Since the fourth millennium BCE, when urban civilizations first appeared in ancient Mesopotamia, humans have strived to achieve proper dental hygiene. Yet the nylon-bristled toothbrush we use today didn’t come along until the 1930s. For the thousands of years in between, people relied on rudimentary tools that evolved with scientific knowledge and technological advancements over time. Some of the earliest toothbrush predecessors date as far back as 3500 BCE. Here’s a look at how people kept their teeth clean before the modern toothbrush.AdvertisementChew Sticks and ToothpicksSometime around the year 3500 BCE, the ancient Babylonians (located near modern-day Iraq) created a...