High
incidence of congenital clefts of the arch of the atlas observed among remains
from Spanish site
The Atlas (C1) vertebra is the
first cervical vertebra of the spine, immediately below the skull. It takes its
name from the Greek Titan Atlas, who is popularly (but incorrectly) supposed to
have held the world on his shoulders. Congenital defects of the anterior or
posterior arches are rare in modern populations, occurring at frequencies of 0.087
to 0.1 percent and 0.73 to 3.84 percent respectively. The condition does not
normally lead to clinical symptoms.
El Sidrón is a cave site in
Asturias, northern Spain that has yielded extensive Neanderthal remains and
stone tools since these were first discovered there in 1994. Over 2,400 human
fossils have been recovered, representing at least thirteen individuals including
seven adults, three adolescents, two juveniles and one infant. The remains are
49,000 years old. Ancient DNA has previously been obtained from the remains,
indicating a small patrilocal (mature males remain within their family birth
group, but females come from outside) group with low genetic diversity. Dental
hypoplasias indicate that around half of the group members had experienced
episodes of growth arrest due to malnutrition.
Researchers now report that two out
of just three well-preserved atlases from the site present respectively a
defect of the posterior arch and the anterior arch. Such a high incidence of a
rare condition could be interpreted as further evidence of low genetic
diversity of the group, and as a possible indicator of inbreeding. The picture
that emerges from El Sidrón is of a small, barely-viable Neanderthal group
struggling for survival in extremely harsh conditions.
References:Ríos, L. et al., Possible Further Evidence of Low Genetic Diversity in the El Sidrón (Asturias, Spain) Neandertal Group: Congenital Clefts of the Atlas. PLoS One 10 (9), e0136550. (2015).
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