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IN THIS ISSUE April 20, 2021 When stimulated, each electrocyte of the electric eel can generate 150 mV via ion transportation through highly selective ion channels on cell membranes. ENGINEERING Printable power inspired by eels Printed energy storage devices can provide power to wearable devices. Lu Yang et al. used electric eels, which rely on sodium and potassium ion gradients to generate currents, for inspiration in developing alternatives to haz- ardous components in batteries. The authors developed two inks from graphene oxide, a permeable material with enhanced conductivity of positively charged ions. The two inks differed in their concentrations of potassium cations. Silver electrodes were also printed onto the paper. When moisture was introduced, reduction and oxidation of the silver produced a current, and potassium ions moved within the 2D nanofluidics in the graphene oxide, generat- ing 1.2 volts per cell. The silver electrodes also served to transform the ion migration into an electric current. When the authors printed 175 of these cells in a series, they generated 192 volts of electricity. In the absence of moisture, such as in a vacuum bag, the voltage was zero. Using this approach, the authors created a 3D cell. According to the authors, the performance of the power source is similar to lithium thin-film batteries and could aid the development of wearable electronics. — T.H.D. Read online PSYCHOLOGICAL AND education. The authors generated 11 were extensively trained on the task and COGNITIVE SCIENCES quadrilaterals, or four-sided shapes, reached a similar accuracy as kinder- that varied in their number of geometric gartners were not sensitive to geometric Geometric intuitions regularities, including parallel lines, equal regularities. The performance of baboons are present in humans angles, equal sides, and right angles. was captured by a simple perceptual During each trial, 605 adults were asked model, whereas human behavior was but not baboons to identify a deviant among six shapes well predicted by a second model that Humans are unique among primates in presented. Both response times and error assumes an additional level of symbolic their ability to create formal symbolic rates decreased as the total number of processing of geometric features. The systems that capture regularities in the geometric regularities rose. Similar results findings reveal a signature of human external world. Mathias Sablé-Meyer et were observed with 28 kindergartners, singularity in grasping abstract geometri- al. provide evidence that humans, but 156 first graders, and 22 Himba adults, cal concepts and challenge nonsymbolic not baboons, use a symbolic strategy who were recruited in small villages in models of human shape perception, to process the regularities of geometric Namibia and did not attend a single year according to the authors. — J.W. shapes, regardless of age, culture, or of school. By contrast, 11 baboons that Read online PNAS 2021 Vol. 118 No. 16 eiti1621118 https://doi.org/10.1073/iti1621118 | 1 of 4 Downloaded by guest on September 28, 2021 EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES Microplastics in the atmosphere Microplastic pollution is a major environmental issue. By combin- ing in situ observations of microplastic accumulation with an atmospheric transport model, Janice Brahney, Natalie Mahowald, et al. examined major sources of atmospheric microplastics as well as the locations where such pollution is concentrated. The authors collected atmospheric microplastics data from the western United States over a 14-month period. Eighty-four percent of atmospheric microplastics came from road dust, whereas 11% came from sea spray and 5% came from agricultural soil dust. Terrestrial microplastic pollution was depos- Microplastic ited on ocean surfaces, and oceanic microplastic pollution was particles in deposited on land. Most continents imported more plastic than atmospheric dust. they exported. Hotspots for terrestrial microplastic sources and accumulation included Europe, Eastern Asia, the Middle East, India, and the United States. Overall, the greatest concentration of atmospheric microplastics was estimated to be over the ocean. Depending on size, microplastics remained in the atmosphere from approximately 1 hour to 6.5 days, the latter duration being sufficient for cross-continental transport. Antarctica also received microplastic pollution from the atmosphere, despite having zero microplastic emissions. The findings suggest that even after atmospheric microplastics settle on land or in water, they may reenter the atmosphere, according to the authors. — M.S. Read online AGRICULTURAL SCIENCES the authors deactivated the compared age-specific mortality EcABCC8 ortholog in rice, rates in the United States with Transporter thereby increasing glyphosate the combined mortality rates of susceptibility by a factor of four France, Germany, Italy, Spain, conferring and doubling cellular levels of and England and Wales. The herbicide the herbicide, compared with combined population size of resistance in genetically unmodified plants. the analyzed European regions Additional analysis suggested is comparable to that of the plants that the EcABCC8 transporter United States. The authors report The ubiquitous use of the is likely located in the plasma that compared with the Euro- herbicide glyphosate has led membrane. Together, the find- pean regions, relative mortality to the evolution of dozens of ings suggest that the transporter conditions in the United States glyphosate-resistant weed spe- can move glyphosate out of the worsened significantly since cies. Lang Pan et al. report that cytoplasm and into the extracel- 2000 and resulted in more than herbicide resistance in plants can lular space, thereby reducing its 400,000 excess deaths in 2017 be mediated by ABC transport- toxicity to plants, according to alone. The same year, US individ- ers, which are also implicated in the authors. — J.W. uals aged 30–34 years were three human cancer drug resistance. Read online times more likely to die than their The plant ABC transporter European counterparts. Overall, gene EcABCC8 exhibited up to the United States experienced tenfold higher expression levels SOCIAL SCIENCES 13.02 million years of life lost to in glyphosate-resistant samples excess mortality in 2017, which of awnless barnyard grass, a spe- Excess mortality represents a 64.9% increase since cies of weed, compared with in the United 2000, after adjusting for changes glyphosate-susceptible sam- States in size and age distribution. The ples. Overexpression of orthol- findings suggest that the excess ogous genes of EcABCC8 Compared with other wealthy mortality rate in the United States conferred glyphosate resistance countries, the United States has in 2017 represents both a larger to rice, maize, and soybean higher mortality rates and lower number of deaths and of lost and decreased cellular levels life expectancy. Using 2000, 2010, years of life than those associated of the herbicide by a factor and 2017 data from the Human with COVID-19 in 2020, according of four. Using the CRISPR/ Mortality Database, Samuel to the authors. — M.S. Cas9 gene-editing technique, Preston and Yana Vierboom Read online 2 of 4 | https://doi.org/10.1073/iti1621118 In this issue Downloaded by guest on September 28, 2021 ENVIRONMENTAL SCIENCES favorable growth conditions accounted for 31% of the foliar later into autumn. The authors senescence timing showed that Declining winds compared the timing of foliar wind speed was more likely than delay onset of senescence with meteorological temperature or precipitation to data, including temperature, be correlated with senescence autumnal leaf precipitation, cloud cover, and timing. The authors report changes wind speed, in northern areas that the most likely effect of above 50 degrees latitude from decreased winds is a decrease The timing of leaf coloration 1982 to 2015. In two meteo- in soil drying, which can extend change and leaf drop, or foliar rological datasets, the authors the growing season. According senescence, varies each autumn, found decreasing wind speed to the authors, the multiple affecting the annual amount trends at these latitudes. Foliar effects of wind on plant growth of carbon uptake by trees. senescence was measured with render it potentially as important Chaoyang Wu et al. report 183,448 historical observa- to carbon uptake and climate that decreased wind speed in tions at 2,405 sites. For 29.3% feedback as temperature and the high northern latitudes is of the sites, wind speed was precipitation. — T.H.D. associated with a delayed onset associated with the onset of of foliar senescence, extending foliar senescence. A model that Read online ANTHROPOLOGY Dating Stone Age middens using ostrich eggshells The stratified layers of shell middens formed from cast-off mussel and limpet shells and other artifacts can offer a window into early cultures. However, radiocarbon dating is accurate to only around 50,000 years. Elizabeth Niespolo et al. report a method for dating ostrich eggshells in a Middle Stone Age shell midden and reveal an older and more intensely settled site than previ- ously known. The authors explored a method to precisely date older shell middens and thus allow comparisons among midden sites using debris from a common food source. The authors analyzed 17 eggshell samples from five strata of a midden at Ysterfontein 1, a collapsed rock shelter on the western coast of South Africa. Next, the authors measured the

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