Flightless New Zealand birds might still carry the genes for flight - they're just not turned on, according to new research.
Scientists from the University of Otago and Harvard have sequenced the genomes of three species of kiwi, the extinct moa, and other flightless birds belonging to a group known as ratites, which can't fly.
"Moa are unique among ratites in that they had no wings left. However, the partial moa genome contains most of the functional genes associated with wing development and flight, creating an evolutionary mystery," said Dr Nic Rawlence, director of Otago University's Palaeogenetics Laboratory.
"This lack of wings is not a simple case of gene loss."
Instead, it appears another part of DNA that control how genes function is responsible.
"These are genetic regions that do not code for proteins, instead controlling their levels of production," said Dr Rawlence.
"Not only that, these regulatory elements are closely associated with the developmental pathways that allow flight, like wing development."
Researchers had been looking in the wrong place.
"As genes control the production of proteins and proteins can directly affect developmental process like the formation of flight muscles, genes are an obvious place to start looking for changes that cause a loss of flight," said Michael Knapp of the University of Otago's Department of Anatomy.
"In contrast, this study found that while there are common processes underlying the loss of flight in kiwi and moa (and other ratites), the loss of flight is not so much caused by changes in genes, but by changes in regions that control the function of genes. These are parts of the genome which, for example, can switch a gene on and off."
The kiwi and moa may even have arrived in New Zealand via the air.
"It supports the hypothesis that the ancestral moa flew here, while the ancestral kiwi, which is related to the emu, may have walked, or indeed flown from the likes of Australia or Madagascar over the ancient Gondwanan continent," said co-author Paul Gardner of the University of Otago's Department of Biochemistry.
Labour MP Trevor Mallard in 2014 suggested scientists find a way to bring back the moa.
"I know that this all sounds a bit like a scene from Jurassic Park. But it is going to happen," he claimed.
But Dr Rawlence says this latest research shows why it won't be that simple.
"This study just goes to show that having a genome does not mean you can bring back the dead - there's a whole lot of regulation of that genome that you would also have to recreate as well. That's a tough call."
As for the kiwi, it could potentially one day take to the skies again.
"With new genome editing techniques, it's a very interesting possibility," said Dr Gardner. "The outcomes of that experiment are very uncertain since we don't know the exact functions of most of these non-coding regions. That experiment would tell us a lot more about what they do."
The research was published in journal Science.