I sure wish people would stop perpetuating old wives tales that have been proven false. Especially those who should know better. It can be harmful to do so. In the 1800s and earlier, it was probably OK to spread anecdotal advice, as false as it may have been. But today with such good research tools available there is no reason to continue telling people that the shape of the egg or the temperature of incubation will determine the sex of hatchlings. Or that hanging a chick by its feet or head is an indication of male or female. It is all nonsense.
As for temperature of incubation, there are scientific studies that show temperature may favor one sex or the other of crocodilians - but that is about survivability. It doesn't mean temperature changes the sex of the embryo. People have extrapolated that information to include chicken egg incubation. If a change of a half degree or more favors male chicks or female chicks, it is about survivability and not sex change. So all that means is that fewer chicks hatch.
There is ongoing research to determine sex chromosomes in ovo so that eggs with potential male embryos aren't set in favor of those that contain potential female embryos but that is expensive and still a long way off. If it was as simple as egg shape, the egg industry would have figured it out over a century ago. That would also mean that certain breeds that lay more round eggs would only hatch out a single sex which would quickly make them extinct.
Sex is determined at fertilization when the yolk drops from the ovary into the infundibulum and a sperm cell enters the blastodisc. Nothing that happens in the next month changes that.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5824995/
https://www.karger.com/Article/FullText/448502
As for temperature of incubation, there are scientific studies that show temperature may favor one sex or the other of crocodilians - but that is about survivability. It doesn't mean temperature changes the sex of the embryo. People have extrapolated that information to include chicken egg incubation. If a change of a half degree or more favors male chicks or female chicks, it is about survivability and not sex change. So all that means is that fewer chicks hatch.
There is ongoing research to determine sex chromosomes in ovo so that eggs with potential male embryos aren't set in favor of those that contain potential female embryos but that is expensive and still a long way off. If it was as simple as egg shape, the egg industry would have figured it out over a century ago. That would also mean that certain breeds that lay more round eggs would only hatch out a single sex which would quickly make them extinct.
Sex is determined at fertilization when the yolk drops from the ovary into the infundibulum and a sperm cell enters the blastodisc. Nothing that happens in the next month changes that.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5824995/
https://www.karger.com/Article/FullText/448502
Last edited:
