Scientists have found evidence that Giardia, an ancient protist long considered to be asexual, may have a sex life. The findings are reported in the January 26 issue of Current Biology.

"The origin and evolution of sex is one of the central unsolved puzzles for biology, and while we haven't solved it, these findings could bring us one step closer," co-author John Logsdon at the University of Iowa told The Scientist.

Giardia and other diplomonads are thought to be a roughly 2 billion year-old lineage, making them among the earliest diverging eukaryotes. Despite more than a century of study, they were not known to have sex, suggesting they might represent a premeiotic stage in eukaryotic evolution.

Logsdon and colleagues ran BLAST searches on the nearly complete Giardia lamblia genome project and then conducted phylogenetic analyses on the genes they found with a Bayesian likelihood method. They...

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