Our knowledge of genetic inheritance expanded exponentially with the completion of the Human Genome Project, an international, thirteen-year collaboration that unraveled the human genetic code by sequencing our cellular DNA. Teasing apart our DNA code was a process of inner discovery and one of our greatest feats of exploration - right up there with the voyages of Magellan.
The very same process of genetic decoding has been applied to other species, like the recently extinct wooly mammoth and the passenger pigeon, both of which some scientists now believe they can bring back from the dead.
A recent article in The Washington Post laid out the genetic basis for “The Return of the Passenger Pigeon” - arguably once the most numerous terrestrial vertebrate in North America, if not the entire post-Ice Age world. The article was picked up by other media and widely distributed.
It proposed for geneticists to reconstruct the passenger pigeon’s DNA sequence from dried museum specimens, which is all that’s left of the billions of wild pigeons that once inhabited the deciduous forests of eastern North America. The last one died in 1914 at the Cincinnati Zoo. Any missing pieces of the genome would come from a close relative, the banded-tailed pigeon of the desert Southwest.
Scientists would add these newly created chromosomes to stem cells that naturally transform into germ cells, which in turn are the antecedent of eggs and sperm. The germ cells would be injected into very early band-tailed pigeon embryos - which would develop and hatch as band-tailed chicks. But, and this is a fascinating but, when the band-tailed pigeon chicks matured, their own offspring would be genetically similar to passenger pigeons.
But I think an ecological component is missing from this Jurassic Park-like process. Passenger pigeons were a nomadic biologic storm that followed the production of mast - that’s the nuts of beech, oak, and other forest trees. And they didn’t just flock; they swarmed.
The miles they covered described the flocks. One over Kentucky was a mile wide and 240 miles long, with multiple layers, like a bird sandwich. Another in Ontario passed unbroken for 8 hours and was estimated to hold nearly four billion birds. Their staggering abundance eclipsed the sun. The sound of these big flocks was compared to the coming of thunder. Colonies were called “cities.” One moderate breeding colony in Michigan extended for 28 miles and was three or four miles wide. A single hemlock tree in Wisconsin supported 317 nests.
Astronomical numbers were necessary to stimulate breeding, overwhelm predators, and locate abundant but unevenly distributed food sources. So if astronomical numbers were necessary to support the passenger pigeon then, it’s hard to see how our much-changed landscape of today could possible resurrect enough of them to remain viable now - no matter how carefully we reconstruct the genetic code.
