The title of the fourth instalment in the Jurassic Park series may have just been announced, but already scientists have poured cold water on any hopes that dinosaurs can be resurrected in the way they are in the films.
Since the first film by Stephen Spielberg was released in 1993, the idea of extracting dinosaur DNA from blood eaten by insects that became entombed in amber 130 million years ago has fascinated the public.
However, a new study by a team of scientists and amber experts has confirmed that such techniques are likely to be impossible.
Using highly sensitive DNA sequencing techniques, researchers at the University of Manchester attempted to extract DNA from insects in subfossilised copal, the harden resin from trees that is a precursor of amber.
Laura Dern and Sam Neill in Jurassic Park
The scientists found they were unable to detect any ancient DNA in the samples they examined, which were between 60 to 10,600 years old.
It suggests that in older amber samples that are millions of years old, the chances of being able to extract intact DNA is even slimmer.
Dr David Penney, an amber expert at the University of Manchester, said: "Intuitively, one might imagine that the complete and rapid engulfment in resin, resulting in almost instantaneous demise, might promote the preservation of DNA in a resin entombed insect, but this appears not to be the case. So, unfortunately, the Jurassic Park scenario must remain in the realms of fiction."
Universal Pictures announced this week that the fourth Jurassic Park film, which is to be called Jurassic World, will be released in cinemas in 2015.
Although details of the film have been sketchy, it will be directed by Colin Trevorrow and Steven Spielberg, who directed the original film and the 1997 sequel The Lost World: Jurassic Park, will be the executive producer.
There have been reports that the film will return to the original setting on the Isla Nublar and will feature new dinosaurs, while it may also be filmed in 3D.
In the original movie, a short sequence explained how scientists had managed to extract dinosaur DNA from insects that had been preserved in amber, the resin from trees that hardens and then becomes fossilised.
The plot revolved around the ability to extract enough of the DNA from blood that had just been sucked by mosquitoes and other insects for it to be combined with DNA from modern amphibians and reptiles to clone dinosaurs.
Sam Neill in Jurassic Park
In the 1990s researhcers at the Natural History Museum attempted to isolate dinosaur DNA in this way from amber but were unable to replicate the process and the technology at the time was known for producing false negatives due to contamination with modern DNA.
In the latest study, which is published in the journal, The Public Library of Science ONE, the researchers used next generation DNA sequencing techniques and the team wore full foresnic suits in pressurised laboratories in an attempt to avoid contamination.
Professor Terry Brown, an expert in ancient DNA who was the senior author of the study, added: "In the original 1990s studies DNA amplification was achieved by a process called the polymerase chain reaction (PCR), which will preferentially amplify any modern, undamaged DNA molecules that contaminate an extract of partially degraded ancient ones to give false positive results that might be mistaken for genuine ancient DNA.
"Our approach, using 'next generation' sequencing methods is ideal for ancient DNA because it provides sequences for all the DNA molecules in an extract, regardless of their length, and is less likely to give preference to contaminating modern molecules."
They used stingless bees encased in copal from Columbia in an attempt to see if they could get DNA from the insect.
A sub-fossilized insect in copal. (David Penney, University of Manchester)
In the youngest specimens they examined, the researchers were only able to obtain DNA sequences of just over 500 nucelotides - the basic molecular building blocks of DNA - in length, probably barely enough to encode a single gene, let alone a whole genome.
When they attempted to match some of the sequences they did isolate, they did not find any that matched genes from modern stingless bees, but they did find a match with part of the genome from a bacterium called Bradyrhizobium japonicum.
In older specimens they were unable to get any clear evidence of DNA.
The researchers said: "Theoretical and empirical data indicate that aDNA fragments might be present in well preserved geological material up to at least 100,000 years in age, and suggest that some material up to one million years might yield sequence data.
"Copal inclusions fall at the lower end of this age range, but according to our results do not contain preserved DNA.
"This raises further doubts about claims of DNA extraction from fossil insects in amber, many millions of years older than copal."
