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This press release is copyright Nature.
VOL.461 NO.7263 DATED 24 SEPTEMBER 2009
This press release contains:
· Summaries of newsworthy papers:
Genetics: Ancient roots for India’s rich diversity
Feature: A safe space for humanity
Climate: El Niño in a warmer world
Glaciers: Speeding on thinning ice
Astrophysics: White dwarf’s slow spin is not just skin-deep
Molecular biology: Direct RNA sequencing
Palaeoclimate: Quantifying the carbon cycle
Quantum physics: Bell’s inequality violated in solid-state system
And finally… Irreversible evolution
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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[1] Genetics: Ancient roots for India’s rich diversity (pp 489-494; N&V)
Current distinctions among groups within the Indian subcontinent are ancient, and strong inbreeding must have shaped marriage patterns in India for thousands of years, according to a study of genetic variation in Indian populations published this week in Nature. The study also reveals that the ‘caste’ system in India has existed for thousands of years, contradicting the view of many historians that caste is an invention of British colonialism.
David Reich and colleagues looked at single nucleotide polymorphisms in people representative of 25 diverse groups from around India. Their results reveal that there are two ancient, genetically divergent, populations that are ancestral to most Indians today. Traditionally upper caste and Indo-European speakers are descended from a group that is genetically close to Middle Easterners, Central Asians, and Europeans. The other group is not close to any group outside the subcontinent.
As well as the historical significance, the research also has medical implications for Indian populations. Recessive hereditary diseases — single gene disorders that occur only when an individual carries two malfunctioning copies of the relevant gene — are likely to be common in populations descended from so few ‘founder’ individuals. Mapping the causal genes will help to address this problem, but the authors caution that false-positive disease associations may occur if researchers do not take into account ancestry differences between cases and controls.
CONTACT
David Reich (Harvard Medical School, Boston, MA, USA)
Tel: +1 617 432 6548; Email: [email protected]
Aravinda Chakravarti (Johns Hopkins University, Baltimore, Maryland, USA) N&V author
Tel: +1 410 502 7525; Email: [email protected]
Feature: A safe space for humanity (pp 472-475)
Humanity must stay within defined boundaries for a range of essential Earth-system processes if we are to avoid catastrophic environmental change, argue Johan Rockström and his co-authors in a Feature article in this week’s Nature.
The concept of ‘planetary boundaries’ represents a new framework for measuring stress to the Earth system, and defines a safe operating space for human existence on the planet.
The authors suggest that nine Earth-system processes are among the planetary boundaries: climate change, ocean acidification, interference with the global cycles of nitrogen and phosphorus, freshwater use, changes in land use, atmospheric aerosol loading, chemical pollution and rate of biodiversity loss — both terrestrial and marine.
For three of these — the nitrogen cycle, the rate at which species are being lost and anthropogenic climate change – they argue that the acceptable boundary level has already been passed. In addition, they say that humanity is fast approaching the boundaries for freshwater use, for converting forests and other natural ecosystems to cropland, for acidification of the oceans and for the phosphorous cycle. Boundaries are also needed for atmospheric aerosol loading and chemical pollution, but there are insufficient data to define these, say the authors.
Transgressing even one of these planetary boundaries for too long could risk triggering abrupt or unacceptable environmental changes that would be very damaging or even catastrophic for society. Furthermore, if one boundary is transgressed, then safe levels for other processes could also be under serious risk.
To accompany this feature, Nature Reports Climate Change will publish seven Commentaries from leading experts — one on each of the proposed planetary boundaries.
A related Editorial will appear in this week’s Nature.
CONTACT
Johan Rockström (Stockholm Resilience Centre, Stockholm, Sweden)
Tel: +46 73 707 85 47; Email: [email protected]
[2] Climate: El Niño in a warmer world (511-514; N&V)
Global warming is having and will probably continue to have a dramatic effect on the El Niño phenomenon, which causes weather disturbances in many parts of the world every few years, suggests a report in Nature this week.
Recent studies have shown that the conventional El Niño pattern, characterized by a warm tongue of water stretching across the tropical Eastern Pacific, is becoming less frequent. A new type, or 'flavour', of El Niño has become progressively more common, in which a horseshoe-shaped region of warm ocean in the central Pacific is flanked by unusually cooler waters. This central Pacific El Niño has been called El Niño 'Modoki', from the Japanese meaning 'similar, but different'.
Sang-Wook Yeh and colleagues analyse a suite of climate models to test how frequently the new kind ofEl Niño occurs compared to the conventional type under projected global warming scenarios. They expect it to occur five times more often by the late 21st century. They conclude that such frequent central Pacific El Niño events could distinctively influence the global climate and lead to more effective forcing of drought over India and Australia.
CONTACT
Sang-Wook Yeh (Korea Ocean Research & Development Institute, Ansan, South Korea)
Tel: +82 31 400 7605; Email: [email protected]
Karumuri Ashok (APEC Climate Center, Pusan, South Korea) N&V author
Tel: +82 51 668 7470; Email: [email protected]
[3] Glaciers: Speeding on thinning ice (AOP)
DOI: 10.1038/nature08471
***This paper will be published electronically on Nature's website on 23 September at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 24 September, but at a later date. ***
Accelerating glacier flow is contributing more to ice loss from the Greenland and Antarctic ice sheets than was previously realized, according to a paper published online in Nature this week. The research has implications for predicting future sea-level rise.
It is known that glaciers at the margins of the Greenland and Antarctic ice sheets are speeding up and that the faster the flow, the more ice is lost — a process known as ‘dynamic thinning’. But until now it has been difficult to assess the full extent of the problem.
Hamish Pritchard and colleagues used the Ice, Cloud and land Elevation Satellite (ICESat) to monitor changes in the height of ice sheets along the entire grounded margins of the Greenland and Antarctic ice sheets. This high-resolution technique allowed the authors to distinguish between causes of height change — glacier dynamics or changes in the surface mass balance caused by changes in precipitation, snowpack, or melt — which could not be systematically assessed by previous methods.
The team show that dynamic thinning is far more extensive than was previously thought, particularly at ocean margins. This is important because the ice lost through dynamic thinning can cause sea levels to rise rapidly.
CONTACT
Hamish Pritchard (British Antarctic Survey, Cambridge, UK)
Tel: +44 1223 221293; Email: [email protected]
[4] Astrophysics: White dwarf’s slow spin is not just skin-deep (pp501-503; N&V)
The pulsations of a young white-dwarf star have been used to probe its internal rotation, revealing that the star’s interior rotates at the same slow speed as its surface. The finding supports theories of stellar evolution that involve significant coupling between a star’s core and envelope in the stages preceding white-dwarf formation.
White dwarfs are the dense, glowing cores of low-mass stars that have exhausted their nuclear fuel. One would expect these compact remnants to spin rapidly, for the same reason that a twirling ice skater speeds up as she draws in her arms. Yet previous observations have shown that, at least at the surface, white dwarfs rotate very slowly, with periods of hours to decades. This has led to suggestions that perhaps these stars hide some of their rotation — technically, their ‘angular momentum’ — at deeper levels.
In this week’s Nature, Gilles Fontaine and colleagues use observations of the oscillation frequencies of a pulsating white dwarf to examine its deep interior. They find that the star rotates with a uniform period of 34 hours through at least 90% of its depth. This implies that the processes that led to its birth were able to remove angular momentum from the star’s core — and that white dwarfs may have nothing to hide.
CONTACT
Gilles Fontaine (Université de Montréal, Québec, Canada)
Tel: +1 514 343 6611 47666; Email: [email protected]
Sung-Chul Yoon (University of Bonn, Germany) N&V author
Tel: +49 228 73 3660; Email: [email protected]
[5] Molecular biology: Direct RNA sequencing (AOP)
DOI: 10.1038/nature08390
***This paper will be published electronically on Nature's website on 23 September at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 24 September, but at a later date. ***
A new technique that enables researchers to sequence RNA directly should boost our understanding of human biology and disease.
Existing approaches to sequence RNA require its initial conversion to DNA followed by multiple manipulations, which can introduce biases and artefacts. The new method, reported by Patrice Milos and colleagues in this week’s Nature, allows even short and small quantities of RNA to be sequenced directly, without the need for the DNA intermediate step.
DNA is converted to RNA en route to making proteins, the ‘workhorses’ of the cell. But whereas the DNA content or genome is by and large the same between cell types, the RNA content or transcriptome can vary depending on which genes are being actively expressed and environmental conditions. So understanding this functional output of the genome is an essential step on the way to understanding biology. It’s thought that the new technique will lend itself to high-throughput and low-cost RNA sequencing, and so should enable a more detailed level of analysis of the transcriptome than was previously possible, and potentially identify new RNA types.
CONTACT
Patrice Milos (Helicos BioSciences Research, Cambridge, MA, USA)
Tel: +1 617 264 1897; Email: [email protected]
[6] Palaeoclimate: Quantifying the carbon cycle (pp 507-510)
Changes in land use caused by early man are unlikely to have been responsible for the steady rise of carbon dioxide levels in the atmosphere before industrial times, suggests a report in Nature this week.
Ice core reconstructions reveal significant changes in atmospheric carbon dioxide concentrations during the most recent 11,000-year Holocene period. An initial decrease of about 5 parts per million by volume (p.p.m.v.) is followed by an increase of about 20 p.p.m.v. to pre-industrial levels of about 280 p.p.m.v. Various explanations have been proposed, but the processes responsible have not yet been definitively identified.
Thomas Stocker and colleagues analyse a high-resolution carbon isotope record from an Antarctic ice core, stretching back 11,000 years to the beginning of the Holocene. With the help of their data and a simple model study the authors show that the increase in atmospheric carbon dioxide during the late Holocene is most probably the result of a combination of carbonate compensation of earlier land biosphere uptake and coral reef formation. The team argue that the idea of early-Holocene man influencing atmospheric carbon dioxide concentration, and thus preventing another ice age, does not hold up.
CONTACT
Thomas Stocker (University of Bern, Switzerland)
Tel: +41 31 631 44 64; Email: [email protected]
[7] Quantum physics: Bell’s inequality violated in solid-state system (pp 504-506)
A superconducting electrical circuit has passed one of the strongest tests of quantum mechanics, by exhibiting quantum correlations in the results of related measurements. The finding, reported in this week’s Nature, provides further clear evidence that the weirdness of quantum mechanics extends to macrosopic systems.
Quantum mechanics theory states that the results of measurements are intrinsically unpredictable, but also that measurements on so-called ‘entangled states’ — such as a pair of particles with opposite spins — will have correlated results not explainable by classical physics. These correlations, referred to as violations of Bell’s inequality, have been observed in entangled pairs of photons or ions. In principle, Bell violations should also be seen in pairs of superconducting quantum bits, or ‘qubits’ — electrical circuits that mimic the behaviour of elementary particles. But the technological challenges involved in making such a measurement are formidable.
John Martinis and colleagues have met these challenges, reporting an unambiguous violation of a Bell inequality in a system of two entangled superconducting qubits. So it seems this macroscopic electrical circuit is indeed a quantum system.
CONTACT
John Martinis (University of California Santa Barbara, CA, USA)
Tel: +1 805 893 3910; Email: [email protected]
[8] And finally… Irreversible evolution (pp 515-519)
Evolution is a one-way road, according to a study published this week in Nature. The research addresses the long-standing question of whether evolution can back-track if environmental selection pressures are reversed.
Joe Thornton and colleagues reconstituted ancient forms of a regulatory protein — the glucocorticoid receptor — and mapped the evolutionary changes that have taken place to give rise to the more recent form of the protein. Looking at this in the context of how the function of the receptor has changed, and which hormone it binds, they find that it’s not possible to re-evolve the ancestral version simply by bringing back the key amino acids that defined the original function of the protein. Other amino acids essential to that ancient form turn out not to affect the receptor’s more recent structure, and so have themselves accumulated changes over time. They now act like a ratchet, locking off the evolutionary path and preventing reversal to its historical state.
The findings indicate that molecular evolution is not strictly reversible, forcing natural selection to forge ahead on ever new paths, even if environmental pressures were just reversed.
CONTACT
Joe Thornton (Howard Hughes Medical Institute, University of Oregon, Eugene, OR, USA)
Tel: +1 541 346 0328; Email: [email protected]
ADVANCE ONLINE PUBLICATION
***This paper will be published electronically on Nature's website on 23 September at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 24 September, but at a later date. ***
[9] STING Regulates Intracellular DNA-Mediated, Type-I Interferon-Dependent Innate Immunity
DOI: 10.1038/nature08476
GEOGRAPHICAL LISTING OF AUTHORS…
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
CANADA:
Montreal: 4
FRANCE
Toulouse: 2, 4
GERMANY
Bremenhaven: 6
India
Hyderabad: 1
Korea
Ansan: 2
SWITZERLAND
Bern: 6
UNITED KINGDOM
Bristol: 3
Cambridge: 3
UNITED STATES OF AMERICA
California
Santa Barbara: 7
Florida
Miami: 2, 9
Georgia
Atlanta: 8
Hawaii
Honolulu: 2
Massachusetts
Boston: 1,
Cambridge: 1, 5
Oregon
Eugene: 8
PRESS CONTACTS…
For North America and Canada
Neda Afsarmanesh, Nature New York
Tel: +1 212 726 9231; E-mail: [email protected]
For Japan, Korea, China, Singapore and Taiwan
Mika Nakano, Nature Tokyo
Tel: +82 3 3267 8752; E-mail: [email protected]
For the UK/Europe/other countries not listed above
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]
Jen Middleton, Nature London
Tel: +44 20 7843 4502; E-mail: [email protected]
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