V057-UGANDA MONOS ALCOHOLICOS

Wild chimpanzees in Uganda have offered fresh support for the "drunken monkey" hypothesis - the idea that primates have long been exposed to, and may even be drawn to, low levels of alcohol in fermented fruit - after urine tests found most samples contained a direct metabolic marker of ethanol, researchers reported in a new study. "To test the "drunken monkey" hypothesis, the first obvious question is, well, would there even be sufficient enough alcohol in the fruits that our ancestors would have been eating to elicit a physiological or behavioural response. And since it's very difficult to study our human ancestors directly, we posed the question indirectly by studying our closest living relative, the chimpanzees," UC Berkeley PhD student, Aleksey Maro, told Reuters. Working at the Ngogo site in Kibale National Park, researchers tested 20 urine samples collected from 19 individually identified chimpanzees and found 17 were positive for ethyl glucuronide (EtG), a breakdown product used in humans as evidence of recent alcohol exposure, according to the study published in the Royal Society journal Biology Letters. The team used commercially available immunoassay test strips. UC Berkeley said 11 of the samples were also assessed using strips with a higher cutoff and 10 were positive, indicating EtG levels above that threshold in most of the subset. "We're seeing that they actually do metabolize some of the ethanol, which is the specific kind of alcohol that gives people the buzz; that they are metabolizing that ethanol and it's in their urine," said Maro. EtG testing in humans is used to confirm alcohol consumption, but the researchers did not attempt to translate the urine readings into measures of intoxication in chimpanzees, and human clinical cutoffs are not directly comparable across species, the team said. However, Maro added: "Hypothetically, depending on what species they're eating and how much alcohol is in it and how fast they're able to get the calories in, it is possible for them to consume enough fruits in a single sitting to get an acute dose like a single drink." The most likely source of ethanol was fermented fruit in the chimps' diet, the researchers said, noting that yeasts can ferment sugars in ripening fruit. They highlighted the African star apple as one food eaten heavily during the field period. The study follows earlier work by the same researchers estimating that, based on measured ethanol concentrations in fruit pulp and feeding rates, wild chimps could ingest meaningful amounts of ethanol from their diet. They added a key outstanding question is whether chimpanzees actively select fruits with higher ethanol content when given a choice. "Can chimpanzees use ethanol and fermentation to somehow infer something about the status of the fruits and make more advantageous foraging decisions and thus be able to survive better than apes that don't? And that would be one of the big evolutionary questions that the "drunken monkey" is still waiting to see resolved," said Maro.

DESCRIPCIÓN DE IMÁGENES

VIDEO SHOWS: CHIMPANZEES IN UGNADA'S KIBALE NATIONAL PARK / FILE FOOTAGE OF CHIMPANZEES / INTERVIEW WITH ALEKSEY MARO FROM UC BERKELEY

SHOWS: KIBALE NATIONAL PARK, UGANDA (FILE) (Aleksey Maro/UC Berkeley - Must courtesy Aleksey Maro/UC Berkeley)

1. CHIMPANZEES EATING FRUIT

2. CHIMPANZEE DROPPING FRUIT AND CLIMBING TREE