The following goes through and comes out the end unchanged:
"We are all Human beings. The Earth is our home. It is our World. We have to learn to share, before it's too late."
"We are all Human beings. The Earth is our home. It is our World. We have to learn to share, before it's too late."
We have to learn to share, before it's too late.
Could be either:
We have to learn to share before it's too late.
or
We have to learn to share, before, it's too late.
with the latter being 'it was' and the former being 'it is.'
Interesting that it manages to get all the way back to the original sentence in any case.