Though its origins are vague, the ancient Chinese gender chart was apparently developed on the belief that a woman's age and the month during which she conceives a child, based on the lunar calendar, are relative to the gender of her future baby. China has a rich history of divination practices, from oracle bone readings in the Shang Dynasty (1600-1046 B.C.) to the ancient divination text, the I Ching, and it is likely this chart's development was influenced by existing practices.
The Chinese gender chart is said to have been found in a 700-year-old royal tomb near ancient Peking, modern day Beijing, and is currently held in the Institute of Science in Beijing. Its creation was likely tied to a preference for male offspring, as men would have been considered a greater asset in agricultural productivity. Additionally, it is common in societies that follow male lineages for male offspring to be favored in order to preserve the family name.
The Chinese gender chart is often reputed to have a very high success rate in its predictive accuracy, even as high as 99 percent, yet no scientific evidence is available to support the claims. Despite this, many websites still provide the chart for entertainment purposes.