Meningeal arterial patterns in great apes: implications for hominid vascular evolution

Area of Science:

• Paleoneurology
• Comparative anatomy
• Evolutionary biology

Background:

• Meningeal arterial patterns in the braincase vary significantly across primate species.
• Previous studies, often using Adachi's system, overlooked orbital contributions in apes.
• Understanding these patterns is crucial for tracing human vascular evolution.

Purpose of the Study:

• To analyze and categorize arterial meningeal patterns in great apes (orangutans, chimpanzees, gorillas).
• To compare these patterns with those found in monkeys and humans.
• To propose a hypothesis for the evolution of middle cranial fossa blood supply in Homo.

Main Methods:

• Examination of 100 great ape endocasts from four species: Pongo pygmaeus, Pan paniscus, Pan troglodytes, and Gorilla gorilla.
• Identification of eight distinct meningeal arterial patterns based on the sources and contributions of arteries to the braincase.
• Statistical analysis of the frequency of these patterns across genera and correlation with cranial capacity.

Main Results:

• Eight distinct arterial meningeal patterns were identified in great apes.
• Orangutans showed high reliance on orbital arteries, while chimpanzees favored the middle meningeal artery.
• A trend for increased cranial capacity correlating with internal carotid artery reliance was observed in African apes, but not statistically significant.

Conclusions:

• The study highlights significant differences in meningeal arterial patterns among great ape genera.
• Comparative data suggest a shift towards middle meningeal artery dominance in human cranial blood supply.
• Adachi's system is inadequate for nonhuman primates; a revised approach incorporating orbital contributions is needed for evolutionary studies.