A group of UK scientists has published research in the scientific journal Nature explaining why one in 10,000 chicks are born gynandromorphous — half male and half female.

The group’s lead researcher told the BBC that the discovery may help the poultry industry breed better birds.


“If we can understand what the differences between the male and female identities are, then we can imagine making female birds with the same growth characteristics as males. That would increase productivity and food security,” said Michael Clinton of the Roslin Institute, who led the research. Scientists from the University of Edinburgh also contributed to the project.

According to their findings, each cell in a chicken’s body is either male or female, and that characteristic is not affected by hormones — unlike in mammals, where hormones are as important as genetics in determining an individual’s sex. As a result, a gynandromorphous chicken is completely female in body structure and coloring on one half, and completely male on the other — right down to wattle and spurs.