As far as we know, around 4,500 million years ago, this rock that we live on coalesced from the dust and debris left over from the formation of our sun.
Without airplanes, pizza delivery, or the Internet, things moved more slowly across the early earth than they do today.
For example, from isolated puddles of water, the oceans formed over the course of 400 to 800 million years.
That's how long it would take for your hair to grow around the earth, twice.
In that same time, bacterial life did spread across the watery globe.
Higher plants and animals, on the other hand, took much longer to develop and disperse.
But we're going to skip those 3 billion years (during which your hair would have grown to the moon) and talk about us, Homo sapiens.
We were much faster than our own hair, which would have grown a meager 27 km in the 180,000 years we took to cross Africa and reach all the unfrozen continents.
In many of these places, we were able to develop useful practices like agriculture, but because we were scattered across the globe, the best ideas and tastiest regional foods could only gain ground through trade or human migration.
Wheat, for example, was domesticated around 8500 BC to make porridge.
