The study identified two genes on chromosomes nine and six and they say 1 in 20 females carry two copies of each of the gene variations which result in menstruation starting earlier - these girls will start menstruating approximately four and half months earlier than those with no copies of the gene variants.

Dr Anna Murray from the Peninsula Medical School, says the study provides the first evidence that common genetic variants influence the time at which women reach sexual maturation and also indicates a genetic basis for the associations between early menstruation and both height and BMI.

Dr Murray says the study brings the understanding of the processes involved in puberty and early growth nearer and what constitutes 'normal' growth and development.

Fellow author John Perry, also from the Peninsula Medical School, says understanding the biological mechanisms behind reproductive lifespan may also offer information about associated diseases that affect many women as they age such as diabetes, heart disease and breast cancer.

The research is published in Nature Genetics.