@ gero ......and not even any mention of pandemics
There is a fairly reasonable chance that the next pandemic will do a massive job on our numbers globally... even so, that wont end our species.
It will be climate of environmental factors... or nuclear war.
And since most people have no idea how to survive outside the comforts of our civilization, that will finish off a lot people as well.
With luck, people who still live outside our global civilisation will survive IF their environment somehow isn't destroyed in the process.
It is possible, in regards to the when, that the last person to exist is alive today.