Geochronologists from the University of Wollongong (UOW) and an international research team dated DNA in frozen soil to reveal molecular fossils of a mammoth and an ancient horse that lived 7600 years ago.

Experts previously thought they disappeared 12,000 to 13,000 years ago, citing human activity, climate or cometary impact as the cause.

"Now the simple answers have disappeared, and it's probably a combination of factors," UOW Director of the Centre for Archaeological Science Professor Richard Roberts said.

The traces of mammoth DNA were found in Stevens Village in central Alaska, 11m below ground level.

Prof Roberts was certain the samples were accurate as the DNA had been covered in ice as soon as it made contact with the soil.

"Some people are asking, 'Are you sure it's mammoth?' But it's literally a deep freeze in genetic information."

Prof Roberts said the research team looked for undisturbed soil, but luck also played a part.

"We could have gone 20m further and not found anything," he said.

"The mammoth has to leave its DNA at that very spot."

It was the analysis of DNA rather than fossils that allowed the team to refute what we know about mammoths.

"Throughout its life, the mammoth is shedding hair and skin, and leaving behind more traces than simply bones," he said.

"There's a much bigger chance of finding these animals by dating DNA."

The UOW team was responsible for dating the sediments used in the project, which took about two years.

"We were the main drivers in designing the project," Prof Roberts said of his team at UOW, Dr Lee Arnold and Dr Martina Demuro.

"You can pull genetics out of sediment but then you still need to know how old the sediment is."