At the last glacial maximum, sea level stood low enough that Tasmania formed part of the Australian landmass. Post-glacial melting flooded the connection around twelve thousand years ago, isolating the island's plants and animals. The emu population left behind became distinct enough in size and plumage detail to be named as a subspecies, showing the reduction typical of island populations of large birds.
European settlement of Tasmania began in 1803, and the emu was hunted for meat and killed as a competitor for grazing land while its lowland habitat was converted to farms. Records thin out through the 1830s and 1840s, and the bird is generally taken to have disappeared in the wild by around 1850, with a few captive individuals surviving slightly longer.
How distinct it really was is still argued. Museum material is scarce, no complete mounted specimen of confirmed Tasmanian origin is universally accepted, and some studies of the surviving bones and DNA find the differences from mainland emus modest. Two other insular emu forms on King and Kangaroo Islands were also lost in the same era.