The History of the Family Is Written in Ledgers Kept to Manage People

The consent doctrine settled by Pope Alexander III in the later twelfth century set the bar for marriage extraordinarily low: two people saying "I take you" in the present tense were married on the spot, with no priest, no witnesses and no parental consent required. Such "clandestine marriages" were illegal but valid—and since marriage carried inheritance and legitimacy with it, the church courts spent centuries drowning in cases nobody could prove.

On 11 November 1563, Session 24 of the Council of Trent passed the decree Tametsi: from then on a marriage had to be contracted before the parish priest and at least two witnesses, and entered in a register, or it was void. It was the first time canon law let a matter of form decide whether a marriage existed at all, and the opposition was loud—many theologians held that it stripped two people of the right to contract for themselves. The Protestant side took another route: Luther called marriage "a worldly thing" in 1530, and the German territories set up marriage courts instead. England, having broken with Rome, left the hole open until the Hardwicke Marriage Act of 1753, and in the meantime a trade in unlicensed weddings grew up around London's Fleet Prison.

Legal recognition for cohabitation and common-law partnership turns on the identical question: when an unregistered relationship goes wrong, what can either side actually prove?

The standard demographic-transition story runs: industrialize first, urbanize, watch infant mortality fall, and only then does fertility follow. France scrambled that order entirely—it was the first country in Europe to decline, while still overwhelmingly agrarian and without any modern means of contraception.

In 1958 Louis Henry and Étienne Gautier of France's national demographic institute published La population de Crulai, paroisse normande. Using family reconstitution—matching a parish's baptism, marriage and burial entries by name to rebuild household after household—they could count how many children each wife bore at each age. The result: marital fertility in France had already begun falling before 1789, and the fall came after the second or third child, an unmistakable pattern of stopping once a family was large enough. The only method was withdrawal, which parish clergy denounced in their reports as "those fatal secrets." The consequence was a reversal of national weight: around 1800 France had roughly 29 million people, the largest population in western Europe; by 1910 France stood near 39.5 million and Germany at 65 million.

East Asian fertility has collapsed far faster than income models predicted, while cash incentives barely move it: if the decline travels as an idea, price levers were never going to pull it.

Into the 1960s the sociological consensus still held that pre-industrial society lived in large multigenerational households, and that factories and cities broke them into nuclear ones. The claim had never been tested against data, because nobody had counted.

In 1964 Peter Laslett and E. A. Wrigley founded the Cambridge Group for the History of Population and Social Structure and began systematically working through parish "listings of inhabitants"—head-counts copied out house by house so parishes could tax and administer poor relief. The 1972 volume Household and Family in Past Time reported that between 1574 and 1821 the English mean household size held steady at about 4.75, and the great majority were nuclear. Three generations under one roof was never the norm. In 1965 John Hajnal drew what became the Hajnal line, from Trieste to St Petersburg: west of it women typically first married in their mid-twenties and between ten and twenty percent never married at all; east of it marriage came early and was nearly universal. The mechanism behind it was life-cycle service—young people spent years working in someone else's household before marrying, saving until they could set up their own. In western Europe marriage was not a rite of passage but a start-up cost you had to pay off first.

First-marriage age rising with housing costs is the old start-up-cost mechanism in modern dress; and designing elder-care policy around the belief that families always used to absorb their old rests on a premise the listings already falsified.

Britain had already legislated limits on child working hours in 1802 and 1819, left enforcement to local magistrates, and watched it come to nothing. Philippe Ariès's Centuries of Childhood (1960) argued that the Middle Ages had no concept of childhood—hugely influential, and repeatedly revised since.

The Factory Act of 1833 did something no previous act had: it created four Crown factory inspectors with powers to enter mills at will, summon, and fine. The text barred children under nine from textile mills and limited those aged nine to thirteen to nine hours a day plus two hours of schooling. Enforcement then hit a wall—an inspector could not prove how old a child was. England had only parish baptism registers, which recorded no date of birth and omitted nonconformists entirely; the act fell back on having a surgeon certify age from appearance, and parents routinely lied. The Births and Deaths Registration Act of 1836 created secular registration, effective the following year, but it placed no duty on parents to report, coverage stayed patchy, and only the 1874 amendment's penalties finally closed the gap. Forty-one years separated "childhood is protected by law" on paper from a law that could be enforced.

The minimum-age rules now being imposed on children's internet use replay the bind of 1833: the threshold comes first, proving age has no reliable answer, and so we are back to estimating from appearance—only now the estimating is done by an algorithm.