IS EXTRATERRESTRIAL ORGANIC MATTER RELEVANT TO THE ORIGIN OF LIFE ON EARTH?

I review the relative importance of internal and external sources of prebiotic molecules on Earth at the time of life's origin 3.7Gyr ago. The efficiency ofsynthesis in the Earth's atmosphere was critically dependent on its oxidation state. If the early atmosphere was non-reducing and CO2-dominated, external delivery might havebeen the dominant source. Interplanetary dust grains and micrometeorites currently deliver carbonaceous matter to the Earth's surface at a rate of 3 × 10⁵kg/yr(equivalent to a biomass in 2Gyr), but this may havebeen as high as 5 × 10⁷kg/yr (a biomass in only10Myr) during the epoch of late bombardment. Much ofthe incoming material is in the form of chemically inactive kerogens and amorphous carbon; but if the Earth once had a dense (10-bar) atmosphere, small comets rich in avariety of prebiotic molecules may have been sufficiently air-braked to land non-destructively. Lingering uncertainties regarding the impact history of the Earth and the density and composition of its early atmosphere limit our ability to draw firm conclusions.     

THE CHILD'S SEXUAL LIFE—A Consideration of Clinical Implications

A healthy sexual life begins in childhood, and the groundwork for later difficulties also begins in childhood. For the child, sexuality is a rather general, pleasurable excitation, not a specific genital stimulation. Excessive attention to the perineal area, operation upon or injury to the genital area and injections are vicissitudes which may have an unhealthy influence on later sexual development. Healthy and informed parental attitudes are the key here, just as they are in the normal exhibitionism, curiosity and intense emotional attachments to parents. Parents infect children, healthily or unhealthily, with their attitudes. In healthy growth exhibitionism and peeping become transformed in socially acceptable ways. In unhealthy growth, either perversions or strong reactions like over-modesty or shame result. Masturbation is common and transitory in most children. Parents, and especially pediatricians to whom parents turn, have a golden opportunity to direct healthy growth by being well informed about the infant and child''s sexual growth and thus be enabled to advise upon or manage the common developmental phenomena with good commonsense and patience. Infants and children do not enter the world possessing the morals, standards or inhibitions of adults.     

REPAIR OF INJURIES TO SOFT TISSUES OF FINGERS—Primary and Secondary Reconstruction

Preservation of maximum function and appearance of the finger can best be attained by wide excision of crushed or traumatized tissue and closure of defects by primary split thickness skin grafts. Primary pedicle flaps are rarely indicated and should be reserved for cover of denuded cortical bone or joint surfaces. In only 1 per cent of fresh injuries were primary pedicle flaps used. Finger length, nail bed and root, bone and tendon can be adequately preserved with minimal morbidity by split thickness skin grafts. Restoration of contour if necessary is best done secondarily, utilizing thenar or hypothenar flaps. These flaps are particularly indicated in the reconstruction of finger tips.     

DOES A NORMAL FOETUS REALLY HAVE A FUTURE OF VALUE? A REPLY TO MARQUIS

The traditional approach to the abortion debate revolves around numerous issues, such as whether the foetus is a person, whether the foetus has rights, and more. Don Marquis suggests that this traditional approach leads to a standoff and that the abortion debate 'requires a different strategy.' Hence his 'future of value' strategy, which is summarized as follows: (1) A normal foetus has a future of value. (2) Depriving a normal foetus of a future of value imposes a misfortune on it. (3) Imposing a misfortune on a normal foetus is prima facie wrong. (4) Therefore, depriving a normal foetus of a future of value is prima facie wrong. (5) Killing a normal foetus deprives it of a future value. (6) Therefore, killing a normal foetus is prima facie wrong. In this paper, I argue that Marquis's strategy is not different since it involves the concept of person--a concept deeply rooted in the traditional approach. Specifically, I argue that futures are valuable insofar as they are not only dominated by goods of consciousness, but are experienced by psychologically continuous persons. Moreover, I argue that his strategy is not sound since premise (1) is false. Specifically, I argue that a normal foetus, at least during the first trimester, is not a person. Thus, during that stage of development it is not capable of experiencing its future as a psychologically continuous person and, hence, it does not have a future of value.     

CLINAL DISTRIBUTION OF A CHROMOSOMAL REARRANGEMENT: A PRECURSOR TO CHROMOSOMAL SPECIATION?

Geographically structured genetic variants provide an effective means to assess sources of natural selection and mechanisms of adaptation to local environments. Correlated selection pressures along environmental gradients favor subdivision of genomes through chromosomal rearrangement. This study examines populations of Drosophila americana to evaluate selection pressures affecting chromosomal forms distinguished by a centromeric fusion. Analyses of chromosomal polymorphism throughout the Mississippi River Valley in the central United States reveal the presence of a distinct latitudinal cline for the chromosomal rearrangement. The cline has a width of 623 km centered at 35.97 degrees N and displays a characteristic sigmoid shape consistent with a balance between selection and dispersal. Extreme low temperature during January, an indicator of winter severity, was identified as the environmental variable that most accurately predicts arrangement frequency. An intriguing relationship identified between the chromosomal cline and operational sex ratio indicates that these alternative arrangements of the X chromosome may influence sex-specific survival. A hypothesis for the cline is presented wherein variation associated with the alternative chromosome forms influences distinct overwintering strategies. The resulting subdivision within the genome embodies a transitory stage of a speciation process in which locally adapted gene complexes provide a foundation for species formation.