A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Adaptive sex ratio variation in pre-industrial human (Homo sapiens) populations?
Tekijät: Lummaa V, Merila J, Kause A
Kustantaja: ROYAL SOC
Julkaisuvuosi: 1998
Journal: Proceedings of the Royal Society B: Biological Sciences
Tietokannassa oleva lehden nimi: PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
Lehden akronyymi: P ROY SOC B-BIOL SCI
Vuosikerta: 265
Numero: 1396
Aloitussivu: 563
Lopetussivu: 568
Sivujen määrä: 6
ISSN: 0962-8452
DOI: https://doi.org/10.1098/rspb.1998.0331
Tiivistelmä
Sex allocation theory predicts that in a population with a biased operational sex ratio (OSR), parents will increase their fitness by adjusting the sex ratio of their progeny towards the rarer sex, until OSR has reached a level where the overproduction of either sex no longer increases a parent's probability of having grandchildren. Furthermore, in a monogamous mating system, a biased OSR is expected to lead to lowered mean fecundity among individuals of the more abundant sex. We studied the influence of OSR on the sex ratio of newborns and on the population birth rate using an extensive data set (n = 14 420 births) from preindustrial (1775-1850) Finland. The overall effect of current OSR on sex ratio at birth was significant, and in the majority of the 21 parishes included in this study, more sons were produced when males were rarer than females. This suggests that humans adjusted the sex ratio of their offspring in response to the local OSR to maximize the reproductive success of their progeny. Birth rate and, presumably, also population growth rate increased when the sex ratio (males:females) among reproductive age classes approached equality. However, the strength of these patterns varied across the parishes, suggesting that factors other than OSR (e.g. socioeconomic or environmental factors) may also have influenced the sex ratio at birth and the birth rate.
Sex allocation theory predicts that in a population with a biased operational sex ratio (OSR), parents will increase their fitness by adjusting the sex ratio of their progeny towards the rarer sex, until OSR has reached a level where the overproduction of either sex no longer increases a parent's probability of having grandchildren. Furthermore, in a monogamous mating system, a biased OSR is expected to lead to lowered mean fecundity among individuals of the more abundant sex. We studied the influence of OSR on the sex ratio of newborns and on the population birth rate using an extensive data set (n = 14 420 births) from preindustrial (1775-1850) Finland. The overall effect of current OSR on sex ratio at birth was significant, and in the majority of the 21 parishes included in this study, more sons were produced when males were rarer than females. This suggests that humans adjusted the sex ratio of their offspring in response to the local OSR to maximize the reproductive success of their progeny. Birth rate and, presumably, also population growth rate increased when the sex ratio (males:females) among reproductive age classes approached equality. However, the strength of these patterns varied across the parishes, suggesting that factors other than OSR (e.g. socioeconomic or environmental factors) may also have influenced the sex ratio at birth and the birth rate.
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