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

Produced by Jonathan Blackwell for BBC World Service

Contributors:

Dr. Kevin Mitchell – Associate Professor of Genetics and Neuroscience, Trinity College Dublin

Dr. Malvina Skorska - Postdoctoral Fellow at the Centre for Addiction and Mental Health, Toronto

Prof. Lisa Diamond - Professor of Psychology and Gender Studies, University of Utah

Prof. Paul Vasey, Professor and Research Chair, Department of Psychology, University of Lethbridge

Vaitulia Alatina Ioelu, Chief Executive Officer, Samoa Business Hub

(Photo credit: Ahmed Umar)

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