Dice games: from knucklebones to the craps table

IBones with four faces

The first dice were the ankle bones of sheep and goats, the astragali. Thrown on a flat surface, an astragalus can only come to rest on one of its four long sides, and players gave those sides fixed values. The Greeks and Romans counted them as 1, 3, 4 and 6. A throw used four bones at once, and the best result, four different sides, was called the Venus. Four ones, the worst, was the dog.

Bones are not fair. The two broad sides land far more often than the two narrow ones, so the chances were uneven from the start, and every player knew which faces came up most. That uneven chance is why the Venus was rare enough to be prized.

IIThe cube settles in

Cubic dice appear in the ancient Near East and the Indus valley, and by Roman times the six-sided die, the tessera, was ordinary. Romans played with both: tali for the old four-sided throws, tesserae for games that needed six values. Many surviving Roman dice already follow the rule that opposite faces add up to seven, the same layout on every die sold today.

Not every Roman die was honest. Excavations have turned up dice with uneven faces or weights inside, which tells us that cheating is as old as the game.

IIIHazard: rules on top of chance

Medieval Europe turned two dice into a game with a structure. In Hazard, the caster first names a number from 5 to 9, the main, and then throws. Depending on the main, some first throws win at once, some lose at once, and anything else becomes the chance, which the caster must throw again before the main comes up. The game was common enough in English taverns by the 14th century for Chaucer to warn against it.

IVCraps strips it down

When Hazard reached New Orleans around 1800, the rules lost their main. The new game fixed the numbers instead: 7 or 11 wins on the first throw, 2, 3 or 12 loses, and anything else becomes the point. The name came from crabs, the old word for the losing low throws. In the early 20th century bank craps let the house take every bet, and the layout casinos still use was born.

VThe Eastern line: three dice under a lid

In southern China a different game grew around three dice shaken in a covered bowl. Players bet on the total being big or small, on single numbers and on triples. Under the name Sic Bo, which means precious dice, it travelled with Chinese communities to Macau and later onto casino floors everywhere, where its lit-up table is a cousin of the craps layout rather than a descendant.

VIWhy seven matters

Two six-sided dice can land in 36 equally likely ways. Six of them make a total of 7, more than any other number, so 7 comes up once every six throws on average. A 2 or a 12 can only happen one way each, once in 36 throws. Almost every rule in Hazard and craps is built around that one fact, and almost every house edge in the casino comes from paying a little less than those odds deserve.