Just by looking at this feature on the hand, you will know if someone can drink alcohol or not.

Imagine you are at a friend's wedding and have been tasked with serving drinks to all the tables. As a responsible and enthusiastic friend, you want to please the guests who have come to celebrate.

However, among the countless guests, there will be people you meet for the first time. Among the guests you meet for the first time, there will be people who can drink alcohol and people who can't.

So how can you tell - at a glance - who at a party can drink and who can't?

The longer the ring finger, the higher the person's alcohol tolerance. (Illustration).

A study published in the American Journal of Human Biology offers a little tip: Just by looking at the length of a person's ring finger , you can judge a person's alcohol tolerance, especially if that person is a man. 

Surveys show that people whose ring fingers are longer than their index fingers tend to drink more alcohol than people with longer index fingers. The longer the ring finger, the higher the person's alcohol tolerance.

But why is there such a strange connection?

The answer turns out to lie in sex-related differences in gene expression. We know that some sex differences are influenced by social factors, but others are rooted in our biological makeup.

For example, there is a distinct difference between the amount of alcohol that men and women can drink, with men generally drinking more than women.

Like many other sex differences, alcohol tolerance can be traced back to our exposure to sex hormones, including testosterone and estrogen, while still in the womb.

When a mother is pregnant with a male child, the fetus's testicles are already capable of secreting testosterone. At the same time, small amounts of sex hormones, including testosterone and estrogen, also diffuse from the mother's blood into both male and female fetuses.

So, in general, men have higher prenatal testosterone levels than women.

Testosterone causes changes in the brain and other organs in the fetus. These changes are then further triggered in boys by the increase in testosterone during puberty.

It is thought that the difference in our testosterone and estrogen is reflected in the relative length of our index and ring fingers (the second and fourth fingers are denoted as D2:D4).

A long ring finger indicates high testosterone and low estrogen levels.

That is, your finger ratio, or D2:D4, reflects your exposure to sex hormones in utero. So a long ring finger indicates high testosterone and low estrogen.

And this is not only true for us humans.

Scientists have observed that many pentapods develop sexual characteristics similar to humans, including the length ratio between the ring finger and the index finger.

In experiments on rats and monkeys, when testosterone was supplemented during the fetal stage, the males were born with ring fingers that were longer than index fingers, proportional to the amount of testosterone injected. Longer ring fingers were also correlated with their tendency to drink alcohol.

But for ethical reasons, we can't do these experiments on humans to confirm whether the characteristics of the index and ring fingers are related to the ability to drink alcohol? However, scientists still have a way to test it.

Establishing Relationships

Overall, men consume more alcohol and have more alcohol-related illnesses than women, with annual cases rising from 4.6 to 7.0 per 100,000 population since the start of the decade.

The longer the ring finger is, the more likely they are to drink alcohol.

Men are also nine times more likely to die from alcohol-related diseases than women. Could this gender difference be affected in the fetus by changes caused by testosterone?

In a new study published in the American Journal of Human Biology, scientists conducted a survey of 169 women and 89 men to find the answer.

They asked participants to measure the length of their fingers and then took a test to identify alcohol use disorders, which included questions about people's drinking habits.

Results showed that participants with ring fingers longer than index fingers reported higher alcohol misuse scores, with higher weekly alcohol consumption. This relationship was true for both men and women, but was stronger in men.

" Several studies have now found a relationship between the length of the ring finger compared to the index finger, and a person's alcohol consumption. A large internet survey of self-measured finger lengths showed that the difference in ring finger length compared to index finger length can predict alcohol consumption in a population, even on a national scale ," the scientists wrote.

" Studies in Europe and Asia have found that alcoholic patients have a very long ring finger compared to the index finger. Our data support these findings and extend them to non-alcoholic subjects ."

In addition to its link to alcohol consumption rates, ring finger length also provides us with a window into many health problems .

The good news is that people with long ring fingers tend to have healthier hearts, and they can perform better in endurance sports, such as marathon running, soccer, basketball, skiing and surfing.

The bad news is that long ring fingers are linked to autism, ADHD, internet addiction and a higher risk of prostate cancer.

Overall, the ratio between your ring finger and index finger is an important indicator of your testosterone levels even before you are born. It is one piece of the vivid puzzle that highlights the powerful impact that sex hormones have on our behavior and physiology.

So next time you're at a wedding and want to know if someone is likely to drink, look at the length of their ring finger.