PASSENGER pigeons once formed flocks so vast that they would darken the sky for days as they flew past. In the 19th century there were some 5 billion individual birds in North America, more than any other wild bird species in the world.
US environmentalist Stewart Brand has an ambitious plan to “de-extinctify” passenger pigeons – bring them back to life by identifying and then splicing the relevant genes into a relative, the band-tailed pigeon. The technical challenges are formidable, and even if it works, the species might still not be viable in the wild. Nor is it agreed that reintroducing extinct animals into the modern world is a good idea. Brand waves this objection away, saying that the pigeon’s old habitat is intact, adding: “In the rare case of unwelcome ecological disruption, we know the vulnerabilities of the formerly extinct animals, so we know exactly how to reduce their numbers or eliminate them again.”