Neanderthal anatomy

Neanderthal anatomy differed from modern humans in that they had a more robust build and distinctive morphological features, especially on the cranium, which gradually accumulated more derived aspects, particularly in certain isolated geographic regions.

Reconstructed Neanderthal skeleton, American Museum of Natural History

Anatomical evidence suggests they were much stronger than modern humans[1] while they were slightly shorter than the average human, based on 45 long bones from at most 14 males and 7 females, height estimates using different methods yielded averages in the range of 164–168 cm (65–66 in) for males and 152 cm (60 in) for females.[2] Samples of 26 specimens in 2010 found an average weight of 78–83 kg (172–183 lb) for males and 63–66 kg (139–146 lb) for females.[3] A 2007 genetic study suggested some Neanderthals may have had red hair.[4][5]

Distinguishing physical traits
Comparison of faces of early European Homo sapiens (left) and Homo neanderthalensis (right) based on forensic facial reconstructions exhibited at the Neanderthal Museum.
Ashley Montagu claimed humans have more neotenized skulls than Neanderthals.[6]
Neanderthal cranial anatomy
Neanderthal footprint in the Natural History Museum in Prague

The magnitude of autapomorphic traits in specimens differ in time. In the latest specimens, autapomorphy is unclear.

The following is a list of physical traits that distinguish Neanderthals from modern humans. However, not all of them distinguish specific Neanderthal populations from various geographic areas, evolutionary periods, or other extinct humans. Also, many of these traits are present in modern humans to varying extent due to both archaic admixture and the retention of ancestral hominid traits shared with Neanderthals and other archaic humans. Nothing is certain (from unearthed bones) about the shape of soft parts such as eyes, ears, and lips of Neanderthals.[7]

While the structure of the head and face were not very far removed from those of modern humans, there were still quite noticeable differences. Notably the neanderthal head is much longer, with a more pronounced facial front. The Neanderthal chin and forehead sloped backwards and the nose region protruded forward more than in modern humans. The common shapes of the nose are not known but in general it was likely more robust, and possibly slightly larger, than in modern humans. The brain space of the skull, and so most likely the brain itself, were larger than in modern humans.

When comparing traits to worldwide average present day human traits in Neanderthal specimens, the following traits are distinguished. The magnitude on particular trait changes with 300,000 years timeline. The large number of classic Neanderthal traits is significant because some examples of paleolithic and even modern Homo sapiens may sometimes show one or even a few of these traits, but not most or all of them at the same time.

In October 2018, scientists announced the 3-D virtual reconstruction, for the first time, of a Neanderthal rib cage, which may help researchers better understand how this ancient human species moved and breathed.[8][9]

In February 2019, scientists reported evidence that Neanderthals walked upright much like modern humans.[10][11]

Cold-adapted theory

Some people thought that the large Neanderthal noses were an adaptation to the cold,[20] but primate and arctic animal studies have shown sinus size reduction in areas of extreme cold rather than enlargement in accordance with Allen's rule.[21] Todd C. Rae summarizes explanations about Neanderthal anatomy as trying to find explanations for the "paradox" that their traits are not cold-adapted.[21] Therefore, Rae concludes that the design of the large and extensive Neanderthal nose was evolved for the hotter climate of the Middle East and went unchanged when the Neanderthals entered Europe.[21] However Neanderthals in Spain date back to 700,000 years, prior to them living in the Middle East. Rae supposes that Neanderthals, due to increased physical activity and a large amount of muscle mass, would have needed increased oxygen uptake.

Levantine Neanderthals had phenotypes significantly more similar to modern humans than European Neanderthals (classic Neanderthals).[22][23] This may be because of gene flow from early modern humans in the Levantine corridor or the fact that the European Neanderthal phenotype is a specialized climatic adaptation.

Pathology

Within the west Asian and European record, there are five broad groups of pathology or injury noted in Neanderthal skeletons.

Fractures

Neanderthals seemed to suffer a high frequency of fractures, especially common on the ribs (Shanidar IV, La Chapelle-aux-Saints 1 'Old Man'), the femur (La Ferrassie 1), fibulae (La Ferrassie 2 and Tabun 1), spine (Kebara 2) and skull (Shanidar I, Krapina, Sala 1). These fractures are often healed and show little or no sign of infection, suggesting that injured individuals were cared for during times of incapacitation. It has been remarked that Neanderthals showed a frequency of such injuries comparable to that of modern rodeo professionals, showing frequent contact with large, combative mammals. The pattern of fractures, along with the absence of throwing weapons, suggests that they may have hunted by leaping onto their prey and stabbing or even wrestling it to the ground.[24]

Trauma

Particularly related to fractures are cases of trauma seen on many skeletons of Neanderthals. These usually take the form of stab wounds, as seen on Shanidar III, whose lung was probably punctured by a stab wound to the chest between the eighth and ninth ribs. This may have been an intentional attack or merely a hunting accident; either way the man survived for some weeks after his injury before being killed by a rock fall in the Shanidar cave. Other signs of trauma include blows to the head (Shanidar I and IV, Krapina), all of which seemed to have healed, although traces of the scalp wounds are visible on the surface of the skulls.

Degenerative disease

Arthritis was common in the older Neanderthal population, specifically targeting areas of articulation such as the ankle (Shanidar III), spine and hips (La Chapelle-aux-Saints 'Old Man'), arms (La Quina 5, Krapina, Feldhofer) knees, fingers and toes. This is closely related to degenerative joint disease, which can range from normal, use-related degeneration to painful, debilitating restriction of movement and deformity and is seen in varying degree in the Shanidar skeletons (I–IV).

Developmental stress
Neanderthal child

Two non-specific indicators of stress during development are found in teeth, which record stresses, such as periods of food scarcity or illness, that disrupt normal dental growth. One indicator is enamel hypoplasia, which appears as pits, grooves, or lines in the hard enamel covering of teeth. The other indicator, fluctuating asymmetry, manifests as random departures from symmetry in paired biological structures (such as right and left teeth). Teeth do not grow in size after they form nor do they produce new enamel, so enamel hypoplasia and fluctuating asymmetry provide a permanent record of developmental stresses occurring in infancy and childhood. A study of 669 Neanderthal crowns showed that 75% of individuals suffered some degree of hypoplasia. Two studies,[25][26] compared Neanderthals with the Tigara, coastal whale-hunting people from Point Hope Alaska, finding comparable levels of linear enamel hypoplasia (a specific form of hypoplasia) and higher levels of fluctuating asymmetry in Neanderthals. Estimated stress episode duration from Neanderthal linear enamel hyoplasias suggest that Neandertals experienced stresses lasting from two weeks to up to three months.

Infection

Evidence of infections on Neanderthal skeletons is usually visible in the form of lesions on the bone, which are created by systemic infection on areas closest to the bone. Shanidar I has evidence of the degenerative lesions as does La Ferrassie 1, whose lesions on both femora, tibiae and fibulae are indicative of a systemic infection or carcinoma (malignant tumour/cancer).

Childhood

Neanderthal children may have grown faster than modern human children. Modern humans have the slowest body growth of any mammal during childhood (the period between infancy and puberty) with lack of growth during this period being made up later in an adolescent growth spurt.[27][28][29] The possibility that Neanderthal childhood growth was different was first raised in 1928 by the excavators of the Mousterian rock-shelter of a Neanderthal juvenile.[30] Arthur Keith in 1931 wrote, "Apparently Neanderthal children assumed the appearances of maturity at an earlier age than modern children."[31] The rate of body maturation can be inferred by comparing the maturity of a juvenile's fossil remains and the estimated age of death.

Wezmeh Child maxillary right premolar tooth (P3 or possibly P4) of an individual between 6–10 years old from Wezmeh Cave

The age at which juveniles can be indirectly inferred from their tooth morphology, development and emergence. This has been argued to both support[32] and question[33][34] the existence of a maturation difference between Neanderthals and modern humans. Since 2007, tooth age can be directly calculated using the noninvasive imaging of growth patterns in tooth enamel by means of x-ray synchrotron microtomography.[35]

This research supports the occurrence of much more rapid physical development in Neanderthals than in modern human children.[36] The x-ray synchrotron microtomography study of early H. sapiens sapiens argues that this difference existed between the two species as far back as 160,000 years before present.[37]

More recent research, published in September 2017 and based on a more complete skeleton of a Neanderthal juvenile (7.7 years old) found in a 49,000-year-old site in Northern Spain, indicates that Neanderthal children actually grew at a similar rate to modern humans. Researchers were able to examine dental, cranial, and postcranial material, allowing the assessment of dental and skeletal maturation with age. In fact the main difference between Neandertals and modern humans was reported in the vertebral column. Several features also indicated ongoing brain growth. It was observed that the pattern of vertebral maturation and extended brain growth might reflect the broad Neanderthal body form and physiology, rather than a fundamental difference in the overall pace of growth in Neanderthals compared to modern humans.[38]

Footnotes
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  4. Laleuza-Fox, Carles; Holger Römpler; et al. (25 October 2007). "A Melanocortin 1 Receptor Allele Suggests Varying Pigmentation Among Neanderthals". Science. 318 (5855): 1453–5. Bibcode:2007Sci...318.1453L. doi:10.1126/science.1147417. PMID 17962522. S2CID 10087710.
  5. Rincon, Paul (25 October 2007). "Neanderthals 'were flame-haired'". BBC News. Retrieved 25 October 2007.
  6. Montagu, A. (1989). Growing Young. Bergin & Garvey: CT.
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  8. University of Washington (30 October 2018). "Study reconstructs Neandertal ribcage, offers new clues to ancient human anatomy". Phys.org. Retrieved 31 October 2018.
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