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Archive for the ‘Fossils’ Category

This is pretty cool, and a tribute to how far sequencing techniques have come in only the past couple of years. With the advent of Next Generation Sequencing, a great deal more can be sequenced, a great deal faster and a great deal more accurately.

The Leipzig team has now developed sensitive novel techniques which have allowed them to sequence every position in the Denisovan  about 30 times over, using DNA extracted from less than 10 milligrams of the finger bone. In the previous draft version published in 2010, each position in the genome was determined, on average, only twice. This level of resolution was sufficient to establish the relationship of Denisovans to Neandertals and present-day humans, but often made it impossible for researchers to study the evolution of specific parts of the genome. The now-completed version of the genome allows even the small differences between the copies of genes that this individual inherited from its mother and father to be distinguished. This Wednesday the Leipzig group makes the entire Denisovan genome sequence available for the scientific community over the internet.

“The genome is of very high quality”, says Matthias Meyer, who developed the techniques that made this technical feat possible. “We cover all non-repetitive DNA sequences in the Denisovan genome so many times that it has fewer errors than most genomes from present-day humans that have been determined to date”.

The genome represents the first high-coverage, complete genome sequence of an archaic human group – a leap in the study of extinct forms of humans. “We hope that biologists will be able to use this genome to discover genetic changes that were important for the development of modern human culture and technology, and enabled modern humans to leave Africa and rapidly spread around the world, starting around 100,000 years ago” says Pääbo. The genome is also expected to reveal new aspects of the history of Denisovans and Neandertals.

The group plans to present a paper describing the genome later this year. “But we want to make it freely available to everybody already now” says Pääbo. “We believe that many scientists will find it useful in their research”.

The project is made possible by financing from the Max Planck Society and is part of efforts since almost 30 years by Dr. Pääbo’s group to study ancient DNA. The finger bone was discovered by Professor Anatoly Derevianko and Professor Michail Shunkov from the Russian Academy of Sciences in 2008 during their excavations at Denisova Cave, a unique archaeological site which contains cultural layers indicating that  occupation at the site started up to 280,000 years ago. The finger bone was found in a layer which has been dated to between 50,000 and 30,000 years ago.

The genome is available at http://www.eva.mpg.de/denisova and as a Public Data Set via Amazon Web Services (AWS):http://aws.amazon.com/datasets/2357 .

Tourists in front of the Denisova Cave, where "Woman X" was found.

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It seems like every other week paleontologists in China are finding new fossils that change our understanding of evolutionary lineages. This week it’s come to light that a new mammalian fossil had been found in China that dates to 160 million-years-old. It’s been named Juramaia sinensis, which means ‘Jurassic mother from China’, and is 35 million years older than the previously oldest known mammalian fossil, Eomaia (dated to 125 million years old).

It’s shrew-like in form, and part of the placental-mammal lineage and is thus a eutherian just like ourselves. So this species may be a direct ancestor of ours, or else a close cousin of our direct ancestors.

There are two other mammalian lineages, monotremes such as platypus and echidnas (lay eggs), and marsupials such as possums and kangaroos (have pouches). Though it’s still a little unclear, it’s suggested that monotremes split off on their own lineage around 170 million years ago, with eutherians splitting off from marsupials more recently.

The fossil has forepaws adapted to an arboreal life, that is one spent climbing trees, and would’ve spent its time in Jurassic forests chasing down small insects and other animals at night. Such a diet doesn’t get you to a huge size, and these guys would’ve reached ~15g. What a beast!

See this BBC article for more information!

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The world’s oldest fossil has been found in Australia according to a study published on Sunday. The bacteria microfossils date to 3.4 billion years ago when the Earth had no oxygen and the oceans were as warm as a hot bath.

It’s believed the microbes survived by consuming sulphur compounds, and they measure to around 10 millions of a meter long.

For more information have a look at this article.

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