The brain-hijacking parasite Toxoplasma gondii seems to be almost everywhere. The microscopic invader is thought to infect up to 50 percent of people, and a range of studies suggests it may alter human behavior, in addition to that of many other animals. The parasite has been linked with a large range of neurological disorders, including schizophrenia and psychotic episodes, and scientists keep uncovering more mysterious effects that may result from infection. In one such new study, researchers found that men and women infected by the parasite ended up being rated as more attractive and healthier-looking than non-infected individuals. On the face of it, that might sound strange and unlikely. But hypothetically speaking, the phenomenon could make sense from an evolutionary biology standpoint, scientists say. Above: Composite images of 10 Toxoplasma-infected women and men (a), beside 10 composite images of 10 non-infected women and men (b). Amidst the many neurobiological changes T. gon