It was hardly a new incentive. Years earlier, during the Greek civil war, the British paid a bounty to right wing thugs for the bearded heads of Greek partisans after an earlier scheme to pay out for pairs of ears backfired when the earless corpses of innocent parties started turning up.

The same thing, we now learn in a fascinating new book by William Kiser entitled The Business of of Killing Indians, happened in North America when the British, French, Mexicans, Canadians and Americans paid bounty hunters for ‘Indian scalps’. Some Native American tribes had always indulged in scalping their opponents, but it was European colonists who supercharged, and monetised, the practice.

There could be good money in scalping and in one Canadian province, much to the irritation of the indigenous peoples, the right to take scalps and to be rewarded for them technically remains on the statute books to this day.

In 1849 a Mexican law stipulated the payment of 200 pesos for every male scalp and 150 pesos for female captives and children under the age of 14 years. That year the authorities in Chihuahua paid out just under 18,000 pesos to scalp hunters at a time when a Mexican worker was lucky to be paid 200 pesos a year.

In 1853 the Californian legislature paid a gang of 36 killers $23,000 for killing 73 Modocs, equivalent to $315 for each dead native. Miners in the Californian gold fields at the time were paid around $3 a day.

Inevitably, these huge financial incentives led to fraud. Horse tails were dressed to look like human hair, scalps were divided in two and the scalps of mixed race mestizos with black hair similar to that of the Native Americans were also taken.

The practice flourished from the late 1600s to the late 1800s and it was only in the 1860s after an exposé by Irish writer J. Ross Browne in Harper’s New Monthly Magazine, in which the gruesome details of numerous massacres in California were revealed, that public opinion began to oppose such methods.

Kiser’s troubling and well-researched book is continent-wide in its scope. Almost one third of its 335 pages are devoted to notes and references.

In it, Kiser is concerned to establish whether state-sponsored scalping which led to the massacres of thousands of Native Americans was genocidal in its intent. There seems little doubt that it was. Consider a speech by Colonel John M Chivington who organised the 1864 massacre of over 100 Native Americans at Sand Creek in Colorado during which the scalps and genitalia of victims were taken. He declared that his policy towards them was to “kill and scalp all, big and little – because nits made lice”.

The Business of Killing Indians by William S Kiser. Published by Yale University Press, 335pp, £30.