One can never have enough lessons in humility. A month or so after publishing a book titled From the Dissident Right, last weekend I found myself among some real dissidents.

This was the dinner for Professor Zhang Yitang I mentioned here. Prof. Zhang is currently famous for having cracked an outstanding mathematical problem earlier this year. [Solving a Riddle of Primes, By Kenneth Chang, NYT, May 20, 2013] The dinner was organized by old friends of his—mainland Chinese who had, like him, come to study in the U.S.A. in the 1980s. Most of them had had some association with the Chinese Alliance for Democracy, which flourished in the 1980s and 1990s among expatriate Chinese intellectuals.

It was humbling to be among these people. One fellow diner had spent eleven years in jail, much of it in solitary confinement. Another had been imprisoned for four years at the age of sixteen after participating in the 1978-79 “Democracy Wall” movement. (She now works for a New York-registered foundation, Women’s Rights In China.)

The word “dissident” may be etymologically correct for those of us Americans who sit apart when the community singing is going on, but it seems a tad impertinent in company like this.

Although the general mood was one of celebration for Prof. Zhang’s achievement, there was a whiff of melancholy about the occasion. The democracy movement’s U.S. branch has quiesced; their magazine has suspended publication; the activists have built lives and careers for themselves here in the U.S.A. and drifted away from each other.

One of them remarked to me wistfully at the dinner that it had been many years since she’d seen so many of that generation of dissidents all together in one place.

It didn’t help that last week marked the 24^th anniversary of the Chinese government’s crushing of the student movement in Tiananmen Square. Twenty-four may not seem like a very round number to Westerners, but it is precisely two duodecadal cycles of the traditional Chinese calendar: 1989 and 2013 are both Years of the Snake. My dinner partners had it in mind.

In the context of U.S. politics, this was also the week when China’s new leader Xi Jinping paid a call on Barack Obama, while Chinese blogs had just got through batting around some controversial remarks Joe Biden made at a commencement speech last month. (The remarks went unnoticed here—who pays attention to anything Joe Biden says?—but caused a stir over there.)

It has therefore been with China on my mind that I’ve been watching the SchMcGRubio Amnesty/ Immigration Surge bill drag its weary length along through the U.S. Senate chamber.

For better or worse, our two nations look set to dominate geopolitics across the next few years, yoked together in a to-and-fro dance of mutual dependency and mutual suspicion.

Some problems we have that they don’t, mainly our vast and unsustainable public debt. Some they have that we don’t: massive environmental degradation, restless border colonies. We also have some problems in common: slowing economies, unemployed college graduates, widening wealth gaps.

(Class resentment in China when I lived there 30 years ago was aimed at the gao-gan-zi-di—the “princeling” offspring of senior Party officials and old revolutionaries. Nowadays there is a whole menagerie of spoiled brats: fu-er-dai, guan-er-dai, xing-er-dai, hong-er-dai…I find it hard to remember which is which. There’s a taxonomy here.)

And then, in the longer term, there are the prospects of demographic disaster, for them and for us.

For us, continued mass non-European immigration will reduce the nation’s founding stock to a minority by mid-century. We shall then be a majority-minority nation. The history of such nations, except under strong imperial-authoritarian control, is not encouraging.

For China, the possibility of demographic disaster arises from decades of low fertility and the associated issue of skewed sex ratios. China’s one-child policy is usually fingered as the main culprit, but given the similar demographic histories of post-WW2 Japan, South Korea, and Taiwan, I doubt the policy has been anything more than an accelerant.

The key statistic here is Total Fertility Rate (TFR): the number of children a woman would expect to have in her fertile years if, at every age, she duplicated today’s rate for that age. Given zero net immigration, a TFR of 2.1 means stable population numbers. The U.S.A., with current TFR 2.06, would be in that blessed state, except of course that we don’t have zero net immigration.

China’s current TFR, based on figures from the 2010 census, is still being argued. Numbers as low as 1.4 have been put forward, but majority opinion among demographers seems to have settled in the zone 1.50-1.55, an international ranking of #184, below Russia but above Switzerland. And that’s for the country as a whole: some of the big cities are recording sensationally low TFRs—Shanghai’s 0.7, for example.

China’s sex ratio at birth (SRB) has been noticeably skewed by selective abortion of females. At 1.133—that is, 1133 male children born for every 1000 female children—it is the highest in the world, though again the overall number hides big regional variations.

There is no general agreement about how much this matters. My own impression is: not much. (See my review of Mara Hvistendahl’s book on the subject.) Given its age-old tradition of female infanticide, China’s SRB was likely always skewed to some degree.

The problem is anyway amenable to government action. South Korea, a country less authoritarian than China, brought their SRB down from a high level in the 1980s to near-normal a decade later by legislation and strict enforcement, and the residual excess of males will likely be “sopped up” by small changes in age differential at marriage.

Further, SRB is keyed to TFR, as SRB only diverges dramatically from normal at second or subsequent births. With a TFR down at 1.5, most births are first births.

If SRB is not a problem, though, TFR may be. As the cliché has it: China will get old before she gets rich. Demographic disaster?

I am sanguine. To quote from that world-historical bestseller We Are Doomed:

If there is any demographic exceptionalism to be noted in the world, it is East Asia's: low birth rates, stiff resistance to mass immigration…

It is a plausible general principle that, when the human race in its overall development comes to some kind of bridge, the first nation to cross the bridge successfully has a great advantage over other nations. Britain was the first nation to industrialize, and dominated world affairs for a century afterwards. If demographic decline is inevitable—which of course it is: the Earth must have some maximum carrying capacity—the first nation to get through the transition intact, and conquer the associated problems, will be at a huge advantage. On current showing, that will be Japan.

Followed by China…

…if there still is a China. For all the nationalistic bluster of recent years, Chinese nationhood has historically been a fragile thing. Lucian Pye’s quip that China is “a civilization pretending to be a nation-state” captures the issue. China’s history contains as much division as unification, and some of the unifications have been short—notably the first, which lasted a mere fifteen years.

Chinese civilization has many glories: national cohesion under stable, rational government has not been prominent among them.

The main problem raised by China’s fast aging may in fact be not a shortage of workers so much as a shortage of security personnel to hold down the restive non-Chinese subject populations of Tibet and Eastern Turkestan (which, by the way, have not been subject to the stricter implementations of the one-child policy).

If China remains intact through the mid-21^st century, it may be as only metropolitan China—the old Ming empire, plus Manchuria and Inner Mongolia, both of which have been (probably) irreversibly Sinified.

That would be a good outcome, comparable to the break-up of the U.S.S.R. A bad outcome would be another spell of core disintegration. A really bad one would be the strained, contested continuation of present control over what is, essentially, the Manchu Empire, minus Outer Mongolia.

In all three cases, though, and however you grade their relative desirabilities, the Chinese people—the historic ethnic bearers of Chinese civilization—would remain the overwhelmingly dominant population in metropolitan China.

From that point of view, the demographic disaster America would bring upon herself by continued mass immigration would be far worse than anything China might expect.

Chinese civilization would survive the loss of her border colonies, and even disintegration of the ethnic metropolitan core, as she has done many times before. That America’s newer civilization would survive a population inflow of one or two hundred million souls from Latin America, Africa, India, Islamia, and East Asia (including of course China) is much less likely.

Demographics is, as I noted in that review of Mara Hvistendahl’s book, surprisingly prone to prediction errors. But, so far as it is possible to see present trends leading to demographic disaster in China and America, I’ll take theirs over ours.