YSM Issue 90.1

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FEATURE human evolution THE EXISTENTIAL CRISIS OF THE FEMALE ORGASM ►BY KRISSTEL GOMEZ The female orgasm has always provoked biologist’s curiosity. From an evolutionary perspective, the male orgasm has a clear purpose: it is required for ejaculation and the subsequent transfer of sperm. Explaining the female orgasm is more difficult, since fertilization and reproduction will occur whether or not a female orgasm occurs. In fact, female orgasms occur more frequently during masturbation or homosexual intercourse than during heterosexual intercourse. Natural selection, the driving process of evolution, favors traits that yield a survival or reproductive advantage to a species, so why has the female orgasm evolved if it provides no apparent survival or reproductive advantage? Yale’s Günter Wagner and his colleague, Mihaela Pavlicev, recently identified that the female orgasm—like the male orgasm—predates the primate lineage. Thus, the human female orgasm likely evolved from an older, functional trait and was passed down through generations. Here, we will explore the history of this trait and how its function has changed since it originated. For species whose ovulation is induced by copulation, it is thought that orgasms stimulate the release of hormones such us prolactin and oxytocin, triggering ovulation. In contrast, women are spontaneous ovulators. Although they too release prolactin and oxytocin during orgasm, their ovulation cycles do not depend on these hormones. Differences in ovulation cycles between species may have evolved in tandem with anatomical differences. Wagner’s study predicted that for spontaneously ovulating animals, the distance between the clitoris and the vaginal opening can be larger than for animals with copulation-induced ovulation, whose clitorises should be within (or near) their vaginal openings. In accordance with this prediction, external, non-penile stimulation of the clitoris is required for many women to achieve orgasm, because the clitoris is relatively far from the vaginal canal. Looking deeper into anatomical evolution, Wagner and his colleague studied databases of veterinary literature comparing female animal anatomy. In spite of a dearth of accurate studies on female genitalia, they found enough data to support their hypothesis. They discovered that in most species of reptiles, birds, and mammals, a single canal is used for urination and copulation. In these animals, the clitoris is often within or nearby the copulatory canal. However, in the ancestors of humans and other primates, the urogenital canal–the canal used for urination and copulation–shortened until the urethra became an entirely independent canal. As these two canals separated, the distance between the copulatory canal and the clitoris also increased. Wagner realized copulation-induced ovulation occurred most often in animals in which the clitoris was located within or near the copulatory canal. Spontaneous ovulators, in contrast, evolved to separate the clitoris and vagina. Together, this information suggests that the common ancestor of many mammals was a copulation-induced ovulator. However, as spontaneous ovulation evolved in humans and primates, clitoral stimulation as a means to induce ovulation became useless, and evolution distanced the clitoris from the copulatory canal. Though researchers have yet to prove that copulation-induced ovulation is triggered by clitoral stimulation and orgasm, the theory is pharmacologically testable. Future studies could use drug-induced anorgasmia–the inability to achieve orgasm–and the subsequent monitoring of an animal’s ovulation cycle, to begin to answer this question. In the context of spontaneous ovulation, clitoral stimulation leading to female orgasm may serve another purpose. For example, orgasm might improve pair bonding. Wagner emphasized that, although the female orgasm may not make a clear contribution to reproductive fitness, this does not reflect its modern importance. “Maybe the way to think about the female orgasm is as a type of art . . . which doesn’t have to have a specific purpose but still has value,” Wagner explained, referencing the way we value our ability to admire art despite its non-existent connection with reproduction or fitness. Wagner’s research has powerful and liberating implications for both men and women, freeing them from preconceived notions about the meaning of female orgasm during heterosexual intercourse. The research will hopefully discourage unhealthy notions, such as Sigmund Freud’s labeling of the clitoral orgasm as “infantile,” or theories that claim the female orgasm occurs more frequently with higher-quality males as a mechanism for retaining larger quantities of their sperm. Wagner and Pavlicev explain the difficulties associated with achieving female orgasm during heterosexual intercourse as an effect of evolution without any intrinsic implications regarding the male’s value. IMAGE COURTESY OF WIKIMEDIA COMMONS ►The female orgasm releases the hormones prolactin and oxytocin, which are theorized to trigger ovulation and fertilization. 26 Yale Scientific Magazine December 2016 www.yalescientific.org
materials science FEATURE PLASTIC PREYS ON DEEP-SEA ORGANISMS ►BY DIANE RAFIZADEH IMAGE COURTESY OF WIKMEDIA COMMONS ►Marine debris, the result of human plastic waste, on the beaches of Dar es Salaam, Tanzania. These large plastic pieces are shredded by weathering into more dangerous, easily ingestible microplastics. The dangers of oceanic plastic pollution are well known: throughout social media, trending videos portray turtles trapped in plastic netting and decomposed birds with plastic in their stomachs. The reality of plastic pollution is heart-wrenching, and researchers are continuously producing more evidence to demonstrate the extent of the problem. Discoveries from the past 20 years have revealed that organisms living in shallow waters and the middle layers of the ocean ingest copious amounts of plastic. Most recently, however, researchers at the University of Oxford discovered that deep-sea organisms—rarely studied in this context until now—are also consuming plastic at alarming rates. Their finding is particularly concerning because it demonstrates the vast impact of human plastic pollution: our trash has reached one of the Earth’s most remote and fragile environments. Conducted primarily by Michelle Taylor and Lucy Woodall at Oxford, the research concentrates on microfibers, the most common type of microplastic found in the environment. Microplastics are small plastic pieces, usually less than five millimeters in diameter (the width of a thumbtack), that are created when larger plastic debris is weathered and broken apart, while microfibers are a sub-class of fiber-shaped microplastics that often come from fibers on clothing. They are particularly dangerous for aquatic wildlife because they can easily get trapped in an animal’s digestive track or gills, lessening its feeding ability, damaging its digestive track, and often leading to its starvation. Organisms also face contamination by concentrated organic pollutants and metals that are harbored by the plastics. Taylor and Woodall’s research was inspired by earlier findings that discovered microplastics in deep-ocean sediments. “We were discussing what deep-sea animals eat, which is mostly particle matter falling from shallower waters—something called marine snow, and if this snow would have microplastics in it,” said Taylor, a senior postdoc at Oxford. The researchers explored deep-sea organisms in the equatorial mid-Atlantic and southwest Indian Ocean by sending a robot to the seafloor to scoop up organism samples. Reaching such depths was a major challenge, but the research team had access to a UK research ship and the Remote Operated Vehicle Isis robot, which can reach depths of 6000 meters. From their collected samples, they studied three distinct phyla: Cnidaria (such as jellyfish and corals), Echinodermata (such as starfish and sea cucumbers), and Arthropoda (such as crustaceans). The researchers recorded the depth where each organism was found, the type of microplastic it had interacted with, and the microplastic’s location on or within the organism. Most of the studied organisms, such as squat lobsters, corals, and sea cucumbers, contained microplastics in their oral areas, stomachs, and gills, indicating that the plastics were either ingested or inhaled. For example, the researchers found microplastics made of polypropylene, a polymer that can carry compounds such as DDE, a pesticide. The logical follow-up question is what we can do about human plastic pollution, but the answer is difficult because of the sheer prevalence of plastics in daily life. “It’s surprising how much clothing we wear is made up entirely of acrylic or polyester—I challenge you to check yours now,” said Taylor. Scientists are currently designing safer plastics. Paul Anastas, the Director of Yale’s Center for Green Chemistry and Green Engineering, says research should focus on developing biodegradable plastics that do not persist in the environment. “There is a worldwide network of people producing these solutions, and they need to be implemented much more rapidly.” The twelve principles of green chemistry include designing safer chemicals, using safer solvents, and reducing energy use. Governments, too, are taking measures to reduce the amount of plastic waste released into marine environments. In December of 2015, President Obama signed the Microbead-Free Waters Act, banning the cosmetics industry from using plastic microbeads, such as the exfoliating beads in facial soaps that are washed down the drain and released into the ocean. The public also has a responsibility to keep plastics out of our oceans. We can trash the “throw-away” mentality that leads us to use disposable plastic cups and utensils and opt for reusable options like cloth bags at the grocery store. In the meantime, Taylor hopes to see further research that probes deep-sea plastic pollution. www.yalescientific.org December 2016 Yale Scientific Magazine 27
Page 1 and 2: Yale Scientific Established in 1894
Page 3 and 4: Yale Scientific Magazine VOL. 90 IS
Page 5 and 6: 3 The year began with the thrilling
Page 7 and 8: in brief NEWS The Miller laboratory
Page 9 and 10: computational biology NEWS SOLVING
Page 11 and 12: medicine NEWS THE FLU SEASON CRAVIN
Page 13 and 14: environmental science FOCUS Surging
Page 15 and 16: STICKING IT TO CANCER FIGHTING TUMO
Page 17 and 18: iomedical engineering FOCUS Targeti
Page 19 and 20: cognitive science FOCUS ABOUT THE A
Page 21 and 22: evolutionary biology FOCUS classifi
Page 23 and 24: physics FOCUS In 2011, Canadian tec
Page 25: evolutionary biology FEATURE A WORL
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Page 33 and 34: From space, most stars never twinkl
Page 35 and 36: BLAST from the PAST Malaria: Findin
Page 37 and 38: ALUMNI PROFILE DR. RALPH GRECO, M.D
Page 39 and 40: cartoon FEATURE ►BY ABHI MOTURI a

YSM Issue 90.1

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