Comparative morphometrics of the primate apical tuft

Area of Science:

• Primate anatomy
• Paleoanthropology
• Functional morphology

Background:

• The structure-function relationship of primate apical tufts is not well understood.
• Apical tuft morphology is hypothesized to relate to locomotion, climate, and tool use.

Purpose of the Study:

• To investigate hypotheses concerning primate apical tuft size and morphology.
• To compare apical tuft size across primate groups and hominin fossil records.

Main Methods:

• Comparative analysis of apical tuft size (expansion and robusticity) in a large primate sample.
• Radiographic analysis of modern humans to correlate apical tuft width with digital pulp width.

Main Results:

• Locomotion and phylogeny influence nonhuman primate apical tuft size; suspensory primates and platyrrhines have smaller tufts than terrestrial quadrupeds and strepsirrhines.
• Cold-adapted humans have smaller apical tufts than warm-adapted humans, refuting the cold-adaptation hypothesis for Neanderthals.
• Neanderthal and early modern human apical tufts are compared, with Neanderthals showing larger, more robust tufts.
• A significant positive correlation exists between apical tuft width and digital pulp width in modern humans.

Conclusions:

• Apical tuft size is shaped by locomotor and phylogenetic factors in primates.
• Climate adaptation does not explain Neanderthal apical tuft size; instead, it may relate to digital pulp support.
• Apical tuft morphology has implications for understanding hominin evolution and tool-making capabilities.