ambisexual with no fixed gender, and go through periods of oestrus, called "kemmer", at which point an individual comes temporarily to function as either a male or a female, depending on whether they first encounter a male- or female-functioning partner during their period of kemmer. The invented biology reflects and exemplifies, according to Parker, the opposing but united dualities of Taoism such as light and darkness, maleness and femaleness, yin and yang. So too do the opposed characters of Genly Ai with his carefully objective reports, and of Estraven with his or her highly personal diary, as the story unfolds, illuminating humanity through adventure and science fiction strangeness. Structure and themes Modern novels sometimes make use of biology to provide structure and themes. Thomas Mann's 1912 Death in Venice relates the feelings of the protagonist to the progress of an epidemic of cholera, which eventually kills him. Richard Flanagan's 2001 novel Gould's Book of Fish, which makes use of the illustrations from artist and convict William Buelow Gould's book of 26 paintings of fish for chapter headings and as the inspiration for the various characters in the novel. Realism The geneticist Dan Koboldt observes that the science in science fiction is often oversimplified, reinforcing popular myths to the point of "pure fiction". In his own field, he gives as examples the idea that first-degree relatives have the same hair, eyes and nose as each other, and that a person's future is predicted by their genetic code, as (he states) in Gattaca. Koboldt points out that eye colour changes as children grow up: adults with green or brown eyes often had blue eyes as babies; that brown-eyed parents can have children with blue eyes, "and vice versa"; and that the brown pigment melanin is controlled by around 10 different genes, so inheritance is along a spectrum rather than being a blue/brown switch. Other authors in his edited collection Putting the Science in Fiction point out a wide variety of errors in the portrayal of other biological sciences. References Sources Fiction