Today, I was watching a great episode of the History Channel show “The Universe“, which was exploring the concept of the nature of the universe. (On the off chance you are some type of physicist or astronomer who has stumbled on to this blog, you might want to skip to the next paragraph. It’ll be less painful for you that way). The episode explored the concept of whether there are alternate universes and, if so, what is their relationship to our universe. Apparently there are several different types of possible alternative universes. The two possibilities (of the four types of multiple universe scenarios) that I vaguely understood were a) parallel universes may coexist in the same physical space as ours or b) many universes may be floating along through “hyperspace” like soap bubbles. When I was a high schooler, I was torn between two career paths: ecology and astrophysics (yes, I know. I’ve always been a woman with broad interests). Honestly, if I had known that such wild theories about the universe were being studied, I might well have made a different decision. It would also have helped if I was better at math.
What caught my attention in this episode, however, was the assumption that, in alternative universes, not only would human beings exist, but I would exist. Having chosen the ecology path, this immediately got me to thinking about evolution. “Replaying the tape of earth history” has long been a thought experiment in the study of evolution. If we reran the history of life from the beginning, what would life look like right now – 4.54 billion years after the formation of the earth? The crux of the question is: how random is evolution? On the extinction side one could ask questions like: Would catastrophes that occurred in the past have the exact same impact on life on earth? Or would subtle differences in timing and conditions of the event or the activity of individuals lead to survival of species that otherwise went extinct – thus altering the web of species’ interactions and evolutionary potential of earth’s biota? On the evolution side: are key mutations and innovations inevitable (i.e. would they occur again if the tape was replayed) and if so, would they occur at the same instance as they did the first time? How would changes in the probability of a mutation occurring again and the timing (occurring sooner or later than it did before) affect how evolution played out? If certain types of mutations are more probable to occur than other types of mutations, and those mutations were key in evolution of life, then perhaps evolution is something more deterministic than a pure random walk through DNA space. Since microevolution is not my field of expertise, I’m not qualified to say. I don’t even know if anyone has tried to address the probability of specific mutations occurring but I suspect that there is more that is random in evolution than predictable. If so, then if we were able to study Earth in the alternative universes, I think I would find that most of them were not populated with copies of me. (In addition to the issue of whether there are human beings on those alternative Earths, there is also the issue of whether all my ancestors actually hooked up again or decided to mate with someone else.) However, for those of you who are really bummed by this idea, I have a ray of hope. The physicists kept talking about an “infinite number of alternative universes”, and when you talk about infinity…well, a small probability multiplied by infinity is technically, I believe, infinity (have to admit that makes my brain hurt), so you probably do exist in alternative universes.
The high school sci-fi fan in me has obviously already imagined a branch of ecological and evolutionary study which uses alternative universes as independent experiments of evolution. Imagine what we could learn. Is DNA the only molecule that could code information stably? Or are their alternative universes where all life on Earth has RNA as its genetic code or even some other molecular structure? How important is the identity of species that go extinct to the overall history of evolution (does the loss of a specific small mammal during the K-T extinction prevent the Age of Mammals? Or does it only result in minor or even no differences in the overall diversification and dominance of mammals that occurred after the demise of the dinosaurs? Inquiring minds want to know. And who knows, maybe in an alternative universe we have already learned how to do this and I never had to make the choice between ecology and astrophysics and I’m currently busy using my knowledge of the multiverse to study ecology and evolution. I just hope that my alternative self is a little better at math!