weights and measures: Africa counting emerged because people had to weigh and measure Systems of mathematics provided people with common units of measurement, which could then be divided by common factors to produce smaller units or multiplied by common factors to produce larger units In this way, for example, the modern yard consists of feet, a foot consists of 12 inches, and so on Trade and exchange, too, required systems of weights and measurements If one country was trading wine for lumber, the merchants making the trade needed some way of measuring and agreeing on the volume of wine and lumber to determine prices The result was that systems of weights and measures were often imported and exported along with the goods they measured When the value of commodities came to be measured by money as a medium of exchange, it was vitally important for merchants to be able to weigh accurately coins and the gold and silver with which they were made AFRICA BY MICHAEL J O’NEAL Historians, archaeologists, and scientists use the term metrology to refer to the study of weights and measures, particularly as it applies to the premodern world, when weights and measures were not universally standardized Metrology, though, does more than simply seek to discover which specific units of measurement and weight the ancients used It also seeks to understand the underlying system that gave rise to weights and measurements Thus, the types of questions metrologists ask include: Were units of weight and measure arbitrary values, or were they based on some phenomenon from the natural world? How was one unit divisible into, or a multiple of, some other unit? How did ancient traders and others convert units of weight and measure into those of another people in the process of striking trading bargains? To what extent were units of measure and weight standardized in a kingdom or region? Did royalty have one unit of measurement or weight and common people another? What can ancient artifacts, such as buildings and their dimensions, reveal about systems of measurement? What was the relationship between systems of weights and measurements and mathematical, astronomical, calendrical, timekeeping, and other systems? The grandest question of all, however, is this: Did ancient systems of measuring weight, volume, distance, and the like derive from some common system that was spread throughout much of the ancient world, including parts of Africa? Many metrologists have devoted careers to finding common units of measurement that underlay the construction of artifacts as widely dispersed as the pyramids of Egypt and Stonehenge in England Some claim to have found commonalities, in various cases based on common astronomical observations from which the circumference of the earth at the equator may have been deduced Many of these conclusions, though, are highly speculative 1173 Few of these questions can be answered with any certainty about ancient Africa (other than Egypt) The absence of written records inhibits the work of metrologists who focus on the continent Further casting a veil over the subject is the fact that ancient African kingdoms, cities, and settlements rose and fell with great frequency People migrated throughout the continent, often in response to climatic change, taking with them their culture and knowledge systems and mingling them with the culture and knowledge they found in their new homes Warfare wiped out some African cultures—the kingdom of Kush, for example, fell to the kingdom of Axum, and the Carthaginian kingdom was totally destroyed by the Romans—contributing to the lack of records and artifacts At the same time, more powerful empires, including that of Egypt and later the Roman Empire, would have imposed their systems on tributary people in Africa; in particular, Egyptian units of measurement probably became the norm throughout much of northern Africa Later, Roman units probably became accepted These units were derived from Greek measurements, which the Greeks in turn had adopted from numerous cultures in the Near East, who in turn had adopted them from such places as Mesopotamia Furthermore, because much of Africa, particularly the northern stretches of the continent (as opposed to the nomadic southern portions), engaged in trade and other activities with a large set of other civilizations who routinely passed through the region known as the Sahel, a strip of settlements that spanned the continent below the Sahara Desert, the notion of any kind of standardized, “African” system of weights and measures remains elusive Despite these problems, historians and archaeologists can make some inferences It is highly likely that ancient Africans, in common with numerous other ancient peoples, measured distances using, at least as a starting point, the human body Thus, for example, hand spans, knuckles, arm length, feet, and forearms were probably used as units of distance Indeed, the cubit is a unit of measurement used throughout the entire region of Africa, Rome, the Near East, and eventually Europe The cubit was a unit of length that originally measured the distance from a man’s elbow to the tip of his longest finger, although eventually the cubit settled into a measurement of about 18 inches Such a unit of measurement, of course, would necessarily be imprecise, since the unit would be longer for a taller man than for a shorter one In the case of royalty, the “royal cubit”—a slightly larger unit of measure—would have been longer than that used by others, in an effort to suggest that royals were larger than common mortals Similarly, it is little accident that in the modern world, the foot continues to be a common unit of measurement The foot was used throughout the ancient world to measure a unit of distance that was, in fact, just about a foot, or 12 modern inches The knuckle of the thumb could be used to measure relatively small distances, and thus corresponded to a modern inch