The dominant thinking about the evolution of lying ties to the idea of cooperation, and how people living in groups (as humans have done for millennia) foster bonds that help them survive the challenges of life. In this philosophy, lying evolved because we needed to manipulate the truth to help keep everybody on our side while also trying to maintain our own position and get fair (or perhaps unfair) shares of all the resources.

According to a 2013 study, the most cooperative primate species are also the ones that feature the highest levels of lying. Lying, according to this perspective, is a way of both producing and taking advantage of other peoples' cooperation; we lie to get people to trust and help us, but we also get the opportunity to lie because humans are hugely social animals with complex webs of relationships and ways in which they help and hinder one another.

"Tactical deception, the misrepresentation of the state of the world to another individual," the scientists behind the study wrote, "may allow cheaters to exploit conditional cooperation by tactically misrepresenting their past actions and/or current intentions." A person alone, obviously, has no need to lie; but a person with a family, a boss, and a best friend has constant motivations to lie, whether to persuade, gain advantage, foster intimacy, get rewards, or stave off poor consequences for themselves or others. Cooperation and lying, it seems, operate hand in hand.

Fascinatingly enough, it seems that the tendency to lie may actually be common to families. In a 1982 study of Hawaiian families and their personality traits, the strongest trait that linked people who were actually related was whether or not they had a tendency to lie. Even when the scientists discarded "outliers" (people who were clearly lying all the damn time), the links still held. Whether this is about environmental lying or genetics, or how this affected the families' cooperation, is unclear (genetics certainly seems to play a role), but it's still intriguing.

Just as there are thousands of different lies to tell, there are also many different functions for lies to serve; and those distinct purposes give us a bit more insight into why we've developed a capacity for falsehoods.

We often think of lying as purely negative, but it can also serve to strengthen societal bonds instead of shredding them. So-called "prosocial" lying is lying that both "misleads and benefits" somebody else, according to scientists from the Wharton School in Pennsylvania; they also allege that prosocial lies can seriously help bring people together. (Think of the "white lie" that spares a friend's feelings about a bad-tasting meal they've prepared or a present you don't actually want.)

Socially speaking, prosocial lying is often about cost: it minimizes the cost and/or maximizes the benefit to other people, while giving us a hit to our reputation and sense of moral strength. Even if people realize we're lying, they may regard our sacrifice of truthfulness as positive and enhance our value as people. (We tend to start doing prosocial lying, instead of just lying to preserve ourselves, quite young; children progress from being terrible, self-interested liars, to being capable of lying about smashing the vase to keep their best friend out of trouble, relatively quickly.)

In that sense, prosocial types of lies bond rather than divide us — though, in one experiment, scientists found that people were hesitant even to tell prosocial lies if they thought they were being watched, because the pull to be honest is more powerful than the need to keep people on our side with fibs.

When you tell a lie, you always run the risk of being found out. That's a problem if you want to avoid getting busted for that tale about how your car got scraped — but it's good for humans in general.

If we'd evolved with the ability to lie but without the ability to notice deception in others, we'd be basically unable to cooperate on any meaningful level, because genuine trust would be impossible. It would also leave us highly vulnerable; Professor William Ray, in the textbook Evolutionary Psychology, notes that "from an evolutionary standpoint, the detection of somebody who was lying to the group would be a critical task." Humans in one group would be completely unable to tell whether people in other groups were taking advantage of them or not, which would lead to conflict, isolation, and other pretty serious issues.

Many of our traditional ways of detecting lying — like looking for eye contact or unnatural body movements — aren't actually all that reliable. However, according to new research from 2015, focusing on someone's actual words could provide the key to finding liars out in a deception. Liars, encouraged to elaborate or asked for small details, are likely to trip themselves up, make mistakes and shift from confidence to concern or defensiveness. Catching somebody in a lie, the experts say, isn't in the eyes; it's in keeping somebody talking long enough to catch them. And when you do catch them, feel free to say, "Conveying false information is an important part of humanity's toolbox for social interaction...but I still wish you hadn't lied to me about borrowing that top."