A growing market for ejiao—a gelatin made from donkey hide believed by practitioners of traditional Chinese medicine to increase libido and slow aging—has led to a global trade of millions of donkey skins each year. Asses are often kidnapped from rural African villages, where their labor is valued highly, then taken to markets and slaughtered for export. “The donkeys,” said a sanctuary manager while visiting a market in Tanzania, “are very stressed.”

James Boswell recorded that during the sale of Henry Thrale’s brewery, Samuel Johnson—an executor of the business—“appeared bustling about, with an inkhorn and pen in his buttonhole, like an exciseman,” and was asked what he considered to be the true value of the property. “We are not here to sell a parcel of boilers and vats,” Johnson responded, “but the potentiality of growing rich beyond the dreams of avarice.”

A hand’s primary function, Elias Canetti writes in Crowds and Power, is as “a claw to grasp whole branches” while climbing; both hands partner in “grasping” and “letting go.” This is like trade, he argues: “one hand tenaciously holds on to the object with which it seeks to tempt the stranger” while the other “is stretched out in demand.” Trading, then, offers “profound and universal pleasure” as “a translation into nonphysical terms of one of the oldest movement patterns.”

One of the most extensive surviving archives of Old Babylonian writing consists of letters sent to Ea-nasir, an eighteenth-century-bc copper merchant from Ur. “You have offered bad ingots to my messenger,” complained one trading partner. “Who am I that you are treating me in this manner?” Another customer appears repeatedly in the archive, each time inquiring about a missing copper shipment. “Do you not know,” he wrote in his third missive, “how tired I am?”

In the eighteenth century, a cash-strapped French government began selling rente viagère, in which an investor paid an up-front sum pegged to someone’s life—sometimes the king or the pope—and received returns until death. A group of Genevan bankers diversified their portfolio in the 1770s by buying rente contracts on the lives of thirty wealthy young Genevan girls. The fund gained popularity; by 1789 a significant portion of French debt was owed on the lives of just these “thirty heads.”