Patrick Boyle on YouTube says that while birth rates in S. India have fallen a lot, not so in the north.  Can you confirm?

Yes, with an important qualification.

Patrick Boyle's broad point is correct: South India completed its fertility transition much earlier than North India, and for decades there was a striking demographic divide. States such as Andhra Pradesh, Karnataka, Kerala, Tamil Nadu, and Telangana all fell well below the replacement level of about 2.1 children per woman years ago. NFHS-5 (2019–21) recorded fertility rates of roughly 1.7–1.8 in those southern states.

However, the situation in the north has been changing rapidly. The large northern states that traditionally had high fertility—especially Bihar and Uttar Pradesh—have also seen substantial declines. NFHS-5 reported Bihar at 3.0 and Uttar Pradesh at 2.4, still well above the south but much lower than in the past.

More recent data suggest the gap is narrowing further. According to 2024 Sample Registration System data reported in 2026, India's overall fertility rate has fallen to about 1.9, below replacement level. Only a handful of states remain above replacement fertility, concentrated in the Hindi-speaking north and central belt: Bihar, Uttar Pradesh, Madhya Pradesh, Rajasthan, Chhattisgarh, and Jharkhand.

So if one were to summarize:

    South India: very low fertility, often comparable to Southern Europe or East Asia.

    North India: still higher fertility, especially Bihar and parts of the Gangetic plain, but declining steadily.

    India as a whole: now below replacement fertility.

One consequence is that political representation is becoming a sensitive issue. Southern states point out that they successfully reduced population growth decades ago, while northern states continue to contribute a larger share of population increase. If parliamentary seats are reallocated strictly by population, the north could gain influence at the south's expense. That demographic debate has become one of the most important long-term political questions in India.

In other words, Boyle is describing a real phenomenon, but today it is more accurate to say "the north still has higher fertility than the south" than to say "birth rates have not fallen in the north." They have fallen a great deal; they just started from a higher level and remain higher.

So I conclude the phenomenon is worldwide, just that different countries are different and India, being a big country, has different regions.

That's essentially how I would see it.

The remarkable thing about the fertility decline of the last century is not that it happened in a few places—it's that it has happened in almost every society that has become more urbanized, educated, and economically developed, regardless of religion, ethnicity, or political system.

You can find low fertility in:

    Catholic countries such as Italy and Spain.

    Orthodox countries such as Greece and Russia.

    Buddhist countries such as Thailand.

    Hindu-majority regions of India.

    Muslim-majority countries such as Iran, Turkey, Bangladesh, and Tunisia.

    Secular countries such as Japan and South Korea.

The timing differs, and the final level differs, but the direction has been remarkably consistent.

India is a good example because it contains populations at different stages of the same process within one national framework. Kerala and Tamil Nadu reached low fertility decades ago; Bihar and Uttar Pradesh started later. If those states were independent countries, demographers might describe them as being at different stages of development rather than as exceptions to a global trend.

One reason demographers became interested in India is that it challenged older assumptions. For a long time, some people argued that high fertility was rooted in particular religions or cultures. Yet Kerala, Bangladesh, Iran, and Tamil Nadu all experienced dramatic fertility declines despite having very different cultures and religions. That pushed researchers toward explanations involving education, child survival, urbanization, women's opportunities, and the economic costs and benefits of raising children.

There are still a few places with relatively high fertility—much of sub-Saharan Africa stands out today—but even there the trend is generally downward. The argument among demographers is usually not whether fertility will fall, but how fast and to what level.

So your conclusion is close to the current mainstream demographic view: the decline in birth rates appears to be a broad global phenomenon, while countries like India remind us that large nations often contain several demographic worlds at once.

Exactly. That is one of the great misconceptions about the ancient world: people often confuse lack of accumulated knowledge with lack of intelligence.

A Greek architect in the 5th century BCE or a Roman engineer in the 2nd century CE had essentially the same human brain as an engineer today. The difference is that they stood at the beginning of a much smaller mountain of accumulated information.

A few examples make the point:

    The builders of the Parthenon had extraordinary command of geometry, surveying, optics, and proportion. They deliberately curved the stylobate (the platform) and columns in ways that compensated for optical illusions. That is not primitive craftsmanship; it is sophisticated visual engineering.

    The builders of the Pantheon solved problems in concrete engineering that are still admired today. The dome gets lighter as it rises because they adjusted the materials, using heavier aggregates below and lighter ones near the top. They created a structure that survived almost two thousand years.

    Ancient Greek astronomers calculated the size of Earth with remarkable accuracy. Eratosthenes estimated Earth's circumference using shadows and geometry. His method was simple; the achievement was knowing what questions to ask and how to reason from observations.

The difference is cumulative knowledge. A modern engineer has access to:

    calculus,

    materials science,

    computer modeling,

    centuries of experiments,

    global collaboration.

An ancient engineer had none of those—but could still be a genius within the tools available.

A useful analogy is chess. A modern chess grandmaster has opening databases, computer analysis, and millions of recorded games. But a brilliant player centuries ago could still have extraordinary insight into the game using only a board and their own mind.

In fact, some ancient achievements are especially impressive because they were done without modern conveniences. Moving enormous stones, coordinating thousands of workers, calculating astronomical cycles, designing ships, creating legal systems—these required organizational intelligence as much as individual brilliance.

Where we probably are different is not raw intelligence but the distribution of knowledge. A larger percentage of ordinary people today have access to advanced concepts because schooling and technology spread them widely. In ancient Athens, Alexandria, or Rome, the highly educated elite were operating at an astonishing level, but most people were not.

So your phrasing—"at least those at the higher levels of intelligence"—is the key. The top minds of the ancient world were not lesser versions of us. They were our intellectual equals working with a much smaller library.

I have the Pantheon a century earlier than you said?

Good catch. I should have been more precise.

The Pantheon that exists today is generally dated to the reign of the emperor Hadrian, with construction usually placed around 118–125 CE (some dates vary slightly). I said "2nd century CE," which is correct, but my wording may have made it sound like I was placing it later than the period you had in mind.

There was also an earlier Pantheon built by Marcus Vipsanius Agrippa around 27 BCE during the reign of Augustus. That building was destroyed and replaced (or substantially rebuilt) by Hadrian's structure. The inscription on the present building still says:

"M·AGRIPPA·L·F·COS·TERTIVM·FECIT"
("Marcus Agrippa, son of Lucius, consul for the third time, built this.")

So if you were thinking of the Agrippan Pantheon, you were indeed about a century off from my Hadrianic one—actually closer to a century and a half earlier.

And this ties nicely into your point about ancient intelligence. The Pantheon is a good example because the engineering tradition behind it did not suddenly appear in 120 CE. It was the product of generations of Roman experimentation with concrete, arches, vaults, and domes. Hadrian's architects inherited a long line of accumulated knowledge, just as modern engineers inherit from theirs. The genius is often not one person having a miraculous idea, but a civilization building a ladder high enough for someone to climb.

Agrippa built, or at least paid for, the first one.  Now that is interesting.  

Yes, and that is one of the fascinating things about Roman architecture: the name on the building was often not the name of the architect or engineer, but the name of the person who commissioned and funded it.

Marcus Vipsanius Agrippa is a particularly interesting figure because he was far more than a wealthy patron. He was Augustus' closest collaborator—military commander, administrator, and a major force behind transforming Rome from a city of brick and wood into an imperial capital of stone and marble.

The first Pantheon was part of Agrippa's building program in the Campus Martius, an area where he created or funded several major public works:

    baths,

    gardens,

    aqueduct improvements,

    temples and monuments.

The Pantheon itself was probably dedicated around 27 BCE. Its exact purpose is debated, but it seems to have been connected with the imperial program of Augustus and the idea of Rome's relationship with the gods.

The irony is that the building we admire today is not Agrippa's structure. The original was destroyed by fire (possibly more than once), and Hadrian rebuilt it. Yet Hadrian deliberately kept Agrippa's inscription on the façade. That was a very Roman gesture: preserving the memory and legitimacy of the original patron.

It also illustrates something about ancient construction that is easy to overlook. A great building required:

    an architect or technical designer,

    skilled craftsmen,

    thousands of laborers,

    quarrying and transport systems,

    and, critically, someone with the political power and money to make it happen.

Agrippa was the person who could make the whole machine move.

There is another interesting contrast with the Parthenon. The Parthenon was a civic project of democratic Athens (though built using imperial tribute from Athens' allies). The Pantheon was an imperial project tied to the power of one man and his circle. Both are masterpieces, but they represent very different political worlds.

And Agrippa himself is a reminder that ancient "great men" were often not just thinkers or warriors. Some were extraordinary organizers—the people who knew how to turn ideas into stone.