Ancient people counted to 12 using their finger joints.

If you hold up one hand and look at your four fingers, you will see each finger has three parts. Use your thumb to touch each part. You can easily count up to 12 on just one hand. This is called base-12 counting. Ancient people in Sumer (modern-day Iraq) used this trick. It was incredibly useful because 12 is a very friendly number for math. You can easily split 12 into halves, thirds, and quarters. Try doing that with 10!