Limb preferences in non-human vertebrates: A new decade

Area of Science:

• Comparative Psychology
• Ethology
• Neuroscience
• Evolutionary Biology

Background:

• Population-level limb preferences (asymmetries) are not unique to humans and exist in various non-human animal species.
• Previous analyses over a decade ago were limited by scarce data, hindering evolutionary reconstruction of human handedness.
• Significant advancements in research, including more studies, larger sample sizes, and meta-analyses, have since filled these data voids.

Purpose of the Study:

• To update the analysis of limb preferences across all non-extinct vertebrate orders.
• To systematically assess and compare limb preferences using cladographic methods.
• To evaluate the current state of empirical evidence regarding vertebrate limb asymmetries.

Main Methods:

• Systematic review and cladographic comparison of existing literature on limb preferences in non-human vertebrates.
• Analysis of data from studies covering 172 different species.
• Categorization of species based on evidence for population-level, individual-level, or no limb asymmetries.

Main Results:

• Empirical evidence for limb preference in non-human vertebrates has strengthened due to increased research and meta-analyses.
• Of the 172 species analyzed, 39.53% showed population-level asymmetries, 32.56% showed individual-level asymmetries, and 27.91% showed no asymmetry.
• The findings indicate that asymmetries are a widespread characteristic of vertebrate motor organization.

Conclusions:

• Limb asymmetries are a prevalent feature across diverse vertebrate species, supporting their widespread role in motor organization.
• The updated data strengthen the understanding of the evolutionary basis of lateralization.
• Future research should focus on addressing identified gaps to further elucidate the evolutionary trajectory of limb preferences.