resources or mates, but some primatologists maintains that such aggression is unnatural and provoked by human impact on their habitat.
“I’m determined my great grandchildren will be able to go to Africa and find wild great apes.”
Jane Goodall
Fights over resources
The long-running war witnessed by Goodall is the only sustained conflict among chimpanzees to have been fully documented, but violence within chimp communities has been recorded many times. Chimps have been observed stealing and killing baby chimps and rounding on a disliked alpha male. In communities studied in Uganda, males routinely beat the females they mate with. It is thought that this violent streak running through chimps may be associated with food resources and meat eating. When food is limited, the chimps become more violent in order to obtain the resources they need. Chimps are known to eat more meat when fruit is scarce.
Kissing cousins
The link between food scarcity and aggression in the common chimpanzee may explain why our other evolutionary cousin in the primate world, the bonobo (pygmy chimp), is so peace-loving. These small, placid chimps are omnivores but live in an environment where fruit is plentiful most of the time. They forage in groups, and tend to use sex to relieve tensions in social situations. Conflict is rare in bonobo societies, which are also matriarchal, unlike the male-dominated chimp communities.
An experiment carried out by researchers at Duke University, North Carolina, in 2017 showed that bonobos are also altruistic. Two bonobos (unknown to each other) were put in adjacent rooms (A and B) with a fence between them and a piece of fruit hanging over one room (B). The bonobo in room A could release the fruit but not get to it himself. The researchers found that this bonobo would consistently release the fruit, so that the other one could reach it, helping a stranger, with no reward for himself.
Researchers also observed how the sight of an unknown bonobo yawning in a film would trigger a yawning response in bonobos watching the film, suggesting a capacity for empathy. Other studies have shown how bonobos comfort each other when in distress. Unlike the “negative” behavior that humans share with chimps, these traits mirror more laudable human characteristics, such as compassion. Understanding such behavior in bonobos could shed light on how our human social behavior developed.
Bonobos are very social primates. Their capacity for empathy makes them less aggressive and may align them more closely with their human cousins than the common chimpanzee.
Conservation of chimpanzees
Orphaned chimps—their mothers killed for bushmeat—walk along a mud track with their keeper at a conservation center in West Africa.
According to the Jane Goodall Institute in Tanzania, the number of chimpanzees living in the wild has plummeted over the last century. In 1900, there were an estimated 1 million chimpanzees in Africa; today, there are fewer than 300,000. Habitat loss due to a rising human population in need of more space has had a huge impact, as
have industries such as logging and mining, which destroy habitat and fragment chimp communities when roads are built through their territories. Roads also encourage another damaging activity—hunting for bushmeat, a highly valued meat in Africa that includes great apes. Roads enable hunters from towns to travel directly into the bush. The protection of chimps focuses on land conservation and on raising awareness both locally and across the globe.
See also: Evolution by natural selection • A system for identifying all nature’s organisms • Animal ecology • Animal behavior
IN CONTEXT
KEY FIGURE
Bernd Heinrich (1940–)
BEFORE
1837 In the UK, George Newport observes that flying insects are capable of raising their body temperature above the ambient temperature.
1941 Danish researchers August Krogh and Eric Zeuthen conclude that the temperature of an insect’s flight muscles just before takeoff determine the muscles’ rate of work during flight.