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Abstract:
I have previously suggested that the sex ratios of multiple births registered in Japan are biased. Data published by Imaizumi[1982a, b] are consistent with the suggestion that this alleged bias diminished during the two decades preceding 1974. If true, this would provide additional evidence for my claim that the sex ratio of monozygotic twins is low.
Insights
The sex ratio in Japanese multiple births may be biased, with evidence suggesting this bias decreased before 1974. This supports the theory of a lower sex ratio in monozygotic twins.
Area of Science:
- Reproductive biology
- Human genetics
- Demography
Background:
- Previous research suggested a potential bias in sex ratios for multiple births in Japan.
- The sex ratio of monozygotic twins has been hypothesized to be lower than expected.
Purpose of the Study:
- To analyze Japanese multiple birth data to assess trends in sex ratio bias.
- To determine if observed trends support the hypothesis of a low sex ratio in monozygotic twins.
Main Methods:
- Analysis of previously published Japanese multiple birth registration data (Imaizumi, 1982a, b).
- Examination of sex ratio trends over two decades preceding 1974.
Main Results:
- Data from Imaizumi (1982a, b) are consistent with a diminishing bias in sex ratios of multiple births registered in Japan.
- This trend occurred during the two decades leading up to 1974.
Conclusions:
- The observed diminishing bias in multiple birth sex ratios provides supporting evidence for the hypothesis.
- The sex ratio of monozygotic twins is likely lower than typically reported.