In 1975, Pol Pot’s Khmer Rouge reset Cambodia’s clock to the year zero. America today has found a less bloodthirsty way of erasing its memory by losing interest in its past. From an already low base, the number of American students majoring in history has dropped by more than a third since 2008. Barely one in two hundred American undergraduates now specialise in history. That old joke about the “United States of Amnesia” is becoming less amusing.

To be sure, Donald Trump is a fitting leader for such times. He had to be told who Andrew Jackson was (the Trump-style 19th century president whose portrait he hung in the Oval Office). He also seems to think that Frederick Douglass, the escaped slave and 19th century abolitionist, is among us still. “Frederick Douglass is an example of someone has done an amazing job and is getting recognised more and more, I notice,” Mr Trump said last year.

But America’s 45th president can hardly be blamed for history’s unpopularity. Culpability for that precedes Mr Trump and is spread evenly between liberals, conservatives, faculty and parents. One university teacher describes US history as split between two camps — the “glory” school, which provides an ennobling story of great American deeds, versus the “gory” school, which focuses on slavery, native American genocide and other atrocities.