A study has found that people with long ring fingers may face a higher risk of developing motor neurone disease.
It is believed that the link comes from the amount of pre-birth male hormone testosterone that is in the womb.
Scientists have claimed that the motor nerves of adults could be less sensitive to the hormone if there has been high prenatal exposure.
The length of the ring and index finger, known as 2D:4D ratio, is believed to be affected by hormones in the womb.
A low ratio, which is commonly associated with men, means that the ring finger is relatively long in comparison to the index finger.
The study has claimed that there may also be a link between a low 2D:4D ratio and amyotrophic lateral sclerosis (ALS) - the most common type of motor neurone disease.
The normally fatal disease causes progressive degeneration of the motor nerves that control movement, as well as weakness and muscle wasting.
Leading physicist Professor Stephen Hawking is one of the best known sufferers of the condition.
Researchers writing in the Journal of Neurology, Neurosurgery and Psychiatry compared 47 ALS patients and 63 healthy individuals.
Although no overall difference in 2D:4D ratio was seen between men and women, it was consistently lower for people with ALS.
The scientists, led by Professor Ammar Al-Chalabi from King's College London, wrote: "This finger length ratio is thought to be a marker of high prenatal testosterone levels, and our results are therefore consistent with the hypothesis that testosterone levels during development modify the subsequent risk of ALS."