Organisms of many species are specialized into male and female varieties, each known as a sex. Sexual reproduction involves the combining and mixing of genetic traits: specialized cells known as gametes combine to form offspring that inherit traits from each parent. The gametes produced by an organism define its sex: males produce small gametes (e.g. spermatozoa, or sperm, in animals; pollen in seed plants) while females produce large gametes (ova, or egg cells). Individual organisms which produce both male and female gametes are termed hermaphroditic. Gametes can be identical in form and function (known as isogamy), but, in many cases, an asymmetry has evolved such that two different types of gametes (heterogametes) exist (known as anisogamy).
When a person is described as sexy, they're interesting in a romantic or arousing way. A sexy song might be incredibly romantic, made for slow dancing, or an ad might tout sexy shoes that look amazing and will be the envy of all your friends. The word sexy is often used more broadly to refer to appealing or enticing things — clothes, cars, even ideas. Before sexy was coined, around 1905, the equivalent word was sexful.
Feeling good about your body, enjoying sexual pleasure, and being comfortable with your sexual orientation and gender identity are also big parts of healthy sexuality. Having a healthy sex life means knowing what you do and don’t want to do sexually and being confident enough to communicate that to your partner. Your partner should respect your boundaries, and you should respect theirs.
Iris observed that her female friends, who were mostly single, were finding more and more value in their friendships. “I’m 33, I’ve been dating forever, and, you know, women are better,” she said. “They’re just better.” She hastened to add that men weren’t bad; in fact, she hated how anti-male the conversations around her had grown. Still, she and various platonic female friends—most of whom identified as straight—were starting to play roles in one another’s lives that they might not be playing if they had fulfilling romantic or sexual relationships. For instance, they’d started trading lesbian-porn recommendations, and were getting to know one another’s preferences pretty well. Several women also had a text chain going in which they exchanged nude photos of themselves. “It’s nothing but positivity,” she said, describing the complimentary texts they’d send one another in reply to a photo (“Damn, girl, your tits!”). She wasn’t ready to swear off men entirely. But, she said, “I want good sex.” Or at least, she added, “pretty good sex.”
A Closer Look: Thanks to high school biology, we are accustomed to thinking of the sex of an organism as being determined by the chromosomes, notably the sex chromosome in humans (designated X or Y). But this is not the whole story, and it applies universally only to mammals and birds. In other animals sex is often determined by environmental factors and can be a variable phenomenon. In a species of slipper limpet (Crepidula fornicata), a kind of mollusk, all individuals begin life as females. Clinging to rocks and to each other, they form piles. The limpet on top of the pile changes into a male. If another limpet attaches itself on top of the male limpet, the newcomer becomes male, and the male limpet beneath it reverts to being female. These slipper limpets show the evolutionarily advanced feature of internal fertilization, and the male on top extends his reproductive organ down the pile of females below him to fertilize their eggs. For some fish, the number of males in the population determines the sex of the fish. If there are not enough males, some females become males. In these examples, the same animal can make fertile eggs and fertile sperm at different times in its life. These animals are not hermaphrodites, like some worms, but literally change sex. Some animals have only one sex. For instance, some species of lizards reproduce only by parthenogenesis-that is, their unfertilized eggs grow into adults, and these species no longer have males. Sometimes the external temperature determines the sex of an animal during its early development. If the eggs of the American alligator (Alligator mississippiensis) are incubated at above 34 degrees Celsius (93° F), all of the offspring become males. If they are incubated below 30 degrees Celsius (86° F), they become females. The midrange of temperatures results in both male and female offspring.
At least among people who don’t use dating apps, the perception exists that they facilitate casual sex with unprecedented efficiency. In reality, unless you are exceptionally good-looking, the thing online dating may be best at is sucking up large amounts of time. As of 2014, when Tinder last released such data, the average user logged in 11 times a day. Men spent 7.2 minutes per session and women spent 8.5 minutes, for a total of about an hour and a half a day. Yet they didn’t get much in return. Today, the company says it logs 1.6 billion swipes a day, and just 26 million matches. And, if Simon’s experience is any indication, the overwhelming majority of matches don’t lead to so much as a two-way text exchange, much less a date, much less sex.
The pleasure of sex arises from many factors including the release of neurochemicals such as oxytocin and dopamine, which flood the system during orgasm, as well as the sense of connection communicated by touching, massaging, and cuddling. Given the enormous variability in activities that people find arousing, there is no one way to be sexual. Men are especially stimulated by visual imagery, and about 90 percent of young men report using pornography with some regularity, often because they lack a partner or don't know how to bridge the differences in sexual appetite and interest that can occur between partners in the absence of discussion of their sexual pleasures. Many people engage in behaviors that were once perceived as atypical, such as dominance play and anal intercourse. Researchers know that flexibility in sexual repertoires is healthy and generally enhances relationships; they regard a specific behavior as problematic only when it creates harm or distress for one or both partners or when the behavior is compulsive—that is, it becomes the only means of arousal. "Sex addiction" is a label often used to suggest excessive interest in sex, but studies show it may be more related to the moral/religious environment in which a person lives.