Some species do it in pairs, some without knowing the other parties involved, and some even do it on their own.
Researchers say they have found that clusters of frog cells can be replicated in a way never before seen in plants or animals. The spherical clumps can give rise to offspring by sweeping up loose cells and washing them into more clusters.
Prof Josh Bongard, a co-author of the research, said that these things move around in the dish and make copies of themselves.
Synthetic lifeforms made from a few thousand cells from frog embryos are called senobots and are what are known as living robots.
After about two weeks, enobots fall apart. Bongard said that the xenobots could use hair-like projections to propel themselves.
They don't grow into Frogs, they keep the form that we impose on them. He said that they look and act differently than normal frog.
The production of offspring is one of those ways. Bongard said that anything that makes a copy of itself can be said to replicate. Plants and animals have previously been found to reproduce by a number of mechanisms.
Bongard and colleagues report in the Proceedings of the National Academy of Sciences that the process of self-replication is different for organisms than formolecules.
The start of life on Earth was important because of the conjugate self-replication in molecule. Bongard said that they don't know if this form of replication played a role in the life's origins.
The team discovered their discovery by watching the actions of the xenobots in petri dishes with room-temperature pondwater and loose cells from frog embryos.
Bongard said that the xenobots move around in the dish in a corkscrew pattern and crash into other loose cells.
The team found that if a pile is large enough, the cells can form a new cluster over the course of five days.
There is a hitch. The xenoBots will make children one generation at a time. Bongard said that the children are too small and weak to make grandchildren.
The researchers found that if the xenobots were formed into certain shapes, such as that of the video game character, they would continue to replicate for further generations.
Bongard said the hope was that self-replicating machines could eventually be developed to do useful work, with the team's computer simulations suggesting the xenobots could fix electrical circuits.
He said that the machines are very small and are happy in the water.
Bongard said biobots made from our own cells could be used to remove the need for surgery.
The director of the Institute of Making at University College London welcomed the research, saying it was amazing science and another step closer to making materials.
