Scientists are studying ancient DNA to reconstruct the genomes of a giant cave bear and a large horse that lived over 780,000 years ago.
Other extinct Ice Age animals such as sabre-tooth tigers and Neanderthals are also next in line to be researched via their genomes, or hereditary information.
"Neanderthals are an obvious target because they are our nearest relative," said Professor Erika Hagelberg of Oslo University. She is a pioneer and expert in the extraction of DNA from ancient bones.
"There are a lot of samples so we can now start looking at them in detail, including how their genes have been passed down to modern humans," she told the Sunday Times.
It's hoped that scientists will soon look further back in time, even reconstructing the genome of homo erectus, an early hominid believed to have come before Neanderthals. Studies of Neanderthal genomes suggest that they bred with modern humans.
Ludovic Orlando, professor of genetics at the Natural History Museum in Denmark will present his findings to the Royal Society in London.
So far, Orlando and his team have analysed DNA from a horse that lived 780,000 years ago.
The results show that the creature was an early ancestor of modern horses, zebras and donkeys who lived around 4 million years ago - twice as long as was previously believed.
Professor Orlando said that unlocking these genetic treasure troves could lead to "next-generation DNA sequencers" - machines that can take millions of fragments of DNA extracted from remains, analysing them in minute detail.
The data would then help to calculate out how they fitted together when the creature was alive.
In future, studies could also focus on other huge extinct mammals such as the cave lion, the woolly mammoth, the Irish elk and a giant rhinoceros.