Autonomy,Equality, and Teaching among Aka Foragers and Ngandu Farmers of the Congo Basin

The significance of teaching to the evolution of human culture is under debate. We contribute to the discussion by using a quantitative, cross-cultural comparative approach to investigate the role of teaching in the lives of children in two small-scale societies: Aka foragers and Ngandu farmers of the Central African Republic. Focal follows with behavior coding were used to record social learning experiences of children aged 4 to 16 during daily life. “Teaching” was coded based on a functional definition from evolutionary biology. Frequencies, contexts, and subtypes of teaching as well as the identity of teachers were analyzed. Teaching was rare compared to observational learning, although both forms of social learning were negatively correlated with age. Children received teaching from a variety of individuals, and they also engaged in teaching. Several teaching types were observed, including instruction, negative feedback, and commands. Statistical differences in the distribution of teaching types and the identity of teachers corresponded with contrasting forager vs. farmer foundational cultural schema. For example, Aka children received less instruction, which empirically limits autonomous learning, and were as likely to receive instruction and negative feedback from other children as they were from adults. Commands, however, exhibited a different pattern suggesting a more complex role for this teaching type. Although consistent with claims that teaching is relatively rare in small-scale societies, this evidence supports the conclusion that teaching is a universal, early emerging cognitive ability in humans. However, culture (e.g., values for autonomy and egalitarianism) structures the nature of teaching.     

A survey of cultivated heirloom tomato varieties identifies four new mutant alleles at the green-flesh locus

The process of crop domestication occurs through the selection and subsequent propagation of novel alleles that improve traits of interest. Cultivated tomato (Solanum lycopersicum), particularly heirloom varieties, exhibit a wide range of variation in fruit size, shape and color. The green-flesh mutant of tomato possesses a stay-green phenotype resulting in fruits that ripen to a red-brown color, due to the retention of chlorophyll and the simultaneous accumulation of lycopene. The recent identification of the GREEN-FLESH gene provides a molecular tool with which to investigate the origin of a subset of cultivated tomato varieties that resemble the green-flesh mutant. Sequence analysis of the GF locus from 26 varieties revealed the existence of four previously unidentified null alleles. This study illustrates the potential of cultivated tomato varieties, including heritage cultivars, heirlooms, and land races, for uncovering new alleles in genes of interest.     

Total synthesis of L-2,2-difluoro-2-deoxy-MYO-inositol 1,4,5-trisphosphate, a potent inhibitor of the enzymes of d-MYO-inositol 1,4,5-trisphosphate metabolism

The synthesis of the enantiomers of 2,2-difluoro-2-deoxy-myo-inositol 1,4,5-trisphosphate is reported. L-2,2-difluoro-2-deoxy-myo-inositol 1,4,5-trisphosphate is a potent inhibitor of 3-kinase and 5-phosphatase.     

Illumination preference and visual orientation of wild-reared mice, Peromyscus leucopus

A two-phase study was conducted with Peromyscus leucopus noveboracensis. In the field, frequency of captures was examined relative to nocturnal cloud cover and moon visibility. No relationships were apparent. In the laboratory, preferences of wild-reared mice for opposing visual cues under contrasting levels of illuminance were studied. Mice preferred an illumination equivalent to that striking a field on a clear, moonlit night (0.020 foot-candle) to the average of that striking the forest floor on a cloudy, moonlit night (0.005 foot-candle). At the lower intensity, mice showed no preference between two identical boxes placed vertically or horizontally. At the higher level of illuminance, there was a preference for the horizontal box, suggesting a tendency to orient toward horizontal objects over vertical ones at certain light levels. Higher natural nocturnal illuminance is not avoided (and may actually be preferred) by P. leucopus. Vision may be an important sensory modality in orientation and navigation under these conditions.     

The measurement of free radical reactions in humans. Some thoughts for future experimentation

The question as to whether free radical reactions are a major cause of tissue injury in human disease, or merely an accompaniment to such injury, is very difficult to answer because of lack of adequate experimental techniques. New techniques that are becoming available are discussed, with specific reference to their use in humans.     

An approach to the focal presentation of chemical stimuli

An olfactometer is described that presents temporally-discretepulses of stimuli to individual chemosensory structures. Thedevice is based on standard pressure injection techniques inwhich pulses of compressed air eject nanoliter volumes of upto six stimulants from small diameter glass micropipettes. Thedevice should be readily adaptable to different chemoreceptorpreparations.