Humans have an innate preference for curves. Even newborn infants fixate on rounded shapes over "sharp" angular ones.
Some argue that this fondness of curves is an evolved defense mechanism. It helps us avoid pointy, potentially harmful objects. Like the teeth of a lion or thorns on a bush.
If this preference for curves really is an evolved behaviour it could be an ancient one. It's easy to see how it may have been useful at almost any point in the past. So, some scientists wanted to test just how old it was.
They examined extant apes - chimps and gorillas - and found they also share a preference for curves. This shows that the fondness for curves evolved in the apes we - being apes - inherited it from them.
Everyday curves
It's easy to imagine how a desire to avoid sharp objects (and the resulting preference for curved ones) would be helpful for our ancestors. However, this innate behaviour continues to influence us in the modern world.
Researchers studying a variety of subjects have found this latent influence of our desire for curves. It determines how react to different architectural designs. It influences what features on other people we find attractive. Even what sorts of products we want to buy (with everything from beef steaks to car interiors being better if its contoured). This sort of preference is something designers, architects, and more take into account when coming up with new designs.
Clearly, our preference for curves is being applied even when it isn't useful. How angular a building is probably won't influence whether I'm safe in it; but it will influence my opinion of it. This over-generalisation is a result of the fact that this bias is an innate behaviour. Instincts like this are "programmed" in. Programming in every type of angular object to avoid would require an awful lot of "programming". Instead, evolution produces general rules (like avoid angular objects). Whilst this minimises the programming needed, it does sometimes create responses that are too general.
Like how ducks can imprint on inanimate objects. They're just following the general rules established by the innate behaviour.
And we do know this preference for curves is innate. It's present in so many individuals in so many different circumstances. But the real piece of evidence is that even newborns show this preference for curves over angles. The emergence of such a behaviour so soon after birth - when there's not really been any time to learn it - strongly indicates that it is an innate tendency.
Testing apes
This preference for curves over angles could have been very useful for our ancestors in the wild. But if you keep running the clock back, it's hard to imagine a time it wouldn't have been useful. Does this mean the behaviour could be very old?
One way to test this would be to examine our close relatives, the apes. For instance, humans and chimps are descendants of a "parent" species that lived ~7 million years ago. If it turns out we both have a preference for curves then this would strongly imply that parent also had it (and we both inherited it from them). This makes the behaviour at least 7 million years old. Examining other apes (whose "parents" lived earlier) could help push back this date even further.
And that's just what these researchers did. They examined whether humans, chimps, and gorillas have a preference for curves over angles. In their experiment all the apes (including humans) saw a touchscreen. Two similar objects (but with different angular properties) were shown then covered up by grey squares. The participants then had to tap one of the squares. The only instruction was that they had to tap a square; not that they had to pick their preferred object.
Yet they still wound up picking the more curved object most of the time. This would suggest that the preference for curves evolved at least as early as the "parent" of all three groups. They lived ~12 million years ago. This makes the preference for curves over angles a truly ancient behaviour. Yet one that still impacts us today.
Ancient defenses
One of the more important parts of this research - apart from its results - is that the experiment could be applied to any number of species. If this experiment was repeated with orangutans, for example, then this could push the origin of this preference back even further to their "parent" (~14-16 million years ago). Repeating it with monkeys has the potential to demonstrate it is even older still.
This trait is still influencing us, but just how long has it been doing that?
And how long will it continue to do it? The researchers also ran a variant of the experiment in which the objects weren't immediately covered up. In this condition humans didn't prefer the curved objects as strongly. This would suggest that - when given time to think about it - we're capable of over-riding our innate preferences (although it's hard to prove this for sure from this one study).
With effort, humans can love pointy things after all.
tl;dr
Humans and apes all share a preference for curves. This would suggest its an innate preference that evolved millions of years ago.
References
Bar M, Neta M (2006) Humans prefer curved visual objects. Psychological Science 17: 645-648. pmid:16913943 doi: 10.1111/j.1467-9280.2006.01759.x
Fantz RL, Miranda SB (1975) Newborn-infant attention to form of contour. Child Development 46: 224-228. pmid:1132272 doi: 10.1111/j.1467-8624.1975.tb03295.x
Lorenz, Konrad (1977). Behind the Mirror: A Search for a Natural History of Human Knowledge. New York: Harcourt Brace Jovanovich. ISBN 0-15-111699-7.
Munar E, Gómez-Puerto G, Call J, Nadal M (2015) Common Visual Preference for Curved Contours in Humans and Great Apes. PLoS ONE 10(11): e0141106. doi:10.1371/journal.pone.0141106
