Here is a question that social scientists have been pondering for years: How much of your success in life is tied to your parents, and how much do you control?

The academic term used for this is "social mobility." And a striking new finding from economic historian Gregory Clark of the University of California, Davis claims your success in life may actually be determined by ancestors who lived hundreds of years ago. That means improving opportunities across generations might be a lot harder than anyone imagined.

Clark did not set out to study social mobility; he was trying to study how the British elite formed in the lead-up to the Industrial Revolution. Someone suggested he trace surnames, because there is a long record of elite names in British society.

"For example, in England, we know the names of most people who went to Oxford or Cambridge from about 1200 right up until the present," Clark says.

But he didn't believe these names would tell him much about the status of families over time. A surname is just one branch in a vast family tree. And all the previous work on social mobility suggests that the status of a name would change in three or four generations. That's what social mobility means — families move up, families move down.

But it turns out that surnames told Clark a whole lot.

"If I just know that you share a rare surname with someone who was wealthy in 1800, I can predict now that you're nine times more likely to attend Oxford or Cambridge. You're going to live two years longer than an average person in England. You're going to have more wealth. You're more likely to be a doctor. You're more likely to be an attorney," Clark says.

This finding was a big surprise.

So Clark and some fellow researchers checked results in other countries. They looked at records of elite status — top colleges, listings of doctors and lawyers. They checked how often certain names showed up in these places compared with how common they were in the general population. Then they checked how that comparison changed over time to see how names were moving in and out of elite positions.

They checked in England, Sweden, the United States, India, China, Japan and Chile.

"And astonishingly, there's no more mobility in Sweden on these measures than there is in South America," says Clark. "And that America looks just like England, looks just like Sweden."

And, even more astonishingly, the numbers were the same in the Middle Ages as they are today.

It's worth pointing out that Clark is talking about relative social position, not overall living conditions or income. Still, what he's claiming is huge: That is, if you come from a common background, your chance of making it into the elite is the same in the United States as it is in South America, no matter when you were born.

"It is shocking that the number is as constant as it is," says Joseph Ferrie, an economic historian at Northwestern University. Ferrie has been following Clark's work on surnames almost from the beginning, and he says it's been fascinating.

"It's hard to find any holes in the argument that he makes suggesting that this really is something that does look the same in a variety of places and times," Ferrie says.

Clark's method is unique among people who study social mobility. Ferrie and most other researchers look at individual families, not just family names. But both approaches have been transformed in the past few years as more information from censuses and household surveys have become searchable online.

Until now, nearly all the research into social mobility has only covered two generations. Now it's finally becoming possible to look at many generations, and when you do that, it looks like there's a lot less mobility than we thought.

If Clark is right, we can actually put a number on it regardless of where or when you were born.

"We can't predict the individual aspects of where you'll end up, but if we want to rank you overall in society, maybe as much as 60 percent of the outcome is determined at the time of conception," Clark says.

And if Clark is right, that number is almost impervious to change. The Industrial Revolution didn't change it. Neither did the communist revolution in China, World Wars I or II, or even social policies like the GI Bill. Clark says he's still working on exactly how to interpret that information.

But it's clear he has growing doubts about whether public policy can really help people move up the social ladder.

"And it really is conveying this message that families are where the action is at in terms of the outcomes and performance for people," Clark says.

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