Fermi Paradox

The Vital Question

Posted by Peter on September 30, 2016
Posted in: Book Reviews, Fermi Paradox. Tagged: , , .

Book review: The Vital Question: Energy, Evolution, and the Origins of Complex Life, by Nick Lane.

This book describes a partial theory of how life initially evolved, followed by a more detailed theory of how eukaryotes evolved.

Lane claims the hardest step in evolving complex life was the development of complex eukaryotic cells. Many traits such as eyes and wings evolved multiple times. Yet eukaryotes have many traits which evolved exactly once (including mitochondria, sex, and nuclear membranes).

Eukaryotes apparently originated in a single act of an archaeon engulfing a bacterium. The result wasn’t very stable, and needed to quickly evolve (i.e. probably within a few million years) a sophisticated nucleus, plus sexual reproduction.

Only organisms that go through these steps will be able to evolve a more complex genome than bacteria do. This suggests that complex life is rare outside of earth, although simple life may be common.

The book talks a lot about mitochondrial DNA, and make some related claims about aging.

Cells have a threshold for apoptosis which responds to the effects of poor mitochondrial DNA, killing weak embryos before they can take up much parental resources. Lane sees evolution making important tradeoffs, with species that have intense energy demands (such as most birds) setting their thresholds high, and more ordinary species (e.g. rats) setting the threshold lower. This tradeoff causes less age-related damage in birds, at the cost of lower fertility.

Lane claims that the DNA needs to be close to the mitochondria in order to make quick decisions. I found this confusing until I checked Wikipedia and figured out it probably refers to the CoRR hypothesis. I’m still confused, but at least now I can attribute the confusion to the topic being hard. Aubrey de Grey’s criticism of CoRR suggests there’s a consensus that CoRR has problems, and the main confusion revolves around the credibility of competing hypotheses.

Lane is quite pessimistic about attempts to cure aging. Only a small part of that disagreement with Aubrey can be explained by the modest differences in their scientific hypotheses. Much of the difference seems to come from Lane’s focus on doing science, versus Aubrey’s focus on engineering. Lane keeps pointing out (correctly) that cells are really complex and finely tuned. Yet Lane is well aware that evolution makes many changes that affect aging in spite of the complexity. I suspect he’s too focused on the inadequacy of typical bioengineering to imagine really good engineering.

Some less relevant tidbits include:

  • why vibrant plumage in male birds may be due to females being heterogametic
  • why male mammals age faster than females

Many of Lane’s ideas are controversial, and only weakly supported by the evidence. But given the difficulty of getting good evidence on these topics, that still represents progress.

The book is pretty dense, and requires some knowledge of biochemistry. It has many ideas and evidence that were developed since I last looked into this subject. I expect to forget many of those ideas fairly quickly. The book is worth reading if you have enough free time, but understanding these topics does not feel vital.

Snowball Earth and Complex Life

Posted by Peter on November 19, 2010
Posted in: Fermi Paradox. Tagged: , , .

Discussions asking whether “Snowball Earth” triggered animal evolution (see the bottom half of that page) suggest increasing evidence that the Snowball Earth hypothesis may explain an important part of why spacefaring civilizations seem rare.

photosynthetic organisms are limited by nutrients, most often nitrogen or phosphorous
…
the glaciations led to high phosphorous concentrations, which led to high productivity, which led to high oxygen in the oceans and atmosphere, which allowed for animal evolution to be triggered and thus the rise of the metazoans.

This seems quite speculative, but if true it might mean that our planet needed a snowball earth effect for complex life to evolve, but also needed that snowball earth period to be followed by hundreds of millions of years without another snowball earth period that would wipe out complex life. It’s easy to imagine that the conditions needed to produce one snowball earth effect make it very unusual for the planet to escape repeated snowball earth events for as long as it did, thus explaining more of the Fermi paradox than seemed previously possible.

Global Catastrophic Risks

Posted by Peter on September 25, 2008
Posted in: Artificial Intelligence, Book Reviews, Fermi Paradox, Molecular Assemblers (Advanced Nanotech). Tagged: , .

Book review: Global Catastrophic Risks by Nick Bostrom, and Milan Cirkovic.
This is a relatively comprehensive collection of thoughtful essays about the risks of a major catastrophe (mainly those that would kill a billion or more people).
Probably the most important chapter is the one on risks associated with AI, since few people attempting to create an AI seem to understand the possibilities it describes. It makes some implausible claims about the speed with which an AI could take over the world, but the argument they are used to support only requires that a first-mover advantage be important, and that is only weakly dependent on assumptions about that speed with which AI will improve.
The risks of a large fraction of humanity being killed by a super-volcano is apparently higher than the risk from asteroids, but volcanoes have more of a limit on their maximum size, so they appear to pose less risk of human extinction.
The risks of asteroids and comets can’t be handled as well as I thought by early detection, because some dark comets can’t be detected with current technology until it’s way too late. It seems we ought to start thinking about better detection systems, which would probably require large improvements in the cost-effectiveness of space-based telescopes or other sensors.
Many of the volcano and asteroid deaths would be due to crop failures from cold weather. Since mid-ocean temperatures are more stable that land temperatures, ocean based aquaculture would help mitigate this risk.
The climate change chapter seems much more objective and credible than what I’ve previously read on the subject, but is technical enough that it won’t be widely read, and it won’t satisfy anyone who is looking for arguments to justify their favorite policy. The best part is a list of possible instabilities which appear unlikely but which aren’t understood well enough to evaluate with any confidence.
The chapter on plagues mentions one surprising risk – better sanitation made polio more dangerous by altering the age at which it infected people. If I’d written the chapter, I’d have mentioned Ewald’s analysis of how human behavior influences the evolution of strains which are more or less virulent.
There’s good news about nuclear proliferation which has been under-reported – a fair number of countries have abandoned nuclear weapons programs, and a few have given up nuclear weapons. So if there’s any trend, it’s toward fewer countries trying to build them, and a stable number of countries possessing them. The bad news is we don’t know whether nanotechnology will change that by drastically reducing the effort needed to build them.
The chapter on totalitarianism discusses some uncomfortable tradeoffs between the benefits of some sort of world government and the harm that such government might cause. One interesting claim:

totalitarian regimes are less likely to foresee disasters, but are in some ways better-equipped to deal with disasters that they take seriously.

Astronomical Waste

Posted by Peter on June 29, 2007
Posted in: Artificial Intelligence, Fermi Paradox. Tagged: , , .

Nick Bostrom has a good paper on Astronomical Waste: The Opportunity Cost of Delayed Technological Development, which argues that under most reasonable ethical systems that aren’t completely selfish or very parochial, our philanthropic activities ought to be devoted primarily toward preventing disasters that would cause the extinction of intelligent life.
Some people who haven’t thought about the Fermi Paradox carefully may overestimate the probability that most of the universe is already occupied by intelligent life. Very high estimates for that probability would invalidate Bostrom’s conclusion, but I haven’t found any plausible arguments that would justify that high a probability.
I don’t want to completely dismiss Malthusian objections that life in the distant future will be barely worth living, but the risk of a Malthusian future would need to be well above 50 percent to substantially alter the optimal focus of philanthropy, and the strongest Malthusian arguments that I can imagine leave much more uncertainty than that. (If I thought I could alter the probability of a Malthusian future, maybe I should devote effort to that. But I don’t currently know where to start).
Thus the conclusion seems like it ought to be too obvious to need repeating, but it’s far enough from our normal experiences that most of us tend to pay inadequate attention to it. So I’m mentioning it in order to remind people (including myself) of the need to devote more of our time to thinking about risks such as those associated with AI or asteroid impacts.

Anthropic Bias

Posted by Peter on March 16, 2005
Posted in: Book Reviews, Fermi Paradox. Tagged: , .

Book Review: Anthropic Bias: Observation Selections Effects in Science and Philosophy by Nick Bostrom

This book discusses selection effects as they affect reasoning on topics such as the Doomsday Argument, whether you will choose a lane of traffic that is slower than average, and whether we can get evidence for or against the Many Worlds Interpretation of quantum mechanics. Along the way it poses some unusual thought experiments that at first glance seem to prove some absurd conclusions. It then points out the questionable assumptions about what constitute “similar observers” upon which the absurd conclusions depend, and in doing so it convinced me that the Doomsday Argument is weaker than I had previously thought.
It says some interesting things about the implications of a spatially infinite universe, and of the possibility that the number of humans will be infinite.
It is not easy to read, but there’s little reason to expect a book on this subject could be both easy to read and correct.
The author has a web site for the book.

Book Review: Rare Earth by Peter Ward, Donald Brownlee

Posted by Peter on November 17, 2004
Posted in: Book Reviews, Fermi Paradox. Tagged: , , , , .

Rare Earth : Why Complex Life Is Uncommon in the Universe provides some fairly strong (and not well known) arguments that animal life on earth has been very lucky, and that planetary surfaces are typically much more hostile to multicellular life than our experience leads us to expect.

The most convincing parts of the book deal with geological and astronomical phenomena that suggest that earth-like conditions are unstable, and that it would have been normal for animal life to have been wiped out by disasters such as asteroids, extreme temperatures, supernovae, etc.

The parts of the book that deal with biology and evolution are disappointing. The “enigma” of the Cambrian explosion seems to have been explained by Andrew Parker (see his book In the Blink of an Eye) in a way that undercuts Rare Earth’s use of it (dramatic changes of this nature seem very likely when eyes first evolve). This theory was apparently first published in a technical journal in 1998 (i.e. before Rare Earth).

They often assume that intelligence could only develop as it has in humans, even suggesting that it couldn’t evolve in the ocean, which is rather odd given how close the octopus is to qualifying. But the various arguments in the book are independent enough that the weak parts don’t have much affect on the rest of the arguments.

I was surprised that they never mentioned the Fermi Paradox, which I consider to be the strongest single argument for their position. Apparently they don’t give it much thought because they don’t expect technological growth to produce effects that encompass more than our planet and are visible at galactic distances.

Their concern over biodiversity seems rather misplaced. I can understand why people who overestimate mother nature’s benevolence think that preserving the status quo is a safe strategy for humanity, but it seems to me that anyone sharing Rare Earth’s belief that nature could wipe us out any time now should tend to prefer a strategy of putting more of our effort into creating technology that will allow us to survive natural disasters.

I am disappointed that they rarely attempt to quantify the range of probabilities they would consider reasonable for the risks they discuss.

Stephen Webb has written a book on roughly the same subject called Where is Everybody? that is more carefully argued, but less entertaining, than Rare Earth.