Every person living today looks extraordinarily impactful when you consider that 1000 years from now there will probably either be a million+ times as many humans or we’ll all be extinct.
This statement looks equally applicable to the year 1900, for example.
We have more reasons now (nuclear weapons, unfriendly AI, grey goo, the great filter) to think we will someday destroy ourselves than people in 1900 did.
A blog post by Athrelon on More Right.