Scientists have used DNA to reach back 750 years into New Zealand's ancient past, revealing a history of extinctions and blows to our native species since humans arrived.
A new study by Australian and Kiwi researchers characterised DNA preserved in fragmented and unidentifiable bones from across the country.
By comparing bones excavated from caves that predate human arrival with bones from ancient human kitchen waste, found in middens, the researchers were able to characterise the biodiversity that had been lost in New Zealand.
Lead author PhD candidate Frederik Seersholm, of Australia's Curtin University, said causes of extinctions were usually hard to identify due to the time that had passed since it happened.
"However, through this study, we were able to examine in more detail the first contact between people and fauna in New Zealand because it only happened 750 years ago."
The research also identified a large faunal diversity with DNA from more than 100 different species uncovered, including 14 species that are extinct today.
"Our results demonstrate that certain species tend to be missed by traditional research methods," Seersholm said.
"For example, we identified species of eel and whale in Māori middens previously unknown in the prehistoric Māori diet."
The research team analysed DNA from more than 5000 bone fragments collected from 21 archaeological middens and 15 paleontological caves.
Study co-author Professor Michael Bunce, also of Curtin University, said genetic signatures were sequenced to identify different species and characterise different genetic lineages within one species.
"For the ground-dwelling parrot, the kākāpō, surprisingly high amounts of genetic diversity was detected in the bone fragments, which demonstrates that the kakapo population has been declining since human arrival in New Zealand 750 years ago," Bunce said.
"Of the 10 kākāpō lineages we identified, only one is still around today and this is an indication of the amount of biodiversity lost from one of New Zealand's iconic flightless birds."
Seersholm said the findings demonstrate how much information is stored in seemingly insignificant bone fragments.
"There is without doubt a great deal of information to be retrieved from fragmented bones, and it is likely that important future discoveries on extinct species and past biodiversity are hidden in neglected excavation bags in the basements of museums and universities around the globe."
Another co-author, Otago University's Dr Nic Rawlence, said DNA is offering scientists a rich picture of what New Zealand once boasted.
"When we are reconstructing prehistoric New Zealand, we've only been able to build the picture off the bones of animals that we can identify," he said.
"So we have a broad picture, but we've been missing a lot of detail – and now we can start to put a lot more of that detail in."
Rawlence said the findings were importantly relevant to conservation today.
"There's a phrase in geology, that the past is key to the present and the future; by being able to fully recreate what New Zealand was like, and the impacts that Europeans had, we can use all of that to inform restoration efforts now.
"It's all vitally important information for conserving what we've got left."
In just a few centuries, New Zealand has lost many species of moa, the world's largest ever eagle, the laughing owl, the New Zealand thrush, several species of wrens, three frog species, one bat species, at least 12 invertebrates such as snails and insects, the world's largest ever gecko and the New Zealand trout.
The most recent extinction was the South Island kokako, last seen in the 1980s.
The country is estimated to have more than 80,000 native animal, plant and fungal species, but only about 30,000 of those have been described, named and classified.
Today, more 1000 species are considered threatened or at risk of extinction, including more than three quarters of our native birds.
The new work, which also involved researchers from Canterbury Museum and the Museum of New Zealand Te Papa Tongarewa, will be taken forward with planned research in other parts of the world.