[LUCID LIVING #8] Universal Biology: the Next Frontier in Science
By Piet Hut
I gave a talk at a workshop on the topic of Universal Biology, a little over a week ago, at the Earth-Life Science Institute (ELSI) in Tokyo, one in a series provided by the ELSI Origins Network (EON). The title of my talk was From Universal Biology to Universal Science.
Unlike physics and chemistry, which are universally valid, anywhere in the Universe, biology describes life on Earth. We don't know whether there is any life elsewhere in the Universe. And if there is, we have no idea what it looks like.
There is a good chance that we will discover hints of the existence of forms of life beyond Earth, within the next few decades. Spacecrafts exploring our solar system may find direct signs of life just below the surface of Mars, or in oceans that are buried under layers of ice on the moons of Jupiter and Saturn. We have already been able to conduct promising chemical analysis when Cassini flew through geysers spouting from cracks in the surface of Saturn's moon Enceladus.
We might even find life forms in the frigid oceans on Titan, the only other planet besides Earth that has rivers, rain and surface oceans. However, where the Earth has its hydrological cycle of rainfall, on Titan it rains methane, mixed with other organic compounds that remain fluid at its surface temperature of -180°C (-290°F). We don't know whether life can exist based based on other solvents than water, and whether chemical reactions would proceed fast enough at those low temperatures, but if so, Titan might be our best candidate within the solar system.
We may also soon find more indirect signs of life on planets and their moons that orbit other stars. Several thousand such exoplanets have been discovered in the last two decades, and the next generation of telescopes, on Earth as well as in space, are likely to provide clues. For example, they may well produce tantalizing hints at the presence of forms of chemistry that might be difficult to produce without life being present to create the type of out-of-equilibrium chemistry that we see on Earth.
However, it will be unlikely that life elsewhere in the Universe will take on the same form as it has on Earth. It seems far more reasonable to expect at least variations on the theme of the specific water and carbon based chemistry that we are familiar with. For example, alien life could well have very different mechanisms for inheritance from the DNA/RNA mechanisms that our bodies rely on. Biology may have started out in ways that we can't currently imagine. Trying to draw the contours of what we can say about the structure of alternative life forms was the major theme of the EON workshop.
In my talk, I tried to explore not only alternatives to biological life, but also alternatives to culture and technology, what humans have produced as a direct consequence and outgrowth of their biological evolution. Here is one of my slides, in which I present the remarkable difference in time scales involved. Societies produce cities and institutions that lead their own life, so to speak, often outlasting the human individuals that create and maintain them, just like cells in our body come and go on a timescale of months, while we live many decades. And our technology is now creating autonomous life-like entities on the internet as well as in the world out there, such as self-driving cars.
Note that in my comparison of the three types of autonomous agents, biological ones, societal ones, and artificial ones, I have added a Japanese notation for the time scales, not only because I gave the talk in Japan, but also because the jumps in time scale are each roughly of a factor 10,000. Japan, like China, does not count in terms of a thousand, million, billion, but 万 (man: 10,000), 億 (oku: 100,000,000), 兆 (cho: 1,000,000,000). So going from nature to culture to technology shortens the timescales, and hence increases the rate of evolution, by roughly one step in their counting system.
The "bottom line" in this slide indicates that among the products of biology, which rests on all of natural science, we have to count culture, which rests on all of social science, as well. In other words, when looking for more universal frameworks for biology, we actually have to look for more universal frameworks for science as a whole. This includes computer science and related disciplines, for the study of autonomous agents that incorporate artificial intelligence.
On Earth, soon after its formation, we had rock, ocean, and atmosphere, but no life yet. These three components, solid, liquid, and gaseous, are also called the three geospheres: lithosphere, hydrosphere, and atmosphere, respectively. After a few hundred million years, life appeared. Since living material has a very different composition and structure, it is called the biosphere. A recent book by Eric Smith & Harold Morowitz, The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere, champions this unified view of our planet as containing four geospheres. Just as H2O can undergo phase transitions between ice, water, and steam, their view is that the three initial spheres underwent a phase transition to produce a fourth phase, in the form of the biosphere.
Here is another slide from my talk, in which I comment on this interpretation, while proposing a complementary division into only two components, the deep lithosphere, starting a few miles below the atmosphere and oceans, and the ecosphere containing everything else.
The main reason to do so, is the observation that there really is a spatial separation between the two, namely at the depth at which life is no longer sustainable. The precise location will vary a bit from place to place, but it is generally thought to be several kilometers down into the lithosphere, marked by the depth at which the temperature rises beyond what life can bear. There is some similarity with the tree line, the height above which no trees can be sustained. We could call this terminal depth a "life line" below which no life of any form can be sustained.
It is a remarkable fact of the biosphere that it penetrates just about anything else, everywhere above the life line. Take a sample of a teaspoon of rock, water, air, or any mixture thereof, and you will find microbes, wherever you care to sample, in any place above the life line.
From a geophysical point of view, the lithosphere is divided, from top to bottom, into a crust, a mantle, an outer core and an inner core. Of these, only the outer core is liquid, the other three components are solid. But from a biological point of view, the lithosphere has only two components, the outer crust where life is ubiquitous, and the inner crust and everything below that which is heat sterilized. The two other spheres, hydrosphere and atmosphere, are simply drenched in life, just about everywhere.
On the following slide I return to the discussion of the alternative division into the three different spheres that were produced by biological evolution. Just like the biosphere itself, they are not spatially located in different places, the way mountains and oceans and air are. Instead, they are integrated parts of the ecosphere, although in a virtual way.
What is virtual about the sociosphere and technosphere? Just like geophysics and biology obey the laws of nature, in a similar way humans obey the laws of society, and computer programs obey the laws of their compilers. These laws are not detectable by any physical measurements; they are purely virtual, forms of information. But they are real nonetheless: in those societies that still maintain capital punishment, disobeying the law of society can kill you as certainly as disobeying the law of gravity while climbing a mountain.
In my slide I compare our solar system with a theater, the bulk of the Earth mass below the life line with the stage in a theater, and the ecosphere above the life line with a collection of players, layered virtually into biosphere, sociosphere, and technosphere.
And here is one more slide, in which I mused about universal biospheres, sociospheres, technospheres and possible other such spheres. If we find life on another heavenly body, near or far, how likely are we to find only a biosphere, or also a sociosphere populated by social entities and structures, and possibly a technosphere populated by autonomous artificial agents?
Judging from the one example of a biosphere that we know of, the one on Earth, if anyone had visited our planet at a random point of time between its formation and now, the chance to find a sociosphere would have been about one in ten thousand (one in 一万, ), and the chance to find a autonomous technosphere about one in a hundred million (one in 一億). But that is only a snapshot calculation we can make looking back in time from today. We don't know how long our civilization will last, nor do we know what shape autonomous technology will take, let alone how long that will last. And who knows what kinds of technology will be produced by future technologies itself (techno-socio-spheres?), and whether there will be other developments that could produce sufficiently different structures to have their own sphere named after them?
A simple minded extrapolation for whatever may follow after technology would predict that it could have a timescale yet another factor 10,000 shorter to develop, which would be a little over a day, with a speed-up over biological evolution of a factor of a trillion (一兆). This would resemble the extreme case of a technological singularity, popularized by Ray Kurzweil and others. While there is little reason to take such a simple extrapolation seriously in a literal way, it is clear that we may still be at the very beginning of a (for us) unimaginably complex possible future evolution of the biosphere on Earth, on time scales far shorter than that of human evolution, let alone biological evolution.
Given that many stars harbor planets, and that there are several tens of billions of galaxies with each several tens of billions of stars within the visible part of our Universe, the potential number of spheres, and even the potential number of types of spheres, as emergent properties that may have been produced by universal biology, in terms of the collection of biospheres in the visible Universe is . . . so far beyond mind boggling that words fail me. The only thing that I have no doubt about is that no science fiction novel has yet been anywhere close to be sufficiently boggling to be realistic, by a very long shot.
Piet Hut is President of YHouse (where this blog is hosted), Professor of Astrophysics and Head of the Program in Interdisciplinary Studies at the Institute for Advanced Study in Princeton, and a Principal Investigator and Councilor of the Earth-Life Science Institute in the Tokyo Institute of Technology.