Despite the huge numbers, humans actually occupy very little space in terms of their physical bodies, in relation to the size of the earth.
You could actually pack everyone standing inside a 27 km x 27 km square. All 7.3 billion of them.
https://waitbutwhy.com/2015/03/7-3-billion-people-one-building.htmlNow, secondly, your maths assumes the human population was larger in the past than it is now in the present, with an unique ancestry to every single living person. In fact the human population is calculated to be much smaller in the past. For example the population of the UK in 1950 was about 50 million. In 1500 it is calculated to have been about 3 million.
So those 50 million people, for the most part, are directly descended from 3 million people, meaning that if you back far enough through the generations you get a lot of inbreeding, although at a remove, such as distant cousins marrying.
What should really concern you is the fact that if you trace your ancestry back through either your paternal or maternal line then 350 million years ago your direct ancestor,, YOUR DIRECT ANCESTOR, PAL, was a FUCKING FISH!
Yeah. That's right. Go through your father's line and eventually your get to a FUCKING FISH swimming around in a Carboniferous sea.
Holy Fuck, doesn't that blow your mind? It should. I mean people get all antsy about us humans being descended from an ape-like common ancestor, but you take evolution to its logical conclusion and we were FUCKING FISH at one time. Fish that passed its sperm on to eggs which gave a new generation of fish and so on down through the vast passage of time until amphibians evolved, then reptiles and then mammals.
Sperm after sperm after sperm. It took a lot of fucking to get you here, young man.
Think about that.
