2. A New Media Presentation by Daniel Gettler

3. In 1859, Charles Darwin published On the Origin of Species  In this book, Darwin introduces the idea of natural selection, which has since been adopted and accepted by modern day biologists Natural selection is now seen as a staple of biology and essential for the evolution of a species

4. Natural selection is:  “A process that causes helpful traits (those that increase the chance of survival and reproduction) to become more common in a population and causes harmful traits to become more rare”

5. An Apparent Paradox:  Assuming that homosexuality is at least in part due to genetic factors (recent research suggests that it is), natural selection appears to fail at explaining homosexuality…

6. A common misconception

7. “There are numerous evolutionary mechanisms that might explain homosexual behavior, which are common in many species of animals”

8. The 4 Main theories:

9. 1. It’s non-exclusive!  Homosexuality exists on a continuum and homosexual behavior is often non-exclusive  “Among animals, homosexual behavior is usually non-exclusive. For instance, in some populations of Japanese macaques, females prefer female sexual partners to male ones but still mate with males”— (they are bisexual)

11. 2. Indirect Benefit  Some research suggests that homosexuality can be beneficial to relatives that carry some of the same genes  Is are they ‘homosexual genes’ or just genes that influence how attracted a male OR female is attracted to men?

12. **The researchers stressed that there is no single gene accounting for sexual orientation

13. 3. Kin Selection  Indirect reproductive success through altruism towards kin  Androphilia = sexual attraction to mature males  This study is based on a group of homosexual males in Independent Somoa and despite the findings, we cannot conclude that the same

14. 4. Hormone Exposure in utero  This theory is based on ‘gene expression’  Gene expression: “The appearance in a phenotype of a characteristic or effect attributed to a particular gene.”

15. Things to keep in mind:  There is more evidence for a genetic basis of male homosexuality than female homosexuality, which might suggest a different mechanism  It is quite unclear how much of male or female homosexuality is due to genetics

16.  Animal studies do not allow researchers to draw accurate conclusions when studying sexuality; it is likely that homosexuality is common in different species for different reasons  Humans are a unique social species The concepts of ‘homosexuality’ and ‘gender’ are socially constructed ideas that have only become ‘relevant’ in the past 1,000 years

17. Conclusion  Genetic sterility guarantees 100% infertility from the moment a person is born. Genetic sterility has not been selected against throughout evolution. Do you think homosexuality ever will be? Probably not! *Because this is such a sensitive subject, I have to stress that this project was created from an inquisitive evolutionary and genetic approach and is in no way criticizing homosexuality

18. Works Cited  http://www.newscientist.com/article/dn13674-evolution- myths-natural-selection-cannot-explain- homosexuality.html#.U1cPWeZdVWY http://www.newscientist.com/article/dn13674-evolution- myths-natural-selection-cannot-explain- homosexuality.html#.U1cPWeZdVWY  http://www.ehbonline.org/article/S1090-5138(06)00069- 9/abstract http://www.ehbonline.org/article/S1090-5138(06)00069- 9/abstract  http://en.wikipedia.org/wiki/Homosexual_behavior_in_ani mals http://en.wikipedia.org/wiki/Homosexual_behavior_in_ani mals  http://en.wikipedia.org/wiki/Sexual_selection http://en.wikipedia.org/wiki/Sexual_selection  http://en.wikipedia.org/wiki/Natural_selection http://en.wikipedia.org/wiki/Natural_selection