A new study showed that Millennials are more tolerant towards premarital sex and same-sex relationships than the earlier generations, revealing a huge generation gap and shift in beliefs about sex and sexuality.

Researchers from San Diego State University looked at the data of more than 33,000 U.S. adults between 1972 and 2012 for the study.

Their findings showed the shifts on the number of sex partners depending on the generation. Those born during the 1930s, also known as the Greatest Generation, had an average of three sex partners while those from the 1940s, also known as the Silent Generation, had five within their lifetime.

While it seems that our great grandparents were born on a seemingly conservative period, things showed a dramatic turn during the Baby Boomers generation, which began in late 1940s and lasted until 1960s, when people had an average of 12 sex partners. After this peak, the trend started to relax beginning the Generation X of 1960s and 1970s, who reported an average of 10 sex partners. The number dropped to an average of eight sex partners only for the 80s and 90s' babies, or Millennials.

"I was surprised that there was a little bit of a decrease," Jean Twenge, study lead author and a professor of psychology at San Diego State University, told HealthDay News. "It has to be taken into context: 8 is still a lot higher than 3, and it's higher than 4. But yes, it's less than the Boomers."

Aside from the lower average number of sexual partners, Millennials are considered to be the most tolerant on premarital sex and homosexuality. In 2012, 58 percent of Millennials were more accepting of premarital sex, while 44 percent said that they were accepting of same-sex relationships.

"Millennials are more accepting of premarital sex than any previous generation, yet have had fewer sexual partners than GenX'ers. This is consistent with their image as a tolerant, individualistic generation accepting others' choices and making their own," Twenge said in a press release.

So why are Millennials delaying sex? Twenge believes that the current generation is more aware of the risks of sexually transmitted diseases and unplanned pregnancies due to sex education and awareness campaigns.

The study was published in the May 5 issue of the Archives of Sexual Behavior.