After the Spike ranges from frustrating and flawed to commendable and valuable

After the Spike is a frustrating book. It sounds the alarm on a real contemporary problem—the worldwide decline in birthrates that may be sending whole societies, even humanity itself, into a demographic death spiral. The “Spike” in the title refers to the graph tracing global population: a giddy rise since 1800 to our current eight billion plus, soon to experience an equally dramatic fall. But its analyses of causes and cures are less persuasive.

The University of Texas economists Dean Spears and Michael Geruso specialize in studying economic demography and its impact on development. Spears is particularly concerned with children’s health in rural India. But After the Spike is aimed at a popular audience, not an academic one. Its chatty pages are packed with graphs, charts, boldface bullet points, pop culture references, and personal anecdotes. The authors’ optimism and confidence are unexpectedly strong for a monitory book.

The peril of plummeting birth rates, which could depopulate the earth, has only recently started to attract attention. Americans are waking up to a possible shortfall in Social Security funding if there are too few young workers to support retired ones. Europeans worry about losing essential social services if tax rolls decline. With lifetime birthrates below 2.1 children per woman, two-thirds of the world’s people are failing to replace themselves.

Every developed nation except Israel, where large ultra-Orthodox families raise the rate to 2.75, is procreating below the replacement level. Regionally, the European Union has the lowest rate (1.5), followed by North America (1.8), the United States (1.6), and then Latin America and the Caribbean (2.0). The world’s lowest rate in 2025 is a virtual tie between Taiwan and South Korea, (.72) which translates to three children per four women. (Figures cited here come from a variety of sources, but the relative sizes are trustworthy.)

Although birth rates are falling globally, women in sub-Saharan Africa bear children at more than twice the replacement rate (4.4). Nine of the ten countries topping the reproductive charts are in sub-Saharan Africa. The tenth is Afghanistan (4.66). Higher birth rates correlate with less economic development and lower average incomes. As living standards rise, birthrates fall.

The surge in world population since 1800 did not result from more childbearing, but from fewer deaths in childhood. Under pre-modern conditions, 30, 40, or even 50% of children born never reached adulthood. Better public health and nutrition, which lowers infant mortality, actually reduces births. When more children can survive, families have fewer of them. After the Spike devotes considerable space to a program in India, which Spears and his wife have worked with, called Kangaroo Mother Care. It uses low-tech methods to save premature babies. The grateful parents of healthier children do not need to keep trying for more pregnancies to achieve their desired family size.

Spears and Geruso argue from many angles that rates, not raw numbers, shape population patterns. (Of the three factors driving demography—fertility, nuptiality, and mortality—only the first is significant in After the Spike.) For example, India, home to 1.4 billion people, is now the world’s largest country. But with births dipping below 2 per woman, it is headed for depopulation. The authors present various scenarios predicting future global depopulation if fertility is not restored to replacement levels. Any mix of family sizes will work so long as the average equals 2.1 children. (This figure is 2.1 rather than 2.0 to allow for infertility.)

But no one has found a way to arrest falling birthrates. Government experiments with child benefits, tax credits, paid parental leave, free IVF, and the like have had little impact. Spears and Geruso strongly condemn Romania’s coercive measures to increase births, just as they do China’s cruelty in reducing them. Whatever the solution, it will be a matter of choice, not policy. Geruso’s ethnic French-Canadian grandmother was one of twelve children, but his mother had just one sibling and bore only two children. This pattern matched population collapse among Quebecois in the middle of the 20th century. Geruso reports approvingly that his pious Catholic mother used contraceptives.

Stabilization—even at high levels—is the authors’ desired outcome. They firmly reject depopulation as a remedy for global warming or ecological ruin because it cannot happen fast enough to matter. One whole section is devoted to arguing the case for more people, another to rebutting objections to it. They maintain that larger populations produce more technological innovation and therefore raise living standards. Progress in other fields has not necessarily required that. Consider fifth-century Athens, Renaissance Florence, or Edinburgh during the Scottish Enlightenment.

After the Spike’s enthusiasm for tightly packed cities will not be universally shared, even though they claim it will address global warming—their prime ecological concern—better than dispersed settlement. Because air pollution is down and food production is up across the world, positive trends will continue indefinitely as science marches on. The book has no room to worry about threats to water, soil, plant, or animal life. If it did, human ingenuity and efficiency would be expected to prevail. But pace, Julian Simon, there really are limits to growth. The law of entropy has not been repealed.

Auctorial optimism shines brightest when discussing the disproportionate burdens childbearing puts on women. When motherhood costs women no more than fatherhood costs men, they predict, women will be open to having more children, easing depopulation. Pregnancy and child-rearing will be easier in perfectly liberalized societies.

For example, because medication now exists for morning sickness—they mention this four times—all other discomforts eventually will be mitigated if researchers only try hard enough. Permit this reviewer to disagree. The only way to make mothers biologically as free as fathers is to grow babies in tanks. As for all couples dividing all parental responsibilities, the world’s “Afghans” will not turn into “Swedes.” Nevertheless, working toward incremental improvements is worthwhile on the “one starfish” principle.

Regrettably, Spears and Geruso insist that women’s status depends on “reproductive freedom.”  They believe that no one must be compelled to have an unwanted child. While ignoring other methods of family limitation, they strongly support artificial contraception, abortion, and IVF. (They are shocked that anyone considers frozen embryos “babies.”) They even quote renowned science fiction writer Ursula K. Le Guin’s justification for aborting her first pregnancy because otherwise she would have never met her husband and had her other three children.

Together, the authors’ own families have seen three live births, four miscarriages, and three failed rounds of IVF. When Roe v. Wade was overturned, Geruso’s wife was newly pregnant. The couple was terrified that she would not receive necessary care if she miscarried because Texas forbade abortions. She did lose the baby while out of state and complained about her hesitant treatment. After the Spike repeats the discredited claim that “women were forced to carry nonviable pregnancies at significant risk to their health and lives.” The Gerusos did not try for another child.

Despite those positions condemned by Catholic teaching, Spears and Geruso are brave to celebrate human life as a “miracle,” not a cancer on the planet. Declaring that “more good is better,” they insist that even lives less rich than their own are still worth living. They offer evidence that high—but stable—population levels are compatible with justice, equality, and abundance.

Such views are shocking to minds still shadowed by Paul Ehrlich’s 1968 bestseller The Population Bomb and the Club of Rome’s 1972 report The Limits to Growth, which predicted mass starvation and resource exhaustion caused by exploding populations. Although events proved them wrong, these books remain influential. Erhlich’s was reissued in 2024, and the Club of Rome report issued a 30-Year Update in 2004. But they did not create fear as much as amplify what had been gathering since Thomas Malthus issued An Essay on the Principle of Population in 1798.

Overpopulation anxiety can be usefully tracked through science fiction, a genre ever sensitive to such trends. It starts showing up as a plot premise in the 1950s, for instance, in Isaac Asimov’s Caves of Steel (1954). It is no accident that three classic novels of overpopulation were written just before Erhlich’s book was published: Harry Harrison’s 1966 “Make Room, Make Room! (filmed as Soylent Green in 1972), Philip K. Dick’s 1968 Do Androids Dream of Electric Sheep? (filmed as Blade Runner in 1982), and John Brunner’s 1968 Stand on Zanzibar. Media audiences still expect dystopias to be overpopulated.

Those tumultuous decades before Spears and Geruso were born were soaked in propaganda for “the child-free lifestyle” and zero population growth, the latter idea named for an advocacy group now called Population Connection. Walter Cronkite’s CBS Evening News ran a regular feature called “Can the World Be Saved?” China and some Third World governments forcibly aborted and sterilized their people. Humanity was being steadily trained away from a taste for children, the most fundamental reason people reproduce—or not.

These antigrowth attitudes remain so embedded in popular consciousness that efforts to discuss the perils of de-population provoke vicious attacks on “pronatalism” as antifeminist racism, a mere mask for white patriarchal Christian nationalism. This is an ironic reversal of the old eugenicist fears of race suicide because the “wrong” sort of people bred too fast.

With their well-burnished progressive credentials, Spears and Geruso are well-positioned to provide hard data that has a chance of being heeded. After the Spike demonstrates that falling birth rates are ominously real and urgently need addressing. To paraphrase Ben Sasse, the future belongs to those who place a bet on life and show up to collect it.

After the Spike: Population, Progress and the Case for People
By Dean Spears and Michael Geruso
Simon & Schuster, 2025
Hardcover, 320 pages