A gene involved in the production of sperm is shared by almost all living animals, including sea anemones, worms, insects, marine invertebrates, fish and humans.
The finding suggests the ability to produce sperm arose just once, 600 million years ago, and has been conserved through all subsequent animal evolution.
"People have thought that there was a single common ancestor because we see sperm reproduction in many animals, but previously there was no conclusive evidence that sperm production has a single common origin in all animals," said geneticist Eugene Xu from Northwestern University, co-author of the study being published July 15 in PLoS Genetics.
Renee Reijo Pera, director of stem cell research at Stanford University, said the result is interesting because sperm cells have so much in common, but also need to be different enough to be specific to each species.
"If a human could produce an egg that could be fertilized by a monkey it would be really bad," she said. "I think this gene and its derivatives have contributed to the specificity while maintaining the conserved function."
To confirm the presence of the gene, called BOULE, across different evolutionary lineages, Xu and his team looked for its presence in the sperm of a sea anenome, a sea urchin, a fruit fly, a rainbow trout, a rooster and a mouse.
The presence of BOULE in the sea anemone, one of the most primitive animals on earth, as well as all the others, pointed to the gene’s ancient origin.
BOULE is the only gene known to function only for the production of sperm, said Xu. This makes it an ideal target for designing a male contraceptive drug or agents that halt the reproduction of infectious parasites or the carriers of germs, he said, because knocking it out wouldn’t harm other bodily processes.
"We’d found genes before that were involved in sperm production but also in other functions in the body like hormonal regulation."
BOULE is not the first gene to be found that is shared among all animal groups. Some genes are shared in eye and heart development, for example.
Plants and fungi lack BOULE, which means the production of plant sperm, or pollen, most likely arose independently of animal sperm.
Image: 1) Sea Anemone, Creativity+Timothy K Hamilton/Flickr. 2) Various animal sperm/Eugene Xu.
See Also:
- Human Evolution Recapped in Kids' Brain Growth
- Air Pollution Could Shrivel Sperm's DNA
- Seeking Sperm, Not Sex, Online
- Evolution's New Foe: Timid School Administrators
- First Ancient-Human Genome Sequence Answers Anthropological Riddle
Follow Jess McNally on Twitter @jessmcnally, and Wired Science @wiredscience.
