A new study, published in Proceedings of the Royal Society B, investigates how variation in both the external shape and internal structure - trabecular or cancellous tissues - of bone at the ankle (the distal tibia or shin bone) may reflect differences in locomotion among living primates.
Inside the ankle: bone structure reveals how primates move
Bone, as a living tissue, is able to adapt its structure to the locomotor-related stress or load a joint incurs during life, and thus has the potential to provide valuable insights into the varied types of locomotion in which primates engage. Pietrobelli and colleagues quantified trabecular bone and how its structure varied with the external shape of the distal tibia in humans, great apes, and monkeys. They found that humans and monkeys display trabecular patterns that reflect more predictable and limited ankle movements, consistent with bipedalism and quadrupedalism, respectively. In contrast, African and Asian apes show more variable bone patterns, reflecting more complex ankle movements related to the broader range of climbing behaviours used by these groups. The study further highlights for the first time that while the trabecular structure adapts to the way primates move and use their ankle joints, it also covaries with the external joint shape. This moves beyond an approach that dichotomizes internal vs. external structure deepening our understanding of the ankle form–function relationship. These findings provide an important comparative context for functionally interpreting fossils of extinct primates for which locomotor behaviour can only be inferred from skeletal remains.
FAQs:
Why is this study important to the general audience interested in science?
It shows that bone at the primate ankle (the distal tibia or shin bone), confirming that biological form is tightly coupled to mechanical function. It shows that internal bone structure does not merely reflect loading in isolation, but it covaries with the external geometry of the joint.
Which implications does it have?
This has two main implications: (1) it proves the ability to distinguish locomotor patterns (e.g., bipedalism vs. climbing) from skeletal remains is central to reconstructing how extinct hominins moved and behaved, providing the toolkit used to interpret fossil evidence; (2) it offers insights into how bone adapts to loading informing our understanding of joint load and adaptive responses to activity.
Contact:
Sandra Jacob
Press Officer
Max Planck Institute for Evolutionary Anthropology, Leipzig
+49 341 3550-122
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