One plus one equals two. There are 60 seconds in one minute. Sixty minutes equals one hour. There are 24 hours in one day. One year consists of 365 days. These are all basic facts that we know by heart, but they highlight the importance of one thing: numbers.

Can you imagine a world without numbers? It’s safe to say that society as we know it today would never have developed without numbers. The scientific and technological advances upon which society is built depend upon mathematics, which in turn depends upon numbers.

Despite their importance, the development of numbers remains mostly a mystery. That’s because the first ancient prehistoric people who likely developed simple methods of counting didn’t leave any records behind to explain themselves.

Common sense and ancient evidence points to the idea that numbers and counting began with the number one. Although they probably didn’t call it “one,” prehistoric people likely counted by ones and kept track by carving lines on a bone.

Evidence that this occurred as long as 20,000 years ago can be found on an ancient artifact known as the Ishango Bone. Found in Africa in 1960, the Ishango Bone (a fibula of a baboon) features a series of lines that look like what we would call “tally marks” today.

Keeping track of small numbers of items with tally marks was sufficient for individuals and small groups. As societies began to form and grow, however, trade became more complex, requiring the development of numbers to perform simple mathematical calculations.

Historians believe numbers and counting expanded beyond one around 4,000 B.C. in Sumeria, which was located in southern Mesopotamia in what is now southern Iraq. One of the first civilizations to feature cities that were centers of trade, the people of Sumeria needed new methods of counting and record-keeping.

While new numbers and counting systems were being developed in Sumeria, so were the basics of arithmetic and writing. Keeping track of goods being traded required writing and basic addition and subtraction in addition to an expanded number and counting system.

All of these foundational ideas developed simultaneously as cities grew and trade flourished. Some historians believe that some of these same ideas developed independently in other areas of the world, too.

For example, the Arabic numeral system we’re all familiar with today is usually credited to two mathematicians from ancient India: Brahmagupta from the 6^{th} century B.C. and Aryabhat from the 5^{th} century B.C.

Eventually, numbers were necessary for more than simply counting things. We can thank the ancient Egyptians for making the leap from using numbers to count to using them to measure things. Historians believe their use of numbers for measurement allowed the ancient Egyptians to build the pyramids and lay the foundation for advanced mathematics concepts, such as geometry.