title: When right differs from left: human limb directional asymmetry emerges during very early development.
abstract: The often observed directional asymmetry (DA) in human limb bones may have a genetic/developmental basis and/or could emerge from different mechanical loadings across sides due to handedness. Because behavioural lateralization in itself has a genetic basis, it has been suggested that DA in limbs could develop prenatally as a pre-adaptation to adult life. However, the presence of consistent differences in the size of left and right limb bones in early development is understudied. We study asymmetry in limb bones during early development (10-20 weeks of gestation) in a sample of 178 aborted foetuses. Statistically significant DA was found in several upper and lower limb bones, where the right-hand side was consistently larger than the left. We argue that this pattern is probably the consequence of developmental processes related to internal asymmetric positioning of organs.
authors.affiliation: a Department of Biology, Evolutionary Ecology Group , University of Antwerp , Antwerp , Belgium.
authors.forename: Stefan
authors.initials: S
authors.lastname: Van Dongen
authors.forename: Frietson
authors.initials: F
authors.lastname: Galis
authors.forename: Clara
authors.initials: C
authors.lastname: Ten Broek
authors.forename: Kristiina
authors.initials: K
authors.lastname: Heikinheimo
authors.forename: Liliane C D
authors.initials: LC
authors.lastname: Wijnaendts
authors.forename: Sofie
authors.initials: S
authors.lastname: Delen
authors.forename: Jessica
authors.initials: J
authors.lastname: Bots
mesh_terms: D037881:Aborted Fetus; D001842:Bone and Bones / Q000033:anatomy & histology / Q000196:embryology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D035002:Lower Extremity / Q000033:anatomy & histology / Q000196:embryology*; D008297:Male; D015203:Reproducibility of Results; D034941:Upper Extremity / Q000033:anatomy & histology / Q000196:embryology*
keywords: Directional asymmetry; Fluctuating asymmetry; Foetus; Handedness; Human