Scientists believe life on Earth began evolving around 3.8 billion years ago. But while they have been able to put a date on when life appeared, they are still far from knowing how it appeared. Now researchers in the US and Italy say they have evidence that DNA-like fragments may have come with 'instructions' that guided their growth into complex life forms 4 billion years ago. Scroll down for video . Scientists believe life on Earth began evolving around 3.8 billion years ago, but they are still far from knowing how it appeared.  Now researchers in the US and Italy say they have evidence that DNA-like fragments may have come with 'instructions' that guided their growth into complex life forms 4 billion years ago . RNA, which stands for ribonucleic acid, is a molecule made up of one or more nucleotides. It is one of three major biological molecules that are essential for all known forms of life, along with DNA and proteins. The main job of RNA is to transfer the genetic code to create proteins from the nucleus to the ribosome. This prevents the DNA from having to leave the nucleus, and protects it from damage. It also acts as an on-and-off switch for some genes. The researchers believe these fragments used their innate self-evolving abilities to grow into repeated chemical chains long enough to evolve into primitive life. The study, by the University of Milan and University of Colorado Boulder, is based on a discovery in the 1980s that RNA can chemically alter its own structure. RNA is similar to DNA, and carries out a number of jobs in our cells, including acting as an on-and-off switch for some genes. Scientists believe that when life was in its early stages, RNA played a leading role in creating complex organisms before DNA and proteins were developed. Many origin-of-life researchers say that RNA chains are too specialised to have been created as a product of random chemical reactions. The new study, however, claims to provide an alternative theory by arguing primordial DNA-like fragments evolved in this way instead. The researchers found the self-assembly of DNA fragments just a few nanometres in length have the ability to drive the formation of chemical bonds. These connect together short DNA chains to form long ones, without the need for a separate biological process. The image shows a droplet of condensed nano-DNA and within it smaller drops of its liquid crystal phase which show up in polarised light on the left. The liquid crystal droplets act as 'micro-reactors' where short DNA can join together into long polymer chains to evolve into more complex life . 'Our observations are suggestive of what may have happened on the early Earth when the first DNA-like molecular fragments appeared,' said CU-Boulder physics Professor Noel Clark, a study co-author. The study suggests that the way in which DNA emerged in the early Earth lies in its structural properties and its ability to self-organise. In the pre-RNA world, the spontaneous self-assembly of fragments of nucleic acids – the building block of life - may have acted as a template for their chemical self-assembly. 'The new findings show that in the presence of appropriate chemical conditions, the spontaneous self-assembly of small DNA fragments into stacks of short duplexes greatly favours their binding into longer polymers, thereby providing a pre-RNA route to the RNA world,' added Professor Clark.
Scientists say early DNA-like fragments guided their own growth .
They claim the process can drive the formation of chemical bonds .
These connect short DNA chains to form long ones for life to evolve .
This self-assembly capability has been shown to take place in RNA .