I decided some people needed to see this, before I could go on:
1. Does society need babies?
The U.S. is the only Western democracy anywhere near fertility replacement levels. (We're just under 2.1, after dipping as low as 1.7 babies per woman in the late 70s)
The norm for the developed world is becoming a serious depopulation crisis:
The European Union's total fertility rate from 1995 to 2000, for example, was only 1.42 children per woman, sufficiently below the 2.1 replacement level that demographers label this "very low fertility." In 2002, 28 nations experienced very low fertility including Switzerland (1.4), Germany (1.3); Austria (1.3); Italy (1.3); Spain (1.2); Greece (1.3); Japan (1.3), Russia (1.3); the Czech Republic (1.1) and most other Eastern European nations. John C. Caldwell and Thomas Schindlmayr, 2003. "Explanation of the Fertility Crisis in Modern Societies: A Search for Commonalities," Population Studies, 57(3):241-263)
In 2004, a U.N. demographer warned:
"A growing number of countries view their low birth rates with the resulting population decline and ageing to be a serious crisis, jeopardizing the basic foundations of the nation and threatening its survival. Economic growth and vitality, defense, and pensions and health care for the elderly, for example, are all areas of major concern." Joseph Chamie, "Low Fertility: Can Governments Make a Difference?", paper presented at the Annual Meeting of the Population Association of America, Boston Massachusetts, April 2, 2004.
There is no agreement on the causes of low fertility, which are likely to be complex. But many experts argue the move away from marriage, as well as a decline in the extent to which marriage is seen as a childbearing institution, play a clear role: Low fertility can also be linked to the movement away from marriage, which many western European countries have experienced for the recent decades. Of course, marriage is no longer a pre-condition for childbearing in most of these populations, but it remains true that married couples have a higher fertility than non-married people, even those who live in a "marriage-like" cohabitation. Patrick Festy, "Looking for European Demography, Desperately?" Paper presented at the Expert Group Meeting on Policy Responses to Population Ageing and Population Decline in New York October 16-18, 2000, Population Division, Department of Economic and Social Affairs, United Nations (2000).
2. Does sex makes babies?
An analysis of contraceptive failure rates in actual use concluded, "About three million pregnancies in the United States (48%) were unintended in 1994. Some 53 percent of these occurred among women who were using contraceptives."
Contraceptive failure rates in the first year of use varied considerably among different demographic groups but were never trivial: About 47 percent of cohabiting adolescent women experience a contraceptive failure (aka unintdended pregnancy) in the first year of contraceptive use, compared to 8 percent of married women age 30 and older. Haishan Fu, et al, 1999. "Contraceptive Failure Rates: New Estimates from the 1995 National Survey of Family Growth," Family Planning Perspectives 31(2): 56-63,
Another analysis of the 1995 National Survey of Family Growth concluded: "The risk of failure during typical use of reversible contraceptives in the United States is not low—overall, 9 percent of women become pregnant within one year of starting use. The typical woman who uses reversible methods of contraception continuously from her 15th to her 45th birthday will experience 1.8 contraceptive failures." James Trussell and Barbara Vaughan, 1999. "Contraceptive Failure, Method-Related Discontinuation and Resumption of Use: Results from the 1995 National Survey of Family Growth," Family Planning Perspectives 31(2): 64ff, 71
Nationally, three-fourths of births to unmarried couples were unintended by at least one of the parents. By their late thirties, 60 percent of American women have had at least one unintended pregnancy. Almost 4 in 10 women aged 40-44 have had at least one unplanned birth. J. Abma, et al., Fertility, Family Planning, and Women's Health: New Data from the 1995 National Survey of Family Growth, 23(19) Vital Health Stat. 28 (Table 17) (National Center for Health Statistics) (1997) (70.4 percent of births to married women were intended by both parents, compared to just 28 percent of births to unmarried mothers.)
Almost all children born to sexual unions of husband and wife begin life with both mother and father committed to raising their children together. Only a minority of children in other sexual unions do.
"National survey data show that children born outside of marriage have relatively little contact with their fathers and that, moreover, greater contact with nonresidential fathers does not signficantly improve child well-being outcomes." Cynthia C. Harper and Sara S McLanahan, Father Absence and Youth Incarceration, 14(3) J. Res. On Adolescence 369, 390 (2004).
3. Do children need mothers and fathers?
Child Trends sums up research family structures that have been well studied (not including children raised by same-sex couples):
"Research clearly demonstrates that family structure matters for children, and the family structure that helps the most is a family headed by two biological parents in a low-conflict marriage. Children in single-parent families, children born to unmarried mothers, and children in stepfamilies or cohabiting relationships face higher risks of poor outcomes. . . . There is thus value for children in promoting strong, stable marriages between biological parents." Kristin Anderson Moore, et al., "Marriage from a Child's Perspective: How Does Family Structure Affect Children and What Can We Do About It?" Child Trends Research Brief, June 2002.
The risks to children when mothers and fathers do not get and stay married include: poverty, suicide, mental illness, physical illness, infant mortality, lower educational attainment, juvenile delinquency and conduct disorder, adult criminality, early unwed parenthood, lower life expectancy and less warm and close relations with both mothers and fathers. (William Doherty, et al, 2002. Why Marriage Matters: 21 Conclusions from the Social Sciences (NY: Institute for American Values)
A few random samplings from a fairly large literature on family structure an crime: : a 2000 study that looked at crime in rural counties in four states concluded, "[A]n increase of 13% in female-headed households would produce a doubling of the offense rate. . . ." D. Wayne Osgood and Jeff M. Chambers, Social disorganization outside the metropolis: an analysis of rural youth violence, 38 Criminology 81, 103 (2000).
A study that analyzed a database following 6403 males from their teens to their early thirties concluded that after controlling for race, income and family background, boys who were raised outside of intact marriages were 2 to 3 times more likely to commit a crime that leads to incarceration. The authors conclude: "The results . . . show that, controlling for income and all other factors, youths in father-absent families (mother only, mother-stepfather, and relatives/other) still had significantly higher odds of incarceration than those from other-father families. . . . Youth who never had a father in the household had the highest incarceration odds." Cynthia C. Harper and Sara S McLanahan, Father Absence and Youth Incarceration, 14(3) J. Res. On Adolescence 369, 385-86 (2004). . The benefits of marriage for children described by this social science literature aren't legal incidents of marriage, of the kind that the state can therefore transfer at will to other family forms. Children living with remarried parents for example, do no better than children with single mothers, on average, e.g.: "[M]ost researchers reported that stepchildren were similar to children living with single mothers on the preponderance of outcome measures and that stepchildren generally were at greater risk for problems than were children living with both of their parents." Marilyn Coleman, et al., Reinvestigating Remarriage: Another Decade of Progress, 62 J. Marriage & Fam. 1288, 1292 (2000).
Existing scientific data thus suggests that the law of marriage protects children to the extent it increases the likelihood that children will be born to and raised by their own mother and father in a reasonably harmonious union.