I recently had a very eminent historian hiss at me that she’d love to strangle every genealogist on the planet. Rather than argue, I just edged slowly towards the exit. Unlike academia, genealogy produces conflict-averse creatures at the bottom of the food chain.

But if you’re in a similar situation, and less timid than me, there are arguments. The most important is that at the root of what historians and genealogists do is the same simple impulse, the urge to understand how the past has shaped the present. Granted, the genealogical present is more limited, largely confined to family, but one of the insights of genealogy is that “family” is a much baggier concept than we assume. Where the borders are drawn to define a tribe or a family or a nation is a cultural and political decision.

A hard-bitten historian will just curl her lip at fluff like this, though. What is harder to deny is the effect genealogy is having on the availability of original sources.

Actual documentary evidence is the lifeblood of history. It is a simple fact that almost none of the historical documents made transparent and universally available online over the past decades would be there without the demand from family historians.

And what documents they are. The most recent are half a million dog licence register records ranging from 1866 to 1913, made available at FindMyPast.ie, the first instalment from a total of more than 10 million.

There, in the register from Boyle Petty Sessions on March 26th 1904, Earl Dudley of Rockingham House is recorded licensing two retrievers, a setter and a spaniel at 2/6 each, dutifully listed between the sheepdogs of a John Healy and a John McDermott.

Fifty years before, such simple equality before the law would have been unthinkable. I can think of no more vivid demonstration of one of the most profound historical changes of the past two centuries.