Welcome to Part 2 of 3 of my Breakthrough Discuss 2019 series (start with Part 1). This post focuses on concepts that I didn’t know before, pieces of information that caused me to change my perspective on something, and questions that I’m still thinking about post-conference. So without further ado:

Defining Life

One operative definition for intelligent lifeforms could be “physical systems who understand how the physical universe works”. As with any definition for life, refinements and counterexamples can be quickly dreamed up, but understanding and quantifying natural laws (physics etc.) is an interesting criterion. This was brought up by Sara Walker with the example of “anti-accretion”: the way that humans have sent mass up into Earth orbit from its surface, based on our understanding of the law of gravitation. Perhaps I’d add a caveat to this definition: “physical systems who understand how the physical universe works and use that to affect significant change in their environment“… but maybe that’s just the technosignature hunter in me!

An operative definition for life in general, put forth in the second panel, was “a unique chemical process with a boundary condition separating entity from non-entity”. Again, there are issues with it, but I like thinking about the “boundary condition” argument and, in the way of a good SETI scientist, wondering what it would look like if that assumption was broken. We definitely spend some time thinking about what would happen if, temporally, there was a gradient between non-life and life. But what if there was a spatial gradient? There’s a sci-fi short story in here somewhere…

Determining Atmospheric Compositions of Exoplanets

We cannot accurately retrieve atmospheric compositions of exoplanets even if we have JWST and TMT observations without knowing the mass of the exoplanet first (degeneracies appear because of mass – log(g) – temperature – scale height relationships). I didn’t realize until this conference that the precise determination of masses would be so vital for atmospheric studies (ex. biosignature gas searches).

Adapting Earth-life for Space

In one of the panel discussions, it was brought up that Earth life has an eerie tolerance for vacuum. Upon hearing this, of course, I immediately got excited. However, it was quickly pointed out that this is likely because vacuum-tolerance (and radiation tolerance) is related to the same mechanisms that protect against dehydration on Earth: very good DNA repair. So it’s not quite evidence for panspermia, but it does make me feel more optimistic about life surviving such a seemingly inhospitable journey in the first place.

But, to my surprise, it turns out that microbial communities and biofilms are far more important in thinking about how bacterial life survives than the analysis of a single microbial genome. The focus on single genomes is an incorrect simplification. Most bacterial strains cannot be cultivated in the lab because they are missing molecules from their original environment, a physical site of a certain structure to attach to, or another organism making something they need. If we ever send life elsewhere, we’ll need to send a full microbial community. This additional complexity is both beautiful and frustrating (to a non-biologist!).

Almost as a consequence of that realization, it’s also possible that Earth life may’ve spent too long adapting to Earth to be useful in a bioengineering (for ex. Mars terraforming) sense. Starting from scratch with synthetic minimal cells (customizable molecular machines that can be built with simple modular recipes) might be easier in the long run. These synthetic minimal cells could be pluripotent, could perform horizontal gene transfer, and could function as genetic circuits (biocomputing) or nutrient/chemical factories. I find not only the possibilities fascinating, but also the outlook of those performing this research; their synthetic cells are just little biochemical machines, and are not alive in any reasonable sense of the word. Oooh, biology is squishy…

Anthropocentrism, Directed Towards Microbes

Microorganisms are not primitive, they have as much evolutionary history as humans and are exceedingly complex, hardy, and good at what they do. I’m definitely guilty of underappreciating them, and I think this conference is a good reminder that non-intelligent, single-celled life is still fascinating.

With a sample size of one, it’s hard to know what properties of life are universal, and which are just funny terrestrial adaptations or random consequences of our particular evolutionary path. For example, are assumptions that all life must have a backbone, a motor, and a ribosome just physics… or terrestrial arrogance?

Probabilities and Rates of Panspermia

Let’s assume abiogenesis is pretty hard and happens slowly and rarely. Then the earlier life is detected on Earth, the more attractive panspermia becomes, which is a cool test! Except it assumes abiogenesis is hard, which is a pretty big assumption.

The rate at which we see life in the universe is a product of the rate at which it emerges and the rate at which it migrates. High origination negates the need for panspermia as a theory. If panspermia did happen in this scenario, any place that the migrating life landed would already be inhabited by lifeforms, thus leaving the rate at which we see life in the universe unchanged. On the other hand, high migration rates can spread life through the universe even if origination rates are low, so panspermia could provide astrobiologists an escape hatch from a tough abiogenesis situation.

Organoid Brains

At this conference I learned that we are growing embryonic stem cells from humans, apes, etc. into “organoid” brains. Not only can we grow these organoids, but we can also use CRISPR to see what happens to them if you modify parts of the genome. Turns out, if you use CRISPR to take out the NOTCH2NL gene, the organoids develop small and stunted – NOTCH2NL appears to be responsible for macrocephaly. It’s amazingly cool that we can determine this experimentally. On the other hand, these organoids produce some amount of electrical activity. Messing around with brain organoids that are evidently active without knowing much about the development of consciousness/intelligence seems reckless. Admittedly, I don’t have any background knowledge here, so maybe I’m making an ethical quandary out of a molehill, but I’m still very surprised about the lack of a single slide about the ethics; it wasn’t in the dialogue at all.

Messages from ETI Hidden in Genomes

A large, fun part of the conference was focused on the possibility that an extraterrestrial intelligence could have seeded the Earth / solar system with life long ago, and left us a message hidden in our genetic code. It sounds very sci-fi, but as with all things sci-fi, there’s no harm in giving it some methodological scientific thought.

However, messages hidden in genomes require a lot of assumptions. ETIs have to exist. Things have to be able to reasonably move from one stellar system to another. An ETI will need biological mastery greater than we have, and will need to have some motivation for bio-based messaging in the first place. They will also have to determine that the best possible way to message is through genetic code (this feels like the weak part to me, see next paragraph). And they will have to assume that living systems are inherently narcissistic in a way, to reasonably want to leave a message “inside” instead of “outside”. This large string of assumptions makes me pretty suspicious about the prospect.

The big scientific hurdle for bio-based messaging is mutation. Mutations happen a lot in biology. In fact, standard DNA codons have adapted to this by having a very specific set of characteristics to minimize the damage caused by random mutations. In other words, a mutation in the code rarely leads to a different amino acid being produced because there’s a lot of redundancy built in. So mutations happen, and then they stay, which is bad for messaging because it will scramble your message over time. On the bright side, we are already able to code something that will instantly stop replicating when a mutation occurs by immediately leading to an “error” or empty codon. This can currently be done with the production of only 15 amino acids, so a limited palette compared to what life has, but it seems possible that bio-engineering could lead to humans being able to leave a bio-based message in this way.

Instead of looking for “hello there” or pi or whatever else hidden in our genome, some suggestions have been made about looking for a “left turn” in our evolutionary pathway for no apparent reason. So something SETI-like to look for in a genome might be an infusion of information in the past that seems to hold a bad assumption and come out of nowhere (ex. a large piece of junk DNA coding for genes important for survival in an atmosphere that Earth has never had). I don’t quite buy this argument, it seems rather contrived, but I like the idea of it.

Convergent Evolution or Second Genesis?

The discovery of a carbon-based lifeform inside the solar system would not be enough to prove a second genesis of life, but, according to the second panel, the discovery of a lifeform with ribosomes would be. At what point between those two things do we stop expecting convergent evolution to be a reasonable explanation? I would love to get more input from biologists on this idea!

Planning for an Interstellar Journey

As soon as you produce a single piece of waste on a spacecraft, you have introduced a rate-limiting factor. We are working on ways to turn human waste into plastic, with the eventual goal of a 0 waste spacecraft. Even then, however, what happens if you forget something or encounter new and unforeseen needs on your journey? Do we bring DNA with us? Or chemicals/molecules/bases as building blocks? Or protons and electrons as building blocks for those?

Single Bad Actor Problems

Recently I’ve been mulling over the idea of domains in which a single bad actor can ruin everything. I have the following list so far:

• Planetary protection (one company ignoring regulations could irrevocably contaminate ex. Mars)
• Radio/light pollution (a single country building on the moon could destroy the idea of a far-side radio telescope)
• Generalized AI safety (one programmer could intentionally/accidentally create malicious artificial life)
• METI (one team with a radio telescope can send a message to the stars with potentially catastrophic consequences)
• Nuclear weapons (one nation with a weapon could make Earth uninhabitable, for humans at least)
• Peaceful protests (one rioter in a crowd of otherwise peaceful protesters can completely undermine the success of the protest)

I’m trying to think about the synergies in what seem like a very diverse set of endeavors, but this is probably a project for a game theorist, not me!

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Part 3 of this blog series will provide perhaps my most important conference summary – a look at some meta-conference commentary. How can we make future conferences more productive and more inclusive? Stay tuned!