An Indo-European Creation Myth?

It would qualify as the world's oldest-known creation myth,
because it would date from when the speakers of ancestral
Indo-European started to go their separate ways, which was
about 4000 BCE or thereabouts.

From the primordial chaos emerged *mannus ("Man") and *
yemos ("Twin") (sometimes > *yemonos). Man killed Twin and
dismembered him, creating the familar Universe from Twin's
body parts.

This survives in various forms, most notably the story of Ymir,
who gets killed and dismembered, with his body parts
becoming the familiar Universe. A less clear survival is in the
form of the story of Romulus and Remus, which is essentially
the creation myth of the city of Rome. Romulus ("a Roman") kills
his twin brother Remus (< *iemus, with alliteration), whose
presence seems unmotivated. There is a tradition about
Romulus eventually getting killed and dismembered by the
Roman Senate; the dismembering would somehow have been
transferred from Remus to Romulus.

-- Loren Petrich