Gallup announced historic results of two polls within a day of each other this week, one for support for same-sex marriage, the other for belief that people who are gay or lesbian were born that way.

Of course, every time Gallup releases a poll on LGBT issues, it seems to be record breaking. With one exception, each survey on same-sex marriage support has either held or increased since 2008, so it doesn't seem unreasonable that the percentage of Americans who believe that sexual orientation is a born trait instead of something that's due to factors like upbringing or environment has also gone up. But according to the polls, that number is still far behind gay marriage support.

[The absolutely stunning rise in support for gay marriage, in 1 chart]

Gallup found 60 percent of Americans support same-sex marriage, but belief that sexual orientation is something someone is born with is nearly 10 percent behind, at 51 percent, with 30 percent believing some nurture-nature or other explanation for it. Here are the numbers for beliefs on why people are gay or lesbian, from 1978 to today:

The finding is significant -- it's the first time that number has cracked 50 percent -- and it goes for people of all political persuasions.  According to the poll, 64 percent of Democrats and Democratic-leaning independents believe sexual orientation is something someone is born with, as do 40 percent of Republicans and Republican-leaning independents, which, although it's not a majority, it's higher than the 36 percent of Republicans who don't.

That number is significant politically because it can reinforce the notion that the marriage battle is a civil rights battle. If sexual orientation is something people are born with and not a choice, there's an argument that can and has been made for same-sex marriage as something people born gay or lesbian have a right to. In fact, it seems like it could be the bedrock of an argument to legalize same-sex marriage.

But that's not how it happened. In a chicken-or-the-egg argument over public opinion of these LGBT issues, support for same-sex marriage has led. Here are results of Gallup's polls laid side-by-side. You'll notice the two tracked together closely until 2009, when support for same-sex marriage began to pull away.

This shows that over the course of the '00s and early '10s, a roughly 15-year window when attitudes on gay and lesbian issues in the U.S. flipped dramatically, there have always been people who supported same-sex marriage but believed that sexual orientation was something other than a born trait. It's never been a prerequisite for supporting same-sex marriage.

There are still millions of Americans who don't support same-sex marriage, but should the trends continue, that number will shrink, and greater acceptance of same-sex marriage will lead to a continued fundamental shift in what the U.S. thinks about sexual orientation.