Two years after the death of the Icelandic film composer Jóhann Jóhannsson, his only movie as director has become available in the UK on streaming platforms. It is a 70-minute cine-novella or essay film: a meditation on humanity’s future and what it means, or will mean, to be post-human.

The score is by Jóhannsson, working with sound artist and composer Yair Elazar Glotman, and this eerie, breathy soundtrack works well with its unearthly images. Last and First Men is inspired by the 1930 novel of the same name by British SF author William Olaf Stapledon, narrated by a figure from humanity’s final evolutionary form billions of years in the future. This voice is performed with crisp lack of affect by Tilda Swinton.

The visual images Jóhannsson finds to accompany this prose-poem are strange and disturbing sculptures that look like something built on Earth by aliens, a mix of Stonehenge and Angkor Wat. I wondered if Jóhannsson had had them designed and built. In fact, these are the brutalist Spomeniks, the socialist-era monuments in former Yugoslavia, mostly in remote windswept landscapes, built in the 1950s and 60s to commemorate the tragedy of the war and the resistance to fascism; they are truly strange in their fierce, concrete giganticism, and have a cult following.

By detaching them from their historical context, Jóhansson finds something very unsettling in these sculptures: they really do look like creations from the future, not the past. Last and First Men is an interesting if minor work, perhaps comparable to Nikolaus Geyrhalter’s Homo Sapiens or Michael Madsen’s Into Eternity.

• Last and First Men is available on BFI Player from 30 July.