Our closest relatives are the Great Apes, who we resemble in many ways. But they are still limited to the tropical forests – and we have spread everywhere, except Antarctica.
How did this happen?
We grew a larger brain, and one that is better organized. It is now the most complex structure in the universe – and we are only beginning to understand how it works. And how it doesn’t work, sometimes.
This large brain enabled our most important advantage – language. This, coupled with our social behavior, made us very successful. We were smart, millions of years ago.
And the large predators, that would have made a meal of us – learned to hunt easier prey. We were always in groups, and always on the lookout for danger. If one spotted danger, we all ran off, at top speed.
And we could run – half our body length consists of our long, powerful legs.
Our upright posture placed our eyes, with their color vision, and depth perception, up in the air, where we could see further.
We had no body hair – and could easily dissipate the heat caused by running. And we had sweat glands in our skin, that could cool us off even more. We could easily outrun any other animal. And by banding together, could kill any other animal we wanted to.
We developed frontal sexual intercourse, that no other animal has. Males developed a large penis, and females a clitorus – that made sex very pleasurable, so we did it a lot. And this produced more people – that gave is the incentive to spread out, and occupy more territory.
We could eat nearly anything, and it didn’t take us long to find new sources of food in our new territories. Life was easy then, and we only had to spend four hours a day looking for food. The rest of the time we could socialize – and we developed many ways of doing this.
We discovered how to use fire – that no other animal came close to using. We could now cook our food, which made the food we had more nutritious – and made other sources of food available. No doubt we learned to flavor our food also. We also made containers to cook our food in – and to carry our belongings in.
All this happened when we were hunter-gatherers, living in small bands of less than a hundred people each – speaking hundreds of different languages.
We knew about our neighboring tribes – and intermarried with them. Warfare in some tribes was common – but generally we were peaceful, because this was easier. We soon occupied all of Africa (a huge continent in itself) – still as a minor species, thinly spread out. But we were there.
We moved north, into Eurasia, a huge landmass – and soon occupied all of it – including the Arctic! Then across the Bering Straits into the Western Hemisphere, and occupied all of it!
We were the most successful species in the world – and we had yet to discover Agriculture and Civilization!