Imagine being able to see what you’re going to look like 50 years from now.

With FaceApp, a new app that’s sweeping the world, it's now possible. Developed by a Russian company, the app uses neural network technology to automatically generate highly realistic transformations of faces in photographs and can show you – at least that’s what they claim – what you can realistically expect to look like 50 years later.

You might think that a generation which spends billions of dollars annually for the sole purpose of looking younger would stay away as far as possible from any reminder of the effects of aging on our facial features. Yet FaceApp is today the most popular app in the app store with more than 150 million downloads. After all in the age of selfies, people can hardly resist an invitation to revisit their selves in different eras as well.

But before you try it, in addition to being aware of the possible security risks, there’s something important you should know about your face and what it says about you.

There is a pseudoscience, going back to the time of the Greeks, which claims that faces tell the story of character and personality in an irrefutable and predestined roadmap for our lives. It was most famously popularized in the late 18th century by the Swiss poet Johann Lavater, whose ideas became a talking point in intellectual circles.

In Darwin’s day, these ideas were more or less taken as a given and fascinatingly enough almost changed the history of science. When, after graduating from college, Darwin heard of an expedition to survey South America, the voyage which would provide him with the basis for his groundbreaking On the Origin of Species, Darwin almost didn’t get to go. The H.M.S. Beagle’s captain, Robert FitzRoy, was an amateur physiognomist who surmised that Darwin’s flabby nose indicated a “lack of energy and determination” and wanted to reject him. During that first meeting at the Admiralty, Darwin’s enthusiasm won the captain over – avoiding his rejection literally “by a nose”.

It was only after the subject became associated with phrenology, which fell into disrepute in the late 19th century, that physiognomy was written off as pseudoscience. Yet the field is undergoing something of a revival. Researchers around the world are re-evaluating what we see in a face, investigating whether it can give us a glimpse of someone’s personality or even help to shape their destiny. What is emerging is a “new physiognomy” which is more subtle but no less fascinating than its old incarnation.

An accepted fact is that first impressions are highly influential, despite the well-worn admonition not to judge a book by its cover. Within a tenth of a second of seeing an unfamiliar face we have already made a judgment about its owner’s character – caring, trustworthy, aggressive, extrovert, competent and so on (Psychological Science, vol 17, p 592). Once that snap judgment has formed, it is surprisingly hard to budge. What’s more, researchers have discovered that different people come to strikingly similar conclusions about a particular face.

So is it then true that our faces accurately reveal our identity? And if that’s a fact – and we have no say in what we look like but we are stuck with the face we have from birth – what happens to the idea of free will and of self-determination?

The answer really shouldn’t surprise us. Do you remember your parents warning you not to scowl or reminding you to smile because “your face is going to grow into that”? Yes, our faces do reflect our personality and our character. Not because our biologically decreed faces determine who we are because we, by the ways in which we lead our lives, create our faces.

In Hebrew the word for face is panim. The word by way of its letters is identical to the word pnim - the inner essence. Our face is the outer expression of our inner selves. It speaks far more of who we have become today rather than of our genes and heredity.

Our personality and our character mold the way our faces look. It is supported by a study two decades ago which found that angry old people tend to look cross even when asked to strike a neutral expression. A lifetime of scowling, grumpiness and grimaces seemed to have left its mark.

This takes us back to Darwin himself. He referred to how “different persons bringing into frequent use different facial muscles, according to their dispositions; the development of these muscles being perhaps thus increased, and the lines or furrows on the face, due to their habitual contraction, being thus rendered more conspicuous.” Darwin was ahead of his time. In an intriguing way he taught us we get the face we deserve.

It is famously said that Abraham Lincoln was advised to include a certain man in his cabinet. When he refused he was asked why he would not accept him. "I don't like his face," the President replied. "But the poor man isn't responsible for his face," he was asked. "Every man over 40 is responsible for his face," countered Lincoln.

Lincoln explained: it wasn't that the man was physically ugly. Rather, he had an ugly personality and a sour disposition, due to an overly pinched expression or bitter, disdainful look about him. Life experiences by that point had shaped the man into who he was going to be. His face was a living portrait of his character. That’s why Lincoln didn't want to hire him.

We've all met people who are beautiful not in the aesthetic sense but in far more significant ways. They radiate spirituality and goodness. Their faces shine with holiness. Their appearance glows with an inner godliness. Their self-acquired greatness literally transformed them.

And that’s why no app can really predict what you will look like in 50 years – because you haven’t finished creating it.