Christians were not always opposed to evolution -- mainly because Christianity has progressed and made slow, significant changes over time.
Darwin's theory of evolution is 160 years old. Christianity has been thriving for more than 1700 years.
So, evolution denial is a new modification for the religion.
Has the church ever been against science before? Yes. Pope Urban VIII condemned The Father of science, Galileo. But by the time of the Internet in 2008, the church decided to erect a statue of the former heretic in the Vatican. A natural selection.
There are many variations of Christians today. They all have a common ancestry but are split off into distinct groups and sub-groups: Different continents and environments have forced different adjustments.
For example, the Inca in Peru had an ancestor ceremony in which at certain times of the year they paraded mummies of their dead relatives through the town square. After the Conquistadors, the same ceremony was re-interpreted. Now they parade statues of deceased Catholic saints instead of the deceased revered locals. The Cathedral de Cusco hangs a painting of the Last Supper showing the Twelve Apostles eating cuy (a Peruvian delicacy of roasted Guinea pig). This is notably a behavior adaptation that isn't found in other Christ-based events.
Christianity has had its own evolutionary dead ends, too. The 19th century had the Shakers -- a subset who believed in the second coming of Christ, spin dancing and absolute celibacy. The lack of procreation proved to be a real hurdle in the advancement of their kind. Thus they're extinct.
There are also mutations of Christianity who survived because of their fitness. Islam has its common descent of Christianity -- a different branch of the same religious tree, with an acknowledgement of Jesus as a prophet in the Quran. Migration and isolation spurred other mutations. Mormonism and Christian Science are native to North America.
Even the Christian Bible, the basic text of Christianity, has evolved. Bart Ehrman's 2005 book Misquoting Jesus masterfully documents modifications made over the millennia. In the Bible's first 1300 years changes were made as it was copied by hand. After the invention of the printing press, the tome was subjected to translations into new languages spawned from other languages; e.g., modern English.
The point is: Christ wasn't against Darwin's theory of evolution, but some Christians clutching to alleged originalism have opted to be. It's a relatively new characteristic.
And like the furry little ferret cousin, the skunk -- it's also a distinctly American mutation. Other developed nations don't deny biological evolution on the basis of religion.
The next thing you'll say is, "Americans are more religious than those other countries."
Many studies have found Americans are not more religious in practice than people in other nations. We just lie to pollsters as to what we're doing on Sundays. Philip Brenner at the University of Michigan's Institute for Social Research did a paper looking at "500 studies over four decades, involving nearly a million respondents." The findings were summed up by Slate's Shankar Vedantam, "Brenner found that the United States and Canada were outliers -- not in religious attendance, but in overreporting religious attendance. Americans attended services about as often as Italians and Slovenians and slightly more than Brits and Germans." So really we attend church as much as other countries -- even European countries. Americans and apparently Canadians just lie about it ... in astonishingly un-Christ-like numbers.
Last week on Bill Maher's Real Time, Congressman Jack Kingston (GA-R) admitted he doesn't think he came from a monkey. Other public figures hold fast to the same conviction. Former Arkansas Governor Mike Huckabee, likely candidate for president again, in the face of all evidence still denies evolution.
They deny all missing links, yet they are straddled between medieval mysticism and medical science. Technology can grow a human ear on the back of a rat (whether members of Congress believe in it or not). Science deniers are starting to look like America's transitional fossils.
American Christianity eventually evolved to oppose evolution, but it's not getting more Americans to church or helping us in science literacy. Then, like the other profound questions in evolution -- male nipples comes to mind -- what is the purpose?