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<jats:p>Physicists at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg announced last week that 3 years of smashing positrons and protons together at high energy have produced a handful of collisions too violent to be easily explained in the current picture of particles and forces. The most dramatic explanation for the excess is the brief appearance in each collision of a long-sought particle called a leptoquark, which would bridge the two known families of particles. But the researchers caution that the excess could still be a statistical fluke.</jats:p>

<jats:p>The end of the Paleocene epoch 55 million years ago was a puzzling time, in which tiny marine animals died, modern mammals suddenly appeared in North America, and isotopic signals indicate a shift in the global carbon cycle. Now a new mathematical model shows that a release of methane gas from the ocean floor could be at the heart of all these changes.</jats:p>

<jats:p> A Report on page <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1281" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5304.1281" xlink:type="simple">1281</jats:related-article> presents new thermoluminescence dates on primitive stone tools from Siberia. The results suggest that early humans lived there as early as 260,000 years ago—long before anthropologists thought they were capable of surviving such a bitter climate. </jats:p>

<jats:p> Intuition may deserve more respect that it typically gets these days. Although it's often dismissed along with emotion as clouding clear, rational thought, a new study reported on page <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1293" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5304.1293" xlink:type="simple">1293</jats:related-article> suggests that it plays a crucial role in humans' ability to make smart decisions. </jats:p>

<jats:p> The brain's ability to learn and remember is at least partly due to the changing strength of its cell-to-cell connections, the synapses. Growth factors, previously thought to confine their action on synapses to the developing organism, can also change synaptic strength in the adult; an example in the invertebrate <jats:italic>Aplysia</jats:italic> is reported by Zhang <jats:italic>et al</jats:italic> . on p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1318" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5304.1318" xlink:type="simple">1318</jats:related-article> of this issue. In her Perspective, Schuman discusses how these new results add to what is known about the actions of growth factors in the adult and developing brain. </jats:p>