While DNA cloning of dinosaurs seemed feasible in Jurassic Park - especially if you were 10 years old when the movie came out - scientists now say it is impossible.
The study found that after cells die enzymes start to break down the bonds between nucleotides that form DNA.
After time micro-organisms and reactions with water further degrade the material, until gradually there is little of the original DNA left.
After about 521 only half of the DNA remains, according to the study in the Proceedings of the Royal Society.
Almost every bond of DNA would be destroyed after 6.8 million years, the study estimates.
It would cease to be readable after about 1.5 million years ago - long enough to perhaps do cool science with a wooly mammoth, but not dinosaurs, the last of which died 65 million years ago.
"This confirms the widely held suspicion that claims of DNA from dinosaurs and ancient insects trapped in amber are incorrect," said Simon Ho, an evolutionary biologist at the University of Sydney in Australia.
The current record for an authentic DNA sequence is currently 500,000 years, meaning scientists can theoretically go further back - but not anywhere close to a velociraptor.
Which, to anyone who's watched beyond the first hour of Jurassic Park, is surely a good thing?Suggest a correction