Theology and Evolutionary Psychology, Chapter 2: On the Sweet Tooth, Snakes, the Magic Moral Number 150, and Weight Watchers for Love

After two posts setting the stage (Faith vs. Science and Evolution 101), it is time to approach evolutionary psychology.

The basic premises of evolutionary psychology are easy to state:

1.The brain is not simply a generalized learning device (although it has these kinds of non-domain specific capabilities). Rather, the brain possesses distinct information-processing biases (cognitive tendencies) that are the product of evolutionary pressures.

2.That is, the brain has an adaptive architecture, shaped by cognitive adaptations to meet adaptive challenges in the ancestral environment.

3.The ancestral environment was the environmental situation during which most of brain evolution occurred (3.5 million years ago until about 10,000 years ago, the end of the Pleistocene era).

4.Thus, the modern human brain reflects the cognitive tendencies that were adaptive in the ancestral environment.

All these premises seem plausible. That is, while the brain was rapidly expanding and evolving it seems reasonable that certain cognitive and behavioral tendencies would have been selected and passed on if they proved adaptive.

What this means is that the brain is a bit like a time capsule, a window on the past. What did this past look like? Well, basically the brain has spent 99% of its history in hunting-gathering-fishing (HGF) cultures. When we speak, then, of the ancestral environment we are speaking of the HGF cultures that existed from 3.5 million years ago until about 10,000 years ago.

For evolutionary psychologists, then, the key to unlocking the mysteries of the brain is to engage in some reverse engineering. That is, we seek to specify the unique adaptive challenges in HGF cultures to locate correlated mental adaptations present in modern brains.

One interesting way to look for these Stone Age tendencies is to look for adaptive “mismatches.” These adaptive mismatches are mental biases that are clearly maladaptive in the modern context but were extraordinarily adaptive in the ancestral environment. This mismatch is easy to explain. Natural selection moves very slowly. But cultural evolution, once it gets started, grows explosively. Thus, over the last 10,000 years cultural evolution (largely due to the technological revolution) rapidly changed the adaptive situation surrounding the brain, outrunning natural selection’s ability to keep up by many orders of magnitude. Basically, we have Stone Age Brains in a Space Age World.

This might seem farfetched so let me give some examples, the last of which goes to issues of theology and ethics.

Example #1: Our Sweet Tooth
Does it ever strike you as odd that God did not equip us with food-preferences that perfectly correlated with the FDA food pyramid? Would not that have been the optimal design? So, why don’t we innately crave the foods that are good for our health and well-being? Why don’t we say, “Johnny! Stop eating your peas and eat some more cake!”?

Well, the issue becomes clear when we look at the situation the way an evolutionary psychologist would. Specifically, sugars and fats are high-energy foods. But in HGF cultures these foods are relatively rare. The HGF diet is rich in nuts, grains, and plants, but poor in sugar and fat. Now imagine a vegetarian in the HGF ancestral environment. Or someone shunning sugars because they want to watch their figure. How will these people fare, adaptively speaking, compared to those who craved and sought out these rare but high-energy food sources? The guess is not very well. In short, our sweet tooth is a cognitive adaptation, an innate bias, which makes sense in the ancestral environment. But cultural evolution has overrun that mental bias, filling our world with cakes, cookies, candy, and sugary drinks. Fats and sugars, once very rare and thus craved, are now common. The sweet tooth, once a beautiful adaptation, is now our burden. And obesity becomes epidemic.

Example #2: Why Cars and Guns Don’t Cause Panic Attacks
The #1 leading class of phobias is small animal phobia: Spiders, snakes, bugs, mice, etc. Why is this? I routinely ask my classes these questions:

1.Raise your hand if you are afraid of snakes. (Many hands go up. My own included.)

2.Great. For those of you who are afraid of snakes keep your hands up. Now, if you hand is up, put it down if you’ve ever been bitten by a snake. (No hands go down.)

3.Great. Keep your hands up. Now, put it down if you’ve actually SEEN a snake in the wild. (A few hands go down, but most stay up.)

Why this crazy response? Many people are deeply afraid of snakes even though they have no personal learning history with snakes (e.g., been bitten). More strangely, many people are afraid of snakes and yet they have never even SEEN a snake it a natural habitat. What is going on? Well, I go on to ask these questions:

1.How many of you are afraid of cars? (No hands go up.)

2.How many of you are afraid of slick bathtubs? (No hands go up.)

The point here is that we are all much more likely to be hurt in car accidents or from slipping in the bathroom than from snakebite. So why don’t our phobia acquisition patterns reflect the REAL dangers in life?

Well, and I bet you can guess the answer, cars and bathtubs just weren’t around in the ancestral environment. Our brains just don’t have an adaptive history with these things. Like the sweet tooth, our innate skittishness in response to certain stimuli, which was once adaptive, was overrun by modern dangers. That is, although there were no cars, guns, or bathtubs in the ancestral environment, there were poisonous insects, snakes and disease-bearing rodents. And those who possessed more of a natural reticence to handle these animals (“Johnny! Put that cobra down and come to dinner! Johnny? Johnny?”) were more likely to pass on their reticence. We are their skittish children.

Example #3: The Magic Moral Number 150
This last example has a more serious application to theology and ethics. HGF societies were small. Without established farming HGF cultures could not create food surpluses and mobility was important. Thus, these cultures were small. How small? Well, the best estimates place the number around 150. That is, most of brain evolution appeared to have taken place in small, kinship-bond groups of about 150.

Interestingly, when we analyze the family/friend lists of modern persons we get numbers of around 150. That is, your current “clan,” those to whom you instinctively extend familial affection (even if they are not biological relatives), is about 150.

These two data points seem to suggest that our brain’s “little black book” for family and friends appears to have only 150 entries available.

What does this mean? It means that we see the world very locally. This means that we have trouble seeing most of the people in the world as worthy of moral attention. We focus most of our time, energy, and effort on about 150 people.

Like the sweet tooth, this ancient cognitive bias (i.e., our mental “black book” got set at 150 entries) is having disastrous consequences on modern living. Racism. Xenophobia. Gated communities. Prejudice. The movie Crash. On and on we see the toll of this bias.

Obviously, Jesus calls us to love everyone. To not just greet “brother and sister.” But we are fighting against human nature. And we need to be prepared for just how hard this battle will be. Personally, I don’t think churches are doing enough in this area. I think they are underestimating just how much resistance human nature is putting up. And thus churches are failing on a wide scale.

Let me put it this way. Compare the Magic Moral Number 150 to the sweet tooth. Now ask yourself, how hard is it to eat healthy or lose weight? How many failures do you experience with diet and eating? Lots I bet.

Well, loving the world is just like that. It’s like trying to stay away from the ice-cream or lose 20 pounds.

So let me ask you this. If loving the world is like losing 20 pounds, are churches putting intensive programs into place akin to Weight Watchers? Is there intensive coaching, accountability, and weigh-ins EVERY WEEK? Because this is what it is going to take.

A Weight Watchers for love.