Meanings of sheer guesswork in English

Xenobiologists and xenopsychologists can't accept the idea that a starpilot scooped them by sheer guesswork.

Predicting what happens next in the five-year saga that has shaken the eurozone to its foundations is sheer guesswork.

He had to make allowance for it by sheer guesswork, unless he was prepared to slow down or even to alight.

In writing up fossils like Brontomerus, we have to be absolutely clear about the distinctions between data, reasonable inference, informed speculation, and sheer guesswork.