The nature/nurture genetics/environment/choice argument continues.
In China, scientists created mice with missing serotonin receptors, resulting in sexual orientation of the female mice, toward other females. In the headline, "By altering serotonin in their brains, researchers caused female mice to prefer to mount and sniff the genitals of other females."
Most people already have opinions about the nature nurture arguments regarding sexual orientation, and another study won't change any minds. But it's interesting reading.