Berry good? ©2015 Chris Whittier

Fool me once, shame on you. Fool me twice… Well, it looks like gorillas don’t get fooled twice, at least not by a cheating plant.

If true, that makes them smarter than humans and almost 50 other primate species all of whom can be tricked by a West African plant that grows super-sweet but low-calorie berries.

Pentadiplandra brazzeana’s fruit is packed with a protein called brazzein, which mimics the taste of high-energy sugary fruits, but costs the plant less to make. So sweet is brazzein that it’s even been suggested as a new artificial sweetener for human consumption.


The problem for hungry primates is that it’s mostly a waste of time eating the plant’s fruit.

Brenda Bradley, an anthropologist at George Washington University, thinks the plant is probably producing cheap, sweet proteins to “trick” African primates into eating the low-calorie berries and dispersing their seeds.

Just checking these ones out ©2015 Chris Whittier

The trick seems to work, she says, as the berries are sought after by local hunter-gatherers, and other primate species have been seen eating them. So far, it seems, it’s been plant 1: primates 0.

But now, Bradley claims, one ape is fighting back: gorillas seem to have lost the ability to taste brazzein, which means they are unlikely to waste effort eating the berries.

Bradley thinks the gorillas have evolved this as part of the arms race against the plant.

Her team analysed the DNA sequence of the gene TAS1R3, which codes for a sweet taste receptor, in 51 primate species, including humans. To their surprise they found that only the gorilla has two mutations that seem to prevent them from detecting the sweetness of brazzein.

Monkeys and bonobos have taste receptors primed to find the protein sweet, says Bradley. “But gorillas – who are not known to eat the plant – have species-specific mutations that likely prevent the false signal.”

That suggests that they have evolved to stay one step ahead of the plant. Bradley says this is the first time researchers have described the genetic basis for a counter-adaptation to a biochemical mimic that manipulates taste receptors.

Next, the plant could acquire mutations changing how the protein binds to the taste receptor to fool the gorillas once again, but we don’t know if this will happen, says Bradley.

However, not everyone is convinced with Bradley’s take on the results. “This new work contains some fascinating data, but what is missing is any direct evidence that the plant specifically evolved the sweetener to support primate seed dispersal,” says Gary K. Beauchamp, president of the Monell Chemical Senses Center in Philadelphia.

“More puzzling, it is difficult to understand the reason why the gorilla specifically evolved a mutant form that renders them unable to detect the sweetness unlike other sympatric primate species who continue to be fooled,” he says.

“We can’t be certain that the sweet proteins are a product of selection favouring mimicry,” Bradley concedes. “Nor can we prove that the gorilla-specific mutations in the taste receptor are a specific counter-adaptation rather than a fluke coincidence.”

“But for now it is a compelling hypothesis, and we’re keen to work with field primatologists to gain a better understanding of the natural ecology of these plant-primate interactions,” she says.

Journal reference: American Journal of Physical Anthropology, DOI: 10.1002/ajpa.23046

Read more: Wild gorillas compose happy songs that they hum during meals; Gigantopithecus: The story of the greatest of the great apes; Red pandas reveal unexpected liking for sweetener