Scientists Achieve World’s First “Behavior Transplant” Between Species

Researchers in Japan have successfully transferred a complex courtship behavior from one species of fruit fly to another. It represents the first example of manipulating a single gene to transfer a foreign behavior to another species.

Two closely related species of fruit flies—Drosophila melanogaster, which courts females by “singing” with its wings, and Drosophila subobscura, where males regurgitate food and offer it as a nuptial gift—were at the center of the experiment. These species diverged around 35 million years ago and have distinct mating strategies.

Both species share a key gene called fruitless (fru), which drives male courtship behavior. However, the neural circuits controlled by this gene differ between the two species. In gift-giving flies, insulin-producing neurons are connected to the brain’s courtship center, while in singing flies, these neurons are disconnected.

The research team activated the fru gene in the insulin-producing neurons of D. melanogaster, triggering these cells to grow long neural projections and connect to the courtship circuit. This rewiring enabled the singing species to perform gift-giving behavior for the first time.

This achievement provides profound insight into evolution, showing that the emergence of new behaviors does not necessarily require new brain structures. Instead, small genetic modifications in existing neurons can reconfigure circuits, leading to entirely new instincts.

Beyond evolutionary biology, the implications could extend to neuroscience and medicine. Since fruit flies share about 60 percent of their genes with humans, understanding how to rewire brain circuits may one day inform therapies for neurological and psychiatric disorders.

“Our findings indicate that the evolution of novel behaviors does not necessarily require the emergence of new neurons; instead, small-scale genetic rewiring in a few preexisting neurons can lead to behavioral diversification and, ultimately, contribute to species differentiation,” said co-lead author of the study, Yusuke Hara, from the National Institute of Information and Communications Technology (NICT).

The findings were published on August 14, 2025, in Science under the title “Cross-species implementation of an innate courtship behavior by manipulation of the sex-determinant gene.”

Source: Nagoya University