Ancient sediments from caves have already been proven to preserve DNA for thousands of years. The amount of recovered sequences from environmental sediments, however, is generally low, which confounds the analyses performed with these sequences. A study led by Ron Pinhasi and Pere Gelabert of the University of Vienna and published in Current Biology successfully retrieved three mammalian environmental genomes from a single 25,000-year-old soil sample obtained from the cave of Satsurblia in the Caucasus (Georgia).
The cave of Satsurblia was inhabited by humans in different periods of
the Paleolithic: Up to date a single human individual dated from 15,000 years
ago has been sequenced from that site. No other human remains have been
discovered in the older layers of the cave.
The innovative approach used by the international team led by Prof. Ron
Pinhasi and Pere Gelabert with Susanna Sawyer of the University of Vienna in collaboration
with Pontus Skoglund and Anders Bergström of the Francis Crick Institute in
London permits the identification of DNA in samples of environmental material,
by applying extensive sequencing and huge data analysis resources. This
technique has allowed the recovery of an environmental human genome from the
BIII layer of the cave, which is dated before the Ice Age, about 25,000 years
ago.
This new approach has evidenced the feasibility of recovering human
environmental genomes in the absence of skeletal remains. The analysis of the
genetic material has revealed that the SAT29 human environmental genome
represents a human extinct lineage that contributed to the present day
West-Eurasian populations. To validate the results, the researchers compared
the recovered genome with the genetic sequences obtained from bone remains of
the nearby cave of Dzudzuana, obtaining definitive evidence of genetic
similarities. This fact validate the results and excludes the possibility of
modern contamination of the samples.
Along with the identified human genome, other genomes such as wolf and
bison have also been recovered from the environmental samples. The sequences
have been used to reconstruct the wolf and bison Caucasian population history
and will help better understand the population dynamics of these species.
The team now plans to perform further analyses of soil samples from the
cave of Satsurbia with the objective of revealing interactions between extinct
fauna and humans and the effect of climatic changes on mammalian populations.
The ability to recover DNA from soil samples allows us the reconstruction of
the evolution of whole past ecosystems .
Source: University of Vienna
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