The Origin of Sex (video)

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Parasites and Pathogens and how sex began
LiveScience.com

Without the pathogens and parasites of the world, there might be no such thing as sex.

A new study finds that in organisms that can reproduce alone or with a partner, sexual reproduction is the result of a deadly arms race between host and pathogen.

Without the presence of pathogens, the host organism sticks with the tried-and-true method of asexual [sexless] breeding. When threatened by a continually evolving pathogen that gets better and better at killing its host, however, the host organism starts seeking out sex partners.

"You actually need these pathogens or parasites to be co-evolving for sex to be maintained," study author Levi Morran, a postdoctoral researcher at Indiana University, told LiveScience. More

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