Extreme selection in humans against homeotic transformations of cervical vertebrae.
Evolution
; 60(12): 2643-54, 2006 Dec.
Article
em En
| MEDLINE
| ID: mdl-17263123
ABSTRACT
Why do all mammals, except for sloths and manatees, have exactly seven cervical vertebrae? In other vertebrates and other regions, the vertebral number varies considerably. We investigated whether natural selection constrains the number of cervical vertebrae in humans. To this end, we determined the incidence of cervical ribs and other homeotic vertebral changes in radiographs of deceased human fetuses and infants, and analyzed several existing datasets on the incidence in infants and adults. Our data show that homeotic transformations that change the number of cervical vertebrae are extremely common in humans, but are strongly selected against almost all individuals die before reproduction. Selection is most probably indirect, caused by a strong coupling of such changes with major congenital abnormalities. Changes in the number of thoracic vertebrae appear to be subject to weaker selection, in good correspondence with the weaker evolutionary constraint on these numbers. Our analysis highlights the role of prenatal selection in the conservation of our common body plan.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Seleção Genética
/
Vértebras Torácicas
/
Vértebras Cervicais
Tipo de estudo:
Diagnostic_studies
/
Prevalence_studies
/
Risk_factors_studies
Limite:
Adult
/
Female
/
Humans
/
Infant
/
Male
Idioma:
En
Ano de publicação:
2006
Tipo de documento:
Article