Bulge above the eye

Bulge above the eye in a young chimpanzee

Bulge above the eye in a gorilla

As a supraorbital torus ( torus supraorbitalis , sometimes incorrectly also: eyebrow bulge ) is a horizontal thickening of the frontal bone immediately above the eye sockets and the root of the nose , which is not interrupted above the root of the nose. This bone bulge is a noticeable feature on the skull of various prehistoric and prehistoric humans as well as some other primates such as chimpanzees and gorillas .

The function of the bulge above the eye has not been clarified with absolute certainty. Since there are no muscles attached to it, this bone thickening is usually interpreted as a stabilizing adaptation: If the skull is exposed to high chewing pressure and thus strong static loads due to a powerful chewing apparatus, a strong supraorbital torus counteracts a possible risk of breakage. It has also been suggested that the protruding bones may originally have been used as protection for the eyes.

This interpretation was contradicted in 2018, however, as a computer simulation based on the Kabwe 1 skull did not reveal any mechanical advantages. The anatomist Paul O'Higgins of the University of York's archeology department , co-author of the simulation, speculated that the bulge above the eye may be a social signal that indicates dominance. The loss of the bulge above the eye in anatomically modern humans ( Homo sapiens ), on the other hand, enabled more subtle social signals in the form of eyebrow movements.

In many people, the frontal bone also has a distinct bulge above each eye; However, these two eyebrow arches ( arcus superciliaris , also: eyebrow ridges) are separated above the root of the nose by the non-bulging and mostly hairless glabella .

In humans, eyebrow ridges mainly occur in men. The reason for this is the sex hormone testosterone , which u. a. during puberty ensures that the facial bones change and that the bone bulge can develop.

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  Bulge above the eye in Homo erectus

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  Fragment of a protruding bulge above the eye in the fossil Sangiran II

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  Bulge above the eye in Paranthropus boisei

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  Eyebrow arches , separated by the glabella , on a 19th century man

Individual evidence

1. ↑ Friedemann Schrenk : The early days of man. The way to Homo sapiens. CH Beck, 5th, completely revised and expanded edition, Munich 2008, p. 93 ( CH Beck Wissen ), ISBN 978-3-406-57703-1
2. ↑ Ordean J. Oyen et al. a .: Browridge structure and function in extant primates and Neanderthals. In: American Journal of Physical Anthropology. Volume 51, No. 1, 1979, pp. 83-95, doi: 10.1002 / ajpa.1330510111
3. ↑ Ordean J. Oyen: Masticatory function and histogenesis of the middle and upper face in chimpanzees (Pan troglodytes). In: Prog. Clin. Biol. Res. Vol. 101, 1982, 559-568, PMID 7156159
4. ^ Maria Doria Russell: The supraorbital torus: A most remarkable peculiarity. In: Current Anthropology . Volume 26, No. 3, 1985, pp. 337-360, doi: 10.1086 / 203279
5. ^ NC Tappen: Studies on the condition and structure of bone of the Saldanha fossil cranium. In: American Journal of Physical Anthropology. Volume 50, No. 4, 1979, pp. 591-603, doi: 10.1002 / ajpa.1330500410
6. ↑ Ricardo Miguel Godinho, Penny Spikins and Paul O'Higgins: Supraorbital morphology and social dynamics in human evolution. In: Nature Ecology & Evolution. Volume 2, 2018, pp. 956–961, doi: 10.1038 / s41559-018-0528-0
7. ↑ Humans may have a surprising evolutionary advantage: Expressive eyebrows. On: popsci.com from April 10, 2018
8. ↑ Surgical feminization of the face (FFS)