Plenty of science fiction stories involves humans who have become immortal or whose lifespans are so long that they seem immortal. But unlike fictional future societies like Ian Banks' "Culture", where genetic engineering and advances in medicine have allowed humans nearly unlimited lifespans, the living in Miracle Day live despite suffering unhealed grievous injuries and unchecked diseases. People suffer and yet they live on.
The crude global death rate is about 8.4 deaths per 1000 in the population in 2009. Given a total world population of 6.7 billion that is about 56 million deaths per year or 154 thousand deaths per day. Without death to intervene Earth's human population grows unchecked. And many of those who survive are sick and hurt and unable to care for themselves. The results are horrifying, as are the measures deemed necessary to stave off the possibility of overpopulation.
While Torchwood often seems closer to fantasy than SF, there is, in fact some science behind the fiction. As show writer Jane Esperson described it:
The amazing writer Bryan Fuller told the Torchwood writers room about the species of immortal jellyfish that Christina Colasanto talks about here [in Episode 8] — and we obsessed over it in the room. The idea that some creature here on Earth works in this way is amazing. That line, "Consider the jellyfish..." started echoing around the room, and here it is, in the episode. For a while, we joked that that should be the title of this episode.The jellyfish Turritopsis nutricula is essentially immortal, as long as it doesn't get eaten or succumb to disease.
As the jellyfish matures it takes on several different physical forms. Fertilized eggs develop into planula larvae which settle on the sea floor. The larvae develop into colonies of polyps which bud off free-swimming medusa jellyfish. When those jellyfish reach sexual maturity after a few weeks they spawn to create a new generation of jellies.
All animals are able to reproduce and create new offspring, that's not what makes Turritopsis special. Turritopsis adults are actually able to revert back to the juvenile polyp form through a process known as transdifferentiation. This process renders the tiny jellyfish biologically immortal. See the video above for an overview.
But besides the concept of immortality that nifty bit of jellyfish biology isn't referenced in Miracle Day at all. I suppose having Gwen Cooper, Captain Jack, and Rex Matheson revert to their juvenile forms in a sort of Torchwood babies episode wouldn't work very well. At the least it would preclude having the usual sex scenes (at least I hope it would).
Miracle Day unfortunately doesn't completely live up to its original premise. The plot is slow to develop, the flashbacks to Jack's early 20th century relationships are long, and the world-wide conspiracy that sets the Miracle in motion I found more confusing than convincing. I think it could be much better if the 10 episodes were trimmed in half.
Torchwood: Miracle Day will be available on DVD in the US on April 3rd. You can preorder a copy at Amazon.com or at Barnes&Noble.