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Siberian live birth sex ratios and the SPrOO hypothesis
  1. P H Jongbloet
  1. Department of Epidemiology and Biostatistics, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, Netherlands;

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    Melnikov and Grech found a highly significant seasonal pattern of the sex ratio (SR) at birth in western Siberia, namely, a peak in the second and a trough in the fourth quarter of the year.1 This peak and trough are in line with the seasonal preovulatory overripeness ovopathy (SPrOO) hypothesis, which states (1) an approach to gender equity at the peak of the “ovulatory” seasons, (2) preferential fertilisation of non-optimally matured oocytes by Y-bearing sperm during the transitional stages between them, and (3) SR reversal because …

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