Monozygotic Twins Seem To Have Higher Genetic Quality (significantly more physically attractive & healthier) than DZ Twins and Singletons; MZ twins may be a quality-maximizing feature of sexual reproduction

Do Monozygotic Twins Have Higher Genetic Quality than Dizygotic Twins and Singletons? Hints from Attractiveness Ratings and Self-Reported Health. Satoshi Kanazawa, Nancy L. Segal. Evolutionary Biology, https://link.springer.com/article/10.1007/s11692-019-09470-0

Abstract: Evolutionary theories generally concur that sexual reproduction and genetic recombination evolved to maximize genetic variability. Thus, the existence of monozygotic (MZ) twins, which do not take advantage of genetic recombination for each offspring, poses a puzzle. Evolutionary logic of inclusive fitness suggests that parents with high-quality genes may be more likely to produce MZ twins. Analyses of data from the National Longitudinal Study of Adolescent to Adult Health show that MZ twins were significantly more physically attractive and healthier than dizygotic (DZ) twins and singletons. These results suggest that MZ twins may possess higher-quality genes than DZ twins and singletons, and support one of the first evolutionary theories of MZ twinning that specifies its ultimate functions.

Keywords: Twin research Monozygotic twin conception Add Health