A study suggests that finger length may reveal a person's sexual orientation.
It claims that those with ring fingers and index fingers are more likely to be gay.
Two people with the same number length may be straight.
The researchers said finger length and sexual behavior were linked to testosterone exposure in the uterus.
Infants exposed to higher levels of male hormones are more likely to become gay.
And the length of their index and ring fingers is also more likely to be different.
This study involves identical twins.
18 for women and 14 for men
One in each group is straight.
Dr. Watt of the University of Essex said Tuesday: "Because the sexual orientation of identical twins may vary, the genes of identical twins account for 100, and other factors must explain these differences in addition to genetic factors.
"Studies have shown that sex is determined by the uterus.
"It depends on the amount of male hormones we are exposed to or how our individuals respond to this hormone, and people who are exposed to higher levels are more likely to be bisexual or gay.
"Because of the connection between hormone levels and differences in finger length, observing someone's hands can provide clues to their sexual behavior.
The findings are published in the journal Sex archives.