When did the first human exist? And when did they start populating the earth?

There is no answer to this, as "humans" are evolved, and are still evolving. When did the first catfish appear? There is no answer.

Thanks and What did humans evolve from?

http://humanorigins.si.edu/education/introduction-human-evolution

So six million years ago?

I just want to know when did humans start populating?

six million years ago is a good estimate. No one wrote it down.

So nothing is accurate? But estimated

Let say the humans started populating six million years ago, how come there is only over 7 billion people? I mean if you calculate the population today should be in 100 trillions

You're not accounting for

~ poor hygiene and understanding of germs
~ diseases and illnesses
~ pandemics
~ infant mortality rates
~ wars
~ accidents

... and all sorts of other reasons for humans' deaths.

I am accounting those too and it still doesn't add up to it.

it's still no where near

"modern" humans (us) arrived on the scene about 30 - 50 thousand years ago

around the end of the last ice age

there was limited interbreeding with the Neanderthals -- who were on the way out

there have NOT been people like us around for 6 million years

plug a different time into your calculation

Apparently you didn't read the site that bobpursley posted. Our human ancestors appeared about 6 million years ago.

the key here is "modern" humans (like us)

Isaiah is using 6 million in some population growth scenario and getting weird results
he's not interested in the start of the genus , he want to count people