36. R. Saffery et al., “Cohort Profile: The Peri/Post-Natal Epigenetic Twins Study,” International Journal of Epidemiology 41, no. 1 (2012): 55–61; L. Gordon et al., “Neonatal DNA Methylation Profile in Human Twins Is Specified by a Complex Interplay Between Intrauterine Environmental and Genetic Factors, Subject to Tissue-Specific Influence,” Genome Research 22, no. 8 (2012): 1395–1406.
Chapter 7: Discoveries
1. S. L. Farber, Identical Twins Reared Apart: A Reanalysis (New York: Basic Books, 1980), 65, 67. Identical female reared-together twins in Finland show average height and weight differences of .62 inches and 11.53 pounds, respectively. See N. L. Segal, Someone Else’s Twin: The True Story of Babies Switched at Birth (Amherst, NY: Prometheus, 2011), 245–46.
2. R. S. Hartley and J. Hitti, “Birth Order and Delivery Interval: Analysis of Twin Pair Perinatal Outcomes,” Journal of Maternal-Fetal and Neonatal Medicine 17, no. 6 (2006): 375–80; B. A. Armson et al., “Determinants of Perinatal Mortality and Serious Neonatal Morbidity in the Second Twin,” Obstetrics & Gynecology 108, no. 3, pt. 1 (2006): 556–64.
3. C. M. Ruitberg, D. J. Reeder, and J. M. Butler, “STRBase: A Short Tandem Repeat DNA Database for the Human Identity Testing Community,” Nucleic Acids Research 29, no. 1 (2001): 320–22.
4. Although DNA can be easily extracted from saliva samples, Dr. Emilio J. Yunis used the twins’ DNA from blood samples because blood contains more cells than saliva and therefore yields more DNA. When he compared twenty-one STRs (short tandem repeats) of the presumed identical partners, they matched exactly. E. J. Yunis and G.A.C. Pérez, Servicios Médicos Yunis Turbay y Cia S. En C. Instituto Genética (DNA Test Report, October 3, 2014). This finding proved beyond question that Jorge and William, and Carlos and Wilber were identical twins—and that the young men who had grown up together (Jorge and Carlos, and William and Wilber) were not fraternal twins as they and their families had believed; in fact, they were not even related.
5. N. L. Segal, “Psychological Features of Human Reproductive Cloning: A Twin-Based Perspective,” Psychiatric Times 23, no. 20 (2006): 22.
6. N. L. Segal, Twin Mythconceptions: False Beliefs, Fables, and Facts About Twins (San Diego: Elsevier, 2017); H. C. McNamara et al., “A Review of the Mechanisms and Evidence for Typical and Atypical Twinning,” American Journal of Obstetrics and Gynecology 214, no. 2 (2016): 172–91.
7. During the taping of the TV show Séptimo Día, Ana called Carlos “Wilber’s little brother”—this may have been a term of endearment or a reference to birth size, rather than birth order.
8. M. R. Yalçin et al., “The Significance of Birth Weight Difference in Discordant Twins: A Level to Standardize?” Acta Obstetricia et Gynecologica Scandinavica 77, no. 1 (1998): 28–31; F. M. Breathnach et al. “Definition of Intertwin Birth Weight Discordance” Obstetrics and Gynecology 118, no. 1 (2011): 94–103; American College of Obstetricians and Gynecologists and Society for Maternal-Fetal Medicine, “Multifetal Gestations: Twin, Triplet, and Higher-Order Multifetal Pregnancies,” Obstetrics and Gynecology (ACOG Practice Bulletin 169) 128, no. 4 (2016): e131–46.
9. Apgar scores give ratings of 0, 1, or 2 across five newborn physical characteristics; a score in the 7 to 10 range is considered to be good. See “Your Child’s First Test: The APGAR,” American Pregnancy Association, 2016, http://americanpregnancy.org/labor-and-birth/apgar-test/.
10. M. P. Umstad, personal communication with author, October 10, 2016.
11. L. Dubois et al., “Genetic and Environmental Contributions to Weight, Height, and BMI from Birth to 19 Years of Age: An International Study of over 12,000 Twin Pairs,” PLoS ONE 7, no. 2 (2012): e30153.
12. J. Dineshshankar et al., “Lip Prints: Role in Forensic Odontology,” Journal of Pharmacy and Bioallied Sciences 5, suppl. 1 (2013): S95–S97; J. Leibach, “What Your Lips Might Say About You,” Science Friday, October 13, 2016, http://www.sciencefriday.com/articles/what-your-lips-might-say-about-you/?utm_source=Weekly+Newsletter+List&utm_campaign=76c1f716a5-Newsletter_Oct_14_2016&utm_medium=email&utm_term=0_10d8eab927-76c1f716a5-53948761; R. V. Prabhu et al., “Cheiloscopy: Revisited,” Journal of Forensic Dental Sciences 4, no. 1 (2012): 47–52.
13. J. V. Peluchette, K. Karl, and K. Rust, “Dressing to Impress: Beliefs and Attitudes Regarding Workplace Attire,” Journal of Business and Psychology 21, no. 1 (2006): 45–63; H. Wolf et al., “Self-monitoring and Personality: A Behavioural-Genetic Study,” Personality and Individual Differences 47, no. 1 (2009): 25–29; K. Kendler, C. O. Gardner, and C. Prescott, “A Population-Based Twin Study of Self-esteem and Gender,” Psychological Medicine 28, no. 6 (1998): 1403–9.
14. H. Alibeik and S. A. Angaji, “Developmental Aspects of Left-handedness,” Australian Journal of Basic and Applied Sciences 4, no. 5 (2010): 877–81; C. E. Boklage, How New Humans Are Made (Singapore: World Scientific, 2010).
15. N. L. Segal, Entwined Lives: Twins and What They Tell Us About Human Behavior (New York: Plume, 2000); L. Mealey, R. Bridgstock, and G. C. Townsend, “Symmetry and Perceived Facial Attractiveness: A Monozygotic Co-Twin Comparison,” Journal of Personality and Social Psychology 76, no. 1 (1999): 157–65; M. T. Liu et al., “Factors Contributing to Facial Asymmetry in Identical Twins,” Plastic and Reconstructive Surgery 134, no. 4 (2014): 638–46.
16. Boklage, How New Humans Are Made; J. Levy, personal communication with author, October 20, 2016; L. Mastin, “An Investigation of Handedness—Some Facts, Myths, Truths, Opinions and Research,” RightLeftRightWrong?, 2012, http://www.rightleftrightwrong.com/statistics.html.
17. Segal, Twin Mythconceptions; M. Roizen, “How Are Fingerprints Formed in the Womb?” sharecare, n.d., https://www.sharecare.com/health/fetal-development-basics-pregnancy/how-fingerprints-formed-in-womb; G. Steinman, “Mechanisms of Twinning: I. Effect of Environmental Diversity on Genetic Expression in Monozygotic Multifetal Pregnancies,” Journal of Reproductive Medicine 46, no. 5 (2001): 467–72; A. K. Jain, S. Prabhakar, and S. Pankanti, “On the Similarity of Identical Twin Fingerprints,” Pattern Recognition 35, no. 11 (2002): 2653–63; B. Karmakar, I. Malkin, and E. Kobyliansky, “Inheritance of 18 Quantitative Dermatoglyphic Traits Based on Factors in MZ and DZ Twins,” Anthropologischer Anzeiger 68, no. 2 (2011): 185–93; T. Reed, R. J. Viken, and S. A. Rinehart, “High Heritability of Fingertip Arch Patterns in Twin-Pairs,” American Journal of Medical Genetics Part A 140, no. 3 (2006): 263–71.
18. W. J. Babler, “Quantitative Differences in Morphogenesis of Human Epidermal Ridges,” Birth Defects Original Article Series 15, no. 6 (1979): 199–208; K. Wertheim and A. Maceo, “The Critical Stage of Friction Ridge and Pattern Formation,” Journal of Forensic Identification 36/51, no. 1 (2002): 35–85.
19. H. S. Bracha et al. “Second-Trimester Markers of Fetal Size in Schizophrenia: A Study of Monozygotic Twins,” American Journal of Psychiatry 149, no. 10 (1992): 1355–61.
20. K. Packard, “Deciphering Your Own Fingerprints—The Tented Arch,” pt. 3, American Academy of Hand Analysis, August 30, 2010, http://academyofhandanalysis.org/deciphering-your-fingerprints-the-tented-arch/.
21. D. T. Lykken, “The Diagnosis of Zygosity in Twins,” Behavior Genetics 8, no. 5 (1978): 437–73.
22. A. Petronis, “Epigenetics as a Unifying Principle in the Aetiology of Complex Traits and Diseases,” Nature 465, no. 7299 (2010): 721; N. L. Segal et al., “Identical Twins Doubly Exchanged at Birth—Genetic and Environmental Influences on the Adult Epigenome,” Epigenomics 9, no. 1 (2017): 5–12.
23. M. Jolly et al., “The Risks Associated with Pregnancy in Women Aged 35 Years or Older,” Human Reproduction 15, no. 11 (2000): 2433–37.
24. E. E. Birch and A. R. O’Connor, “Preterm Birth and Visual Development,” Seminars in Neonatology 6, no. 6 (December 2001): 487–97; S. J. Woo et al., “A Co-Twin Study of the Relative Effec
t of Birth Weight and Gestational Age on Retinopathy of Prematurity,” Eye 25, no. 11 (2011): 1478; H. L. Koch, Twins and Twin Relations (Chicago: University of Chicago Press, 1966); W. H. Knobloch et al., “Eye Findings in Twins Reared Apart,” Ophthalmic Paediatrics and Genetics 5, no. 1–2 (1985): 59–66.
25. H. Hinrichsen et al., “Social Anxiety and Coping Strategies in the Eating Disorders,” Eating Behaviors 4, no. 2 (2003): 117–26; I. Jáuregui-Lobera et al., “Psychometric Properties of Spanish Version of the Three-Factor Eating Questionnaire-R18 (Tfeq-Sp) and Its Relationship with Some Eating- and Body Image-Related Variables,” Nutrients 6, no. 12 (2014): 5619–35; B. M. Neale, S. E. Mazzeo, and C. M. Bulik, “A Twin Study of Dietary Restraint, Disinhibition and Hunger: An Examination of the Eating Inventory (Three Factor Eating Questionnaire),” Twin Research 6, no. 6 (2003): 471–78; S. J. Elder et al., “Genetic and Environmental Influences on Eating Behavior—A Study of Twins Reared Apart,” The FASEB Journal 23, no. 1 (2009): conf. ab. 545.7. The Elder at al. study has not been published.
26. H. H. Newman, F. N. Freeman, and K. J. Holzinger, Twins: A Study of Heredity and Environment (Chicago, IL: University of Chicago Press, 1937), 356.
27. N. L. Segal and J. H. Stohs, “Age at First Intercourse in Twins Reared Apart: Genetic Influence and Life History Events,” Personality and Individual Differences 47, no. 2 (2009): 127–32.
28. A. Campo-Arias et al., “Factores asociados con el inicio temprano de relaciones sexuales en estudiantes adolescentes de un colegio de Bucaramanga, Colombia” (“Factors Associated with the Early Onset of Sexual Intercourse in Adolescent Students at a School in Bucaramanga, Colombia”), Revista Colombiana de Psiquiatria 33, no. 4 (2004): 367–77; G. A. Ceballos and A. Campo-Arias, “Sexual Intercourse Among Adolescent Students of Santa Marta, Colombia: A Cross-sectional Survey,” Colombia Médica 38, no. 3 (2007): 191–96.
Chapter 8: Another World
1. K. T. Krizek, J. Horning, and A. El-Genedity, “Perceptions of Accessibility to Neighbourhood Retail and Other Public Services,” in Accessibility Analysis and Transport Planning: Challenges for Europe and North America, ed. K. T. Geurs, K. J. Krizek, and A. Reggianai (Cheltenham, UK: Edward Elgar, 2012), 96–117.
2. N. L. Segal, Born Together—Reared Apart: The Landmark Minnesota Twin Study (Cambridge, MA: Harvard University Press, 2012).
3. J. H. Fowler, L. A. Baker, and C. T. Dawes, “Genetic Variation in Political Participation,” American Political Science Review 102, no. 2 (2008): 233–48; R. D. Arvey et al., “The Determinants of Leadership Role Occupancy: Genetic and Personality Factors,” The Leadership Quarterly 17, no. 1 (2006): 1–20; J. Scourfield et al., “The Development of Prosocial Behaviour in Children and Adolescents: A Twin Study,” Journal of Child Psychology and Psychiatry 45, no. 5 (2006): 927–35.
4. Segal, Born Together—Reared Apart.
5. I. Morgan and K. Rose, “How Genetic Is School Myopia? Progress in Retinal and Eye Research 24, no. 1 (2005): 1–38.
6. “Your Premature Baby’s Appearance,” Raising Children Network, May 13, 2016, http://raisingchildren.net.au/articles/premature_baby_appearance.html/context/1403.
7. K. Cathey, Colombia (London: Kuperard, 2014).
8. “Translocation Down Syndrome,” University of Rochester Medical Center Health Encyclopedia, 2017, https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02153.
9. V. Prasher, “Comparison of Physical and Psychiatric Status in Individuals with Translocation and Trisomy 21 Down Syndrome,” Down Syndrome Research and Practice 3, no. 1 (1995): 9–13.
10. N. L. Segal, “Laboratory Findings: Not Twin, Twins, Not Twins,” Twin Research & Human Genetics 9, no. 2 (2006): 303–8.
11. N. L. Segal, Someone Else’s Twin: The True Story of Babies Switched at Birth (Amherst, NY: Prometheus, 2011).
12. M. J. Russell, T. Mendelson, and H. V. Peeke, “Mothers’ Identification of Their Infant’s Odors,” Ethology and Sociobiology 4, no. 1 (1983): 29–31.
13. B. Schaal, “Presumed Olfactory Exchanges Between Mother and Neonate in Humans,” in Ethology and Psychology, ed. J. Le Camus and J. Cosnier (Toulouse, France: Privat-IEC, 1986), 101–10.
14. S. Nishitani et al., “Maternal Prefrontal Cortex Activation by Newborn Infant Odors,” Chemical Senses 39, no. 3 (2014): 195–202; E. Hoekzema et al., “Pregnancy Leads to Long-Lasting Changes in Human Brain Structure,” Nature Neuroscience 20 (2016): 287–96, doi: 10.1038/nn.4458.
15. J. Selwyn and S. Meakings, “‘She Just Didn’t Smell Right!’ Odour and Adoptive Family Life,” Adoption & Fostering 39, no. 4 (2015): 294–302.
16. M. Kaitz, A. M. Rokem, and A. I. Eidelman, “Infants’ Face-Recognition by Primiparous and Multiparous Women,” Perceptual and Motor Skills 67, no. 2 (1988): 495–502.
17. D. Formby, “Maternal Recognition of Infant’s Cry,” Developmental Medicine & Child Neurology 9, no. 3 (1967): 293–98; M. Kaitz et al., “Parturient Women Can Recognize Their Infants by Touch,” Developmental Psychology 28, no. 1 (1992): 35–39.
18. Segal, Someone Else’s Twin.
19. Segal, Someone Else’s Twin.
20. M. Santora, “Rolling DNA Labs Address the Ultimate Question: ‘Who’s Your Daddy?’” New York Times, November 8, 2016, A24.
Chapter 9: Different Versions of the Same Song
1. P. Watson, Twins: An Uncanny Relationship? (Chicago: Contemporary Books, 1981); T. J. Bouchard, Jr., et al., “Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart,” Science 250, no. 4978 (1990): 223–28.
2. P. Nugent, “Self-Esteem,” Psychology Dictionary, April 13, 2013, http://psychologydictionary.org/self-esteem/. The Rosenberg Self-Esteem Survey (RSES) was developed in 1989 by Professor Morris Rosenberg at the University of Maryland. Sample items are “I feel that I have a number of good qualities,” and “I feel I do not have much to be proud of.” People taking the survey either “strongly agree,” “agree,” “disagree,” or “strongly disagree” with each statement.
3. R. F. Baumeister et al., “Does High Self-Esteem Cause Better Performance, Interpersonal Success, Happiness, or Healthier Lifestyles?” Psychological Science in the Public Interest 4, no. 1 (2003): 1–44; M. B. Donnellan et al., “Low Self-Esteem Is Related to Aggression, Antisocial Behavior, and Delinquency,” Psychological Science 16, no. 4 (2005): 328–35; U. Orth, R. W. Robins, and B. W. Roberts, “Low Self-Esteem Prospectively Predicts Depression in Adolescence and Young Adulthood,” Journal of Personality and Social Psychology 95, no. 3 (2008): 695–708.
4. N. L. Segal, “Personality Similarity in Unrelated Look-Alike Pairs: Addressing a Twin Study Challenge,” Personality and Individual Differences 54, no. 1 (2013): 23–28.
5. D. P. Schmitt and J. Allik, “Simultaneous Administration of the Rosenberg Self-Esteem Scale in 53 Nations: Exploring the Universal and Culture-Specific Features of Global Self-Esteem. Journal of Personality and Social Psychology 89, no. 4 (2005): 623–42.
6. R. D. Arvey et al., “Job Satisfaction: Environmental and Genetic Components,” Journal of Applied Psychology 74, no. 2 (1989): 187–92; R. D. Arvey and B. P. McCall et al., “Genetic Influences on Job Satisfaction and Work Values,” Personality and Individual Differences 17, no. 1 (1994): 21–33.
7. J. S. Peper et al., “Genetic Influences on Human Brain Structure: A Review of Brain Imaging Studies in Twins,” Human Brain Mapping 28, no. 6 (2007): 464–73; J. N. Giedd, J. E. Schmitt, and M. C. Neale, “Structural Brain Magnetic Resonance Imaging of Pediatric Twins,” Human Brain Mapping 28, no. 6 (2007): 474–81; M. A. Lodato, M. B. Woodworth, L. Semin, G. D. Evrony, B. K. Mehta, A. Karger, S. Lee et al., “Somatic Mutation in Single Human Neurons Tracks Developmental and Transcriptional History.” Science 350, no. 6256 (2015
): 94–98; R. Plomin et al., Behavioral Genetics, 7th ed. (New York: Worth, 2017); R. Plomin and J. C. DeFries, “Genetics and Intelligence: Recent Data,” Intelligence 4, no. 1 (1980): 15–24.
8. C. Cliffordson and J. E. Gustafsson, “Effects of Age and Schooling on Intellectual Performance: Estimates Obtained from Analysis of Continuous Variation in Age and Length of Schooling,” Intelligence 36, no. 2 (2008): 143–52; H. H. Newman, F. N. Freeman, and K. J. Holzinger, Twins: A Study of Heredity and Environment (Chicago: University of Chicago Press, 1937).
9. C. N. Brinch and T. A. Galloway, “Schooling in Adolescence Raises IQ Scores,” Proceedings of the National Academy of Sciences 109, no. 2 (2012): 425–30; I. J. Deary and W. Johnson, “Intelligence and Education: Causal Perceptions Drive Analytic Processes and Therefore Conclusions,” International Journal of Epidemiology 39, no. 5 (2010): 1362–69.
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