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<jats:p>Thirty years after the discovery of HIV-1, the early transmission, dissemination, and establishment of the virus in human populations remain unclear. Using statistical approaches applied to HIV-1 sequence data from central Africa, we show that from the 1920s Kinshasa (in what is now the Democratic Republic of Congo) was the focus of early transmission and the source of pre-1960 pandemic viruses elsewhere. Location and dating estimates were validated using the earliest HIV-1 archival sample, also from Kinshasa. The epidemic histories of HIV-1 group M and nonpandemic group O were similar until ~1960, after which group M underwent an epidemiological transition and outpaced regional population growth. Our results reconstruct the early dynamics of HIV-1 and emphasize the role of social changes and transport networks in the establishment of this virus in human populations.</jats:p>

<jats:title>Illuminating oxygen out of carbon dioxide</jats:title> <jats:p> It has long been known that high-energy ultraviolet light can split carbon dioxide into CO and O fragments. Lu <jats:italic>et al.</jats:italic> have now uncovered a parallel pathway that appears to yield C and O <jats:sub>2</jats:sub> instead (see the Perspective by Suits and Parker). By precisely measuring the energy and trajectory of the carbon fragment after CO <jats:sub>2</jats:sub> irradiation, O <jats:sub>2</jats:sub> formation could be inferred. The results introduce a potential mechanism for abiotic oxygen production in CO <jats:sub>2</jats:sub> -heavy atmospheres of other planets. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="61" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1257156">61</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="30" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1259119">30</jats:related-article> </jats:p>

<jats:title>High-resolution tectonic solutions</jats:title> <jats:p> Detailed topographic maps are available for only a small fraction of the ocean floor, severely limited by the number of ship crossings. Global maps constructed using satellite-derived gravity data, in contrast, are limited in the size of features they can resolve. Sandwell <jats:italic>et al.</jats:italic> present a new marine gravity model that greatly improves this resolution (see the Perspective by Hwang and Chang). They identify several previously unknown tectonic features, including extinct spreading ridges in the Gulf of Mexico and numerous uncharted seamounts. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="65" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1258213">65</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="32" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1260459">32</jats:related-article> </jats:p>

<jats:title>Controlling the flow of light with nanoparticles</jats:title> <jats:p> Light propagating through optic fibers could provide the ultimate in information flow, but controlling the direction of flow is a key requirement. Petersen <jats:italic>et al.</jats:italic> show that the directional flow of light in a fiber can be controlled by placing a single gold nanoparticle on or near the surface of the fiber. By exploiting the chiral properties of light (the spin-orbit interaction), the authors demonstrate that the “handedness” or polarization state of the light hitting the particle determines in which direction the light flows in the fiber. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="67" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1257671">67</jats:related-article> </jats:p>

<jats:title>Tricks for boosting yeast's ethanol yields</jats:title> <jats:p> To become a widely used source of fuel, widespread industrial production of ethanol using yeast needs to be simple and efficient. However, two conditions ideal for boosting production—tolerance of higher temperatures and high concentrations of ethanol—have been limiting (see the Perspective by Cheng and Kao). Now, Caspeta <jats:italic>et al.</jats:italic> have used adaptive laboratory evolution to find yeast strains that can tolerate high temperatures and Lam <jats:italic>et al.</jats:italic> have identified a route to improve yeast's resistance to high concentrations of ethanol. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="75" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1258137">75</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="71" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1257859">71</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="35" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1260127">35</jats:related-article> </jats:p>

<jats:title>Tricks for boosting yeast's ethanol yields</jats:title> <jats:p> To become a widely used source of fuel, widespread industrial production of ethanol using yeast needs to be simple and efficient. However, two conditions ideal for boosting production—tolerance of higher temperatures and high concentrations of ethanol—have been limiting (see the Perspective by Cheng and Kao). Now, Caspeta <jats:italic>et al.</jats:italic> have used adaptive laboratory evolution to find yeast strains that can tolerate high temperatures and Lam <jats:italic>et al.</jats:italic> have identified a route to improve yeast's resistance to high concentrations of ethanol. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="75" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1258137">75</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="71" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1257859">71</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="35" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1260127">35</jats:related-article> </jats:p>

<jats:title>The costs and benefits of stalking and chasing</jats:title> <jats:p> Organisms live under a constant balance between getting and using energy. Large carnivores may feel this balance more acutely because of the large amounts of energy needed to capture and subdue their prey. Williams <jats:italic>et al.</jats:italic> and Scantlebury <jats:italic>et al.</jats:italic> used remote measures of physiology and behavior to identify the hunting strategies of the stalking North American puma and the speedy African cheetah (see the Perspective by Laundré). In both cases the cats' hunting strategies are well matched to produce a balance between the energy they spend on the hunt and the energy they acquire from their prey, despite their very different strategies and levels of competition. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="81" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1254885">81</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="79" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1256424">79</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="33" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1260170">33</jats:related-article> </jats:p>

<jats:title>The costs and benefits of stalking and chasing</jats:title> <jats:p> Organisms live under a constant balance between getting and using energy. Large carnivores may feel this balance more acutely because of the large amounts of energy needed to capture and subdue their prey. Williams <jats:italic>et al.</jats:italic> and Scantlebury <jats:italic>et al.</jats:italic> used remote measures of physiology and behavior to identify the hunting strategies of the stalking North American puma and the speedy African cheetah (see the Perspective by Laundré). In both cases the cats' hunting strategies are well matched to produce a balance between the energy they spend on the hunt and the energy they acquire from their prey, despite their very different strategies and levels of competition. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="81" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1254885">81</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="79" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1256424">79</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6205" page="33" related-article-type="in-this-issue" vol="346" xlink:href="10.1126/science.1260170">33</jats:related-article> </jats:p>