Monkeys, too, notice if others earn more than themselves, and don't like it one bit.
A few years ago, we re-enacted the wealthy CEO scenario with tufted capuchin monkeys at the Yerkes National Primate Research Center, in Atlanta. Some monkeys played fat cat, while others played lowly clerk. Unfortunately, we couldn't go nearly as far as American society, with CEO's earning hundreds of times more than the average worker, but even small inequities proved effective.
Testing two monkeys at a time, we offered each a pebble, which they could return for a cucumber slice. Alternating between them, both monkeys happily bartered twenty-five times in a row. The atmosphere turned sour, however, as soon as we introduced inequity. One monkey would stay on cucumber, but its partner now received grapes, which monkeys like a whole lot better. Seeing their partner munching on juicy grapes, the disadvantaged monkey got agitated, hurling his pebbles out of the test chamber, and even those paltry cucumber slices. A food normally devoured with gusto had become distasteful.
From this experiment and others like it, we believe in an inborn sense of fairness. But there is more: primate studies also tell us something about empathy and altruism. In contrast to inequity, which is on the rise in our society, empathy appears in decline. If the audience of a CNN/Tea Party debate can happily shout "Yeah!" at the suggestion that the lack of health insurance amounts to a death sentence, and if David Brooks in The New York Times can deny the moral value of empathy, it is time to watch your back. Societies that put duty and loyalty before compassion, as advocated by Brooks, have existed in the past, but several genocides later their model has lost appeal.
Experiments on empathy in our closest relatives, the apes, have shown that they voluntarily share food even if they can keep it all for themselves. They also will donate tools to those who need them or open a door so that another can access food that remains inaccessible to themselves. I watch expressions of empathy every day, such as when chimpanzees tenderly embrace and kiss those who have lost a fight, or when in a choice test they prefer rewards for everyone over rewards for just themselves. Given that the latest empathy research also includes dogs, elephants, and even rodents, the underlying brain circuitry is thought to be a mammalian universal, which would make it two-hundred million years old. This explains why empathy, at least with in-group members, is automatic and anything but fragile.
One of the most empathic presidents this country has ever known famously halted his carriage for a squealing pig mired in the mud, and dragged it out while soiling his good pants. This was Abraham Lincoln, who often mentioned the bonds of sympathy that held the nation together. He acknowledged that the decision to fight slavery was born from feelings for the plight of slaves. The memory of seeing slaves in the South shackled together with irons was a "continued torment" to him, he wrote a friend.
The sturdiest pillars of human morality are compassion and a sense of justice. That both may antedate our species should give pause to anyone proposing to ignore them. These tendencies may be inconvenient for the 1% who control the nation's wealth, but the rest of us surely would like to honor our heritage as social animals.