No relationship between vertebral column shifts and limb 1 fluctuating asymmetry in human foetuses

11 Disturbance from the normal developmental trajectory of a trait during growth – the so-called 12 developmental instability – can be observed morphologically through phenodeviants and subtle 13 deviations from perfect symmetry (fluctuating asymmetry). This study investigates the relationship 14 between phenodeviance in the human vertebral column (as a result of axial patterning defects) and 15 limb fluctuating asymmetry. Since both types of markers of developmental instability have been 16 found associated with congenital abnormalities in humans, we anticipate a relationship between 17 them if the concept of developmental instability, measured through either phenodeviants or 18 asymmetry, would reflect an organism-wide process. Yet, we did not find any support for this 19 hypothesis. We argue that the vast differences in the developmental processes involved in both 20 systems renders these two markers of developmental instability unrelated, in spite of their 21 associations with other congenital abnormalities. Our results thus contribute to the growing 22 awareness that developmental instability is not an organism-wide property. 23