RECEIVED wisdom, among both scientists and breeders, is that a modern, thoroughbred racehorse runs about as fast as it is possible for anything horse-shaped to run. Examinations of historical records, conducted over the past few years, have concluded that winning times have stagnated. Undermining received wisdom, though, is one of the most enjoyable pursuits in science. And, in a paper just published in Biology Letters, Patrick Sharman and Alastair Wilson of the University of Exeter, in England, have done just that.

Those previous studies of equine velocity focused on results from the winners of a small number of elite races. Mr Sharman and Dr Wilson used two much bigger sets of data—one covering 2,243 races run in Britain between 1850 and 1996 and the other more than 50,000 races held (also in Britain) between 1997 and 2012.

In all, they looked at 616,084 times set by 70,388 horses. They found that, contrary to received wisdom, the average speed of racehorses has continued to increase—with a particularly rapid improvement after 1975. At the top of the sport, in elite competitions such as Royal Ascot, the picture is more complicated. Over middle distances (8-12 furlongs, a furlong being just over 200 metres) and long ones (14-20 furlongs) Mr Sharman and Dr Wilson found that winning times had indeed stagnated in recent decades. But over the shortest distances (five to seven furlongs) things had continued to improve. Specifically, the speed of the best short-distance horses rose by about 0.1% a year between 1997 and 2012. That might not sound much, but it was enough to reduce the average winning time over six furlongs from 72.92 to 71.74 seconds—a difference at the finishing line of more than seven lengths.

Mr Sharman, who describes himself as a racing fan first and a geneticist second, offers two explanations for his contrarian result. One is the sheer size and diversity of his data-sets, which offer a much more comprehensive view of the field than was previously available. Prestigious races of the sort focused on in the past tend to be middle-distance events, so the short-distance effect was not perceived.

The other explanation lies in the level of detail he examined. As any racing fan will tell you, the harder the ground, the faster a horse can run. Surprisingly, previous analyses had ignored this and looked merely at raw running times. Mr Sharman, by contrast, tried to account for the going. Horses have tended to run on softer ground in recent years, he notes (perhaps because harder ground is riskier as well as faster), and that tends to drag times down.

All this suggests that horses have not actually reached a hard, genetic limit to their performance. A little more imagination by breeders might thus pay dividends.

At the moment, breeders of thoroughbreds have only limited genetic material to work with. The animals in their stables are all descended from but a few dozen sires and dams. Indeed, 95% can trace their lineage back to a single 18th-century stallion called the Darley Arabian. Other parts of the horsey population—despite being slower overall—may contain genes that, if they could be isolated, might let thoroughbreds go faster still.

Extracting these genes using the tried and trusted methods of selective breeding would, however, be a decades-long project, and Mr Sharman notes that racing has been slow to adopt the sophisticated genetic techniques which have caused things like poultry yields to shoot up recently. It might therefore be worth trying a bit more science before declaring that horses will never run faster than they do today.