It’s a pattern found throughout the world, and it augers a far more conservative future — one in which patriarchy and other traditional values make a comeback … Childlessness and small families are increasingly the norm today among progressive secularists. As a consequence, an increasing share of all children born into the world are descended from a share of the population whose conservative values have led them to raise large families. … This dynamic helps explain the gradual drift of American culture toward religious fundamentalism and social conservatism. Among states that voted for President Bush in 2004, the average fertility rate is more than 11% higher than the rate of states for Sen. John Kerry. … Tomorrow’s children, therefore, unlike members of the postwar baby boom generation, will be for the most part descendants of a comparatively narrow and culturally conservative segment of society. To be sure, some members of the rising generation may reject their parents’ values, as often happens. But when they look for fellow secularists with whom to make common cause, they will find that most of their would-be fellow travelers were quite literally never born.
There are several standard objections to this kind of line. One is that it’s always been with us: someone’s always worried that group x are breeding like flies. (Indeed, Longman even quotes Oswald Spengler on the decline of civilization by way of reproductive enervation.) A second is that it ignores the dynamics of rebellion against one’s parents. Longman tries to avoid this one by saying that prospective liberal rebels from conservative families will have no secularist “fellow-travelers” to back them up, but why should they need them in the first place? Third, the terms “conservative” and “liberal” are moving targets. Even assuming all the kids of conservative parents grow up relatively conservative, does this mean they’ll hold the same substantive views as their forebears? Insofar as there has been any drift in generally shared ideas, it seems to have been in the direction of adopting views that would have been considered liberal or radical in previous generations, not ones that would have been thought conservative or reactionary. Finally, as Simmel and Durkheim pointed out, in modern societies more people means more differentiation, more differentiation means more social roles, and roles are the raw material that you make individual identities from. If Salt Lake City continues to grow and fill with young people, increased heterogeneity (on all kinds of dimensions) is more or less inevitable—even more so if these new people are geographically mobile and well-educated. That doesn’t tell you which political views are likely to thrive or die out or change, but it should make you skeptical of the idea that a stable set of political preferences is likely to become dominant just because one group is having a lot of children.
On the other hand, it would be pretty funny if Longman were right and conservative christianity became dominant in the U.S. for essentially Darwinian reasons of reproductive success and relative fitness.