Scientists have successfully completed early experiments that show it might be possible to make babies without using eggs. They used healthy baby mice, tricking the sperm into believing that they were fertilizing normal eggs. This could mean that women could one day be removed from the baby-making process.
While this is still a while away, the report helps to explain how it happens.
The University of Bath researchers started with an unfertilized egg in their experiments and then used chemicals to trick it into becoming a pseudo-embryo. These "fake" embryos have a lot in common with ordinary cells because they divide and control their DNA.
The researchers believe that since they could inject sperm into these pseudo-embryos, they might be able to do the same with humans.
In the mouse experiments, there was a one in four chance of a successful pregnancy.
Dr. Tony Perry, one of the researchers, said: "This is the first time that anyone has been able to show that anything other than an egg can combine with a sperm in this way to give rise to offspring. It overturns nearly 200 years of thinking."
The baby mice were completely normal and had healthy babies of their own.
The goal of the research was to understand the mechanisms of fertilization because what actually happens during the fusing of a sperm and an egg is still unclear. We do know that the egg completely strips the sperm's DNA of its chemical coating. This stops it from acting like a sperm and encourages it to act like an embryo - but no one is sure how it happens.
Eliminating the need for an egg could have a wider impact on society.
Dr. Perry said: "One possibility, in the distant future, is that it might be possible that ordinary cells in the body can be combined with a sperm so that an embryo is formed."
This means that two men could have a child that is biologically theirs, one giving an ordinary cell and the other giving a sperm. Or a man could give two of his own cells and sperm, which would result in a child being a non-identical twin - not a clone, this isn't Orphan Black.
A team in China has been working on ways to make sperm from stem cells so that something similar could happen for women.
Their findings were reported in Nature Communications.