Human sexuality comes in many forms, from exclusively heterosexual to exclusively homosexual. But seeing as homosexuality creates apparent reproductive and evolutionary disadvantages, listener Ahmed from Oslo wants to know: why are some people gay?

CrowdScience presenter Caroline Steel examines what science can - and can't - tell us about the role of nature, nurture and evolution in human sexual attraction. She asks a geneticist what we know of the oft-debated 'gay gene', as well as looking into why homosexual men on average have more older brothers than heterosexual men.

Caroline looks into the role of nurture with a developmental psychologist to answer a question from a CrowdScience listener from Myanmar. He wonders if the distant relationship he has with his own father has impacted his own feelings of attraction.

She also learns about research into a group of people in Samoa who may shed light on the benefits of traditionally non-reproductive relationships for communities as a whole.

Presented by Caroline Steel

Contributors:

(Photo credit: Ahmed Umar)