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 .