An old joke goes that sex was invented on or around the release of the first Rolling Stones record.But the sexual culture of yesteryear’s teenagers is nothing like the one their children — and grandchildren — are growing into today: inescapable social media, ever-sharpening identity politics, gender-transition facilitated by modern medicine. Parents raising children in this new, strange, hyper-complex landscape may feel like there’s good reason to be freaked out.But is it really so different? Sex has been around longer than Mick Jagger, reportedly, and it’s always been a complex and confusing business; but now, it’s become the focus of major attention. That’s long overdue, said L. Kris Gowen, a sexuality researcher and educator based at Oregon Health & Science University.“It may seem more complicated to some of us now, as more people get comfortable embracing a broader range of identities and developing language to fit that,” Gowen said.Gowen is the author of “Sexual Decisions: The Ultimate Teen Guide,” which covers everything teens need to know in order to make health choices for themselves — from basic anatomy and the value of abstinence versus safe sex, to social media and gender identity. Gowen will give Wednesday’s “Science on Tap” talk, at downtown Vancouver’s Kiggins Theatre, on “The New Adolescent Sexuality: Life, Lust and Learning.”She’ll start with some very basic basics, she said: dating and relationships, sex and virginity (a common kid question: “What actually counts as sex?”). Then she’ll move on to today’s news: modern technology, the newly fluid matters of sexual orientation and identity.