This might be the most depressing finding in social science. A new study tried to assess intergenerational mobility by looking at last names and found the highest earners in Florence in 2011 were the descendants of the highest earners in the year 1427, nearly 600 years earlier. Social mobility, or the lack thereof, persisted "despite the huge political, demographic, and economic upheavals that occurred between the two dates."

Lest you think this problem is quarantined to Italy, let me assure you: It is not. There have been similar findings across various countries that possess vastly different cultures, histories, and political and economic systems, including Sweden, England, the U.S., and even China, in spite of the Maoist revolution.

Those of us in the modern democratic West tend to think intergenerational mobility is desirable and achievable. Sure, social stratification exists, but, we think, with just the right policy tweaks, we can ensure every child at the bottom rung has a shot at joining, if not the 1 percent, then at least the 10 percent.

But what if social mobility on a large scale simply isn't possible? If Chairman Mao, who sent his country's entire elite to death camps and labor camps, couldn't shuffle the deck, do you really think Bernie Sanders will?

Regardless of circumstances, people with the money will always have the power to pass on their privilege, whether that power takes the form of actual political power, or money, or status, or social capital and social networks, or human capital.

In this matter, the importance of family ties can't really be overstated. Staunchly progressive parents will do anything to ensure their kids go to the right schools and have every advantage they can, even at the expense of the less privileged. And why shouldn't they? Trying to help your progeny succeed is just about the most powerful instinct there is, wired into our genes over millennia of evolution. If you add to that the finding that cognitive ability is heritable, you get a picture of why aristocracy is here to stay, probably forever.

So what does this mean, and what can we do about it?

Well, it might pose a problem for conservatives who typically oppose redistributive programs, pointing to equality of opportunity, but not equality of outcome. But it turns out equality of opportunity is a sham. When the left says the deck is stacked against the little guy, well, they're right.

But it might be an even bigger problem for liberals. Indeed, their entire raison d'être could be based on a sham. The left wants social equality and mobility, but it might turn out these things aren't just hard to achieve, but completely impossible. Sanders and his supporters believe it's a huge deal whether he or Hillary Clinton gets the nomination, but whatever Sanders does won't really influence social mobility. The choice between these two candidates is like choosing between a spitball or a BB gun to attack a Panzer division.

Forget about our insane left vs. right battles for a second and realize this is a problem for democracy itself. As Alexis de Tocqueville pointed out, the real appeal of democracy is not liberty but equality. Democracy appeals to us because we want to be equal with our neighbors. Well, judging by these findings, that ain't happening.

It's almost enough to make you buy the Marxist critique that democracy is a lie designed to exploit the proletariat more easily by making them believe they have a voice.

After all, if social stratification is simply impossible to change, we should probably just accept it. That would mean to accept an aristocracy, and even a bloodline-based aristocracy. But you know what? That's just too much to contemplate.