Front Matter

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• Science and Culture: How fish innards inspire art
  An intense exploration of museum specimens allows a textile artist to see the complexity of bony structures, insights that influence her work. Image courtesy of Dan Meyers (© Dan Meyers Photography).

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• Core Concept: Are we in the “Anthropocene”?
  Some geologists want to define the present epoch based on humankind’s indelible footprint. Others aren’t so sure the label is a good idea. Image courtesy of Shutterstock/Chris Kolaczan.

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• News Feature: The Mars anomaly
  The red planet’s size is at the heart of a rift of ideas among researchers modeling the solar system’s formation. Image courtesy of NASA/JPL-Caltech.

PNAS in the News

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• Mite-virus mutualism in honey bee colony loss
  A study suggests that the mutualistic association between a parasitic mite and the virus it transmits is crucial to unraveling the dynamics of honey bee colony losses.
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• Unraveling skewed sex ratios in IVF offspring
  Skewed sex ratios, previously associated with IVF, may result from impaired X chromosome inactivation (XCI), a phenomenon that helps balance gene dosage in male and female offspring, and overexpressing a protein implicated in the XCI pathway helped partially rectify skewed sex ratios among mouse IVF offspring.
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• Parallel computing with biomolecules
  Researchers report that a computer comprised of a network of nanofabricated channels traversed by molecular motor-propelled protein filaments correctly found all possible solutions to a combinatorial problem in a parallel fashion, while using several orders of magnitude less energy per operation than electronic computers.
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