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Selective breeding for high endurance running increases hindlimb symmetry
Theodore Garland1, Patricia W Freeman
1Department of Biology, University of California, Riverside 92521, USA. tgarland@ucr.edu
Evolution; International Journal of Organic Evolution
|December 7, 2005
Summary
Mice selectively bred for high running activity evolved larger femoral condyles and reduced hindlimb asymmetry, not classical cursoriality traits. These findings suggest limb symmetry and enlarged femoral condyles are key adaptations for sustained, high-speed locomotion.
Area of Science:
- Evolutionary biology
- Comparative biomechanics
- Animal locomotion
Background:
- Morphological adaptations for cursoriality (running ability) in mammals are well-documented, often indicated by long limbs and high limb bone ratios.
- Enlarged femoral condyles have been proposed as an adaptation for endurance running in humans (Homo).
- The impact of locomotor appendage asymmetry on performance lacks rigorous evolutionary study.
Purpose of the Study:
- To investigate morphological adaptations associated with high voluntary wheel running using experimental evolution in mice.
- To test whether classical indicators of cursoriality evolve with increased activity levels.
- To examine the role of limb symmetry in locomotor performance.
Main Methods:
- Selective breeding of mice for high voluntary wheel running activity over multiple generations.
- Comparative analysis of hindlimb bone morphology (femur, tibia, metatarsals) between high-running and control lines.
- Measurement of limb bone lengths, ratios, and directional asymmetry.
Main Results:
- High-running mice did not evolve classical cursoriality indicators like longer limb bones or higher metatarsal/femur ratios.
- Significant evolution of larger femoral condyles was observed in high-running mice.
- Reduced directional asymmetry of hindlimb bones was a key adaptation in high-running mice.
Conclusions:
- Sustained high-speed locomotion may favor adaptations like enlarged femoral condyles and reduced limb asymmetry over classical cursoriality traits.
- Limb symmetry appears crucial for efficient and high-performance locomotion.
- These findings provide an evolutionary context for understanding adaptations related to endurance running.
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