Non-Human Primate Tool Use: Gorillas Wielding Weapons, Macaques & Mirror Neurons

I’m scouring the American Journal of Primatology for a paper on gorillas using tools as weapons in the wild. National Geographic News says the paper is out, but I can’t find it anywhere in the early edition nor in the current issues. I’ll continue looking, but in the mean time here’s what we got to run on (and it ain’t much)

“Researchers [doing a three year study of Cross River gorillas (Gorilla gorilla diehli)] in Cameroon have documented three cases in which the [gorillas] threw clumps of grass or tree branches at humans.”

The people who documented the behavior suggest that the gorillas possibly learned their unusual behavior from interactions with humans. Captive gorillas have been documented picking up stone throwing from their chimpanzee neighbors, so it’s not too improbably that wild gorillas could pick up grass and branch hurling from human neighbors. How did these gorillas learn the behavior? Could it be possibly due to mirror neurons? Conveniently this is a perfect transition into an upcoming PNAS paper on tool use and mirror neurons in macaques, that was announced in this ScienceNOW news article,

“To investigate how the brain performs this sleight of hand, [the team] recorded brain activity in two macaque monkeys. Each was trained for 6 to 8 months to grasp items of food with pliers. The team documented the activity of 113 neurons in F5 and in a brain area called F1, which has also been implicated in the manipulation of objects. The researchers first established the brain’s firing sequence when the monkeys grasped only with their hands. The experiment was then repeated while the monkeys used normal pliers that required first opening the hand and then closing it to grasp the food. The same neurons fired in the same order. Remarkably, the same neurons also fired, in the same order, when the monkeys used “reverse pliers” that required them to close their fingers first and then open them to take the food.”

The research is coming from the University of Parma which seems to be specializing in this sorta research because about a year and half ago they documented mirror neurons role in mimicry. In the new paper, the researchers,

“conclude that when learning to use a tool, the pattern of neuronal activity is somehow transferred from the hand to the tool, “as if the tool were the hand of the monkey and its tips were the monkey’s fingers.” As for how the same neurons could affect both the opening and the closing of the hand, the team speculates that they may be connected with other sets of neurons that more directly control these movements. The authors also point out that area F5 is rich in so-called mirror neurons, a type of nerve cell discovered earlier… that fires both when a primate performs an action and when it observes another individual doing the same thing. Mirror neurons in F5, the authors suggest, may be involved in this transfer process as a monkey learns how to use a tool by watching others.”

The first observations of gorillas using tools in the wild was made a couple years ago, and last year we saw (albeit not too convincingly) a chimp fashioning a spear to hunt, so I’m not too surprised about this news… I just wanna see it!

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