The only Tasmanian tiger people will see will be in museums, on black and white film or on beer bottles, according to a Melbourne DNA expert.
Janette Norman said it was impossible to clone the extinct thylacine, despite claims earlier this year that the animal's genome could be rebuilt.
Dr Norman, a molecular biologist and head of the population and evolutionary genetics unit at Museum Victoria, will today give a lecture entitled Cloning the Thylacine: Fact or Fantasy? at the museum.
She will challenge a claim in May by Professor Michael Archer - who last week gave a lecture called Bringing Back the Thylacine - that the animal could be "rebuilt" from a pup preserved in ethanol for 136 years.
"It's impossible to do," Dr Norman said. "There's all sorts of basic science missing.
"One of the things that Mike's group suggested was that because the pup was in ethanol, they would be able to extract - intact - chromosomes from it.
"Anyone who works with DNA would tell you DNA will break down in those time frames, even in ethanol. When something dies, cells die and enzymes attack your own DNA.
"They've found DNA out of the pup and they've found exactly what I and others have said they would find and that is DNA that is degraded."
The last known thylacine died in Hobart Zoo on September 7, 1936.
Jeremy Austin, of the University of Queensland, concurred with Dr Norman.
"It's a waste of time and research dollars," he said.
Dr Austin likened the task of reconstructing a thylacine's genome to trying to rebuild, in order, a complete set of encyclopedias that had been torn into little pieces and had had some of pages burnt or singed.
Professor Archer disputed that, saying: "That might be what he anticipated but we found great big chunks, torn into big chunks. The challenge is enormous but it is not what he is describing."
Professor Archer won the Australian Sceptic of the Year award in 1998 and was nominated earlier this year for the Sceptics Bent Spoon Award, for "the perpetrator of the most preposterous piece of paranormal or pseudo-scientific piffle".
But he remained defiant yesterday, saying: "We have the whole genome."
He also said the DNA from the pup was of a high quality.
He said he welcomed criticism, but "scientists tend to assume that what hasn't happened, can't happen".