I remember my mother sobbing because she had "nothing to wear" to dinner with a friend who wore lots of jewels. We knew those jewels were paid for with money from criminal enterprise. Why did my mother care about measuring up to someone so base? I couldn't understand her feelings.

This happened in 1969, when I earned $1.60 an hour after school. Other kids lusted for Ford Mustangs, and I couldn't understand it. To me that translated into 3,000 work hours. Why would anyone waste 3,000 hours of their time and effort to please the eyeballs of passers-by?

In college, my professors were constantly railing about the evils of "consumer culture." I had no lust for consumption and couldn't understand why they repeated the same message in every course.

Obviously I had a thing or two to learn about human nature. The world is full of people willing to ruin their quality of life and even break the law to buy stuff they don't need. The reason, I learned, is that people care how they stack up against others. Our ancestors sought ways to look important in the eyes of others long before money was invented. Before humans evolved, apes and monkeys looked for ways to assert superiority over their troop mates. Every generation finds new ways to rise above peers, but the urge to rise is constant.

In the Middle Ages, laws regulated the finery a person could wear. These "sumptuary laws" prevented a low-born person from donning the symbols of high rank. Everything from the fabric of your underwear to the trim on your cap was prescribed. Amazingly, Asia and Europe both had such laws in range of countries, reaching back to ancient times. The urge to distinguish one's self clearly runs deep.

A recent study of the reward centers of the brain helps explain why. We seem to respond the same way to praise and to material rewards, according to For Love or Money: A Common Neural Currency for Social and Monetary Reward. The research suggests that social acceptance is the common currency of the brain. Money and praise are two different avenues to social acceptance.

We mammals crave social acceptance for good reason. A mammal without a social group quickly finds itself in the jaws of a predator. Brains that sought social support were more likely to survive. Mammal with larger brains are more helpless at birth, and learn to depend on social skills for survival more than smaller-brained animals.

Every mammalian herd or pack or troop has a social hierarchy. Mammals try to rise in their status hierarchies because it promotes survival. Of course they don't consciously choose this strategy. Brains that rewarded status-seeking were naturally selected for. The mammal brain releases serotonin when it's in the superior social position. The serotonin feels good, which rewards a mammal every time it puts itself above a troop-mate.

In nature, a mammal must be good at reading the status of others in order to survive. When an animal encounters a stronger group-mate, it quickly shows deference to avoid injury. When it encounters a weaker troop-mate, it sees an opportunity to go ahead and meet its needs. Natural selection produced a brain good at reading the status signals of others.

Wild chimpanzees often try to raise their status by making noise. A dominance-seeker might find a large branch and drag it behind him while running through a gathering of his troop-mates. It makes an impressive noise and gets respect. The chimps at the zoo I work at often do this with the toys that we give them for "enrichment." When our visitors see a chimp dragging a child's plastic scooter, they don't realize it's a natural behavior designed to make an impressive noise.

Early humans tried to impress each other with body modifications. Various forms of body modification have continued into modern times. Often it's painful, but it gets the respect of the herd.

If the urge for status symbols is universal, why didn't I get it when I was young? Because early experience builds the neural links to the reward circuits and thus tell us which social behaviors are likely to get respect. I came from a very distressed home where I learned that nothing I did got rewarded. I learned not to expect others to help me survive. I was too busy surviving to waste effort doing things just for social acceptance that might never come.

When I look at a pair of high heels, I think: why live with the pain? Will it really make people respect me? I wear flats.

I could be wrong. I might have missed out on all kinds of opportunities because I didn't choose the right "look." But I get to make my own calls in this laboratory of life. I'm grateful for that, so I don't complain about the consequences. The freedom to make choices brings the responsibility to live with the consequences.

It's not easy being a mammal. Our limbic system scans constantly for information that can help meet our survival needs. For big-brained mammals, sending and receiving social signals is an essential survival strategy. My book I, Mammal: Why Your Brain Links Status and Happiness shows how to stimulate your brain's sense of strength in a world where everyone else is a mammal.

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