Birth order and fluctuating asymmetry: a first look

Lalumière, Martin L.; Harris, Grant T.; Rice, Marnie E.

doi:10.1098/rspb.1999.0930

Cited by 29 publications

(20 citation statements)

References 28 publications

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“…Fourth, fraternal birth order was not associated with FA in our study as previously reported (Lalumiere et al, 1999). The association between birth order and FA has been considered to result from maternal immunoreactivity to male-specific features of the fetus (Lalumiere et al, 1999).…”

Section: Discussioncontrasting

confidence: 41%

“…The association between birth order and FA has been considered to result from maternal immunoreactivity to male-specific features of the fetus (Lalumiere et al, 1999). Maternal immunoreactivity, in turn, would have more deleterious effects on the males because male fetuses ''are more antigenic'' to the mother than female fetuses (Gualtieri and Hicks, 1985).…”

Section: Discussionmentioning

confidence: 99%

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Season of birth and fluctuating asymmetry

Benderlioglu

Nelson

2004

American J Hum Biol

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Fluctuating asymmetry (FA) refers to random, small deviations from perfect bilateral symmetry in morphological traits. These minor deviations from the ideal phenotype reflect environmental and genetic perturbations experienced during ontogeny. FA has been associated with negative health outcomes and many developmental disorders in humans. The prevalence of developmental disorders and adult health vary according to the month of birth, suggesting that seasonal stressors may leave enduring signs in the adult body, marked by high FA. The current study examined the relationship between FA and birth season. Data were collected for 205 males and females (average age = 20.39 years) on FA of 10 bilateral traits (second, third, fourth, and fifth digit length, palm height, wrist diameter, elbow width, ear height, foot breadth, and ankle circumference). Additional relationships were also investigated among FA, testosterone (T), and birth order. Results indicate that ear FA was lower for fall births compared to winter births in males. In females, palm FA was lower for fall births compared to those of the spring. FA of the digits was positively associated with T in males. Average FA, excluding the digits, decreased as the number of maternal siblings increased for both sexes. T concentrations in males were positively associated with the number of younger brothers. Our results generally confirm previous research on seasonal variation in adult longevity and neurological and psychiatric disorders, suggesting that winter and spring births are at risk for asymmetric developmental trajectory.

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Section: Discussioncontrasting

confidence: 41%

Section: Discussionmentioning

confidence: 99%

Season of birth and fluctuating asymmetry

Benderlioglu

Nelson

2004

American J Hum Biol

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“…In the present study, none of the studied factors exhibited an association with the extent of FA (except for signed right-to-left scores of centroid size in non-fused greater horns which is likely due to sampling bias). This applies in particular to an individual's sex, which suggests that both sexes are susceptible to the same extent and that the hyoid bone may be resistant to the so-called "male-specific maternal immunoreactivity", which assumes that a mother's immune response to a male foetus increases developmental instability (Lalumière et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

The Asymmetry and Modularity of the Hyoid Bone

et al. 2014

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SUMMARY:Morphological variation is a result of interplay among multiple intervening factors. For hyoid bones, the shape and size differences have been scarcely covered in the literature and in majority limited to studies of sexual dimorphism or age dependency. To our knowledge, the human hyoid bone, in complete opposite to other cranial bones, has not been fully utilized to address development questions in terms of asymmetry or modularity. In the present paper, we used landmark-based methods of geometric morphometrics and multivariate statistical approach to study human hyoid morphology represented by the hyoid body and greater horns in a sample of 211 fused and non-fused bones. Within a sample variation analysis, we showed that the hyoid bone is, by nature, asymmetrical bone which exhibits both directional and fluctuating types of asymmetry and is composed of well-integrated anatomical elements for which the biomechanical load of attached muscles is the most determining factor of variation. Yet, the covariance and evidence of unequal amount of fluctuating asymmetry among modules suggests a certain degree of independence during early stages of development.

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“…Among humans, increased FA has been linked to several specific stresses, such as maternal obesity, maternal nicotine, and alcohol use (Kieser, 1992;Kieser, Groeneveld, & Da Silva, 1997), severe malnutrition during prenatal development (Kieser & Groeneveld, 1988), and exposure to a maternal immune response evoked by multiple exposures to male fetuses (Lalumière, Grant, & Rice, 1999). One outcome in animals exposed to prenatal stress is a modification of sexual behavior with sex-atypical behaviors becoming more common (Ward, 1972).…”

Section: Introductionmentioning

confidence: 99%

Sexual Orientation and Fluctuating Asymmetry in Men and Women

Hall

Schaeff

2007

Arch Sex Behav

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Previous research suggests that individuals' sexual orientation may be affected by developmental instability (DI) induced by exposure to prenatal stresses. We tested this relationship using fluctuating asymmetry (FA), the small random deviations from symmetry that arise in otherwise bilaterally symmetrical traits as a consequence of developmental noise and developmental instability. Differences among individuals reflect variation in their exposure to and ability to accommodate for stresses experienced during development as well as to developmental noise that arises due to cellular stocasticity. FA measurements for 156 heterosexual and 132 homosexual men and women participants provided strong support for the developmental instability hypothesis: FA was significantly higher in both male and female homosexuals (men: four of seven bilateral traits and composite FA values (cFA); women: five of seven bilateral traits and composite FA values). Although finger-length ratios (FLRs), an indirect marker for prenatal hormones, were sex-atypical (e.g., feminized) for homosexual men, we failed to detect any relationship between FA levels and 2D:4D finger-length ratios (FLRs). Hence, although elevated levels of developmental stress appear to be linked to shifts in sexual orientation, the underlying mechanism does not seem to be connected to sex-atypical prenatal hormones. Additional analyses with sex atypical individuals are needed to confirm this.

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Birth order and fluctuating asymmetry: a first look

Cited by 29 publications

References 28 publications

Season of birth and fluctuating asymmetry

Season of birth and fluctuating asymmetry

The Asymmetry and Modularity of the Hyoid Bone

Sexual Orientation and Fluctuating Asymmetry in Men and Women

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