Mongooses recall cooperation to reciprocate in kind
Dwarf mongooses. Image courtesy of Shannon Wild (photographer).
Social animals exchange services, such as grooming, in return for others, such as enabling access to food and mates and warding off rival groups. However, whether nonhuman animals reciprocate based on a memory of recent cooperation remains unclear. Julie Kern and Andrew Radford (pp. 6255–6260) examined a wild population of dwarf mongooses (Helogale parvula) in South Africa and found that the extent to which individuals served as sentinels—guards who watch for predators and warn the group using alarm calls—was directly linked with the number of grooming partners they boasted and the number of grooming bouts they received. Increased grooming, which improves hygiene and reduces anxiety, offsets the heightened predation risk and reduced foraging time tied to performing sentinel duty. When the authors simulated an increase in the sentinel contributions of selected mongooses by playing back recordings of their surveillance calls, which are used to announce the sentinels’ presence, those mongooses received increased grooming later in the day at their sleeping refuge compared with mongooses whose sentinel contributions had not been manipulated. By contrast, playing back foraging calls, rather than surveillance calls, of the same mongooses did not result in increased grooming later in the day. According to the authors, the findings suggest that nonhuman animals are capable of recalling recent cooperation to reciprocate in kind. — P.N.
High-accuracy face recognition
Minimizing errors in facial identification has implications for forensic science. However, tests of accuracy of professional face identifiers are rare, and methods to maximize the accuracy of face identification are lacking. P. Jonathon Phillips et al. (pp. 6171–6176) compared face identification by humans and computers. The authors tested human face recognition ability and demonstrated that various forensic professionals, including forensic facial examiners with extensive training, were more accurate than control groups at identifying faces in a face identification test. Subsequently, four computer algorithms trained for facial recognition took the face identification test. The algorithms, which were developed between 2015 and 2017, performed within the range of human accuracy, with the most recent algorithm scoring higher than the median of the forensic facial examiners. However, the authors found that combining a single forensic facial examiner with the top-performing algorithm produced the most accurate face identification, resulting in improved accuracy, compared with the combination of two forensic face examiners. The results may help improve accuracy in face identification, according to the authors. — C.S.
Regional offsets in radiocarbon dates influence southern Levant chronologies
Juniperus phoenicea doors and doorway at Taybet Zaman (now the Hyatt Zaman Hotel & Resort), Jordan.
Researchers construct high-precision Holocene radiocarbon chronologies using standardized Northern and Southern Hemisphere calibration curves. Backed by theoretical and empirical studies, the current Northern Hemisphere standard curve, IntCal13, requires that premodern atmospheric radiocarbon levels remain stable on annual timescales. Addressing recent challenges to this assumption, Sturt Manning et al. (pp. 6141–6146) attempted to uncover offsets in atmospheric 14C values in the southern Levant, a region where high-resolution chronologies during the Late Bronze and Iron Ages are of archaeological interest. The authors measured 14C ages for tree rings from southern Jordan with established calendar dates between AD 1610 and 1940 and report that contemporary plant material growing in the southern Levant exhibits an average offset of approximately 19 14C years, compared with IntCal13. In addition, the offset appears to have fluctuated over time between significant and insignificant values, possibly as a consequence of climatic changes modulating the local growing seasons. According to the authors, applying the results to previously published chronologies demonstrates how the relatively small offsets can nonetheless shift calendar dates far enough to sway ongoing archaeological debates. — T.J.
Gene drive strategy to eliminate insect pests
CRISPR/Cas9 gene-drive systems could enable the rapid spread of desired traits in wild populations of insects, including disease vectors, such as mosquitoes, and agricultural pests, such as the Mediterranean fruit fly (Ceratitis capitata). One potential insect-control strategy is to introduce mutations in sex-determination genes, causing population collapse through the conversion of females to fertile males capable of passing on the mutated genes to potentially all offspring. Mohammad KaramiNejadRanjbar et al. (pp. 6189–6194) report that a CRISPR/Cas9-based sex conversion strategy could help manage populations of the Mediterranean fruit fly, which damages fruit crops. Due to safety concerns, the authors performed experiments using the common fruit fly (Drosophila melanogaster), given that males that harbor XX sex chromosomes are always sterile. The authors designed a homing CRISPR/Cas9 system that targets a specific DNA sequence in the transformer gene, which plays a pivotal role in female-specific development in various insects. However, this system showed limited efficiency at converting D. melanogaster females to males. Using population dynamic simulations, the authors demonstrated that a CRISPR/Cas9 gene-drive system targeting multiple DNA sequences in the transformer gene could serve as a potential pest-control strategy for the Mediterranean fruit fly. According to the authors, the findings provide a potential approach for the elimination of insect pests or disease vectors. — J.W.
Mechanotransduction, gene regulation, and embryonic development
Mechanotransduction during sea anemone gastrulation.
Human embryos develop according to a precise genetic program of spatiotemporal gene expression and cellular differentiation. However, a growing body of work indicates that mechanotransduction—the ability of cells to transform mechanical forces into biochemical signals—regulates gene expression and may thus play a pivotal role in embryonic development. To investigate the universality of mechanotransduction during embryonic development in animals, Ekaterina Pukhlyakova et al. (pp. 6231–6236) examined mechanosensitive gene expression during gastrulation of the starlet sea anemone Nematostella vectensis. The authors report that mechanical pressure activates or restores the expression of brachyury, an ancient protein found in all bilateral animals that is crucial to embryonic development. Furthermore, brachyury expression in N. vectensis via mechanotransduction depends on the signaling molecule β-catenin, mirroring the signaling pathway used by vertebrates. The authors suggest a feedback loop, in which mechanical and genetic regulation work together to ensure robust brachyury expression. In addition, because β-catenin–dependent mechanotransduction and brachyury expression occur in other bilateral animals, the findings suggest that this form of gene regulation dates to at least 600 million years ago, a time that marks the evolutionary split between Bilateria and Cnidaria, according to the authors. — T.J.
Aerial remote sensing aids archaeology
An ancient temple at Jerash against the backdrop of the rapidly expanding modern city.
Rapid development of cities in the Middle East can endanger archaeological sites, which are abundant in the region and susceptible to irreversible damage that could hamper understanding of how ancient societies responded to economic or environmental change. David Stott et al. (pp. E5450–E5458) used historical aerial imagery of the city of Jerash in Jordan dating to 1917 and modern airborne laser scanning (ALS) data to establish the locations of archaeological structures. The authors used historical imagery to identify likely sites and structures and ALS imagery to assess the remaining structures in the wake of development in the eastern half of the city. The authors report a substantial number of possible structures that were not previously mapped and refine the position of the city’s walls and the scale of previously identified structures compared with earlier maps. The combined ALS and historical imagery suggests connections between aqueducts, cisterns, and siphons that provide insight into the structure of the water supply system for the ancient city. According to the authors, similar historical and modern remote sensing methods can help uncover and evaluate archaeological data. — P.G.