Biomedical subjects

Karin Isler

Publications and source records attributed to Karin Isler.

8 recordsLinked to original sources

PubMed2006

Metabolic costs of brain size evolution.

In the ongoing discussion about brain evolution in vertebrates, the main interest has shifted from theories focusing on energy balance to theories proposing social or ecological benefits of enhanced intellect. With the availability of a wealth of new data on basal metabolic rate (BMR) and brain size and with the aid of reliable techniques of comparative analysis, we are able to show that in fact energetics is an issue in the maintenance of a relatively large brain, and that brain size is positively correlated with the BMR in mammals, controlling for body size effects. We conclude that attempts to explain brain size variation in different taxa must consider the ability to sustain the energy costs alongside cognitive benefits.

Animals↗

PubMed2006

On being small: brain allometry in ants.

Comparative neurobiologists have provided ample evidence that in vertebrates small animals have proportionally larger brains: in a double-logarithmic plot of brain weight versus body weight all data points conform quite closely to a straight line with a slope of less than one. Hence vertebrate brains scale allometrically, rather than isometrically, with body size. Here we extend the phylogenetic scope of such studies and the size range of the brains under investigation to the insects, especially ants. We show that the principle of (negative) allometry applies as well, but that ants have considerably smaller brains than any ant-sized vertebrate would have, and that this result holds even if the relatively higher exoskeleton weights of ants (as compared to endoskeleton weights of mammals) are taken into account. Finally, interspecific comparisons within one genus of ants, Cataglyphis, show that species exhibiting small colony sizes (of a few hundred individuals) have significantly smaller brains than species in which colonies are composed of several thousand individuals.

Animals↗

PubMed2006

Costs of encephalization: the energy trade-off hypothesis tested on birds.

Costs and benefits of encephalization are a major topic of debate in the study of primate and human evolution. Comparative studies provide an opportunity to test the validity of a hypothesis as a general principle, rather than it being a special case in primate or hominid evolution. If a population evolves a larger brain, the metabolic costs of doing so must be paid for by either an increased energy turnover (direct metabolic constraint) or by a trade-off with other energetically expensive costs of body maintenance, locomotion, or reproduction, here referred to as the energy trade-off hypothesis, an extension of the influential Expensive Tissue Hypothesis of Aiello and Wheeler (1995, Curr. Anthropol. 36, 199-221). In the present paper, we tested these hypotheses on birds using raw species values, family means, and independent contrasts analysis to account for phylogenetic influences. First, we tested whether basal metabolic rates are correlated with brain mass or any other variable of interest. This not being the case, we examined various trade-offs between brain mass and the mass of other expensive tissues such as gut mass, which is approximated by gut length or diet quality. Only weak support was found for this original Expensive Tissue Hypothesis in birds. However, other energy allocations such as locomotor mode and reproductive strategy may also be reduced to shunt energy to an enlarged brain. We found a significantly negative correlation between brain mass and pectoral muscle mass, which averages 18% of body mass in birds and is indicative of their relative costs of flight. Reproductive costs, on the other hand, are positively correlated with brain mass in birds. An increase in brain mass may allow birds to devote more energy to reproduction, although not through an increase in their own energy budget as in mammals, but through direct provisioning of their offspring. The trade-off between locomotor costs and brain mass in birds lets us conclude that an analogous effect could have played a role in the evolution of a larger brain in human evolution.

Animals↗

PubMed2006

Inertial properties of hominoid limb segments.

Quantitative, accurate data regarding the inertial properties of body segments are of paramount importance when developing musculo-skeletal locomotor models of living animals and, by inference, their ancestors. The limited number of available primate cadavers, and the destructive nature of the post-mortem, result in such data being very rare for primates. This study builds on the work of Crompton et al. (Am. J. Phys. Anthropol. 1996, 99, 547-570) and reports inertial properties of the body segments of gorillas, chimpanzees, orangutans and gibbons. Segment mass, centre of mass and the radius of gyration of five ape cadavers were measured using a complex-pendulum technique and compared with the results derived from external measurements of segment lengths and diameters on the same animals. With additional data from external measurements of eight more hominoid cadavers, and published data, intergeneric differences between the inertial properties and the distribution of mass between limb segments are analysed and related to the locomotor habits of the species. We found that segment inertial properties show extensive overlap between ape genera as a result of large interindividual variation. Segment mass distribution also overlaps between apes and humans, with the exception of the shank segment. However, owing to a different distribution of mass between the limb segments, the centre of mass of both the arms and the legs is located more distally in apes than in humans, and the natural pendular period of ape forelimbs is larger than that of the hindlimbs. This suggests that, in contrast to the limbs of cursorial mammals and cercopithecoid primates, hominoid limbs are not optimized for efficiency in quadrupedal walking, but rather reflect a compromise between various locomotor modes. Common chimpanzees may have secondarily evolved a more efficient quadrupedal gait.

Animals↗

PubMed2006

Arboreal locomotion in wild black-and-white snub-nosed monkeys (Rhinopithecus bieti).

This paper presents spatiotemporal gait parameters of arboreal locomotion in the colobine Rhinopithecus bieti in its natural habitat. While adult females used exclusively either extended-elbow vertical climbing or pulse climbing, the much larger adult males preferred the less demanding flexed-elbow vertical climbing on thin trees or on trunks with handholds. If sex-specific differences are taken into consideration, the differences between flexed-elbow and extended-elbow vertical climbing in Rhinopithecus parallel those observed in Ateles. During flexed-elbow vertical climbing, the gait parameters of R. bieti are very similar to those of spider monkeys (Ateles fusciceps) or bonobos (Pan paniscus). Maximum limb joint excursions also lie in the range of hominoids and atelines and are clearly larger than in Macaca fuscata. It seems likely that climbing kinematics may differ more between Rhinopithecus and macaques than between Rhinopithecus and hominoids or atelines.

Aging↗

PubMed2005

3D-kinematics of vertical climbing in hominoids.

Vertical climbing has played an important role in theories about the evolution of habitual bipedalism in early hominids and of locomotor specialization in hominoids. However, empirical data on vertical climbing in nonhuman primates are scarce, especially regarding kinematics. In this paper, the kinematics of flexed-elbow vertical climbing of four hominoid species are reported: western lowland gorillas (Gorilla gorilla gorilla), bonobos (Pan paniscus), Sumatran orangutans (Pongo pygmaeus abelii), and yellow-cheeked crested gibbons (Hylobates concolor gabriellae). The climbing sequences were recorded simultaneously by four digital video cameras in European zoos. Analyzed parameters include intersegmental flexion/extension angles of the shoulder, elbow, hip, and knee joints, horizontal abduction/adduction angles of the upper arm and thigh, and distance of the body center of gravity from the substrate. Analyses reveal that differences in climbing kinematics between individuals of different age/sex classes of one species are mostly size-related, whereas interspecific differences reflect specific locomotor adaptations. The climbing kinematics of bonobos and gorillas are more similar to each other than to those of orangutans or gibbons. The range of motion of the major limb joints in adult orangutans is larger than in African apes, although the hip is not more extended. Gibbons horizontally abduct the arm more and the thigh less during climbing than any of the great apes. These results allow us to question some qualitative descriptions of vertical climbing kinematics reported in the literature, and to discuss implications for the evolution of locomotor adaptations in hominoids.

Age Factors↗

PubMed2003

Gait parameters in vertical climbing of captive, rehabilitant and wild Sumatran orang-utans (Pongo pygmaeus abelii).

Vertical climbing is central to the locomotor and foraging strategies of the great apes and, indeed, to theories about the evolution of locomotor specialisations of hominoid primates. Nevertheless, its kinematics have yet to be fully evaluated. Here, we present spatio-temporal parameters of 80 climbing sequences containing 560 limb cycles obtained from video recordings of captive, rehabilitant and wild Sumatran orang-utans (Pongo pygmaeus abelii). Gait parameters such as cycle duration, duty factor, laterality of footfalls, relative stride length and normalised speed were analysed to identify the influence of body size (through an intraspecific comparison of age/sex classes), the influence of the environment (through an intraspecific comparison of animals living in different habitats) and the influence of morphology (through an interspecific comparison with the climbing characteristics of other primates) on climbing ability in orang-utans. Results show that there are only few differences between the climbing of wild, rehabilitant and captive individuals. Cycle duration is longer and speed is lower for the wild individuals than for other groups due to the complexity of their environment and lack of familiarity with each substrate, which results in a more cautious gait. Sex/age-related differences in climbing were found to be small, although juveniles generally exhibited a shorter cycle duration and lower duty factor than other groups. The spatio-temporal gait parameters of adult females carrying infants were not found to differ significantly from those for females without an infant, which suggests that climbing kinematics are not affected by the presence of a clinging infant. Extended-elbow vertical climbing is primarily characterised by a higher duty factor than flexed-elbow climbing, indicating that the former is an energetically more demanding form of locomotion. In comparison with other primates, orang-utans exhibit a longer cycle duration, longer strides but lower climbing speed, reflecting a compromise between the demands of a large body mass and extreme joint mobility.

Age Factors↗

PubMedDate not supplied

Footfall patterns, stride length and speed of vertical climbing in spider monkeys (Ateles fusciceps robustus) and woolly monkeys (Lagothrix lagotricha).

Vertical climbing is central to theories surrounding the locomotor specialisations of large primates. In this paper, we present spatiotemporal gait parameters obtained from video recordings of captive spider monkeys (Ateles fusciceps robustus) and woolly monkeys (Lagothrix lagotricha) in semi-natural enclosures, with the aim of discovering the influence of body weight and differences in general locomotor behaviour on vertical climbing kinematics on various substrates. Results show that there are only few differences between gait parameters of climbing on thin trees, vertical and oblique ropes, while climbing on large-diameter trees differs considerably, reflecting the higher costs of locomotion on the latter. At the same speed, Ateles takes longer strides and the support phase takes a smaller percentage of cycle duration than in Lagothrix. Footfall patterns are more diverse in Ateles and include a higher proportion of ipsilateral limb coupling. Compared to other primates, the gait characteristics of vertical climbing of atelines most closely resemble those of African apes.

Analysis of Variance↗