Human bipedal instability in tree canopy environments is reduced by "light touch" fingertip support

Johannsen, L.; Coward, S. R.L.; Martin, G. R.; Wing, A. M.; Casteren, A. Van; Sellers, W. I.; Ennos, A. R.; Crompton, R. H.; Thorpe, S. K.S.

Abstract

© 2017 The Author(s). Whether tree canopy habitats played a sustained role in the ecology of ancestral bipedal hominins is unresolved. Some argue that arboreal bipedalism was prohibitively risky for hominins whose increasingly modern anatomy prevented them from gripping branches with their feet. Balancing on two legs is indeed challenging for humans under optimal conditions let alone in forest canopy, which is physically and visually highly dynamic. Here we quantify the impact of forest canopy characteristics on postural stability in humans. Viewing a movie of swaying branches while standing on a branch-like bouncy springboard destabilised the participants as much as wearing a blindfold. However "light touch", a sensorimotor strategy based on light fingertip support, significantly enhanced their balance and lowered their thigh muscle activity by up to 30%. This demonstrates how a light touch strategy could have been central to our ancestor's ability to avoid falls and reduce the mechanical and metabolic cost of arboreal feeding and movement. Our results may also indicate that some adaptations in the hand that facilitated continued access to forest canopy may have complemented, rather than opposed, adaptations that facilitated precise manipulation and tool use.

Citation

Johannsen, L., Coward, S. R., Martin, G. R., Wing, A. M., Casteren, A. V., Sellers, W. I., …Thorpe, S. K. (2017). Human bipedal instability in tree canopy environments is reduced by "light touch" fingertip support. Scientific reports, 7(1), Article 1135. https://doi.org/10.1038/s41598-017-01265-7

• Journal Article Type: Article
• Acceptance Date: Mar 20, 2017
• Online Publication Date: Apr 25, 2017
• Publication Date: Dec 1, 2017
• Deposit Date: Feb 22, 2019
• Publicly Available Date: Feb 22, 2019
• Journal: Scientific Reports
• Print ISSN: 2045-2322
• Electronic ISSN: 2045-2322
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 1
• Article Number: 1135
• DOI: https://doi.org/10.1038/s41598-017-01265-7
• Keywords: Biological anthropology; Evolutionary ecology; Experimental evolution; Human behaviour
• Public URL: https://hull-repository.worktribe.com/output/532975
• Publisher URL: https://www.nature.com/articles/s41598-017-01265-7