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Origin of language found in fruit fly gene

June 26, 2014

Troy Zars

Troy Zars, associate professor of biological sciences, co-authored the new study

While language is a distinguishing feature of being human, scientists may have discovered an origin in the gene of a fruit fly.

In a new study published in the June 25 issue of the online, open-access journal PLoS ONE, researchers report that the Forkhead Box P, or FoxP, gene in fruit flies is necessary for operant learning. A relative of the gene, FoxP2, has been implicated in normal language and speech development in humans. The researchers say this latest discovery suggests that one of the roots of language can be placed 500 million years ago to an ancestor who had evolved the ability to learn by trial and error.

Troy Zars, associate professor of biological sciences at the University of Missouri and co-author of the current study, was first to identify and characterize the FoxP gene in fruit flies in 2007. He says that the evolution of the fruit fly gene offers a unique glimpse into the past.

“The FoxP2 gene is one of four members of the FoxP gene family, which have evolved in vertebrate animals from a single ancestral FoxP gene by serial duplications,” says Zars. “In fruit flies, these duplications never took place, so the single currently existing FoxP gene in fruit flies can serve as a model for studying the function of the ancestral gene that gave rise to language.”

To uncover that function, Zars teamed up with scientists in Germany. Björn Brembs, professor of neurogenetics at the University of Regensburg, led the project and is corresponding author of the new study.

Of course, fruit flies can’t talk, nor did the researchers expect them to start. Instead, they hypothesized that FoxP was involved in fruit flies’ ability to engage in so-called operant learning, a type of learning that has features conceptually similar to vocal learning.

“Operant learning is a process by which an individual modifies its behavior through the use of trial-and-error and sensory feedback,” explains Zars. “The individual’s actions will be highly variable and exploratory, at first, and then sensory feedback shapes future behavior and reduces variability.”

“More than fifty yeas ago, B. F. Skinner proposed that language might be acquired through an operant learning process,” says Brembs. “The first more or less random utterances, or babbling, of infants are rewarded by their parents, and correct utterances more so than incorrect ones, until eventually what they utter matches what they want to say.”

Songbirds do essentially the same thing, says Constance Scharff, a professor of animal behavior at the Freie University in Berlin. “Young songbirds try out different variants of sounds similar to how infants babble,” says Scharff, who is also a co-author of the current study. In an earlier study, her lab showed that birds with an altered copy of the FoxP2 gene imitated their tutor’s song imprecisely and sang more variably than controls.

You can

A video of the fruit fly flight simulator and the operant learning experiment is available online.

To test for a role of FoxP in operant learning in fruit flies, the scientists used a custom-built flight simulator to train the fruit flies to move in certain directions. A heat source was applied whenever the fly moved in the wrong direction. The goal, says Zars, is for hte fruit fly to learn to avoid the heat.

“If it turns left, it gets the high temperature. If it turns right, the temperature goes down,” says Zars. “The only predictor that the fly can use to say the hot temperature is going to come on or turn off is its own behavior.”

The experiment included an 8-minute training period, followed by  2-minutes without the heat punishment to see if the fruit fly had learned to avoid the heat.

The researchers found that fruit flies with an altered version of the FoxP gene flew more variably and were less likely to avoid the heat than controls.

This result, conclude the authors, strongly supports that the FoxP-dependent component of language evolved from an ancestral operant self-learning mechanism.

“Presumably, the ability to learn from trial and error was harnessed when vocal learning in vertebrates and language acquisition in humans evolved,” adds Brembs.

Other contributors to the new study, titled “Drosophila FoxP mutants are deficient in operant self-learning,” include Ezequiel Mendoza, Julien Colomb, and Hans-Joachim Pflüger from the Freie University in Berlin; Jürgen Rybak from the Max-Planck Institute for Chemical Ecology in Jena, Germany.

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Written by: Melody Kroll

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Related research strengths:
Behavior, Genetics & Genomics, Neurobiology