Birth order and hand preference in chimpanzees (Pan troglodytes): Implications for pathological models of handedness in humans.

Abstract

The effect of birth order on hand preference was assessed in a sample of 154 captive-born chimpanzees. Subjects were classified as first, middle, or latter born using 2 classification criteria based on their birth order. Hand preference was measured using a task that elicited coordinated bimanual actions. Significant birth-order effects were found for both classification criteria, with firstand latter-born subjects exhibiting a lesser degree of right-handedness compared with middle-born subjects. These data suggest that biological rather than sociological factors play a greater role in explaining the observed birth-order effects on hand preference in humans.Approximately 85% to 90% of humans report themselves as being right-handed (Annett, 1985;Porac & Coren, 1981). Explaining the pervasive degree of right-handedness in the human species has fostered considerable theoretical debate and empirical investigation. Genetic, biological, and environmental models have been proposed to explain this population-level right-handedness, each with varying amounts of empirical support (Annett, 1999;Collins, 1985;Corballis, 1997;Laland, Kumm, Van Horn, & Feldman, 1995;Previc, 1991;Provins, 1997;Trevarthen, 1996). Equally important are theoretical models proposed to explain the occurrences of left-handedness or non-right-handedness in human populations. That genetic factors may play a role is supported by the observation that approximately 70% of individuals born to two left-handed parents are right-handed, which is significantly lower than the proportion of fight-handed individuals born to two right-handed parents (McGee & Cozad, 1980;McManus & Bryden, 1992). Genetic explanations account for only part of the variance, however, leaving error or other factors to explain the remaining variability. Rather than emphasize genetic factors, others have suggested that both pre-and postnatal environmental factors play a role in determining non-right-handedness. Such factors include but are not limited to birth season, birth order, maternal age, and prenatal hormones. In these models, righthandedness is perceived as being the normative path of development, and therefore non-righthandedness reflects a deviation from normal development that is due to pathological factors (see Satz, Soper, & Orsini, 1988). Of specific interest to this study are the reports focusing on the effect of birth order on hand preference in humans.Bakan and colleagues (Bakan, 1971;Bakan, Dibb, & Reed, 1973) first reported and theorized about the relationship between birth order and hand preference in humans. Bakan (1971) reported that there was a higher percentage of left-handedness in first-and latter-born offspring (defined as more than 4 birth orders) and postulated that the effects were due to birth trauma experienced by offspring born to primiparous or older women. Bakan (1971) proposed that birth trauma is more likely in women who are giving birth for the first time or for older women who present a higher risk group for prenatal insult. Researchers who ...

Parental and perinatal factors influencing the development of handedness in captive chimpanzees

“…With respect to birth order, the evidence of increased left-handedness among 1st and latter-born chimpanzees revealed in this study (which included more than 300 chimpanzees from two additional facilities) is consistent with previous results based on the YERKES chimpanzees alone (see Hopkins & Dahl, 2000). This suggests that the earlier observations are not restricted to the YERKES colony and generalize to at least two other colonies of apes.…”

“…Specifically, in previous research, we have found that there is a higher proportion of left-handedness among 1st and latter-born (parities >6) chimpanzees (Hopkins & Dahl, 2000). Moreover, we have previously found that concordance rates among maternal half-siblings are significantly higher when adjusted for the parity of the offspring.…”

Where Evolutionary Psychology Meets Cognitive Neuroscience: A Précis to Evolutionary Cognitive Neuroscience

“…Hopkins also attempts to demonstrate a genetic expression of handedness in chimpanzees, but discovers that there is not a significant relationship between handedness in the offspring and maternal or paternal handedness. A study of handedness and birth order indicated that in middle-born offspring there is significant heritability of handedness (Hopkins and Dahl, 2000: Hopkins, Dahl and Pilcher, 2000). The significance of these findings for cognitive evolution is yet unknown, but under close scientific scrutiny.…”

Διερεύνηση Του Ρόλου Της Κινητικής Ασυμμετρίας Στην Οστεοπόρωση Γυναικών Τρίτης Ηλικίας Με Τη Μέθοδο Της Απορροφησιομέτρησης Με Ακτίνες Χ Διπλής Ενέργειας (DXA)

“…The genetic factors may play a role and this is supported by the observation that approximately 70% of individuals born to two left-handed parents are right-handed, which is significantly lower than the proportion of right-handed individuals born to two right-handed parents (McGee & Cozad, 1980;McManus & Bryden, 1992). Genetic explanations account for only part of the variances, however, leaving error or other factors to explain the remaining variability (Hopkins & Dahl, 2000). Most researchers agree that hand preference has a hereditary component, but not all agree as to the genetic mechanisms involved (reviewed in Levy, 1977).…”