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Genitalia Genesis: Lizard Limbs?

According to a study recently published in the journal Nature, the secret to the origin of genitalia—for lizards and snakes anyway—lies in the limbs. The new research reveals new data on the evolutionary development of sex organs after research team scientists from Harvard Medical School in Boston, Massachusetts turned lizard limbs into genitalia in a laboratory.


Growing genitalia from limbs/Image: Patrick Tschopp/Harvard

Snakes and lizards have two sex organs. In contrast to human genitalia, the paired parts of reptiles are located in proximity of their limbs. Lizard genitalia come from tissue that produces back legs. Mammalian genitals come from the tailbud.

Initially researchers wanted to learn why snakes don’t develop limbs. It was not until later that the investigative team learned that the beginning stages of sex organ development were very similar to the formation of limbs. Even more importantly, with a little push, lizard limbs were transformed into lizard genitalia.

Lead author of the study, Dr. Patrick Tschopp, told BBC News: “It demonstrates that there is flexibility with what kind of cells can get recruited during development to form genitalia.”

Harvard Medical School genetics department chair Clifford Tabin stated: “While mammal and reptile genitalia are not homologous in that they are derived from different tissue, they do share a ‘deep homology’ in that they are derived from the same genetic program and induced by the same ancestral set of molecular signals.”


Patrick Tschopp/Image: GenPath/Harvard

In lizards and snakes, the cloaca is located close to tissues that birth limbs. In order to create genitalia in the lab, Tschopp and his team of scientists relocated the cloaca—a small “signaling source” that informs the nearby tissues and cells to create external genitalia—into either limb or tail bud cells. The cells near the cloaca changed into genitalia cells in both cases.

Tschopp explained: “In other words, by misplacing a molecular signal you can misguide these cells in their developmental trajectory.” The results demonstrated how limbs and genitalia “have a shared ancestry” and that the evolution of genitalia was an “adaptive “step in order to exist on land.

 Genitalia Genesis: Lizard Limbs?

About Will Phoenix

W. Scott Phoenix, B.A., B.S. was born in Hawaii, raised in Pennsylvania and resides in California. He has been a published writer since 1978. His work has appeared (under various names) in numerous places in print and online including Examiner.com. He is a single parent of three children and has also worked as an actor, singer and teacher. He has been employed by such publications as the Daily Collegian and the Los Angeles Times.