First demonstration that a single gene can alter animal behaviour

In 1956, Margaret Bastock published what would become a landmark study in the history of behavioural biology. Working with the fruit fly Drosophila melanogaster, she investigated the effects of the yellow gene mutation—previously known only for its visible effect on cuticle pigmentation—and discovered that it also produced measurable, specific alterations in male courtship behaviour.

This was the first documented evidence that a single gene mutation could change an animal's behaviour, specifically demonstrating that the yellow mutant males performed courtship displays less effectively than wild-type males, resulting in reduced mating success. Bastock's careful ethological analysis broke courtship behaviour down into discrete, quantifiable components, allowing her to pinpoint exactly how the mutation disrupted the normal behavioural sequence.

The significance of this finding cannot be overstated: it provided a crucial bridge between the fields of genetics and ethology, showing that behaviour—long considered too complex and environmentally malleable to be genetically tractable—could in fact be traced to specific genetic loci. This insight helped establish the foundations of what would later be called behavioural genetics, a field that has since grown to encompass everything from Drosophila courtship to human behavioural traits.

Because the exact month and day of the 1956 publication are not documented in accessible bibliographic sources, this achievement is dated to 1 January 1956 as a placeholder representing the year of publication.