922 science: Africa harden metals Copper workers discovered that by combining copper with tin, they could create bronze, a much harder and more useful metal that defined a historical period, the Bronze Age Later scientists discovered that they could convert iron, an abundant but somewhat soft metal, into hard and durable steel by the addition of carbon The earth also provided abundant building materials The earliest structures were built with logs, reeds, and mud bricks, but in time people learned to quarry stone such as marble, limestone, and sandstone to make buildings Along the way they discovered principles for engineering these buildings and in some cases developed sophisticated mathematics to help them Early farmers became chemists and botanists by learning how to domesticate crops, cultivate them, store them, and convert them into food Chemistry, for example, enabled them to convert milk from livestock into cheese Perhaps one of the most successful plant-breeding programs in history was carried out by the ancient Mesoamericans, who domesticated maize (corn) from a wild plant Other farmers became chemists when they learned that the dung from their domesticated animals or from animals such as bats promoted crop growth or that burning the stubble from last year’s crop provided the soil with nutrients that encouraged this year’s crop This leads to fire, the second element Ancient civilizations learned to use fire not only for warmth and light but for other purposes as well Ancient miners, for example, learned to crack stone during the quarrying process by building a fire next to the rock to heat it and then dousing the rock with cold water The rapid temperature changes cracked the rock, making it easier to mine They also learned to create blast furnaces that achieved the high temperatures they needed to refine and melt metal ores Meanwhile, ancient pottery makers were making detailed scientific observations about materials that would work best for clay pots, substances that could be used as dyes for coloring the pots, and ways to fire and glaze the pots to make them more durable They also learned to make such materials as glass, using silica (sand) and fire, and to use minerals mined from the earth to make decorative objects With regard to air, ancient civilizations observed the power in a gust of wind and decided that they could put the air to work This led to at least two primary developments One was to attach sails to boats, giving these boats far greater range for purposes of exploring, trading, and conquest The other was the development of the windmill, allowing ancient farmers to pump water, irrigate land, and thresh grain in far greater amounts and with much greater efficiency Meanwhile, ancient astronomers were looking into the heavens and observing regularities in the movements of the sun, moon, and stars Water posed a particular problem for ancient civilizations, particularly those that settled near rivers The ancient Egyptians, for example, found their livelihoods tied to the Nile River and the thin strip of fertile soil along its banks The problem they faced was that the river flooded each year When the floodwaters receded, they left behind a great deal of fertile silt In ensuing dry months, however, the ground dried out, threatening the survival of the crops Out of necessity, the ancient Egyptians developed skills as hydrologists and engineers They learned to build systems of dikes, canals, dams, and storage grounds for water, which could then be released when necessary to irrigate crops In order to become engineers and build these facilities, they had to acquire knowledge in materials science, construction techniques, and the like, all of which required some ability in mathematics and measurement The modern world takes for granted an extensive base of information about the physical world and how it works Ancient civilizations had to discover this information out of nothing Without their scientific achievements it is unlikely that they would have survived in any appreciable numbers Had that happened, the world might still be a frightening place of pure mystery and magic AFRICA BY TOM STREISSGUTH Ancient Africans viewed the natural world and all that occurred within it as expressions of the unseen realm of spirits Events on earth were predetermined, the result of malevolent or benign forces that acted at whim Humans could never hope to control the fertility of the soil, the coming of the rains, the occurrence of drought or illness, or the seasonal flood of rivers and lakes They could only propitiate the spirits of the natural world, look for guidance in signs appearing on the earth and in the heavens, and seek out the environments that were best suited to their own survival They did not pursue science for its own sake or by the modern method of testing theories in controlled experiments Ancient chemistry, botany, metallurgy, physics, medicine, astronomy, and so on came in the form of practical knowledge applied to everyday needs: growing food, fighting wars, curing the sick, or relieving the pain of giving birth Further, there was no sharp line between religious and scientific practices, since a spiritual outlook governed virtually all aspects of life Generally speaking, any activities that ancient Africans carried out for the purpose of enhancing their livelihood and manipulating their environment should be considered science TOOLMAKING: THE FIRST APPLIED SCIENCE Early human beings needed to master the environment in order to find food, protect themselves from hostile strangers, and hide from dangerous animals A vital ingredient in these endeavors was the use of tools The shaping of stone implements, according to archaeologists, first occurred in Africa At Olduvai Gorge (in present-day Tanzania) primate species probably ancestral to modern humans were using sharp rocks as tools some 2.6 million years ago They may have created these rudimentary tools simply by cracking brittle stones to