Very little happened in those 300k years which is why we survived so long. There are a lot more human created existential threats now than 500years ago such as

Very little happened in those 300k years which is why we survived so long. There are a lot more human created existential threats now than 500years ago such as climate change and nuclear weapons. If shit goes wrong enough just once the next 400M years we have a nuclear war on our hands. Even extremely low probabilities are likely to occur over such long time ranges. Add to that that bootstrapping a new complex society like we have now is going to be a lot harder without easily accessible fossil fuels and it seems highly unlikely that we will survive in such a way that we could save life on earth from some future crisis.