Chimpanzees are smarter than humans. Orangutans are smarter than chimpanzees. Humans are smarter than chimpanzees. Which of these statements is true? More at Huffington Post.
Male chimpanzees in West Africa raid fruit from farms and orchards to share with females. In most cases, the males shared their booty with reproductive females in a food-for-sex swap. PLoS One.
Alpha males reward their buddies by giving them sexual access to the most desirable females. Is anyone surprised by this? Current Biology
Chimpanzees take revenge upon one another, but only if it doesn't cost them. Humans, however, will inflict suffering on themselves in order to punish someone else. It may be that our willingness to punish others even if it hurts us is as important to the evolution of human society as our ability to cooperate with each other.
This week's PNAS describes an experiment where a chimpanzee that has access to a rope which can collapse a table with food on it (sending the food onto the floor and out of reach of all chimpanzees) will yank the rope 30% of the time if it can see the food but not reach it, or if it cannot reach the food itself but can see another chimpanzee eating it. It will yank the rope significantly more if another chimpanzee has pulled the food out of its reach. What chimpanzees won't do is send the food to the floor to punish
another chimpanzee if they themselves are
eating. New Scientist, Science Now.
Two of the researchers behind these findings, Josep Call and Michael Tomasello, appear in The First Word. Tomasello was also behind the research on generosity in humans and chimpanzees, reported in the July 8 post.
In this week's PNAS, scientists have compared how much energy is used in human bipedal walking compared to the four-legged gait of chimpanzees (and even bipedal walking in chimpanzees). In general, they found that energy is saved with longer steps and less active muscle mass, and in fact that humans use about 75% less energy getting around than apes do. The difference is huge. It is said that natural selection generally proceeds by very small advantages but if the first human to start walking more upright was able to conserve even a percentage of this, it must have given them a great opportunity to spend that energy elsewhere (Feeding a large brain? Using language?). USA Today, NatGeo.
The latest research on altruism in apes may not be as surprising as the selfless rats in the previous post--because, of course, chimpanzees and humans are much more closely related--but it's all good, solid evidence that sharing can be as sensible an evolutionary move as selfishness, even if these chimpanzees reported in PLoS do it with non-family members. The same researchers show that both human infants and chimpanzee young will help without expecting a reward. BBC.
Meaningful, communicative gestures are shared by humans and other great apes. As with human groups, different groups of chimpanzees and bonobos may use the same gesture to mean completely different things. New Scientist, The Economist, PNAS.