Simon & Schuster provided me with an advanced copy of the superb book After the Spike: Population, Progress, and the Case for People, scheduled for release on July 8, 2025.

The University of Texas authors, Dean Spears and Michael Geruso, have written a mind-blowing book! It's my second favorite book of 2025! My favorite 2025 book is They're Not Gaslighting You.

https://www.youtube.com/watch?v=x-JfpjJRkok

When I was born, Paul R. Ehrlich's book, The Population Bomb, was a mega-bestseller. Although I never read the book, my generation believed the book's message that humanity is dangerously overpopulated. The book gave me one major reason not to have children. The book made intuitive sense, built on Thomas Malthus's observations, that if our population continues to expand, we will eventually hit a brick wall.

However, Ehrlich, a Stanford biologist, made these stunningly wrong predictions in The Population Bomb:

Instead of all this doom and gloom, here's what happened: we went from 3.5 billion (when Ehrich wrote his doomsday book) to 8 billion people today, most of whom are fat. Today, our biggest problem isn't famine but obesity.

Dean Spears and Michael Geruso's new book should have been called The Population Whimper because it says the opposite of what The Population Bomb said. Forget a catastrophic demographic explosion. We're going to suffer a catastrophic demographic implosion.

The graph on the cover of After the Spike sums up the problem: during a 200-year time period, the human population will have spiked to 10 billion and then experienced an equally dramatic fall.

For a book packed with counterintuitive arguments, it's remarkable that I can only spot three flaws. Admittedly, these are minor critiques, as they will disappear if we stabilize below 10 billion.

The authors correctly argue that the environment has been improving even as the human population has been growing rapidly. For example:

There's one metric that authors overlooked: wildlife.

As the human population doubled, we've needed more space for growing food. This has led to a decrease in habitat, which is why biologists refer to the Anthropocene Extinction.

I imagine that the authors of After the Spike would counter:

And they're correct. There are bright spots. 

However, as we approach 10 billion, wildlife will continue to suffer and be marginalized. The book should have mentioned that.

Dean Spears and Michael Geruso would likely agree that if humans continue to grow nonstop, wildlife will continue to suffer.

However, they aren't arguing for nonstop human expansion. They want stabilization.

When you combine stabilization with technology (e.g., vertical farming and lab-grown animal products), we would reverse the downward trend in wildlife habitat.

Dean Spears and Michael Geruso celebrate humanity's progress in energy efficiency and productivity. However, they overlook these facts:

1. The Rebound Effect (Jevons Paradox):

As energy efficiency improves, the cost of using energy services effectively decreases. This can lead to:

2. Economic Growth and Rising Living Standards:

3. Population Growth:

While efficiency might improve per unit of output, the overall global population continues to grow. More people, even if individually more efficient, will inherently consume more energy in total.

4. Shifting Economic Structures:

5. Energy Price and Policy Factors:

Conclusion: While technological advancements and efficiency measures reduce the energy intensity of specific activities, these gains are often outpaced by the aggregate increase in demand for energy services driven by economic growth, rising living standards, population increases, and the adoption of new, energy-intensive technologies and behaviors. The challenge lies in achieving a proper decoupling of economic growth from energy consumption, and ultimately, from carbon emissions.

Humanity's per capita energy consumption has been steadily increasing with each passing century, a trend that is unlikely to change soon. Therefore, humans of the 26th century will consume far more energy than those of the 21st century. 

The authors of After the Spike would probably argue that in 2525, we'll be using a clean energy source (e.g., nuclear fusion), so it'll be irrelevant that our per capita energy consumption increases ten times. 

Again, short term, we're going in the wrong direction. However, in a stabilized world, we won't have a problem.

The authors of After the Spike never addressed the potential impact that designer babies may have. I coined the term "Homo-enhanced" to address our desire to overcome our biological limitations. 

Couples are already using IVF to select the gender and eye color of their babies. Soon, we'll be able to edit and select for more complex traits such as height or even intelligence. It's easy to imagine a world like Gattaca, where parents collaborate with CRISPR-powered gene tools to create custom-made babies.

One reason some people don't want to reproduce is that it's a crap shoot. Any parent who has more than one child will tell you that each of their children is quite different from the others. Given that they grow up in the same environment, it suggests that genetics is a decisive factor.

Until now, we couldn't mold our children's DNA. Soon, we will. 

If we were to remove the lottery aspect of having a child and allow parents to design their children, perhaps there would be a baby boom.

Dean Spears and Michael Geruso would probably argue that this is unlikely or centuries away from happening. We'll be descending the steep population slope long before we are homo-enhanced.

In the Bulgaria chapter of The Hidden Europe, I observed that Bulgaria is depopulating faster than any other European country. Having peaked at 9 million in the late 1980s, a century later, it will be half that size.

Despite that, in that chapter, I predicted that in 500 years, we'll have one trillion humans in the solar system, with at least 100 billion on Earth.

This video explains how and why that may happen: 

https://www.youtube.com/watch?v=8lJJ_QqIVnc

In 2075, will After the Spike: Population, Progress, and the Case for People look as stupid as The Population Bomb looks 50 years after publication? Does After the Spike make the same errors as The Population Bomb?

Paul Ehrlich's underestimated technology and the continued collapse in fertility rates. As Dean Spears and Michael Geruso point out, fertility rates have been declining since they were first measured. Had Ehrlich extrapolated the trendline, he would have realized that our demographic collapse was imminent, not an explosion. Furthermore, technology solved many of the problems Ehrlich imagined.

Is After the Spike making the same error?

Fertility rates won't fall forever. They must stop. Otherwise, we'll become extinct.

However, will fertility rates soar due to technology or some other reason? What could make our fertility rates return to three or more? Here are a few ideas:

Admittedly, these scenarios are unlikely to occur during the next 50 years, so After the Spike won't become the joke that The Population Bomb became in 50 years.

Still, I predict that Ehrlich's great-great-granddaughter will write The Population Bomb II: Thomas Malthus Will Be Right Someday.

10 out of 10 stars!

The excerpts below are from an advanced copy, which may have undergone edits. Hence, some of these excerpts may have been reworded or deleted in the final print. The reason I am quoting them is that even if the excerpts are removed in the final edition, they illustrate the book's overall message. 

It would be easy to think that fewer people would be better—better for the planet, better for the people who remain. This book asks you to think again. Depopulation is not the solution we urgently need for environmental challenges, nor will it raise living standards by dividing what the world can offer across fewer of us.

Despite what you may have been told, depopulation is not the solution we urgently need for environmental challenges like climate change. Nor will it raise living standards by dividing what the world can offer across fewer of us. To the contrary, so much of the progress that we now take for granted sprang up in a large and interconnected society.

Part I’s big claim: No future is more likely than that people worldwide choose to have too few children to replace their own generation. Over the long run, this would cause exponential population decline.

Whether depopulation would be good or bad depends on the facts and depends on our values. We ask about those facts and values, building up to an overall assessment: Part II and Part III’s big claim: A stabilized world population would be better, overall, than a depopulating future.

Part IV’s big claim: Nobody yet knows how to stabilize a depopulating world. But humanity has made revolutionary improvements to society before— we can do it again if we choose.

We won’t ask you to abandon your concerns about climate change; about reproductive freedom and abortion access; or about ensuring safe, healthy, flourishing lives for everyone everywhere. We won’t ask you to consider even an inch of backsliding on humanity’s progress toward gender equity. We insist throughout that everyone should have the tools to choose to parent or not to parent.

This book is not about whether or how you should parent. It’s about whether we all should make parenting easier.

In 2012, 146 million children were born. That was more than in any year of history to that point. It was also more than in any year since. Millions fewer will be born this year. The year 2012 may well turn out to be the year in which the most humans were ever born— ever as in ever for as long as humanity exists.

Within three hundred years, a peak population of 10 billion could fall below 2 billion.

The tip of the Spike may be six decades from today.

For every 205 babies born, human biology, it turns out, would produce about 100 females.

Average fertility in Europe today is about 1.5. That means the next generation will be 25 percent smaller than the last.

Birth rates were falling all along. For as long as any reliable records exist, and for at least several hundred years while the Spike was ascending, the average number of births per woman has been falling, generation by generation.

In the United States in the early 1800s, married white women (a population for whom some data were recorded) gave birth an average of seven times.

If life expectancy doubles to 150 years, or quadruples to 300 years, couldn’t that prevent the depopulating edge of the Spike? The surprising answer is no.

The story of the Spike would stay the same, even if life expectancy quadrupled to three hundred years. In contrast, if adults’ reproductive spans also changed, so people had, say, one or two babies on average over their twenties, thirties, and forties and then another one on average over their fifties, sixties, and seventies, then that would stop depopulation— but it would be because births changed, not because later-adulthood deaths changed.

Where exactly should humanity stabilize? Six billion? Eight? Ten? Some other number? This book makes the case to stabilize somewhere. Exactly where will have to be a question for public and scientific debate.

So the extra greenhouse gas emissions contributed by the larger population would be small, even under the assumption here that the future is bleak and we go on emitting for another century.

The environmental costs of a new child are not zero. Not by a long shot. Not yet. But they are falling. Each new person who joins the ranks of humanity will add less CO2 than, well, you over your lifetime.

Humanity could choose a future that’s good, free, and fair for women and that also has an average birth rate of two. There is no inescapable dilemma. In that kind of future, people who want to parent would get the support that they need (from nonparents, from taxpayers, from everyone) to choose parenting.

The most plausible way humanity might stabilize— and the only way this book endorses— is if societies everywhere work to make parenting better.

Globally, we now produce about 50 percent more food per person than in 1961.

“endogenous economic growth.” Endogenous means “created from the inside.” Ideas do not come from outside the economy. They come from us.

Because scale matters, a depopulating planet will be able to fill fewer niches.

A threat with a fixed cost: A threat has arisen that will kill all humans (however many) unless a large cost is paid to escape it (such as by deflecting an asteroid) within a certain time period.

Could a kajillion lives ever be the best plan? That question goes beyond the practical question that this book is here to answer.

Between our two families, we have had three live births, four miscarriages, and three failed IVF rounds.

Parenting will need to become better than it is today. That’s what we, your authors, hope and believe.

The opportunity cost hypothesis: Spending time on parenting means giving up something. Because the world has improved around us, that “something” is better than it used to be.

In no case is there evidence that more support for parents predicts more births.

Nobody— no expert, no theory— fully understands why birth rates, everywhere, in different cultures and contexts, are lower than ever before.

I hope these excerpts compel you to buy the book. If you're still undecided, consider that the book features numerous graphs and illustrations that will rewire your brain. Buy After the Spike: Population, Progress, and the Case for People.

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