Elephant bird eggs measure up to about thirty-four centimetres along the long axis with a circumference exceeding a metre, and internal volumes are usually given as around eight to nine litres. That exceeds the largest known dinosaur eggs, which are constrained by the need for gas exchange through the shell. Fragments are common enough in Madagascan dune deposits that whole eggs are occasionally reassembled or found intact.
The closest living relative is not the ostrich or the emu but the kiwi of New Zealand, a bird weighing a few kilograms. DNA work established that pairing, which means the two lineages diverged before the elephant bird's massive size evolved, and it undermines the old assumption that ratite distribution simply tracked the break-up of Gondwana.
Humans reached Madagascar well before the birds disappeared. Cut marks on elephant bird bones have been dated far earlier than the archaeological record of settlement implies, suggesting a long overlap. The birds are generally thought to have died out within the last thousand years, with egg harvesting a likely pressure on a slow-breeding animal.