Two years ago, the public was evenly divided, Gallup reported Thursday.
In answer to the question "In your view, is being gay or lesbian something a person is born with, or due to factors such as upbringing and environment," 47 percent responded that homosexuals were born with the orientation. Some 33 percent said homosexuality was caused by upbringing or environment.
When Gallup asked the question in 1977, the response was the opposite. Some 56 percent said homosexuality was due to upbringing, while 13 percent said people were born with the orientation.
While movement in the last two years toward the belief sexual orientation was inherent was found among all categories, the greatest change was seen in the 18-29 age group. In 2011, 38 percent of those respondents said they believed gays and lesbians were born with the orientation, while this year 49 percent held that belief.
Conversely, 47 percent in 2011 said sexual orientation was a matter of upbringing. In 2013, only 33 percent said that.
The poll found more than 50 percent of respondents now believe gays and lesbians should be able to marry. Some 75 percent of those polled said they know a friend, family member or coworker who is gay.
The poll was conducted May 2-7 with 1,535 adults in all 50 states and the District of Columbia. The margin of error is 3 percent.