Primates

Chimpanzees understand fairness in games

 Chimpanzees understand fairness in games  Behaviour, Primates, Recently  Comments Off on Chimpanzees understand fairness in games
Jan 182013
 

chimpanzeeResearchers at the Yerkes National Primate Research Center, Emory University, are the first to show chimpanzees possess a sense of fairness that has previously been attributed as uniquely human. Working with colleagues from Georgia State University, the researchers played the Ultimatum Game with the chimpanzees to determine how sensitive the animals are to the reward distribution between two individuals if both need to agree on the outcome.

The researchers say the findings, available in an early online edition of the Proceedings of the National Academy of Sciences (PNAS) available this week, suggest a long evolutionary history of the human aversion to inequity as well as a shared preference for fair outcomes by the common ancestor of humans and apes.

According to first author Darby Proctor, PhD, “We used the Ultimatum Game because it is the gold standard to determine the human sense of fairness. In the game, one individual needs to propose a reward division to another individual and then have that individual accept the proposition before both can obtain the rewards. Humans typically offer generous portions, such as 50 percent of the reward, to their partners, and that’s exactly what we recorded in our study with chimpanzees.”

Co-author Frans de Waal, PhD, adds, “Until our study, the behavioral economics community assumed the Ultimatum Game could not be played with animals or that animals would choose only the most selfish option while playing. We’ve concluded that chimpanzees not only get very close to the human sense of fairness, but the animals may actually have exactly the same preferences as our own species.” For purposes of direct comparison, the study was also conducted separately with human children.

In the study, researchers tested six adult chimpanzees (Pan troglodytes) and 20 human children (ages 2 – 7 years) on a modified Ultimatum Game. One individual chose between two differently colored tokens that, with his or her partner’s cooperation, could be exchanged for rewards (small food rewards for chimpanzees and stickers for children). One token offered equal rewards to both players, whereas the other token favored the individual making the choice at the expense of his or her partner. The chooser then needed to hand the token to the partner, who needed to exchange it with the experimenter for food. This way, both individuals needed to be in agreement.

Both the chimpanzees and the children responded like adult humans typically do. If the partner’s cooperation was required, the chimpanzees and children split the rewards equally. However, with a passive partner, who had no chance to reject the offer, chimpanzees and children chose the selfish option.

Chimpanzees, who are highly cooperative in the wild, likely need to be sensitive to reward distributions in order to reap the benefits of cooperation. Thus, this study opens the door for further explorations into the mechanisms behind this human-like behavior.

Source: Emory University

What can we learn from the bonobos?

 What can we learn from the bonobos?  Human History, Primates  Comments Off on What can we learn from the bonobos?
Mar 142011
 

Humans share 98.7 percent of our DNA with chimpanzees, but we share one important similarity with one species of chimp, the common chimpanzee, that we don’t share with the other, the bonobo. That similarity is violence. While humans and the common chimpanzee wage war and kill each other, bonobos do not.

"There has never been a recorded case in captivity or in the wild of a bonobo killing another bonobo," notes anthropologist Brian Hare. 

http://www.youtube.com/watch?v=6esyaqOvcEY

Dec 202010
 

 Chimapanzee mother and baby - remarkably like humansResearchers have reported some of the first evidence that chimpanzee youngsters in the wild may tend to play differently depending on their sex, just as human children around the world do. Although both young male and female chimpanzees play with sticks, females do so more often, and they occasionally treat them like mother chimpanzees caring for their infants, according to a study in Current Biology, a Cell Press publication.

The findings suggest that the consistently greater tendency, across all cultures, for girls to play more with dolls than boys do is not just a result of sex-stereotyped socialization, the researchers say, but rather comes partly from "biological predilections."

"This is the first evidence of an animal species in the wild in which object play differs between males and females," said Richard Wrangham of Harvard University.

The double-edged sword of dominance

 The double-edged sword of dominance  A Study Shows, Primates  Comments Off on The double-edged sword of dominance
Dec 122010
 

 A study of chimpanzees has revealed that dominant animals with higher testosterone levels tend to suffer from an increased burden of parasites. Researchers writing in BioMed Central’s open access journal BioPsychoSocial Medicine observed the primates’ behavior and studied their droppings to draw the link between dominance and infection status.

Dec 052010
 

A grinning chimpanzee - different species react differently to different pheromones Humans have the same receptors for detecting odors related to sex as do other apes and primates. But each species uses them in different ways, stemming from the way the genes for these receptors have evolved over time, according to Duke University researchers.

Varying sensitivity to these sex-steroid odors may play a role in mate selection — and perhaps prevent cross-species couplings, the researchers speculate.

The researchers analyzed the sequences and functions of the gene for the odorant receptor OR7D4 in terms of perceiving two steroid molecules related to testosterone, androstenone and androstadienone. The study did not try to examine how the receptors and odor perception might relate to behavior.

"There’s variation in sensitivity of the odorant receptor from this gene (all primates) have," said Hiroaki Matsunami, associate professor of  and microbiology and  at Duke University Medical Center. "Maybe these molecules operate in the process of reproduction. The fact that there is variation fits with this theory. Reproduction demands that an animal avoid attraction to other species, so variation in the receptor’s sensitivity to these odors may prevent any cross-species attraction."

Dec 012010
 

 photograph by Fernando A. Campos ©What sets mankind’s closest relatives — monkeys, apes, and other primates — apart from other animals? According to a new study, one answer is that primates are less susceptible to the seasonal ups and downs — particularly rainfall— that take their toll on other animals. The findings may also help explain the evolutionary success of early humans, scientists say.

"Wild animals deal with a world that’s unpredictable from year to year," said study lead author Bill Morris, a biologist at Duke University. "The weather can change a lot; there can be years with plenty of food and years of famine," he explained.

To find out how well primates cope with this unpredictability compared with other animals, researchers working at the National Evolutionary Synthesis Center (NESCent) in Durham, N.C. analyzed decades of birth and survival data for seven species of wild primates: muriqui monkeys and capuchin monkeys in Central and South America, yellow baboons, blue monkeys, chimpanzees and gorillas in Africa, and sifakas (lemurs) in Madagascar.

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