Lucía Prieto Godino, the scientist who transferred a behavior from one species to another

A fly’s brain is the size of a grain of sand, but Spanish neuroscientist Lucía Prieto Godino is convinced that this tiny organ holds the keys to the colossal human nervous system, which is capable of creating Don Quixote, the smallpox vaccine, and the Great Pyramid of Giza. The 42-year-old researcher directs her own laboratory at the Francis Crick Institute in London, which is dedicated to studying neural circuits: the connections between cells upon which thoughts, memories, and behaviors depend. “In recent years, we have learned a great deal about how the brain works, but we still understand almost nothing about how it evolves. That is the big question of our laboratory,” she says.

The question is fundamental. The brains of a person, a seahorse, a wasp, a goat, or a toucan are as different as their behaviors. They are so distinct that comparing them and drawing conclusions is not practical. Prieto Godino has chosen to examine much more familiar and simpler animals: different species of flies that, at first glance, appear identical, but behave in very different ways. “It’s not that we’re interested in what flies do. If we find out how their brains evolve, we’ll be one step closer to understanding how our own brains evolve,” says the neuroscientist, sitting on the Arganzuela Monumental Bridge, a Madrid footbridge whose shape, a double metallic spiral, is reminiscent of the structure of DNA. It’s the neighborhood where she has lived all her life.

Modern neuroscience, a field barely a century and a half old, is still in its infancy. The first complete map of an animal’s brain, presented in 2023, was that of the fruit fly larva. One of its lead authors was another Spanish researcher in the U.K., Albert Cardona, from the legendary Laboratory of Molecular Biology at Cambridge, home to 16 Nobel laureates. That pioneering atlas revealed a structure with just 3,000 neurons and half a million connections between them. A year later, an international consortium produced the first map of an adult brain: that of the adult fruit fly itself, with 140,000 neurons and about 55 million connections. These are monumental advances that still pale in comparison with the colossal challenge ahead, a million times more complex: the human brain, with 86 billion neurons and trillions of connections between them.

“We want to understand how neural circuits evolve: how different animals can have different brains and different behaviors,” says Prieto Godino, who is also the founder of TReND, an NGO that supports African scientists. The researcher has chosen two fly species separated by 10 million years of evolution: the fruit fly, or Drosophila melanogaster, which eats almost anything; and a West African relative, Drosophila erecta, which feeds almost exclusively on the fruit of a shrub endemic to the region. By comparing maps of their brains, Prieto Godino’s team has observed that their different behaviors are not due to a change in the type of neurons, or even their number, but rather to how they connect with each other, especially at certain critical points.

A team of Japanese researchers made an astonishing announcement in August 2025. The group, from Nagoya University, succeeded for the first time in transferring a behavior from one species to another by manipulating a single gene. In their case, they identified the genetic key to the peculiar mating ritual of the fruit fly Drosophila subobscura, in which the female, to accept copulation, requires the male to regurgitate food directly into her mouth. In Drosophila melanogaster, this innate behavior is not observed; instead, courtship is based on “music” — sounds emitted by the males through the vibration of their wings. By activating a master gene in specific neurons, the Japanese scientists caused male Drosophila melanogaster to regurgitate food into the mouths of females before copulating. Their results were published in the journal Science, one of the leading publications in world science.

Prieto Godino’s laboratory had achieved a similar breakthrough even earlier, according to her colleague Albert Cardona. The researcher and her team not only analyzed why the West African fly has such a strong preference for a specific fruit, but also managed to transfer that quirky preference. They made the omnivorous fruit fly, Drosophila melanogaster, become obsessed with that African fruit by altering its neural connections. “We ran experiments in which we genetically manipulated the flies to try to transfer the behavior of one species to another — and we succeeded,” Prieto Godino says. Their results have not yet been published in a peer-reviewed journal and are currently under review by the scientific community.

The Spanish researcher is fully aware of the evolutionary gulf separating flies from humans, but she is searching for deep, ancestral principles in the brain’s organization. “Flies have 75% of the genes that cause diseases in humans,” she points out. History backs her up. In 1909, U.S. scientist Thomas Hunt Morgan began crossing Drosophila melanogaster flies to understand how traits are inherited from parents to offspring. In 1933, he won the Nobel Prize in Medicine for demonstrating that genes are stored in chromosomes within the cell nucleus.

Half a dozen Nobel Prizes have gone to scientists who turned to flies to understand human biology. The U.S. scientist Hermann Muller won the 1946 Nobel for discovering that X‑ray radiation causes mutations, thanks to his experiments with flies. In 1995, Germany’s Christiane Nüsslein‑Volhard and U.S. researchers Edward Lewis and Eric Wieschaus received the Nobel Prize for uncovering the genetic control of embryonic development — again, using flies.

Drosophila specimens were also key to the 2004 Nobel awarded to U.S. scientists Linda Buck and Richard Axel for mapping the organization of the olfactory system. Another laureate, Jules Hoffmann, studied how these insects fight infections and went on to win the 2011 Nobel for revealing the workings of innate immunity. Finally, U.S. researchers Jeffrey Hall, Michael Rosbash, and Michael Young received the 2017 Nobel after discovering, in fruit flies, the molecular mechanisms that control the circadian rhythm — the internal clock that adapts to the natural cycle of light and darkness. With that background, the scale of the achievement becomes clearer: transferring a behavior from one species to another, whether it’s a preference for a fruit or a courtship ritual involving regurgitation.

― Is it possible for a behavior to be transferred to a human being?

― That question has two parts. Ethically, no, obviously. Scientifically, it’s something that’s so far off... We don’t even fully understand how the neural circuits of the fly work, let alone how they work in humans. First, we have to understand very well how everything works before we can even think about transferring it.

—So scientists aren’t going to make us regurgitate before copulating.

―No, no one needs to worry.

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