Philip Ball : How Life ( and Death ) Spring from Disorder
How Life ( and Death ) Spring from Disorder ( abridged )
By Philip Ball ; via Quanta Magazine [ Informatic ( Information Theory ) ]
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A Related Article [ Origins of Life ] : First Support for a Physics Theory of Life
by Natalie Wolchover
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... Biological systems don’t defy physical laws, of course — but neither do they seem to be predicted by them. In contrast, they are goal-directed: survive and reproduce. We can say that they have a purpose — or what philosophers have traditionally called a teleology — that guides their behavior.
... The teleology and historical contingency of biology, said the evolutionary biologist Ernst Mayr, make it unique among the sciences. Both of these features stem from perhaps biology’s only general guiding principle: evolution. It depends on chance and randomness, but natural selection gives it the appearance of intention and purpose.
... Mayr claimed that these features make biology exceptional — a law unto itself. But recent developments in nonequilibrium physics, complex systems science and information theory are challenging that view.
... Once we regard living things as agents performing a computation — collecting and storing information about an unpredictable environment — capacities and considerations such as replication, adaptation, agency, purpose and meaning can be understood as arising not from evolutionary improvisation, but as inevitable corollaries of physical laws. In other words, there appears to be a kind of physics of things doing stuff, and evolving to do stuff. Meaning and intention — thought to be the defining characteristics of living systems — may then emerge naturally through the laws of thermodynamics and statistical mechanics.
This past November, physicists, mathematicians and computer scientists came together with evolutionary and molecular biologists to talk — and sometimes argue — about these ideas at a workshop at the Santa Fe Institute in New Mexico, the mecca for the science of “complex systems.” They asked: Just how special (or not) is biology?
It’s hardly surprising that there was no consensus. But one message that emerged very clearly was that, if there’s a kind of physics behind biological teleology and agency, it has something to do with the same concept that seems to have become installed at the heart of fundamental physics itself: information.
... Looked at this way, life can be considered as a computation that aims to optimize the storage and use of meaningful information.
... So living organisms can be regarded as entities that attune to their environment by using information to harvest energy and evade equilibrium.
... How far can this picture then take us? Genes honed by natural selection are undoubtedly central to biology. But could it be that evolution by natural selection is itself just a particular case of a more general imperative toward function and apparent purpose that exists in the purely physical universe? It is starting to look that way.
... Darwinian evolution can be regarded as a specific instance of a more general physical principle governing nonequilibrium systems.
... “A thermodynamically optimal machine must balance memory against prediction by minimizing its nostalgia — the useless information about the past,” said a co-author, David Sivak, now at Simon Fraser University in Burnaby, British Columbia. In short, it must become good at harvesting meaningful information — that which is likely to be useful for future survival.
... Hildegard Meyer-Ortmanns, a physicist at Jacobs University in Bremen, Germany, thinks that ultimately aging is a physical process, not a biological one, governed by the thermodynamics of information.
... “Most of the soft material we are made of is renewed before it has the chance to age,” Meyer-Ortmanns said. But this renewal process isn’t perfect. The thermodynamics of information copying dictates that there must be a trade-off between precision and energy. An organism has a finite supply of energy, so errors necessarily accumulate over time. The organism then has to spend an increasingly large amount of energy to repair these errors. The renewal process eventually yields copies too flawed to function properly; death follows.
Empirical evidence seems to bear that out. It has been long known that cultured human cells seem able to replicate no more than 40 to 60 times (called the Hayflick limit) before they stop and become senescent. And recent observations of human longevity have suggested that there may be some fundamental reason why humans can’t survive much beyond age 100.
There’s a corollary to this apparent urge for energy-efficient, organized, predictive systems to appear in a fluctuating nonequilibrium environment. We ourselves are such a system, as are all our ancestors back to the first primitive cell. And nonequilibrium thermodynamics seems to be telling us that this is just what matter does under such circumstances. In other words, the appearance of life on a planet like the early Earth, imbued with energy sources such as sunlight and volcanic activity that keep things churning out of equilibrium, starts to seem not an extremely unlikely event, as many scientists have assumed, but virtually inevitable. In 2006, Eric Smith and the late Harold Morowitz at the Santa Fe Institute argued that the thermodynamics of nonequilibrium systems makes the emergence of organized, complex systems much more likely on a prebiotic Earth far from equilibrium than it would be if the raw chemical ingredients were just sitting in a “warm little pond” (as Charles Darwin put it) stewing gently.
... Those qualities that Ernst Mayr thought essential to biology — meaning and intention — may emerge as a natural consequence of statistics and thermodynamics. And those general properties may in turn lead naturally to something like life.