If you're wondering why some people look quite older or younger than their actual age, then the answer may be in the DNA.
A new study suggests a variation of a particular gene can make people appear about two years older or younger than they already are.
The specific gene is called MC1R (melanocortin 1 receptor), which has already been linked to certain facial features such as red hair and freckles.
For the research, David Gunn, a scientist of Unilever who provided some funding, and his team worked with people whose job was to assess digital images of 2,700 Dutch seniors and guess their age. Based on this experiment, the team discovered that assessors viewed more women to be older than their age, and men, younger.
The team then looked into the supplied DNA of these seniors and found that those whose perceived age was older carried certain risk variants of MC1R.
They also observed the same thing when they replicated the test, this time with 1,200 seniors from the UK and 600 from the Netherlands.
If that discovery isn't interesting enough, the link between the older perceived age and the risk variant remains even if other factors such as age and sun exposure are taken into consideration.
The study didn't explain how the risk variants make one appear older, especially since it's not associated with the appearance of wrinkles.
"There are two things we don't know: what part of perceived age does it influence, and how does it do it," said Manfred Kayser, Erasmus Medical Center forensic molecular biology professor who worked with the Unilever team.
There are a couple of theories, however. One, they change other aspects of the face such as the height of the lip or the sagging of the jaw skin. It's also possible that it's related to the non-repair of damaged DNA or inflammation.
The study can be a "different approach" to understanding how a person ages.
"By finding more genes involved in perceived age, we can better understand the relationship between how old you look and how healthy you are," Kayser further explained.
Don't forget too that putting all the blame to genes may not be the best idea as other factors can just as make you look old. These include the food you eat, exposure to sunlight, smoking, and even your attitude.
The study is now available in Current Biology.