The oldest known dice are roughly 5,000 years old, found in a backgammon set excavated from the Burnt City in southeastern Iran. They were made from bone, and they were probably not very fair. Fairness in a die depends on symmetry — equal weight distribution, identical face geometry, sharp edges, and consistent material density — and achieving all of that in carved bone with Bronze Age tools was more aspiration than reality. But our ancestors didn't need perfection. They needed a way to introduce chance into games and divination rituals, and a roughly cubical piece of bone that landed somewhat unpredictably was good enough.
For most of human history, dice were cubes. The six-sided die is the natural shape for randomization from a solid material: it's easy to carve, it sits flat on a surface, and each face has an equal area. The Romans standardized the convention of opposite faces summing to seven (1 opposite 6, 2 opposite 5, 3 opposite 4), a layout that persists on virtually every modern d6. But the twentieth century brought tabletop role-playing games, and tabletop role-playing games brought an appetite for probability distributions that a cube couldn't provide. You can't roll a d6 and get a uniform result between 1 and 20. So the hobby adopted the full family of Platonic solids — the d4 (tetrahedron), d8 (octahedron), d12 (dodecahedron), and d20 (icosahedron) — plus the d10, which is technically not a Platonic solid but a pentagonal trapezohedron, a shape that exists primarily because game designers needed a way to generate percentile results.
The question of whether a given die is fair is more subtle than it appears. For a die to produce each outcome with truly equal probability, every face must have the same relationship to the center of mass. In a perfect Platonic solid made from a uniform material, this is guaranteed by geometry. In a mass-produced plastic die, it's guaranteed by nothing. Manufacturing imperfections — air bubbles in the resin, uneven paint fill in the numbered pits, slight asymmetries from the injection mold — all introduce bias. The numbered pits themselves are a source of asymmetry: the face with a single shallow pit (the 1) has slightly more material, and therefore slightly more weight, than the face with six deeper pits (the 6). On a well-made casino die, this is corrected by filling the pits with paint of the same density as the surrounding material and maintaining tolerances of fractions of a millimeter. On a four-dollar set from a game shop, it isn't.
Several hobbyists and researchers have tested this empirically. One well-known experiment involved rolling a d20 thousands of times and recording the results. The distribution was not uniform. Certain faces came up significantly more often than others, consistent with the die having a slight center-of-mass offset. Other tests using salt water flotation (placing the die in saturated salt water and observing which face consistently rotates to the top) have shown that many commercial dice have detectable bias. Whether this bias is large enough to materially affect gameplay is debatable — over the course of a four-hour D&D session, a 1-2% deviation from uniform probably doesn't swing outcomes in a noticeable way — but it's real, and for anyone who cares about the integrity of their rolls, it's worth knowing about.
This is part of why virtual dice rollers have a legitimate place even among tabletop purists who love the tactile ritual of a physical roll. A digital dice roller using cryptographically secure randomization produces a mathematically uniform distribution with zero bias, every time, instantly. It doesn't replace the experience of rolling physical dice across a table — that clatter is half the fun of the hobby — but for situations where fairness is the priority over atmosphere, it's the better tool. High-stakes competitive play, remote sessions over video call, quick rolls during theater-of-the-mind combat — these are all contexts where a reliable digital roll serves the game better than a cheap acrylic icosahedron with an air bubble near the 14.
Dice are one of humanity's oldest technologies, and the fact that we're still using them, arguing about them, and trying to make them fairer after five millennia says something about how fundamental the need for randomness is. We want chance in our games and decisions, but we want it to be honest. That tension hasn't changed since the Burnt City.