Functional tradeoffs in specialization for fighting versus running

Journal ArticleBoth locomotion and fighting are critical to survival and reproductive fitness in many vertebrate species. Yet, characters that make an individual good at fighting may, in many cases, limit locomotor performance and vice versa. Here I describe tests of three functional tradeoffs in the limb muscles of two breeds of domestic dogs that have undergone intense artificial selection for running (Greyhound) or fighting performance (Pit Bull). We found that Greyhounds differ from Pit Bulls in having relatively less muscle mass distally in their limbs, weaker muscles in their forelimbs than their hindlimbs, and a much greater capacity for elastic storage in the in-series tendons of the extensor muscles of their anlde joints. These observations are consistent with the hypothesis that specialization for rapid or economical running can limit fighting performance and vice versa. Variation in body form among dog breeds has been suggested to be largely a consequence of selection on the ontogenetic variation present in individual wolf-like dogs (Wayne, 1986a,b). This, plus recent work on the genetics of the caned skeleton, raise the possibility that pit bulls are a breed that has evolved by the retention of juvenile shape (i.e., neoteny) and greyhounds may represent an acceleration of shape ontogeny. Finally, functional tradeoffs that prevent simultaneous evolution of optimal performance in both locomotor and fighting abilities appear to be widespread taxonomically and may have been particularly important in the evolution of hominid anatomy and physiology

The effect of foot posture on capacity to apply free moments to the ground: implications for fighting performance in great apes

In contrast to most other primates, great apes have feet in which the heel supports body weight during standing, walking and running. One possible advantage of this plantigrade foot posture is that it may enhance fighting performance by increasing the ability to apply free moments (i.e. force couples) to the ground. We tested this possibility by measuring performance of human subjects when performing from plantigrade and digitigrade (standing on the ball of the foot and toes) postures. We found that plantigrade posture substantially increased the capacity to apply free moments to the ground and to perform a variety of behaviors that are likely to be important to fighting performance in great apes. As predicted, performance in maximal effort lateral striking and pushing was strongly correlated with free moment magnitude. All else being equal, these results suggest species that can adopt plantigrade posture will be able to apply larger free moments to the ground than species restricted to digitigrade or unguligrade foot posture. Additionally, these results are consistent with the suggestion that selection for physical competition may have been one of the factors that led to the evolution of the derived plantigrade foot posture of great apes

Human flight and exercise in microgravity

Journal ArticleEarly experimenters in human flight learned, sometimes with fatal consequences, that the human body lacks the muscular power to fly (1). Indeed, the power demands are so great that only relatively small animals (less than 12 kg) are able to fly actively due to the interplay of morphologic scaling (muscle mass, wing area, power output) and organism weight (2). But this might not be true in a space station. Could humans fly in air when subject to microgravity? How demanding would such flight be

Electromyographic pattern of the gular pump in monitor lizards

Journal ArticleGular pumping in monitor lizards is known to play an important role in lung ventilation, but its evolutionary origin has not yet been addressed. To determine whether the gular pump derives from the buccal pump of basal tetrapods or is a novel invention, we investigated the electromyographic activity associated with gular pumping in savannah monitor lizards (Varanus exanthematicus). Electrodes were implanted in hyobranchial muscles, and their activity patterns were recorded synchronously with hyoid kinematics, respiratory airflow, and gular pressure. Movement of the highly mobile hyoid apparatus effects large-volume airflows in and out of the gular cavity. The sternohyoideus and branchiohyoideus depress, retract, and abduct the hyoid, thus expanding the gular cavity. The omohyoideus, constrictor colli, intermandibularis, and mandibulohyoideus elevate, protract, and adduct the hyoid, thus compressing the gular cavity. Closure of the choanae by the sublingual plicae precedes gular compression, allowing positive pressure to be generated in the gular cavity to force air into the lungs. The gular pump of monitor lizards is found to exhibit a neuromotor pattern similar to the buccal pump of extant amphibians, and both mechanisms involve homologous muscles. This suggests that the gular pump may have been retained from the ancestral buccal pump. This hypothesis remains to be tested by a broad comparative analysis of gular pumping among the amniotes

Porphyre et les universaux dans les Communia logice du ms. Paris, BnF, lat. 16617

Cet article offre la première édition du début des Communia logice (et grammatice), une substantielle compilation didascalique issue de la Faculté des arts de l’Université de Paris au milieu du xiiie siècle et contenue dans un manuscrit légué par maître Pierre de Limoges († 1306) à l’ancienne bibliothèque de la Sorbonne. Après une présentation générale (section I) et avant des précisions sur la Ratio edendi (section III), l’étude doctrinale (section II) qui précède cette édition (section IV) montre comment l’auteur-compilateur des Communia logice répond — en le reformulant — au célèbre questionnaire porphyrien relatif aux universaux.This article offers the first edition of the beginning of the Communia logice (et grammatice), a substantial didascalical compilation emanating from the Arts faculty of the University of Paris during the first half of the thirteenth century and preserved in a manuscript bequeathed by master Peter of Limoges († 1306) to the old library of the Sorbonne. After a general presentation (section I) and before some clarifications on the Ratio edendi (section III), the doctrinal study (section II) which precedes this edition (section IV) shows how the author-compiler of the Communia logice answers — while reformulating it — to the well known porphyrian set of questions about the universals

Coupled evolution of breathing and locomotion as a game of leapfrog

Journal ArticleBecause the increase in metabolic rate related to locomotor activity places demands on the cardiorespiratory apparatus, it is not surprising that the evolution of breathing and of locomotion are coupled. As the respiratory faculty becomes more refined, increasingly aerobic life strategies can be explored, and this activity is in turn expedited by a higher-performance respiratory apparatus