The most recent episode of Neil deGrasse Tyson’s show Cosmos aired on Sunday. This episode, called “The Immortals” dealt with questions of life and death, including the origin of life, so a friend of mine asked me to review it. As I ponder the tone and content, I hope to post more about the deeper questions of life. For now, I can only make a few brief comments.
Overall, I thought the show was provocative and interesting, tying together history, biology, astronomy, and cosmology in interesting ways. As usual, the show was intent on sharing some of the showier, yet not agreed upon models produced in science, instead of talking about the concrete data and controversies. This is, perhaps appropriate for a show aimed at intriguing, rather than informing people. With luck it will inspire you and many others to learn more. Along those lines, here are some of my thoughts as I watched.
1) Tyson suggests that the story of Noah in the Bible is a modern incarnation of the story of Gilgamesh. Scholars have noted remarkable similarities between the tale of Noah in Genesis and the tale of Utnapishtim in the Epic of Gilgamesh, an ancient epic poem that predates the Bible (and almost every other piece of literature we know of). The Epic is nearly 4000 years old and matches many points of the flood narrative in detail. I consider the story an amazing piece of history. Some have expressed concern that the story of Noah is simply a copy of an older tale. The danger in that sentence lies in the word “simply.” Christians and Jews have known for at least 100 years that portions of the Bible closely match earlier, non-Biblical stories. One possibility is that the stories are true and were available not just to Hebrews, but other people as well. Another possibility is that Hebrew writers, with God’s help, recognized the truth in foreign tales and included them in Hebrew scriptures. A third possibility, the one I favor, is that the authors of the Old Testament, again with God’s help, re-purposed the story. Many of you will be familiar with both The Wizard of Oz and the more recent Wicked. The two stories follow the same events point for point, but bring the reader to radically different perspectives. My own experience of Utnapishtim and Noah is that they send different messages about life, death, and divinity. Thus, I see the two as very different, but I’d encourage you to read them for yourself. (In case you’re worried, knowing about Utnapishtim need in no way diminish the value of Noah or of scripture. I’m fully convinced God can work with and through other peoples without caring less about Israel.)
2) Tyson shamefully glossed over the origin of life. This has become popular among biologists and I really don’t know why. The general story is that molecules somehow developed the ability to reproduce themselves, starting evolution; natural selection did the rest. It’s a plausible story and consistent with the facts, but that’s not to say we strong evidence for it. Based on cosmology, we presume that there was a time before life. Before stars and planets, when the universe was an incredibly dense, hot maelstrom of plasma, the environment was such that we cannot imagine life as we know it. There wasn’t life then; there is life now; therefore life must have arisen from non-life. This isn’t an observation, but more of a philosophical conviction that “life from non-life” makes more sense that “life not as we know it.” Observation still suggests that life simply cannot arise from non-life. For the record, I agree with the philosophical conviction, but it’s important for me to state that that is what it is. Alas, we have no good “definition” of life making it impossible to have scientific consensus on the issue.
Perhaps the most interesting aspect of life from a scientific viewpoint is that living things are capable of evolution by natural selection – they come in populations that change through time. We want to know how that process came about, because once it did, surprising levels of complexity and functionality arise. Getting from an amoeba to a reptile would seem to take a very long time (hundreds of millions of years), but we have a pretty good theory for how it could have happened (change and speciation through natural selection a la Charles Darwin). Getting from nothing to an amoeba remains a mystery.
The problem is that you need just the right amount of accuracy in making copies of yourself. Crystals copy themselves too perfectly to allow natural selection. Fire propagates to haphazardly. Life gets it just right; enough offspring survive and survive in such diversity that the fitter offspring can reproduce and lead the population in a new direction. So far, no one has been able to figure out how that first Darwinian replicator arose. In the late 20th century, it was popular to assume that the first replicator was an ribonucleic acid (RNA), because RNA molecules can act as chemical catalysts in their own reproduction. We are now less certain as we have not been able to make just the right kind of RNA. After decades of trying, Gerald Joyce and others have discovered some fascinating things, but still no origin of life. The first replicator is a hard problem and we don’t even know if we’re asking the right questions. Life could have started as a metabolic network, or a vesicle, or information. (Check out my book Life in Space for more info.)
3) Tyson glossed over the question of organisms surviving in space. While we have made some fascinating discoveries about the durability of organisms, I am not (yet) convinced that it would be possible to successfully transit from one planet to another. First, the organism would have to survive the journey and, second, the organism would have to land in an environment sufficiently similar to the one it came from on it’s home planet. As with origin of life research, I have hope that such a mechanism could be discovered. I think it’s worth investigating. As with the origin of life, I’m not reporting it as established science just yet. Tyson didn’t give you details, so I will. The gram-negative bacterium Streptococcus mitis survived a trip to the moon and back. Several organisms have survived exposure in low Earth orbit, the most complex of which are microscopic animals called Tardigrades or water bears. Another great candidate for interstellar travel is Tersicoccus phoenicis, so far only found in environments we have tried to sterilize. Wikipedia has a list of organisms that have survived in space. It’s wonderfully long.
As to 8 million year old organisms, Paul Falkowski, Kay Bidle and colleagues found activity in 8 million year old ice thawed in sterile conditions, but were unable to culture anything. I am unaware of the current state of this research.
4) We have good reasons to expect bacteria and other organisms would evolve an ability to survive in space. Deinococcus radiodurans and other radiation tolerant bacteria apparently evolved in response to dehydration. It turns out the same mechanisms necessary for surviving with very little water serve to protect you from radiation. You need durable, repairable DNA and other molecules.
5) Tyson refers to impact sterilization, the idea that meteorite bombardment on the early Earth (>3.9 billion years ago) would be so heavy that there would be regular sterilization events. The force of impact from some impacts was great enough to vaporize the oceans and kill anything living on the surface. This theory has become less popular in the last decade as planetary scientists looked more closely at the ridiculous amount of energy necessary for such a feat. I believe this is still an active area of research, but opinion is turning away from the idea that one impact could have sterilized the planet. Impacts in “Late Heavy Bombardment” period would have made Earth a tough place to live but, since we have evidence of life from 3.6 to 3.9 billion years ago, it is at least plausible that life existed during LHB.
6) Finally, I will note Tyson’s unbridled optimism that science will give us the power to deflect asteroids, lance super-volcanoes, and travel to other stars. I have hopes, but I also think it dangerous to see science as an all pervasive answer to our problems. Even if science could provide all knowledge (which I don’t think it can), and even if knowledge could solve all problems (which I know it cannot), it still might not provide solutions in time. I’ll be putting my faith in science, but also philosophy, theology, and good old fashioned caring.