Mobility as an emergent property of biological organization: Insights from experimental evolution

Abstract

Anthropologists accept that mobility is a critical dimension of human culture, one that links economy, technology, and social relations. Less often acknowledged is that mobility depends on complex and dynamic interactions between multiple levels of our biological organization, including anatomy, physiology, neurobiology, and genetics. Here, we describe a novel experimental approach to examining the biological foundations of mobility, using mice from a long-term artificial selection experiment for high levels of voluntary exercise on wheels. In this experiment, mice from selectively bred lines have evolved to run roughly three times as far per day as those from nonselected control lines. We consider three insights gleaned from this experiment as foundational principles for the study of mobility from the perspective of biological evolution. First, an evolutionary change in mobility will necessarily be associated with alterations in biological traits both directly and indirectly connected to mobility. Second, changing mobility will result in trade-offs and constraints among some of the affected traits. Third, multiple solutions exist to altering mobility, so that various combinations of adjustments to traits linked with mobility can achieve the same overall behavioral outcome. We suggest that anthropological knowledge of variation in human mobility might be improved by greater research attention to its biological dimensions.

Maternal exposure to Western diet affects adult body composition and voluntary wheel running in a genotype-specific manner in mice

“…Interestingly, we found that individuals with the mini-muscle phenotype (found only in two of the HR lines in the present sample of mice) had statistically higher VO 2 max. Previous studies have generally not found this to be the case [40,50], although mini-muscle individuals did have higher VO 2 max when tested in hypoxia [34] and in a comparison of only one control and two HR lines [51]. …”

“…All 10 focal males in line 3 (4 SD and 6 WD) and 3 of the 15 focal males in line 6 (1 SD and 2 WD) were mini- muscle individuals. Among several other phenotypic effects observed in adult mice, mini-muscle individuals were reported previously to have enlarged internal organs [e.g., 33,50,51] and an elevated cost of transport during voluntary wheel running [52]. …”

Circulating levels of endocannabinoids respond acutely to voluntary exercise, are altered in mice selectively bred for high voluntary wheel running, and differ between the sexes

“…An ongoing artificial selection experiment (currently in generation 81) has produced four replicate high-runner (HR) lines while also maintaining four non-selected control (C) lines (Swallow et al 1998; Wallace and Garland, Jr. 2016; Garland, Jr. et al 2017). In the routine breeding protocol, mice are allowed access to wheels for six days as young adults, and mice in the HR lines are selected to breed based on the average number of wheel revolutions on days five and six.…”

What moves us? How mobility and movement are at the center of human evolution

“…For example, the Western diet, with an emphasis on high‐fat foods, reduces SPA in most rodent models . However, in a group of rodents bred to run long distances voluntarily (high‐runner or HR mice; see Wallace and Garland) a high‐fat diet actually leads to increased voluntary locomotion . These HR mice have often been described as a model for the evolution of high levels of physical activity in humans .…”