Why evolution isn’t always good for us

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Harvard evolutionary psychologist Deidre Barrett says that the instincts humans developed hundreds of years ago to survive still govern today. But nowadays those instincts cause overindulgence in things like salt and sugar, as well as behaviors such as watching television at the expense of human relationships.

Barrett’s  book, “Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose,” explores the differences between normal and supernormal stimuli, and the science behind how the latter leads to overindulgence and behavioral addictions.

“A normal stimulus is whatever the instinct evolved for in the first place,” Barrett explains. “Like our instincts about sex is supposed to lead us to another adult human being that we can have a sexual relationship with. Our nurturing instincts are supposed to lead us to our own children and taking care of them; whereas a supernormal stimulus is something like pornography or it’s the ‘pocket pet’ with the big eyes hollering for feedings at certain times. It’s the things that take a few of these traits and exaggerates them.”

Fat, salt and sugar are examples of supernatural stimuli, and because humans instinctively crave these things, and are able to get them in concentrated amounts in today’s modern environment, we overindulge.

Back when humans were hunting and gathering food,  salt, sugar and fat were rare, but necessary for survival, Barrett says. “Leafy green vegetables were things that we ate, but they were so abundant that we didn’t need a strong craving for them. But now we can suck all of this fat and sugar and salt out of things and concentrate it in foods, and yet it’s still what we’re craving the most, so we eat way too much of it.”

In our modern environment, Barrett argues, humans need to trust their intellect instead of their instincts.

The same goes for our instincts around potential harm and social interactions, and Barrett says the kind of supernatural stimuli we get from entertainment takes advantage of our hard-wired signals.

“King Kong or wolf man gets a lot more of our attention to ‘woops that looks scary, I better find out more about that guy,’ than something like global warming in terms of alarm instincts,” said Barrett. “Likewise, a show like ‘Friends’ can just have more people smiling at you, more laugh track sounds, more social push-your-button things per minute than any real social interaction is likely to.”

Our brains can save us from the supernatural stimuli, says Barrett. “The human cortex, that big area for abstract thinking is there exactly to override the simpler instincts in the lower part of our brains when they’re leading us astray.”

Addictions are the result of humans not being able to protect themselves from supernatural stimuli. From junk food to pornography to drugs, our instincts lead us to overindulge when we’re unable use our intellect to identify potential dangers.

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