Was it possible Tribulation Force members were not the only intelligent life-forms in this alien universe?

"As we will be the only life-forms present, the depletion should not reach critical levels for another forty-nine point six five hours."

The only life-forms they had discovered were long, ovoid insects with too many short legs that burrowed into the sand.

Humanoids were not the only common life-form that appeared to have been seeded through the galaxy in antiquity.

The only large indigenous life-forms he knew of were the sandworms.

As the only noncorporeal life-form aboard, and therefore the only one able to survive the transition, I was chosen for the mission.

One of the discoveries Man had made when settling the galaxy was that he represented the only highly-developed, intelligent life-form.

One of the things they told me was that, in their galaxy, human beings were the only intelligent life-form.

He and Retief were the only macroscopic life-forms present.

"The planet's still in its Devonian period; the only native life-forms on land are insects."