The Knowable Futures of Life

I recently finished reading A New History of Life by Peter Ward and Joe Kirschvink. The book traces the history of earth from 4.5 billion years ago to the present day. It was a good refresher for me to go through the different eras in the Geological Time Scale. Much of what was written was familiar to me from other reading, but there were a few new things I did not know about. I did not realize the Neo-Proterozoic era had been subdivided such that there is now a Cryogenian era from 850 to 635 Mya. I also got up to speed in the recent Ediacaran discoveries. Although I had read Nick Lane’s book Oxygen a while back, I found it interesting to reminded of the close correlation between CO₂ and O₂ levels, and extinctions/evolutionary “explosions”. My knowledge of plant evolution was also rather scant and I found it fascinating to read about the effect of CO₂ and O₂ on the evolution of grasses, trees, flowering plants, C₃ and C₄ species, and more.

Given that I asked my students about the “faint young sun hypothesis” in a recent quiz, it was interesting to read the final chapter in Ward and Kirschvink’s book titled “The Knowable Futures of Earth Life”. The luminosity of the sun has increased by some 30 percent since the Earth’s formation, but it is only going to get brighter and more intense. The result, according to Ward and Kirschvink, will be “loss of oceans [and] hellish conditions, similar to those that exist on Venus.” While Earth is currently well-positioned in a “Goldilocks” habitable zone, this zone will move further out. In fact, Mars will move into such a zone.

Much has been speculated about life on Mars. As the intensity of the sun increases, and temperatures rise, we would expect the melting of the polar ice caps. Unfortunately there is hardly any atmosphere and it is unclear that Mars will be able to support one so all that water may simply evaporate. Could Mars be terraformed? That could prove very difficult. And it’s unclear if there is sufficient geothermal energy to support an underground complex (like Zion in the Matrix movies). It might be easier to build an Elysium-like space-station if our technology actually gets sufficiently advanced.

One of the authors, Peter Ward, is credited as the originator of the Medea hypothesis – that life essentially destroys itself over time, as evidenced by the series of mass extinctions in the past. The authors comment that “it seems appropriate to us to end this book with some comments about the most Medean of all species ever evolved: our own. What will the future be for our own species?” There are a number of speculations made and questions posed in this section, ending with “Is humanity but the builder of the next dominant intelligence on Earth – the machines?” For some reason this makes me want to watch the Terminator movies again. The future may be knowable unless we can go back in time to change it!