Genetic and selective factors in reduction of the hallux in Pongo pygmaeus

Extreme reduction of the hallux is unique to the orang-utan (Pongo pygmaeus) among Primates. Hallucal diminution has advanced so far that 60% of orang-utans lack both distal phalanges and nails. Absence of these structures occurs significantly more often in females than in males. Hypotheses on possible genetic control of the condition have been tested and indicate that either single gene inheritance or polygenic inheritance with variable expressivity is involved. Reduction of pollex and of hallux in Pongo have advanced with selection for a specialized four-digit grasp in hands and feet. Diminution has progressed farther in the great toe than in the thumb due to selection for fine manipulation in the latter digit.     

The Avian Shoulder: An Experimental Approach

SYNOPSIS. This essay is in two parts. The first describes functionalstudies of the shoulder in modern vertebrates that led to theformulation of the hypotheses that motor patterns of homologousmuscles have been maintained during the evolution of the tetrapodshoulder, and that a primitive organization of the neural controlcomponents has persisted in derived groups. The second part of this essay focuses upon a longstanding questionin vertebrate evolution: what neuromuscular and musculoskeletalchanges in the tetrapod shoulder accompanied the evolution offlight in birds? The lack of empirical data on shoulder functionin extant birds limited our insight into this question, andprompted our initiation of experimental studies. Preliminarykinematics of the furcula and humerus of European starlings(Sturnus vulgaris) flying in a wind tunnel, as revealed by highspeed cineradiography, are presented. The two halves of thefurcula, which contact the coracoids dorsally, are bent laterallyduring downstroke and medially during upstroke by as much as60% of the intrafurcular resting distance. High speed film andelectromyographic studies of freeflying pigeons (Columba livia)reveal that the supracoracoideus muscle is strongly activatedduring wing elevation and, as predicted from studies of Varanusand Didelphis, an additional activation burst occurs at mid-downstrokein 48% of the recordings.     

Laetoli toes andAustralopithecus afarensis

The probable misfit between feet, particularly toes II–V, of 3.0-million-year-oldAustralopithecus afarensis from Hadar, Ethiopia, and the 3.5-million-year-old hominid footprints at Site G, Laetoli, Tanzania, casts doubt thatA. Afarensis made the Laetoli trails. We suggest that another species ofAustralopithecus or an anonymous genus of the Hominidae, with remarkably humanoid feet, walked at Laetoli. It would be imprudent to declare thatHomo was present at Laetoli 3.5 million years ago (my) because there is no evidence of brain expansion, advanced tool manufacture, or other non-locomotor hallmarks of the human condition at Site G.     

The effects of injection of amphetamine on female insemination in the black blow fly, Phormia regina (Diptera: Calliphoridae)

Abstract. An earlier study on the blowfly Phormia regina (Meigen) demonstrated that the injection of amphetamine (12 μg) depletes biogenic amine levels in the CNS. In the present study, P. regina females were injected with amphetamine (12 μg), each female was placed with three males and insemination success was determined. Amphetamine inhibited female insemination by 43.3% at 2–90 min post-injection and by 70% at 10–60 min post-injection. At 180–270 min post-injection, there was no significant inhibition of female insemination. This study indicates a possible role in insects for the biogenic amines in female insemination.