Английский - Проверьте часть рассказа на грамматику (можете поправить на свой вариант)

We all live on one planet. Our planet is our home. Our ancestors lived here many years ago and our children will live here in the future. But let’s stop for one moment, an important moment, and think about our future on this planet and the future of our descendants too.
For centuries human beings have been creating things on this planet, things that have changed our world. Some might say that this is really good. Maybe it is because they didn't live here many years ago when our planet was more beautiful and green than it is now. Maybe It is because they were born in big cities with dirty/polluted air and concrete roads. Mankind has only existed on this planet for a short time. We are consumers.

Последние два предложения как-то нелогичны, впечатление такое, что многое пропущено.

Our ancestors have lived here....and our children will live here....
For a long time the human beings had made many things on this planet and they changed our world...
Maybe it's because....(в обеих случаях).... with polluted air and grey roads. People (the human beings) have lived here not for a long time.

We all live on our planet. Our planet is our home. Our ancestors were living here many years ago and our children will be living here in the future. But let’s stop on one moment, it will be the important moment - it is our future on this planet and the future of our descendants too.
For a long time the human had made many things on this planet and he had changed our world. Somebody can say that it is really good. Maybe, but they didn't live here many years ago when our planet was more beautiful and green than it is now. Maybe, they were born in big cities with air pollution and gray roads. The human doesn't live here so long time. We are consumers.