Because in this historical era both of humanity's possible futures exist at the same time.

"But then you're saying that their future still exists," Hunahpu protested.

The future did not exist; there was only the timeless present.

Time is presented as 'fluid', where the past, present and future can all exist in the same timeframe.

Everything was behind them and the future didn't exist.

The past and, more important, the future do not exist.

If the future did not exist now, how could we journey toward it?

These myriad futures no longer existed in the same form.

The future- all that is still to come- does not exist yet for us.

No future existed for him in such a sleepy backwater.