By Chris Eppig

*Before we begin, be sure to read my post on the naturalistic fallacy. Science cannot condemn or justify any behavior — it can only identify the behavior and explain why it exists. In this post I will attempt to explain greed as I understand it, without mixing in any of my own ideology or the ideology of anyone else.

My dictionary defines greed thusly: “Intense and selfish desire for something, especially wealth, power, or food.” It is the wealth part that I will focus on.

To understand greed, or many other human behaviors, we first have to understand evolution — the human mind, of course, is a product of evolution. Every behavior and thought that we have is not necessarily the direct result of natural selection, but natural selection lays the foundation for our behavior. Natural selection works on a relative level. Traits are successful if they are passed on more frequently than other traits, which means that more individuals with that trait must be born and survive than individuals with other traits. Traits will evolve faster if there is a greater “selective advantage” — that is, the difference in survival and reproduction between individuals with and without the trait is very large.

If a squirrel, for example, has three offspring that survive, it and its traits are doing better than a squirrel that only has one offspring that survives. But it is not doing as well as a squirrel that has 10 surviving offspring. For this reason, natural selection does not give animals a target number of offspring that they want to have over the course of their lives but not exceed. If a squirrel has 10 surviving offspring but could produce more, it will lose the evolutionary race to an individual that could produce more than 10 surviving offspring and does. Said differently, natural selection does not produce squirrels that are satisfied with a particular number of offspring and will not have more. Rather, natural selection produces squirrels that will produce as many surviving offspring as they can. This is true for all organisms, not just squirrels.

For all organisms, resources are the most important thing for reproduction. It takes a lot of calories to produce an offspring, and raising it (in species that provide parental care) takes even more. Animals will produce as many offspring as they can, and it is resources that determine how many this really is. There is a large selective advantage for individuals who can acquire the most resources because they can produce more offspring that are healthy and survive long enough to reproduce themselves.

Modern humans aren’t so different. Estimates vary, but it costs somewhere in the area of $100,000 – $200,000 to raise a child to age 18 these days. This means that you need to have at least this amount of money coming in for every child that you want to have.

But let’s go back in time for a minute. Back in the day, let’s say 50,000 years ago, there was no money. If someone got a windfall of resources by killing a mammoth, they couldn’t put it in the bank, or even horde it underneath their mattress. If they did not use this material wealth, it would rot.

Modern wealth is easily storable, so it can be accumulated in ways that was not possible in the past. Prehistoric people could not stuff an uneaten mammoth under their mattress for later, but modern people can easily stuff the equivalent of a thousand or a million mammoths into a bank account or a mutual fund and keep it for as long as they want.

As animals, we have a strong drive to do better than everyone by as much as possible. Humans obviously have complexities to our behavior that make us more nuanced, but this drive is still rattling around in our brains and affecting our behavior. Just like the squirrel that tries to have more surviving offspring than the other squirrels, people like to have more wealth than others. Natural selection has made us very interested in acquiring more resources than other people.

There is an old joke about a farmer who is granted a wish, but whatever he wishes for will be doubled for his neighbor. He can’t wish for a wealth of gold because his neighbor will be given double the gold. He can’t wish for five strong sons because his neighbor will get ten strong sons. He eventually decides to wish for half of his crops to be destroyed. This solution, or one like it, is the only way he can come out ahead of his neighbor. Coming out ahead, as I have already discussed, is the only way to win at natural selection.

Nobody particularly needs a billion dollars, but lots of people want it. When natural selection built us with an interest in accumulating more wealth than other people (what you might call an intense, selfish desire for it), it did not build an off switch.

And that, in a nutshell, is why we have what we call greed.

See the followup to this post: The Tragedy of the Commons

Chris Eppig is the Director of Programming for C2ST. He blogs about science at christophereppig.wordpress.com