Two teams in the US and Europe have achieved the apparently impossible, recovering genetic material from a 38,000-year-old Neanderthal bone, writes Dick Ahlstrom
This in turn has allowed direct genetic comparisons to be drawn between the modern human, Homo sapiens, and our nearest hominid relative, Homo neanderthalensis.
We walked the earth with Neanderthals as recently as 30,000 years ago in Europe. Yet we could only speculate on the relationship, if any, between the two species.
Now two research teams, one led by the US, the other led by Germany, have given us two methods able to pull readable DNA fragments from ancient bones. The methods are different but also complementary in that one is effective for looking at large pieces of the genome while the other is particularly good for finding genes hidden in DNA.
"Our knowledge of Neanderthals is based on a limited number of remains and artifacts from which we must make inferences about their biology, behaviour and relationship to ourselves," writes the US-led team this morning in the journal Science.
This new ability to reassemble DNA fragments potentially into an entire genome now allows us to study Neanderthals "from a new perspective", the authors add.
The German-led group writing in Nature describe how it identified "a 38,000-year-old Neanderthal fossil that is exceptionally free of contamination from modern human DNA". The bone was discovered in a cave in Croatia.
From this they were able to extract many small fragments of cell nucleus DNA between 100 and 200 steps or "base pairs" long. This group then used a method called "pyrosequencing" to reassemble and record a million base pairs of Neanderthal DNA.
The US team used a different method, "metagenomics" to sequence 65,000 base pairs of Neanderthal DNA. "This initial analysis of the Neanderthal genome advances our understanding of the evolutionary relationship of Homo sapiens and Homo neanderthalensis and signifies the dawn of Neanderthal genomics," they say.
The two teams were able to infer much about the genetics of the two species despite having a tiny fraction of the full Neanderthal genome. The human genome is 3.2 billion base pairs long and the assumption must be the Neanderthals had a comparably sized genome given we share an estimated 99.5 per cent of our genetic make-up.
The Science group estimated the most recent common ancestor of the two species lived 706,000 years ago and the two populations finally split into distinct groups by 370,000 years ago.
They also believe the data indicates the two species remained apart from one another. There was no evidence that Neanderthals contributed to the modern human gene pool through interbreeding. Palaeontologists have long believed however that the two groups probably learned about tools and ornaments from each other.
The Nature group produced a slightly different set of numbers. They believe human and Neanderthal DNA diverged about 516,000 years ago. They also found that the Neanderthals were derived from a small ancestral population of about 3,000 individuals. This is similar to the estimated ancestral population from which modern humans developed.
The two teams were able to learn so much by using existing human and chimp genomes as a kind of scaffold or guide. The small Neanderthal DNA fragments were long enough to find matches in the other genomes, so they could be placed in the correct position along specific chromosomes.
The metagenomic method also allowed the recovery of DNA associated with 29 out of 35 genes that had been targeted under this method.
"Although these studies will not immediately answer many of the questions about the biological differences between Neanderthals and humans, they foreshadow an exciting developmen - the recovery of the complete Neanderthal genome," write David M Lambert of Massey University, New Zealand and Craig D Millar of the University of Auckland in an accompanying article in Nature.
This will allow scientists to assess the specific differences that produced humans in one case and Neanderthals in the other.
"More fundamentally, these combined studies show that when predicting the limits of science, one should never say never," they add.
It's official: we have the technology - we can rebuild them.
Data taken from Neanderthals can now be compared to that of modern humans and chimps.
The development of two methods to recover genetic material from ancient Neanderthal bones is the most important discovery in this field in 150 years, according to commentators.
It suddenly becomes possible in theory to reconstruct the full genomes of extinct animals, including hominids such as the Neanderthals.
Until now researchers were only able to recover fragments of DNA from the mitochondria in bones, something that provides limited information about the animal's maternal genetic inheritance.
Instead scientists wanted DNA not from mitochondria but from the cell nucleus, genetic material that would provide the fullest possible picture of the animal's genetic make-up. This was thought impossible however because ancient DNA over time breaks up into tiny fragments.
The two groups, one involving US and German researchers writing in Science, the other involving German, US and Croatian scientists writing in Nature, turned this assumption on its head.
The teams developed two methods that allowed the short DNA fragments found in 38,000-year-old bones to be copied and reassembled to give an incomplete but tantalising glimpse of the Neanderthal genome. The implications of the research are staggering. The Nature group believe they have a method and access to sufficient Neanderthal material to sequence the entire Neanderthal genome within two years. They still lack funding for this work.
Scientists would be keen to do detailed comparisons between the human, Neanderthal and chimpanzee genomes to better understand the genetic differences between these three, so closely related, species.
It also means that it may be possible to reconstitute the fragmented DNA sequences of other long-dead animals.
Dick Ahlstrom