New evidence found by researchers at Northwestern University Feinberg School of Medicine indicates that mammals' ability to produce sperm is very ancient, probably originating as early as 600 million years ago.
The researchers have found that there is one sex-specific gene so vital that its function has remained unaltered throughout evolution and is found in almost all animals.
They discovered that the gene, called Boule, which is responsible for sperm production also, appears to be the only gene known to be exclusively required for sperm production from an insect to a mammal.
"This is the first clear evidence that suggests our ability to produce sperm is very ancient, probably originating at the dawn of animal evolution 600 million years ago," said Eugene Xu, assistant professor of obstetrics and gynaecology at Feinberg.
"This finding suggests that all animal sperm production likely comes from a common prototype," added Xu.
The discovery of Boule offers a better understanding of male infertility, a potential target for a male contraceptive drug and gives a new direction for future development of pesticides or medicine against infectious parasites or carriers of germs.
"Our findings also show that humans, despite how complex we are, across the evolutionary lines all the way to flies, which are very simple, still have one fundamental element that's shared," said Xu.
"It's really surprising because sperm production gets pounded by natural selection.
"It tends to change due to strong selective pressures for sperm-specific genes to evolve. There is extra pressure to be a super male to improve reproductive success. This is the one sex-specific element that didn't change across species. This must be so important that it can't change," added Xu.
For the study, Xu searched for and discovered the presence of the Boule gene in sperm across different evolutionary lines- human, mammal, fish, insect, worm and marine invertebrate.
"A sperm-specific gene like Boule is an ideal target for a male contraceptive drug," noted Xu.
The study is published in PLoS Genetics.