Cosmic Natural Selection

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If you regularly read this blog, you already know that I believe adaptive evolutionary processes explain system order in the universe. There does appear to be a unity between how systems evolve (whether they be chemical, biological, cultural, technological, etc.). In this sense, selection-like processes generate order in the natural world that many cultural groups assumed was intelligently designed. But can selection be extended to explain the universe itself?

Before humans knew that there were other planets in the universe, many people believed that Earth could only be explained by intelligent design (e.g., God). However, we now know that the Earth’s existence can be explained by probability. There are likely way more than sextillion planets in the observable universe, so it is not necessarily surprising that one suitable for complex life exists. In fact, it would not be surprising if billions of planets suitable for complex life existed just within our own galaxy.

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But people who make the God-of-the-gaps argument never really go away. Now that it is intellectually bankrupt to argue Earth (or life, or our star, or our solar system, or our galaxy) was intelligently designed, many turn to the universe itself. As physicists have pointed out, our universe is well-designed for the emergence of intelligent life (although not that well-designed).

Therefore, it is the job of 21st century science to uncover the mysteries as to why our universe appears to have the physical constants it does. At the moment, the theory is far ahead of the empirical evidence (unlike the situation in evolutionary biology). A dominant theory proposed to explain our universe’s physical constants is Cosmic Natural Selection (CNS). This theory, first explored by physicist Lee Smolin suggests that:

black holes may be mechanisms of universe reproduction within the multiverse, an extended cosmological environment in which universes grow, die, and reproduce. Rather than a “dead” singularity at the centre of blackholes, a point where energy and space go to extremely high densities, what occurs in Smolin’s theory is a “bounce” that produces a new universe with parameters stochastically different from the parent universe. Smolin theorizes that these descendant universes will be likely to have similar fundamental physical parameters to the parent universe (such as the fine structure constant, the proton to electron mass ratio, and others) but that these parameters, and perhaps to some degree the laws that derive from them, will be slightly altered in some stochastic fashion during the replication process. Each universe therefore potentially gives rise to as many new universes as it has black holes.

The analogy with how selection operates in biological systems is impossible to miss. Given that this is how complexity is generated by other natural systems, it seems logical that this could be the case of our universe (within the multiverse). In fact, a study published this month in the journal Complexityposits that Smolin’s CNS theory would mathematically be in concordance with the production of universe’s increasingly likely to produce black holes (and therefore universe’s conducive to complex life).

Let that sink in. If Smolin’s theory is true, our universe exists the way it does because of a cosmic natural selection between universe’s within a multiverse of universes with different physical laws.

But all theories need empirical evidence. There is currently no evidence for the existence of either a multiverse or successive generations of universes that transmit their fundamental constants. And it’s possible we won’t have that evidence in the near future (or ever).

Either way, I’m optimistic. Advances in physics theory are likely to further support the idea of a multiverse and the CNS. And I wouldn’t bet against CNS being lifted from theoretical obscurity. The idea has a certain Copernican principle to it. Just as scientific inquiry revealed that our planet, solar system, and galaxy were not particularly special, it seems increasingly likely that scientific inquiry will do the same for our universe as well.

What do you think of Cosmic Natural Selection?  Let Cadell know on Twitter!

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Should We Send Messages to Space

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Should we purposefully transmit messages to space? That is the question posed by a team of earth and space scientists in the February 2013 edition of Space Policy.

The question has been raised because various independent groups have been sending purposefully directed high-intensity messages intended for extraterrestrial intelligences (ETI), or METI’s.

The authors of this study made two conclusions regarding METI:

1) The benefits of radio communication on Earth today outweigh any benefits or harms that could arise from contact with ETI

2) Current METI efforts are weak, mostly symbolic, and harmless

But are the answers to independent groups sending messages into the cosmos really that simple? I mean I think it is fairly obvious that the potential for ETI in our galaxy should not deter our species from continuing to improve our communication abilities. We have no evidence to support the idea that there are intelligent civilizations in our galactic neighbourhood, much less evidence to support the idea that there is an ETI civilization that poses danger to our existence. However, expanding Earth’s radiosphere and directly sending messages into the cosmos are two very different things. For example, SETI astronomer Seth Shostak has claimed that, due to decreasing signal strength our radiosphere is not detectable beyond five light years. Whereas purposefully directed, high-intensity messages significantly increase Earth’s detectability beyond the radiosphere.

Essentially, this is the reason SETI pioneer Philip Morrison believed that we, “the newest children” in the cosmos, should be passive and just listen for a long time. We should not ‘shout at the cosmos’. We should not explicitly make our presence known before we know the types of intelligence that may exist.

This is a very complex issue. What should we do moving forward? Should we be engaged in an active search for ETI? Or should we be passive?

For me personally, I mostly agree with astrophysicist and science fiction author David Brin. He supports the International Academy of Astronautics Second Protocol for dealing with Transmissions from Planet Earth. This protocol states that:

all of those controlling radio telescopes forebear from significantly increasing Earth’s visibility with deliberate skyward emanations, until their plans were first discussed before open and widely accepted international fora.

To me, this seems like a reasonable position. If we are to purposefully send a METI, that message should be first discussed by an international panel of experts in astronomy, physics, biology, anthropology, history, and politics. And the message should be collectively sent as a message from Earth and by Earth; not from an independent collective. As David Brin stated, no one should feel free to:

broadcast from Earth, whatever, whenever, and however they want.

On the other hand, there are those who would prefer to completely ban METI’s; I disagree with that stance. Don’t get me wrong, I see wisdom in the perspective that we should remain silent, passively listening to the cosmos for thousands of years, before sending messages into a cosmic environment we are just beginning to understand. However, I feel as though we should send controlled and well thought out messages from our species and planet for two main reasons:

1) If there are highly advanced civilizations in the Milky Way, they would know we are here by studying the physical and chemical patterns of our planet, regardless of our radiosphere.

2) I believe it to be probable that any civilization with the capability of traveling to another solar system would not do so with the intention of eradicating life and high intelligence.

The first point is simple, not controversial, and easily explained: a sufficiently advanced civilization could easily detect the presence of our civilization by analyzing the spectrum of reflected ultraviolet, optical, and near-infrared sunlight for our planet’s surface. They could also, perhaps more easily, become cognizant of our existence from artificial nighttime lighting and the unusual chemical composition of our planet due to the excessive burning of fossil fuels.

The second point is far more complex, certainly controversial, and not easily explained. Biologists have often warned that contact between species that evolved in different ecosystems often leads to one species going extinct. Likewise, historians have argued that “first contact” between more advanced and less advanced civilizations have often led to disastrous inter-human relations (e.g., slavery, colonialism, civilization collapse, etc.). From this reasoning, they often conclude that if we make our presence known to a vastly more advanced civilization than our own, we are placing own existence in extreme peril.

However, consider the following: as our species has become more knowledgable and technologically advanced, we have also moved strongly in the direction of compassion, altruism, and the inclusion of all within the protection of law. I believe that this is directly tied to satiation. As we create a world of abundance; a world with drastically reduced levels of hunger and poverty, we elevate our cultural ideals. David Brin referred to this as:

an abstract sympathy, unleashed by full bellies and brains that are capable of seeing enlightened self interest in the long term survival of the world.

Natural selection is the driving force for the creation of our biosphere. It may be that natural selection is the driving force for all biological evolutionary processes in the universe. Natural selection permits populations to evolve via differential survival rates. And although we are a very young species, we are already close to releasing our species from this process. In essence, natural selection is permitted to operate because of resource scarcity. But as we continue to raise the standard of living for our speciesas a whole, we accelerate ourselves into a world where we all live long enough to reproduce. Differential survival rates will no longer drive our evolution. As a result, we also accelerate ourselves towards a world free of the byproducts of resource scarcity (i.e., extinction, war, slavery, etc).

When we create science fiction work depicting human-alien conflict, we are projecting biological system conflict produced from a world governed by natural selection. But the interaction between two highly advanced technologically-based systems will not likely be governed by that type of system conflict. A new, more intelligently directed form of evolutionary change should take the place of natural selection. Surely, any species with the capability of visiting our planet would have long ago released themselves from the biological tyranny of the process that created them.

As many scientists have pointed out, including theoretical physicist Paul Davies, biological intelligence is likely to be a fleeting phase in the evolution of the universe. If this is the case, it stands to reason that any civilization able to receive our messages and visit our planet would undoubtedly be post-biological. This essentially means they would be post-singularity. And a post-singularity species has not only lifted itself from a world governed by differential survival, but has also lifted itself from finite sentience and death. Therefore, I would not expect conflicts produced by the mechanism of natural selection to dominate an encounter between us and an advanced space faring civilization.

At least, that is my reasoning, and it is why I fully support a controlled, globally agreed upon form of METI. I think the benefits of discovering extraterrestrial intelligence and making “first contact” would outweigh the risks.

That being said, I am sure many would disagree with me. Perhaps it is foolish of me to assume that all advanced intelligent species would have lifted themselves from natural selection and tend towards extraterrestrial altruism. But that is why we must have open dialogue about METI. We can’t tolerate random independent groups to send messages without first consulting the global community. If we send messages we must be prudent. And, from my perspective, prudence would be making sure that any message is sent from Earth and by Earth. No one should be allowed to send whatever messages they want, whenever and however they want.

What do you think?  Let Cadell know on Twitter!

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The Largest Living Systems

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For anyone who studies evolution, it is important to realize that there are characteristic evolutionary patterns. For example, evolution tends towards greater complexity (although not always). Evolution also has a variable speed (which is often contingent on the environment). And a study recently published in PNAS indicates that evolutionary processes generally select for species-level living systems with universal size distribution. Science Daily summarized the importance of this universal size distribution well:

Flocks of birds, schools of fish, and groups of any other living organisms might have a mathematical function in common [… researchers] showed that for each species studied, body sizes were distributed according to the same mathematical expression, where the only unknown is the average size of the species in an ecosystem.

For the researchers of this study, these apparent universal size distribution may be useful for understanding how systems of living matter operate. However, this study made me think of the role of size in evolutionary processes. Specifically, what causes different living systems to evolve different sizes? And what living system has evolved the largest overall size?

The role of size in evolutionary processes has always been a contentious issue for evolutionary theorists. Central to the issue of size has been the idea that natural selection tends to drive the evolution of larger and larger overall size, regardless of whether the living system is a bacterium, a hydra, or a chimp. This observed trend has been labeled Cope’s rule after Edward Cope, a 19th century paleontologist who first proposed the trend. The late evolutionary theorist Stephen J. Gould disregarded Cope’s rule as a “psychological artifact”, however recent studies have provided empirical evidence to support the general pattern.

Paleontologist Joel Kingsolver supports the idea that evolution tends to favour large body size, stating that:

In 80 percent of the studies, there’s consistent selection favouring larger size.

Disappointingly, the theory to explain this pattern is still underdeveloped. In fact, Kingsolver contends that there may not be any universal driver of larger body size:

My guess is that it’s a mix of particular reasons for particular speices. You may be able to make through lean times better than someone who’s smaller. Females that are larger are able to produce more eggs. If males are competing for females, larger size is often favoured.

Paleontologist and science blogger Brian Switek echoed a similar perspective recently in an article about large dinosaur body size:

The evolutionary driving forces behind the evolution of truly huge body size are not clear, and likely differed from one group to the next.

Although evolutionary theory explaining the drive behind selection for larger body is underdeveloped, we do have a better idea of proximate determinants of body size. For example, many theorists have demonstrated that mode of locomotion and reproduction are both important factors either constraining or enabling large body size.

As Brian Switek discussed at length recently, the monstrous sauropod infraorder was able to “sidestep” the costs and risks that constrain mammalian size by “externalizing birth and development.” The size distribution of sauropods dwarfed the size distribution of all other known terrestrial organisms to ever exist.

So of these supermassive sauropods, what species holds the title of largest? The answer to this question was far more difficult to find than I originally thought. Michael Stevens from VSauce recently claimed that Giraffatitan was the largest known “with certainty of a complete skeleton”. Estimates of Giraffatitan come from one skeletal sample, and was thought to be 72-74 feet in length and weigh ~30-40 tons. Compare that to the largest known African elephant which weighed ~12 tons.

However, there is general consensus in the paleontological community that there were larger sauropods than Giraffatitan. Thankfully, I had some help from Brian Switek to better understand the contemporary debate:

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According to Switek Argentinosaurus and Supersaurus
are the leading contenders for heavyweights in the dinosaur world. The longest known of these giants was a Supersaurus that is estimated to be 108-111 feet long. The heaviest was a Argentinosaurus estimated to have weighed 73 tons. They were the giants of the gigantic sauropoda order.

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But we can’t forget about a living clade of animals that has experienced an explosive increase in size distribution: cetaceans. The largest (by far) of our mammalian cousins is the blue whale. And the blue whale is not just a contender for largest living animal, they are also contenders for largest animal of all time. In fact, in terms of absolute weight, it doesn’t appear to be close at all. Whereas Argentinosaurus weighed 73 tons, the largest known blue whale weighed over 200 tons! More than double the weight of the largest known dinosaur! But to be fair, blue whales don’t have to worry as much about the crushing weight of Earth’s gravity. The battle is much closer when we compare length: Supersaurus was between 108-111 feet and the largest known blue whale was ~110 feet.

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Blue whale Balaenoptera musculus = heaviest of all time?

The SV-POW paleontology blogger team made a brilliant point that we should suspect that Supersaurus was on average longer than blue whales because we are comparing with biased sample sizes:

A huge sample of blue whales included none longer than 110 feet, while our comparatively pathetic sample of sauropods has already turned in one animal (Supersaurus) that may have just edged that out, and another (A. fragillimus) that – assuming it was really as big as we think – blows it out of the water.

In case you were wondering, A. fragillimus is estimated to have been between 130-200 feet long! It completely blows my mind that a terrestrial organism can reach those sizes on our planet (just imagine how big they would have been if they had evolved on a planet the size of Mars!).

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The red image represents A. fragillimus, potentially the longest organism ever

In case you were wondering, no primate species has ever been a contender for largest living system. The primate order is comparatively small, with the largest contemporary species (gorillas) weighing between 300-400 lbs (or about 0.15-0.2 tons!). Even if we consider extinct species, no primate has ever even been a contender for largest land mammal. The largest, Gigantopithecus, weighed approximately 1,200 lbs (or about 0.6 tons). Of course, I think Gigantopithecus is aptly named (and I think sympatric populations of Homo erectus would agree); but they are only aptly named in comparison to our relatively puny order. Primate size has probably always been constrained by underdeveloped quadrupedalism and selection for long-term infant dependence.

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Reconstruction of Homo erectus and Gigantopithecus in Southeast Asia

However, it is interesting to know that all species body sizes (from prokaryotes to sauropods) are distributed according to a potentially universal power law. This universal describes how ecology influences average species size, while genetics contains variability around that average. In the future, I’ll be interested to see whether evolutionary theorists can better describe the adaptive pressures selecting for larger size. It is useful to have a grasp on the proximate causes of body size, but the ultimate causes will be necessary to better describe how living systems develop over time.

What do you think about the evolution of large size?  Let Cadell know on Twitter!

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Extreme Evolution

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The coelacanth is the oldest living species of lobe-finned fish. In fact, it is so old that it has acquired the nickname “living fossil.” The distinction is probably more an artifact of the history of science than of the coelacanth’s ancientness. In the early 20th century scientists believed that the coelacanth went extinct 70 million years ago (15 million years before the K-T mass extinction!). So when a live specimen was discovered off the coast of South Africa it came as a major shock. Upon first analyzing the fish, South African chemistry professor JLB Smith famously wrote the cable:

MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED

Since this discovery scientists have been perplexed by this Lazarus taxon. How has the coelacanth managed to persevere over the past 300 million years without changing at all?

This question really gets at the heart of a bigger evolutionary conundrum: does evolution have a uniform speed? Or is the speed of evolutionary change intrinsically variable?

Evolutionary theory pioneer Stephen J. Gould was one of the first to propose that evolutionary change varied tremendously. In order to explain this change he proposed the idea of punctuated equilibrium. This theory proposed that species change is largely contingent on environmental change. Gould recognized that morphological stasis could be correlated with ecological stasis. Therefore, he reasoned that massive ecological changes would prove to be the major drivers of rapid selection over the scale of evolutionary time.

This contradicted dominant theory in the 1970s because all theorists embraced phyletic gradualism: the idea that evolution was steady state with gradual transformations changing lineages. In reality, both punctuated equilibrium and phyletic gradualism are not mutually exclusive. We know now that some species can change quickly (in evolutionary terms) in response to major ecological pressures. However, change can also occur gradually over millions of years in response to more subtle ecological changes.

This brings us back to the “living fossil”: the coelacanth. Has this species really remained unchanged for nearly 300 million years? Is it really a “living fossil”? If so, its history would be a remarkable example of how an organisms environment can stabilize selection.

A recent study published in Nature finally gave us some insight into this decades-old evolutionary mystery. In this study the first genome sequence for the coelacanth was reported. The data revealed what had been obvious to many, the coelacanth’s protein-coding genes are evolving slower than any other known animals. One of the researchers in this study, Kerstin Lindblad-Toh explained that:

We often talk about how species have changed over time, but there are still a few places on Earth where organisms don’t have to change, and this is one of them. Coelacanths are very likely specialized to such a specific, non-changing, extreme environment – it is ideally suited to the deep sea just the way it is.”

However, Lindblad-Toh was also quick to emphasize that the term “living fossil” is unscientific and not an accurate representation of a extant species:

It’s not a living fossil; it’s a living organism, it doesn’t live in a time bubble; it lives in our world, which is why it’s so fascinating to find out that its genes are evolving more slowly than ours.

Here is where we can highlight an interesting (and extreme) example of just how variable evolutionary change can occur. Our species, Homo sapiens sapiens, have evolved very quickly. Let’s put this in comparison by comparing our evolution to our slowly evolving coelacanth cousins. Coelacanth fossils have been found that stretch back to the mid-Paleozoic. This is approximately the time the last supercontinent, Pangaea, first formed. That means the coelacanths emerged 70 million years before the entire Dinosauria clade.

In contrast, our genus, Homo, is approximately 2 million years old. Over this period of time our brain has tripled in size. That is unparalleled evolutionary change. I have written extensively about our genetic origins in the past so I won’t repeat myself here. However, I do want to emphasize that one of the drivers of this change has been ecological disequilibrium. Recent studies by several geoscientists have convincingly demonstrated that the East African savanna was characterized by rapid environmental change during a 200,000 year period approximately 2 million years ago. Clayton Magill, a graduate student involved in one of these studies elucidated how these changes could have stimulated punctuated equilibrium-like effects on human brain growth:

Changes in food availability, food type, or the way you get food can trigger evolutionary mechanisms to deal with those changes. The result can be increased brain size and cognition, changes in locomotion and even social changes – how you interact with others in a group. We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use.

Since that period environmental change has played a tremendous role in the creation of our species genotype and phenotype. As modern humans exploded throughout the world, we were forced to adapt quickly to previously alien environments. Most of this adaptation was made possible by our unique ability to drive cultural and technological evolution. However, pertinent contemporary phenotypic differences within our species, like skin colour variation, were also caused by biological adaptation to extreme differences in environmental conditions.

Exploring evolutionary change in the coelacanth and humans represent two major biological evolutionary extremes. Both organisms perfectly encapsulate Stephen J. Gould’s theory of punctuated equilibrium. Ecological pressure can either strongly stabilize selection or drive rapid changes over relatively short periods of time. However, I do want to emphasize that these are the extremes. For many species, phyletic gradualism is king because ecology will change, but it will change slowly.

And don’t forget, today is DNA Day! A time to celebrate the discovery of the molecular backbone of all life on our terraqueous globe! Without the discovery of DNA our knowledge of our own evolutionary past would be relatively impoverished, and this article would not have been possible!

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#DNAday

What do you think about extreme evolution?  Let Cadell know on Twitter!

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Life Before Earth?

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A few days ago biologists Alexei Sharov and Richard Gordon published a paper that sent shock waves throughout the academic community. In their paper titled Life Before Earth they propose that life originated before the formation of our planet. But just in case that wasn’t radical enough, they further state that:

adjustments for potential hyperexponential effects would push the projected origin of life even further back in time, close to the origin of our galaxy and the universe itself.

In my last post I discussed the transition from non-life to life. However, no where in that article did I discuss the timing of that transition. The dominant view at present is that life originated ~3.5 billion years ago. This estimation comes from direct and indirect evidence of prokaryotic (single-cell organism) activity in Western Australia and South Africa. Although it is hard to prove empirically, most biologists are confident that life on Earth did not exist before this period. This is because between 4.6-4.0 billion years ago Earth can best be described as a chaotic hellscape of magma oceans and planetesimal collisions (i.e., not the best place for RNA replication).

But this latest paper by Sharov and Gordon claims life existed before earth (before even the formation of our galaxy). To be precise they calculate the time of origin for life to be 9.7 ± 2.5 billion years ago. For context our galaxy is ~8 billion years old, and our solar system and planet is 4.6 billion years old.

How could this be?

The authors propose that biologists have neglected to acknowledge the “cosmic time scale” of life. In their paper they posit that in terms of genetic complexity life has grown exponentially (they measure genetic complexity by the number of non-redundant functional nucleotides). Prokaryotes, eukaryotes, worms, fish, and mammals were included in the authors study sample and genetic complexity was plotted on a logarithmic scale (Figure 1). With these data they found that genome complexity doubled every 376 million years. They conclude that if genome complexity doubles at this rate prokaryotic complexity could not have been achieved by 3.5 billion years ago. Both Sharov and Gordon blame biologists of presuming a rapid primordial evolution in order to fit the time scales required by our planet’s age.

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Figure 1

Within this new proposed framework the authors suggest that this exponential doubling time is an inherent evolutionary process accelerating quickly with new, more efficient forms of information storage than genomes (e.g., highly complex brains, language, books, computers, internet). Now I am definitely someone that believes exponential growth is an inherent property of evolutionary processes. I am also someone that thinks evolutionary processes generally tend towards greater and greater levels of system complexity (even though recent research has demonstrated that this is not always the case). However, more than doubling the time of the origin of life proposes a radical re-imagining of life and our universe. Such a proposition demands tremendous evidence. I commend Sharov and Gordon for proposing a bold idea and approaching the evolution of life from a novel perspective, but they did not provide us with tremendous evidence.

Biologist PZ Meyers was first to point out that they cherry picked their data. They did not include many organisms that would have completely thrown off their logarithmic scale. Furthermore, even if the logarithmic scale with all organisms plotted remained unchanged it would not be scientific to assume you can project it back to single nucleotide replicators that existed 9.7 billion years ago. Finally, biologists have only started to understand what is and what is not functional within the human genome. Therefore, we cannot assume that measuring genome complexity based off of our current understanding of functional non-redundant nucleotides is useful.

Unfortunately the claim that life originated 9.7 billion years ago might destroy the credibility of both the paper and the authors. I say unfortunately because within this paper the authors actually make a profound claim that I agree with:

The Drake Equation of guesstimating the number of civilizations in our galaxy may be wrong, as we conclude that intelligent life like us has just begun appearing in our universe. The Drake Equation is a steady state model, and we may be at the beginning of a pulse of civilization. Emergence of civilizations is a non-ergodic process, and some parameters of the equation are therefore time-dependent.

Recently I wrote about why I think it is highly probable that we are the first intelligent civilization to develop in our galaxy. My main reasons for thinking this are:

A) Our universe was not always well-suited for the evolution of life

B) Biological evolution requires billions of years of planetary stability

C) Biological evolution can produce trillions of species without ever selecting for high-intelligence and civilization

There are actually many more reasons why I think this is likely so I suggest reading my entryIntelligent Life in the Milky Way if you want to know more about it. Either way, my line of reasoning is certainly in line with Sharov and Gordon’s assertion that “intelligent life like us has just begun to appear in the universe.” Although they come at it from a slightly different perspective, I obviously find this assertion profound and compelling.

In the end I think Life Before Earth is worth a read if you are interested in learning more about Sharov and Gordon’s claims; but I am personally not sold. Biologists may never know the precise historic pathway of inanimate to animate matter and the specific materials present on the prebiotic earth, but I still think a 3.5 billion year origin for life is more likely than a 9.7 billion origin.

In the future biologists do need to demonstrate how biological evolution was able to produce highly complex prokaryotic genomes in a relatively short period of time. There could be a number of currently unknown reasons for this that do not require a single-nucleotide replicator with pre-galactic origins.

That is not to say that life could not have originated completely or partially from space. The idea that asteroids with complex organic compounds seeded our planet during the late-heavy bombardment 4 billion years ago is quite possible. But positing the chemical compounds necessary for life existed 9.7 billion years ago requires more evidence than a logarithmic scale with cherry picked data points.

What do you think?  Let Cadell know on Twitter!

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From Non-Life to Life: The Unity of Evolutionary Processes

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The origin of life. If there is a more controversial (or complex) scientific problem I have yet to encounter it. Well… the origin of everything, or why there is anything at all is perhaps a little more controversial and complex. But the origin of life is certainly in the top 5. I know it is a scientific problem that has consistently perplexed me. But I shouldn’t feel too bad because it seems to have stumped even the brightest scientific minds. However, a study by chemists Addy Pross and Robert Pascal published in Open Biology last month seems to have laid out one of the most impressive working hypotheses I have seen to explain the transition from non-life to life. The paper is boldly titled: The origin of life: what we know, what we can know and what we will never know. It is open access and a tremendous read.

For several decades evolutionary theorists have been working hard to extend the concept of biological evolution into the realms of physics, chemistry, culture, and technology. In my mind this extension is imperative because it will help us more clearly understand major system transitions and the processes that drive change in our universe. The most important of these major system transitions is the transition from non-life to life. We know that biological evolution via well-understood mechanisms (e.g., selection, mutation, gene flow, genetic drift, etc.) allows for the existence of a complex and diverse biosphere. But we do not know how inorganic matter becomes organic matter.

In the recent publication by Pross and Pascal, they first outline what they feel we will never know about this transition: a) the precise historic pathway of inanimate to animate and b) the specific materials present on the prebiotic earth. I agree with them and I can’t overstate how important it is that they recognize this. I feel like attempting to re-create the environment of prebiotic earth is the biggest theoretical and methodological flaw scientists make when investigating the transition from non-life to life. Those experiments are admittedly interesting, but they are not falsifiable.

What we need to do is build an understanding of the relationship between chemistry and biology. Pross and Pascal believe that they have successfully elucidated this relationship. They state that:

In the context of the [origin of life] debate, there is one single and central historic fact on which there is broad agreement – that life’s emergence was initiated by some autocatalytic chemical system.

Adding that:

It follows that the study of autocatalytic systems in general may help uncover the principles that govern their chemical behaviour, regardless of their chemical detail. Extending Darwinian theory to inanimate chemical systems: The recognition that a distinctly different stability kind, dynamic kinetic stability (DKS), is applicable to both chemical and biological replicators, together with the fact that both replicator kinds express similar reaction characteristics, leads to the profound conclusion that the so-called chemical phase leading to simplest life and the biological phase appear to be one continuous physicochemical process, as illustrated in scheme 1.

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Under this working framework it does not necessarily matter what organic molecules were present on the prebiotic earth. What matters is that we can understand how replicating systems work, whether they be chemically based, biologically based, or some grey zone between these two replicating worlds.

A theory to unite how replicating chemistry forms the basis of biological systems has been long in coming. Addy Pross suspects there has been such a lack of progress on this unification because chemists have a much better grasp on the static “regular” chemical world. However, he contends that there are “two chemistries”: one static and one dynamic. And both of these worlds produce stability (i.e., persistence over time) in very different ways.

Pross believes that there is enough empirical evidence from the study of systems chemistry to conclude that replicating molecules can persist via Dynamic Kinetic Stability (DKS). This type of chemical stability is vastly different than regular chemical stability. With regular chemical stability molecules lack reactivity. A good example of this is the molecule H2O, which is a hydrogen-oxygen mixture that forms a stable bond over time (it persists as a “thing” and we call that thing water). This hydrogen-oxygen mixture can form rivers, lakes, and oceans that can persist as a stable entity for an indefinite amount of time. However, replicating chemistry has a different type of stability that must operate on the population level because they are highly reactive. DKS essentially is the product of a group of replicating molecules that can be stable over time as a “population” even though their individual members are constantly changing (which is very different from how a “population” of H2O molecules achieve stability). These systems tend to drift from less stable to more stable over time non-randomly. The quantitative level of stability for the replicating system is dependent on a) its overall size and b) the amount of time it has existed. Again, this is very different from something like water that can possess the same level of stability regardless of its size or how long it has existed.

If this is difficult to conceptualize you could apply the same concept of a biological species and it should come into clear focus. Think of the human species. We have persisted for over 150,000 thousand years as a single biological system, and yet our individual members are always changing (at least for the time being #singularity). Other biological systems have achieved even greater stability. For example, cyanobacteria have remained essentially unchanged for 2.5-3.5 billion years. This ancient form of life, a dynamic system, has achieved greater stability than Mount Everest! And within this analogy resides the key to the discoveries within modern systems chemistry: replicating chemical systems essentially “behave” in the same way that replicating biological systems do. This means that abiogenesis – chemical process by which the simplest life emerged from inanimate beginnings – may have an underlying physicochemical continuity with biological evolution that had previously been unrecognized. A non-random selection for stability and complexity.

For me this research is incredibly fascinating for two reasons: 1) systems chemistry reveals that evolution operates at deeper, more fundamental levels of reality via potentially analogous mechanisms and 2) we are now theoretically able to build models of understanding that the origin of life is a non-random evolutionary process.

This research has very deep implications for how common we should expect life to be in our universe. If life is a product of replicating chemical reactions that acquire stability and increase in complexity via selection mechanisms, we should expect molecular life to be ubiquitous.

This discovery could represent a critical reformation of how we understand and conceptualize the universe. If studies of systems chemistry had revealed that at the molecular level there was only random chemical reactions, then our existence would begin to look extremely bizarre. I mean really, really bizarre. The chances of random chemical processes leading to the complexity we find at even the simplest biological levels is essentially zero. Pross and Pascal eloquently end their paper stating as such:

There is good reason to think that the emergence of life on the Earth did not just involve a long string of random chemical events that fortuitously led to a simple living system. If life had emerged in such an arbitrary way, then the mechanistic question of abiogenesis would be fundamentally without explanation — a stupendously improbable chemical outcome whose likelihood of repetition would be virtually zero. However, the general view, now strongly supported by recent studies in systems chemistry, is that the process of abiogenesis was governed by underlying physicochemical principles, and the central goal of [origin of life] studies should therefore be to delineate those principles.

I am very excited to see what future studies in systems chemistry reveal about these underlying principles. I am already formulating my hypotheses! It seems likely to me that the basic evolutionary mechanisms that have been so profoundly useful for describing all life, will also help us explain how other dynamic systems change over time. And hopefully this research will not always remain theoretical. Although we cannot recreate the prebiotic Earth, but if we ever go to Europa or peak at another Earth maybe we will be able to see the transition from non-life to life first hand.

It is an exciting time to be alive!

What do you think about the non-life to life transition?  Let Cadell know on Twitter!

Also posted via Svbtle:

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Complexity by Subtraction

At the age of 17, I had never given any serious thought about “how life got here.” If you had asked me at the time I would have said I had no clue, which is ironic considering I now study and write about evolution for a living (well… trying to make a living).

Either way, as a young adult without any science background or knowledge, I was introduced to the world of science through the pseudoscientific concept of Intelligent Design. A family friend had introduced the idea to me and told me that it was a concept that could explain all of life. He sent me a book by biochemist Michael Behe titled Darwin’s Black Box. Of course, the book was way over my head but it seemed reasonable, logical … and scientific.

Throughout Darwin’s Black Box Behe argued that life could not have arisen via evolution because cells and organisms were “irreducibly complex.” He used examples of how the human eye is functionless in a “simpler” or “less complex” form, and therefore could not have been selected for gradually via natural selection. He also used the analogy of the mousetrap to explain that if you take out any one part of a mousetrap it will no longer be functional. He reasoned that that was because it required an intelligent designer, and that biological systems operated in the same way so their existence was proof of an intelligent designer.

I thought the ideas were certainly plausible. But more than anything it stimulated me to learn about the processes he was critiquing: biological evolution. After reading On the Origin of Species and several modern science books describing the processes by which evolution occurs, I instantly realized that Intelligent Design was a pseudoscientific attempt to legitimize creationism.

Several scholars have demonstrated that irreducible complexity is empirically false. There may be no “irreducibly complex” structures in nature. Eyes for example, while complex have (and do) evolve from simpler forms and structures. There are several examples of eyes in nature that can only detect a few photons of light. These are called “eyespots.” Eyespots are simple patches of photoreceptor proteins in unicellular organisms. The ability for eyespots to detect photons is minimal, however being able to distinguish between light and dark could be the difference from a meal or becoming a meal. Researchers have demonstrated that even very primitive eyes are adaptive and can evolve complexity gradually to suit various functions.

But the point of this article is not to provide another redundant analysis of why Intelligent Design is pseudoscience. This morning an article titled Complexity by Subtraction was published in the journal Evolutionary Biology that proposes an alternative evolutionary process to disprove irreducible complexity. In the article, evolutionary biologists Dan McShea and Wim Hordijk propose that it is also possible for complex structures to evolve from complex beginnings and then gradually become simpler. They call this idea “complexity by subtraction”. In this sense, the idea of complexity by subtraction counters the dominant mode of evolutionary thinking that posits that adaptation tends to select for ever more complex forms and structures. In their words:

Standard thinking says that the evolution of complex functionality is driven by selection, by the functional advantages of complex design. The standard thinking could be right, even in general. But alternatives have not been much discussed or investigated, and the possibility remains opent hat other routes may not only exist but may be the norm.

However, they do more than posit that adaptive processes may not always tend towards increasingly complex functionality. They used a computational model simulation to demonstrate that complexity by subtraction is theoretically possible. And they also used an example of skull complexity in nature to show that vertebrate skulls have actually decreased in complexity over time. Co-author Dan McShea stated:

The skulls of fossil fish consist of a large number of differently shaped bone types in the evolutionary transitions from fish to amphibian to reptile to mammal. In some cases skull bones were lost; in other cases adjacent bones were fused. Human skulls, for example, have fewer bones fish skulls.

The authors defined complexity in a biological structures as having “many different parts.” To me, both authors propose an interesting aspect of evolutionary theory that has yet to be explored fully. The notion that simplicitic functional structures could become adaptive is certainly counter to dominant thinking at the moment in evolutionary science. In the few examples I have heard of biological structures becoming less complex involve structures that were once functional, but are no longer. However, if functional biological structures can become simpler, this will really change our understanding of evolutionary theory. Although I am only aware of examples of complexity by subtraction from this paper, I do find both their computational simulation and examples of skull evolution from the paleontological record compelling. Of course there research raises more questions than answers and should spur interesting new research. For example:

  • Do functional structures tend towards simplicity or complexity?
  • Are their certain environmental situations that would lead towards one over the other?
  • Does complexity by subtraction impact evolution on the microevolutionary scale?
  • How does increased simplicity become adaptive?

This is all very interesting, but a report by Science Daily emphasized that this studies primary intellectual importance was to provide evolutionary scientists with “an alternative route” to debunking Michael Behe’s concept of irreducible complexity. To me, this seems like an unnecessary overstatement.

I am not sure whether McShea and Hordijk also believe this, but this concept is in no way an “alternative route” to debunking irreducible complexity (not that evolutionary scientists need a new concept to debunk irreducible complexity). The concept of complexity by subtraction simply explains how adaptation of a functional biological structure can become less complex over time; it does not explain how biological complexity itself evolves in nature. To explain increasing biological complexity an understanding of gradual adaptation is still all that is really necessary.

Either way, McShea and Hordijk have proposed and demonstrated an interesting evolutionary concept that complicates current theory. If I were to guess, I would suspect gradual adaptation for increasingly complex functional structures to be far more common than complexity by subtraction. Despite this, I am certainly excited to see what future research reveals about the role complexity by subtraction plays in the origin of species.

What do you think of complexity by subtraction?  Let Cadell know on Twitter!

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