Starting at the beginning is a tricky concept because, if you think about it, there is nothing more controversial. Every group has its own theories; the Big Bang, God, the world has just been a giant turtle this whole time...
So I think it's hard, almost impossible, to start at the beginning. So you, person reading, fill in the blanks with however you think the world started. Because really, as sentient beings, we can choose our universes. And they started however we believe they started.
Likewise, I will skip the creation/evolution of life, and then humanity. Let's just move on, straight to People.
When people became people (however you believe that went down) we became hunter-gatherers. This was exactly what it sounds like. Food was hunted with a stick and picked of bushes. I am told this was actually not a bad way to live.
We started out in Africa, then spread out to various parts of the world. During this process, evolution kicked in again. It turns out that different areas get different amounts of sunlight. Too little sunlight means Vitamin D deficiency; too much means sunburn. So the humans that went to the continents now known as Europe, Asia, Australia, and the Americas started producing different amounts of sun-blocking pigment in their skin than those who had remained in Africa, which started causing a lot of trouble later.
Then, some geniuses on various continents figured out that if you put the seeds in the ground, they would grow. And then you had a steady supply of food, you had free time. You could trade with other, less clever tribes (until they discovered your secret). And bam! Agricultural revolution! Suddenly, civilizatins were popping up all over the place, from Cambodia to Egypt. And as those civilizations fell, new ones picked themselves up and tried again, inventing more advanced weapons and other stuff that probably had some use along the way. And over a few hundred years, civilizations got good enough at being civilizations to start fighting.
One group of civilizations in Europe eventually came out on top. They succeeded in traveling all over the world, where they conquered others. Suddenly they were connected, and the connections kept strengthening as the years passed and technology improved and one by one countries rose from the ashes of colonization, to become part of a new, world-wide civilization.