At first glance, my title this week might seem like an odd question or the opening to a joke. In fact, the question is asked and answered in the Pāḷi Mahāvedalla Sutta (MN 43). This is one of those suttas that seems to be an attempt to comprehensively summarise Buddhism as it was understood at the time, but not in a standard Theravāda way.
The Mahāvedella is a teaching by Elder Sāriputta for Elder Mahā-Koṭṭhita. The pair are also portrayed as speaking together in the Koṭṭhita Sutta (AN 9.13) and another Koṭṭhita Sutta (SN 35.232).
In this case, the sutta includes some ideas that are rare elsewhere. What the Pāḷi texts repeatedly show is that different ancient Buddhists thought about the same terms in different ways. Not everything that we find in a Pāḷi sutta was incorporated into Theravāda Buddhism, even in theory.
The Mahāvedalla Sutta
The Mahāvedalla Sutta is a series of questions and answers. For example, the first question asks for a definition of "faulty pañño" (duppañño; Skt duḥprajñā) and compares this with someone endowed with pañño (paññavā; Skt. prajñāvat). Note how these are not quite opposites. The natural opposite of duppañño would be supañño; while the opposite of paññavā would be apaññavā. No doubt there was a story here, but it's lost to time. It's not clear how the Mahāvedalla-kāra understood pañño, the adjectival form of paññā, but in Prajñāpāramitā it seems to connote the knowledge gained by undergoing cessation (nirodha). The series of questions continues. Define "discrimination" (viññāṇaṃ; vijñāna)? What is the difference between viññāṇaṃ and paññā? The answer here is that paññā is to be cultivated; discrimination is to be comprehended (paññā bhāvetabbā, viññāṇaṃ pariññeyyaṃ).
This explanation leaves me in the dark about the distinction, I think, because I lack the context in which to understand it. There is one other reference to cultivating paññā in Pāḷi. The Rāga Sutta (AN 6.107) describes a group of three things to be abandoned (raga, doha, moha) and three to be cultivated (asubha, mettā, and paññā) in order to eliminate them, i.e. cultivating understanding (paññā) dispels confusion (moha). This one is comprehensible on its own, but doesn't help us to distinguish paññā from viññāṇa. It seems that the Mahāvedalla-kāra did not see viññāṇa as something that could be cultivated or abandoned. But this doctrine was not developed by Buddhists and all we have is this incomplete snapshot. This happens a lot in the Pāḷi suttas.
Then the sutta asks, what is valence (vedanā) and recognition (saññā)? And are these three—saññā, paññā, vedanā—inseparable? The sutta-kāra says they are not separable because "what one experiences, that one recognises; what one recognises one discriminates" (yaṃ hāvuso, vedeti taṃ sañjānāti, yaṃ sañjānāti taṃ vijānāti MN I 293). Note that the traditional skandha meditation practice is predicated on being able to distinguish these three, while here the three are said to be impossible to distinguish individually (na ca labbhā imesaṃ dhammānaṃ vinibbhujitvā vinibbhujitvā* nānākaraṇaṃ paññāpetuṃ).
* The repetition of vinibbhujitvā here is odd, but seems to be in the original texts.
Then a change of pace. "Comrade, what can be inferred by purified mental discrimination that dismisses the five [physical] senses?" (Nissaṭṭhena hāvuso, pañcahi indriyehi parisuddhena manoviññāṇena kiṃ neyyan ti?)
* Ñāṇamoḷi & Bodhi "Friend, what can be known by the purified mind-consciousness released from the five faculties?
Interestingly, what can be inferred or understood (neyyan) from this are precisely the āyatana states. From the statement (or thought) "space has no limits" we can infer the stage of limitless space (ananto ākāso’ti ākāsānañcāyatanaṃ neyyaṃ); from "there is no limit to discrimination" we infer the stage of limitless discrimination can be inferred (anantaṃ viññāṇan ti viññāṇañcāyatanaṃ neyyaṃ); and from "there is nothing" we infer the stage of nothingness can be inferred (natthi kiñcī ti ākiñcaññāyatanaṃ neyyaṃ). And we know this phenomenon through the eye of paññā (paññācakkhunā). And what is the purpose of paññā? It is higher knowledge (abhiññatthā), exact knowledge (pariññatthā), and abandonment (pahānatthā). The latter refers to eliminating sensory experience (cf. Pahāna Sutta SN 35.24).
More questions follow on right view (sammādiṭṭhi), being (bhava), first jhāna, the five faculties, and then the section that really interests me.
Life and Heat
The pertinent question is, "On what condition do the five faculties depend?" (pañcindriyāni kiṃ paṭicca tiṭṭhantī ti); where the five faculties are eye, ear, nose, tongue, body. The Mahāvedalla Sutta says that they depend on āyu "life" (Skt āyuḥ; as in āyurveda). Life itself depends on the condition of "heat" (āyu usmaṃ paṭicca tiṭṭhati) but, at the same time, heat depends on the condition of life (usmā āyuṃ paṭicca tiṭṭhati). The relation between the two is explained by an analogy: it's just like how seeing the light of a lamp is dependent on seeing the flame, and seeing the flame is dependent on seeing the light. This mirrors the analogy between mutually conditioning viññāṇa and nāmarūpa in the Mahānidāna Sutta (DN 15) there conceptualised as two sheaves of harvested grain that lean against each other (called a "stook" in English).
Life and heat are not a common topic in Pāḷi; they occur together in just three texts including the Mahāvedalla Sutta, and I will digress briefly to consider the other two. We find life and heat together in a verse at the end of the Pheṇapiṇḍūpama Sutta (SN 22.95) where death is equated with the absence of āyu, usmā, and viññāṇa (SN III 143). In the Kāmbhū Sutta (SN 41.6), which features a discussion between the patriarch* Citta and the bhikkhu Kāmbhū, we find a similar discussion of the difference between a corpse and a meditator experiencing cessation (Starting at SN IV 294). Here the bodily, verbal, and mental formations (kāya-, vācī-, and citta-saṅkhāra) cease in a meditator undergoing cessation. However, they still have life and heat, and their "faculties are serene" (indriyāni vippasannāni).
*Gahapati refers to the patriarch of an extended household or possibly an extended family within a clan structure. Standard translations like "householder" seem to miss the point.
Note the inconsistency here: a living person in both texts has life and heat, but the third factor is viññāṇa in one account and indriyāni in another. Here we might conjecture that viññāṇa is intended as the function of the indriyāni, i.e. objectification is the function of the sense faculties. We could, at a pinch, see the two terms in this context as synonyms. Though this is a neat solution, we have to consider other possibilities as well. The two texts may be trying to say something different and incompatible that we no longer understand (this is not uncommon between two Pāli texts).
I don't understand how we came to translate viññāṇa as "consciousness" but it seems plain wrong to me. Notably, viññāṇa is an action noun rather than an abstract noun, so viññāṇa and consciousness are not even on the same level of abstraction. It is my view that no Pāḷi word can be translated into English as an abstract noun "consciousness" and that our whole philosophical concept of "consciousness" is absent from ancient Buddhist dialogues (see also The 'Mind as Container' Metaphor). The use of "consciousness" in discussing ancient Buddhist discourses is a Whiggish anachronism (in which we imagine ancient Indians to be primitive precursors of ourselves).
In any case, the gist here is clear. It can be very difficult to distinguish a meditator from a corpse by the usual signs of life that we look for in a conscious and aware person, because we cannot interact with them. We could say that following cessation a person becomes completely unresponsive to the world around them. People undergoing cessation of sensory experience necessarily lack all sense of time, since all of the clues to the passing of time have, by definition, ceased. Hence, perhaps, the Buddhist insistence that the Buddhadharma is akāliko "timeless", though in a culture where death is often referred to as kālaṅkato "having done one's time", akāliko could also be a synonym for amata "deathless" (Skt. amṛta). The phenomenon of people sitting lost in samādhi for days on end is likely related to their undergoing cessation and having no sense of time passing. It is likely that thirst, i.e. a need for water, is what rouses them. Being dragged out of samādhi by thirst may explain why "thirst" (Skt. tṛṣṇa;P. taṇha) became such a key word in the Buddhist lexicon.
Life Force
Coming back to the Mahāvedalla Sutta and moving to the next section the subject is now "life" (āyu) and the "constituents of life" (āyu-saṇkhārā). The sutta explicitly states that these "constituents of life" are not phenomena that one can experience (na kho, āvuso, teva āyusaṅkhārā te vedaniyā dhammā). And then it says that, if the āyu-saṅkhārā were phenomena to be experienced, the one who experienced the cessation of awareness and experience would not emerge from their meditation, that is to say they would die. The logic here is that if āyu and āyu-saṅkhāra were part of the experienced world, then when the experienced world ceased, so too would life. Rather, the text makes the apposite observation that life continues even when all sensory experience ceases.
What did the sutta-kāra mean by āyu and āyu-saṇkhārā? It is difficult to say, because the terms are not defined. Sujato has blogged about how the words āyusaṇkhāra and jīvitasaṇkhāra are used. There is not a great deal more to be said. In the Mahāparinibbāna Sutta (DN 16) the Buddha mentions jīvitasaṅkhāra in a sense that Sujato interprets as a "will to live". He is, I think, here relying on the traditional idea that saṅkhāra means "volition" because it is explained as the six kinds of cetanā associated with the six sense spheres.
This meaning of saṅkhāra derives from the earlier Brahmanical use of the Sanskrit equivalent. In Vedic ritual, a saṃskāra is a rite of passage. When performing these rites, the Brahmin priests carry out a series of actions (karman). Hence, in Buddhist usage, saṇkhāra/saṃskāra is "an opportunity for doing karma". Keeping in mind that all intentional acts carry a karmic debt. At the same time, the unique but influential passage in AN 6.63 famously says "intention is how I talk about karma, monks" (cetanāhaṃ bhikkhave kammaṃ vadāmi). Thus an opportunity for doing karma becomes an intention to act.
Whether this meaning can be applied to āyusaṅkhāra is moot and, since Sujato doesn't make this case, we are none the wiser. He finds a way to make sense of jīvitasaṇkhāra as "the will to life" and then retrospectively relates āyusaṇkhāra to this as a kind of "vital force". In the end, however, Sujato concludes that distinction between āyusaṇkhāra and jīvitasaṇkhāra probably emerged later and that the two words are synonyms for "vitality" and "vital energies" and are best translated as "life force". This is a self-consistent explanation and it might be right. But there is presently no way to confirm such conjectures: we are trying to make sense of how a word was used in the absence of any contemporary explanation and from just a few instances that are vague and/or ambiguous. This is a common problem when dealing with older Buddhist texts (in any language).
Across the ancient world we repeatedly encounter the idea of a "life force", but it is almost always conceptualised as breath. Words indicating breath as life force include: psyche, anima, spirit, qi 氣, and prāṇa. For more on this theme see my 2014 essay: Spiritual I: The Life's Breath. In the Indian context the vital force is āṇa "breath" which itself is caused by the action of the element of wind (vāyu). Vāyu conceptualises all forms of movement. The word āyu,however, does not refer to "breath". Rather, it is related to the words aeon and age, and often refers to lifespan or longevity. Breath (āṇa) is what animates the body (kāya); the resulting animation seems to be called āyu (and is accompanied by usmā). Similarly, jīva is not related to breath but is cognate with Greek bio, Latin vivarus, and Germanic quick; all meaning "life; living".
These are not ideas that were integrated into later Buddhism. Nor does the concept of a life-force as distinct from mind and body ever become mainstream. The reason is obvious, and has also bothered European philosophers. If there were a "life-force", then it would surely have a roll to play in facilitating life after death. And if it is present in all living things, as appears to be implied, then we are in the realms of eternalism: that is to say āyu starts to sound suspiciously like ātman. Not surprisingly most Buddhist schools of thought set the idea of a "life force" outside of their orthodoxy and āyusaṅkhāra never became a mainstream Buddhists' technical term. Moreover, Buddhist knowledge of physiology never really developed beyond this Iron Age conception.
Conclusions
To answer the question in the title, a meditator and a corpse are similar in that signs of life in the form of actions of body, speech, and mind are absent. Even though the meditator is insensate, or even catatonic, they are still alive; still warm. The corpse is cold and lifeless (and decay sets in almost immediately).
Presumably, this was enough of an issue for the early Buddhists thought that it required some doctrinal explanation. That said, the terms used to explain the difference—like āyu and āyusaṅkhāra—did not seem to need an explanation in the minds of the author(s). Leaving us scratching our heads.
This sutta is not consistent with Theravāda Buddhism, if only because it unequivocally states that vedanā, saññā, and viññāṇa cannot be distinguished from each other. Nor is this statement consistent with any form of Buddhism I am familiar with. The Mahāvedella Sutta appears to be from an unknown sect of Buddhists, missing from the historical record. Their text was preserved, but the teaching lineage associated with it was not. I suspect this is true in a large number of Pāḷi suttas.
However, that āyu and usmā occur together in three texts suggests that at least some Buddhists believed in some kind of "life force" as distinct from a soul (ātman). A life force (jīva) was also important in Jain theology, where it provided the necessary continuity for rebirth. At least some Buddhists further conceptualised life as composite and posited life-constituents (āyu-saṅkhāra). However, in the end we don't know precisely what words like āyu or āyusaṅkhāra meant to those people then, because they didn't say and there is not enough context to guess.
In this case it is very tempting to smooth over the difficulty by conjecturing an answer that solves all the problems, is plausible, and self-consistent. However, this is not sufficient to establish how the author(s) thought. Any number of plausible, self-consistent answers are possible. But we have no objective facts available to help us choose between them.
In an essay in my series on Vitalism (Crossing the Line Between Death and Life, 30 May 2014), I mentioned the Miller-Urey experiment in 1953 as a breakthrough in the study of abiogenesis - the emergence of living things from non-living matter. It turns out, however, that having produced amino-acids and some other medium-sized organic molecules, nothing much else happens in these "organic soup" style experiments. Getting a soup of organic molecules to do anything interesting has proved an intractable problem and neither electrocution, bombardment with ultraviolet light, nor physical shocks help. New research has shown that Miller's estimates of the early atmosphere of the earth were probably wrong. He assumed the atmosphere of Jupiter would provide a good model for the early atmosphere of the earth: ammonia, methane and hydrogen. However, the heavy asteroid bombardment during the early epoch of the solar system, during which our moon was formed, blasted off the existing atmosphere and it was replaced with an atmosphere of mainly carbon-dioxide and nitrogen, with only traces of methane and other gases. Similar gases make up the modern day atmospheres of both Mars and Venus. Unfortunately, this mix of gases is very much less likely to get even as far as amino-acids in the Miller-Urey set up. So the idea of a naturally occurring organic soup fails on two counts: it probably never existed, and even if it had, nothing interesting happens in sterile soup (more on this below). Some comets and meteorites have a mixture of water and organic compounds similar to those produced by Miller-Urey and thus some of the building blocks of life may have come from space, but this still leaves us with the organic soup problem.
Another hypothesis of how life emerged from non-living matter has recently emerged and been promoted by British scientist, Nick Lane (amongst others), This is described in his book Life Ascending: The Ten Greatest Inventions of Evolution (2009). This hypothesis is known as the Alkaline Hydrothermal Vent Origin of Life. For the full detail of this hypothesis, see Russell et al (2013) and the "further reading". In this essay I will both paraphrase and embellish the version of the theory set out in Lane (2009).
We begin with a caveat. Even if we show that this theory is possible and plausible, it still won't tell us exactly how life began here. That is impossible to know. But if we can show that the chemical reactions that underpin life can be started in similar conditions, then we may be able to better understand life more generally. There will be general rules that govern the emergence of life and we can specify some of those rules. In addition if we can show that life emerging from chemistry is plausible it further undermines any remaining tendency to explain life through forms of Vitalism.
One thing we can already identify is the basic chemistry of life. For example all life on earth involves reducing carbon-dioxide (CO2) to methane (CH4) and water (H2O). Some organisms do this directly, most do it indirectly, but this is what all organisms do at a minimum. And since this doesn't happen spontaneously in an organic soup, we need to specify the kind of conditions in which it will happen.
By 3400 million years ago, the signs of life on earth are unequivocal. The first life seems to have been in the form of bacteria or archaea. Taxonomists now recognise five kingdoms of living things: animal, plant, fungi, bacteria, and archaea. On the surface bacteria and archaea can be indistinguishable, but internally, chemically there are major differences (I'll say more on this later in the essay). Archaea are typically found in niches involving high temperatures, extremes of pH (both acid and alkali) or other factors that would kill most organisms. They are sometimes called extremophiles.
We can see in fossils of this early period, and perhaps earlier, the ratio of carbon isotopes that we expect to see from fossilised living things. This ratio, which sets life apart from non-living chemistry, is the basis of Carbon-14 (14C) dating. We also see fossilised structures of a form of life that we still see in shallow oceans today, i.e. the stromatolite. Archaea and bacteria continued to be the dominant forms of life for 2500 millions years before fossils of complex organisms begin to appear. Arguably they still are the dominant form of life, exploiting a vast range of ecological niches and far outweighing any other form of life in terms of biomass.
Replicators, molecules which copy themselves accurately, seem to be essential to any form of life and thus most existing theories have focussed on how such molecules might have been produced, usually in a soup of organic precursor compounds (like Miller-Urey). However, Lane refers to the various "organic soup" theories as "pernicious" because the idea deflects attention away from the underpinnings of life. As Lane says, if you take a tin of actual (sterilised) soup and leave it for a few million years it does not spawn new life, instead all the complex molecules gradually break down into simpler molecules. In other words following the dictates of thermodynamics the soup goes in the wrong direction. "Zapping" it with electricity or radiation only accelerates the degradation. The laws of thermodynamics means that a soup is far too unlikely a route to life. One can never ignore thermodynamics as they govern everything.
Thermodynamics - The Science of Desire
The physics of matter is a story of attractions and repulsions and thus, according to Lane, "it becomes virtually impossible to write about chemistry without giving in to some sort of randy anthropomorphism." (13-14) I'll do my best. Chemical reactions happen if all the participants want to participate or can be forced to. Molecules "want" to exchange elections or can be induced to overcome their shyness.
The molecules in food want very much to react with oxygen, but don't do so spontaneously, fortunately or we'd all go up in flames! Even reactions that result in a net release of energy often require some "activation energy" to overcome their "shyness" or initial reluctance to react. Another way of looking at the chemistry of life is that it boils down to the juxtaposition of two molecules, hydrogen and oxygen, out of equilibrium. They react with a discharge of energy, leaving warm water. And this is the problem with the organic soup theory - nothing wants to react, so nothing happens. There is no disequilibrium that might drive the necessary reactions. Disequilibrium is a key to life.
Some origin of life theories focus on RNA, the single-stranded counterpart of DNA, which under certain conditions can self-replicate (normally in a cell RNA replication is dependent on large protein complexes called ribosomes). The idea that a very complex molecule like RNA might have come about without a thermodynamic disequilibrium driving the reactions is not credible. Thus although self-replicating RNA is plausible, there must be more to it. RNA is composed of nucleotides which combine an amino-acid, a sugar (ribose) and a phosphate group. As monomers (ATP), dimers (NADH), and polymers (RNA, DNA), nucleotides play several vital roles in living cells. Although we get amino acids from the Urey-Miller experiment, nucleotides are very much more difficult to make. Nucleotides do not just form spontaneously. One cannot just throw amino acids, ribose, and phosphate into a bucket and expect nucleotides to form. In fact it is worse than this because the conditions required for the synthesis of ribose and amino-acids are very different and they could not happen in the same bucket. They must be synthesised separately and then brought together. But then the reaction will not take place in the presence of water. Nor do nucleotides easily polymerise in the absence of a catalyst to form RNA or DNA. Although aspects of RNA based explanations of the origin of life remain plausible, RNA is certainly not the first step in the direction of life. Many conditions had to exist in order for RNA to be synthesised. If life did not evolve in a chemical soup, where did it come from?
An important clue was the discovery of vents on the sea-floor close to the great ocean ridges where the tectonic plates are forced apart by up-welling magma. These vents, known as "black smokers", spew out hot (300-400°C), acidic water, laden with chemicals, particularly metal and hydrogen sulphides (which account for the dark colour). They support a variety of lifeforms at densities rivalling rain forests. Bacteria use hydrogen sulphide (H2S) to power their metabolism. Effectively they detach the hydrogen from H2S and attach it to carbon dioxide to form organic matter and elemental sulphur (and this is one of the most direct processes for reacting H2 with CO2). This conversion requires energy and it comes from the juxtaposition of two worlds in dynamic disequilibrium, i.e. from cold sea water and the hot vent water. The bacteria that sustain this world live at the margins where the two meet and mix. Then some animals graze on the bacteria and a food chain is established. Or else the bacteria live in symbiotic relationships inside the animals. Tube-worms for example host such bacteria which feed them and because of this do not have a digestive system.
These hot vents became a candidate for the origin of life since the disequilibrium solved the thermodynamic problem. Possible mechanisms for life emerging at these hot vent sites were proposed by German chemist and patent attorney, Günter Wächtershäuser. These involved chemistry taking place on surfaces of iron-pyrites. Unfortunately conditions on the early earth make this route unlikely. Oxygen is still central to the metabolism of the vent archaea and bacteria. They still react hydrogen and oxygen, if only indirectly. There is also the concentration problem, that is, bringing enough of the reactants together in open water to make a self-sustaining reaction. For life to come about organic molecules must dissolve in water and somehow react to form polymers like RNA. But this is extremely unlikely if they are not contained (by a membrane) and concentrated.
Alkaline Vents
Serpentenized olivine
A second kind of hydrothermal vent was predicted Mike Russell, now working at NASA's Jet Propulsion Lab. Russell had conjectured that these other vents would be an even better candidate for the origin of life. Alkaline vents are not volcanic, but rely on the reaction between a type of rock called olivine and sea water. Such rock undergoes a process known as serpentinization after a common form of this rock, serpentine, which is green and thought to resemble the scales of a snake. In serpentinization, water becomes incorporated into the structure of the rock which expands and fractures. The volume of water incorporated in this way is believed to equal the volume of the all the oceans. But the water and rock also chemically react, producing highly (chemically) reduced compounds such as hydrogen, methane and hydrogen sulphide and a high pH value, i.e. the water in serpentinized rock is strongly alkaline. The reaction is also exothermic, i.e. heat producing, and so drives the convection that powers the alkaline vents. The reaction can be represented in simplified form as:
olivine + H2O → serpentinite + H2 + heat
or
2Fe2+ + 2H2O → 2Fe3+ + 2OH- + H2
Alkaline vent Structure
Note that hydrogen and methane were key ingredients in the Miller-Urey experiments in the 1950s. Having been first predicted by Russell in the 1980s, living vents were discovered in 2000 during a submarine expedition to the mid-Atlantic. The vents form spectacular coral-like structures (right) that can be 60m in height.
The water coming from these vents is warm (70-80°C), highly alkaline (ph 9-11) and filled with chemicals produced by serpentinization, particularly hydrogen. By contrast, in the early oceans, the water would have been cool, slightly acid (pH ~5.5), and much richer in CO2 and iron than the present day ocean. As the hot, chemical rich water mixes with the cold sea-water some of the chemicals precipitate out to form porous limestone structures, filled with tiny chambers roughly the size of an organic cell. The compartments could provide a natural means of concentrating organic molecules. While modern vents tend to lack iron, the composition of the ocean 4 billion years ago would have meant that the early vents did have iron and other metal compounds (particularly nickel, magnesium, and molybdenum) with catalytic properties embedded in their walls. Mike Russell has argued that the iron/sulphur minerals in these structures resembled enzymes that some modern living cells, especially archaea, use to catalyse chemical reactions. The flow through these early vent structures replenished basic reactants, carried off by-products, and prevented catalyst surfaces from becoming fouled, while also allowing for organic molecules to concentrate. The thin walls of the chambers provided membranes, one of the essential features of living things, with very different conditions of temperature and especially pH on either side, thus creating exactly the kind disequilibrium required to power living things.
Disequilibria
The vents provide two kinds of disequilibria that can act as drivers of chemical processes. These are quite technical and I'll try to simplify.
highly reduced electron donors
pH imbalance or proton gradient
Electron Donors
1. Bubbling up from the vent are gases like hydrogen and methane produced by the reaction of water with mantle minerals like olivine. In the presence of iron and molybdenum catalysts in the walls of the vent structures, these come into contact with CO2 and nitrogen oxides dissolved in the water. When hydrogen reacts chemically it readily gives away its single electron to another molecule to create a hydrogen ion or proton. In chemical terms this giving away of an electron is called "reduction". Oxygen is the prototypical acceptor of electrons and thus this side of the reaction is called "oxidation". When iron is oxidised to rust, what is happening is that oxygen in the air is accepting electrons from (i.e. is reduced by) metallic iron (Fe) which is converted into ferrous (Fe2+). Red rust can be further oxidised to black ferric (Fe3+) iron. Atoms will tolerate a net positive or negative charge if they can obtain a more stable arrangement of electrons (this is a consequence of the quantum mechanics of electrons). Serpentinization involves water oxidising ferrous iron in olivine to ferric iron, with water being reduced to hydrogen gas and hydroxide ions.
H2 and CO2 react with a little difficulty. Although the overall reaction is exothermic, meaning that it is thermodynamically favoured, some initial energy is required to get the reaction going and a catalyst to help it along. The catalyst in the archaea that do this reaction directly is a complex of iron, nickel and sulphur atoms, which are very like the kind of minerals deposited at vent sites. "This suggests that the primordial cells simply incorporated a ready-made catalyst" (Lane 28). The activation energy seems to come from the vents themselves, which we can tell from the presence of acetyl thioesters. These molecules are the result of CO2 first reacting with free-radicals of sulphur in the vent water, and these free-radicals provide some of the energy. We will return to this observation below.
The combination results in reactions that produce methanol (CH3OH), methanal (CH2O), and ultimately ethanoic acid (CH3COOH) aka acetic acid). Such molecules can accumulate and concentrate in the cells and this allows for more complex molecules to form and polymerise in tiny versions of the Miller-Urey experimental apparatus. This gives us a more dynamic version of the organic soup. The constant flow of water from the vent solves another problem associated with surface catalysts: fouling. As reactions happen on a surface the products of the reaction build up and prevent new reactants getting to the surface. To have a sustainable reaction at a surface one must combine concentration (enough to bring molecules together) with a flow that carries away products and replenishes reactants. The pores of the vent structures seem to provide for both.
Proton Gradient
2. A feature of all living things is the creation of a proton gradient across a membrane. By this we mean that one side of the membrane has a surplus of protons (in other words an acid pH) and the membrane allows them to diffuse to the other side where there is a deficit (an alkaline pH). Since protons are positively charged this is also amounts to an electrical potential (i.e. a voltage) across the membrane.
In our mitochondria for example, this gradient is achieved by a process called electron chain transport involving four complexes of proteins that pump protons across the membrane to create a pH or proton gradient. These protons then diffuse back into the cell by a process called chemiosmosis, via another protein complex called ATP-Synthase, and in doing so power the creation of adenosine triphosphate
triphosphate - ribose - amino-acid (adenosine)
At first sight ATP-Synthase appears so miraculous that, like the eye, it is often pointed to as evidence of intelligent design. It is difficult to imagine how something so complex could have evolved from simple steps by chance, though its evolutionary path is in fact known to some extent. ATP synthase is a complex nano-machine. A rotary engine in the cell-membrane is made up of a protein complex (with three subunits) and driven by proton diffusion or chemiosmosis; the engine uses a protein-based crank-shaft to deliver mechanical energy to a separate complex of proteins (with three subunits) inside the cell; the deformation and relaxation of this second complex catalyses the synthesis of ATP from ADP and a phosphate ion. Several good animations are available showing how ATP-Synthase works, for example this YouTube video.
ATP is a universal energy currency in all living cells. It is how energy is stored and moved around the to where it is needed. ATP is a nucleotide, the basic unit, or monomer from which polymers like RNA and DNA are produced. The right-hand group is adenine, an amino-acid, and the middle part is ribose, a saccharide or sugar. And on the left is the phosphate. Compare to the units of DNA or RNA (below):
ATP adds two more phosphate groups, the last of which is detachable to make adenosine diphosphate with the release of energy. The reaction that powers life thus looks like this.
ATP ↔ ADP + PO42- + energy
The pH difference between the two bodies of water, kept separate by the membranes of the vent structure creates a voltage across the membrane that can drive a similar kind of reaction, the transformation of orthophosphate into pyrophosphate:
Note how the left-hand side of ATP is very like the pyrophosphate molecule. Russell thinks that pyrophosphate might be the precursor of ATP, that it could do the same job of providing energy to power other reactions, though less efficiently.
Scaling Up.
So in these vents we have the following essential ingredients for chemistry related to life (especially if we consider them as they might have been 4 billion years ago).
CO2 and nitrogen-oxides (in seawater) + H2 (in vent water) reacting to form organic molecules
Iron-sulphur and other metallic ion complexes that can act as catalysts
A mechanism for concentration and replenishment
A porous membrane formed from calcium carbonate with distinct environments on either side.
A proton gradient
Potentially, a pyrophosphate based energy transfer mechanism to provide activation energy for "shy" molecules.
Thus the vents provided natural reactors for sustaining chemical reactions that produce organic molecules in a far more dynamic environment than that envisaged in organic soup theories. They also provide the range of environments necessary to create the conditions for replicators like RNA. However the kind of chemical reactions that might take place in such environments are relatively simple compared with even a bacterial cell, let alone a eukaryote cell. How did we get from there to here? In attempting to answer this question Lane switches from a bottom-up to a top-down perspective.
One of the clues to how life might have proceeded can be found in the common elements of metabolism shared by almost all living cells. By comparing all living things we can reconstruct the common elements shared by all life. In this vein, a paper published in Science on 25 March 2016 (Hutchison et al 2016) has attempted to reduce the genome of a bacteria to just those genes essential for it to live. The resulting partly-synthetic organism has just 473 genes. The function of 149 of them has yet to be determined. Lane discusses the last universal common ancestor of all current forms of life, known by the acronym, LUCA. In order to identify what features LUCA might have possessed scientists compared the two oldest forms of life: archaea and bacteria. Archaea appear very similar to bacteria, but there are important differences in metabolism and biochemistry. Features in which bacteria and archaea differ include,
Chemical structure of cell membranes structure
Methods of lipid synthesis
Methods of glycolysis (conversion of sugars to pyruvate)
DNA replication
Respiration pathways
Features which bacteria and archaea share include:
DNA
Ribosome (proteins which transcribe DNA into RNA)
RNA to protein translation
Krebs cycle
ATP synthesis
The features that archaea and bacteria have in common are those likely to have been found in LUCA and those features where they differ were unlikely to be features of LUCA. Note that cell membrane structures are not included in the list of shared features. Archaea and bacteria appear to have separately (and in parallel) evolved lipid-based cell-membranes and methods for synthesising lipids. This is consistent with life having evolved as metabolic pathways in a physical substrate and then later having found ways to create membranes, with bacteria and archaea developing independently. In retrospect, the alkaline vent hypothesis predicts multiple parallel solutions to such problems as cell-membranes and some metabolic pathways.
The Krebs Cycle (aka Citric Acid Cycle) is shared by all forms of life. Lane refers to it as "the metabolic core of the cell". It is central to how we take the complex molecules in food and break them down into hydrogen and carbon-dioxide and in the process produce ATP to power other cell processes.
The cycle can also go backwards. In which case it consumes ATP and produces complex organic molecules, which can be used to build the components of a cell. This backwards Krebs Cycle is not common in life generally, but it is common in the archaea that live in hydrothermal vents. Crucially, given appropriate concentrations of the necessary ingredients including ATP, the chemical reactions of the backwards cycle will happen spontaneously. It is what is sometimes called "bucket chemistry", from the idea that one pours reagents into a bucket and the reactions just happen. And as the products of one step of the process build up in concentration they will automatically start to undergo the next step. No genes are required to mediate this process. It is exactly the kind of reaction that could have got started in the pours of vent structures, perhaps powered initially by pyrophosphate rather than ATP. Once this process got going, side reactions would have been almost inevitable producing amino-acids and nucleotides (the units of the DNA or RNA polymer).
We mentioned acetyl thioesters above. These turn out to be very important, because when they react with CO2 they produce molecules called pyruvates. When our cells take up simple sugars these are broken down by enzymes into pyruvates. These then enter the Krebs Cycle where they are transformed into other molecules to form many building blocks for complex chemistry. So the naturally occurring acetyl thioesters could have produced the pyruvates necessary to set off the backwards Krebs cycle to produce complex organic molecules.
"In other words, a few simple reactions, all thermodynamically favourable, and several catalysed by enzymes with mineral-like clusters at their core... take us straight into the metabolic heart of life, the Krebs cycles, without any more ado." (28)
We now hit the limits of the progress of science. Experiments designed to test how accurate this hypothesis is have been proposed. Lane speculates that peptides and small proteins and RNA are likely products. Some experiments have been performed and generally they seem to throw up problems with the model. So the field is still in the phases of repeatedly testing and redesigning to find the right parameters. However, there is reason to be optimistic that refining the model should produce a self-sustaining series of chemical reactions analogous to the first living systems, and that contain metabolic pathways which hold the key to all life: the proton gradient, a phosphate based energy transfer, and the Krebs cycle. Lane concludes that LUCA, the common ancestor of all life was most likely,
"...not a free-living cell but a rocky labyrinth of mineral cells, lined with catalytic walls composed of iron, sulphur and nickel, and energised by natural proton gradients. The first life was a porous rock..."
The conditions required for all this to happen are unusual, but happen to be exactly the conditions that prevailed on the earth 4 billion years ago. Once the conditions were in place, life was more or less inevitable and probably came about quite quickly.
Of course this story is still quite hypothetical. Some parts of the alkaline vent hypothesis are better attested than others. As far as I can tell the experimental results are still ambiguous, though promising. Other models for origins of life do exist and are being explored. See for example, Keller et. al. (2016), though this group also see a vital role for iron compound catalysis. The more we understand the biochemistry of life, the better we understand what the conditions must have been for the beginning of life. Major advances in understanding that biochemistry are still being made. Elucidating the basic structure of ATP Synthase won Paul Boyer and John E. Walker a Nobel Prize in 1997, less than 20 years ago. This is ongoing work, most of the sources cited in this essay are less than five years old (at the time of writing).
Conclusions
A sceptical Buddhist reader, if they even got this far, may say, so what? What has any of this got to do with Buddhism? By my own admission, I don't usually countenance the idea that science supports the standard kinds of medieval worldview held by Buddhists. In fact here I am doing the opposite. By showing the plausibility, even the thermodynamic inevitability, of biochemistry emerging from geochemistry, I want to try to eliminate the last vestiges of Vitalism. No supernatural element need be added to the organic soup to make it come alive, merely some form of chemical disequilibrium across a permeable barrier (in our case a proton gradient across porous calcium carbonate). There is no equivalent of the Lord breathing life into Adam or Dr Frankenstein pumping electricity into the monster to shock it into life. Certainly energy must be available, but this is simply energy in the normal sense used by scientists, not some supernatural vital spark. Life proceeding in this manner is no less mysterious, but it is entirely natural. There is no need to introduce any supernatural element. The picture above might not be correct in every detail, but it identifies the basic elements that must be in place for life to be thermodynamically feasible: ie. H2 and CO2 in an environment of disequilibrium separated by a porous membrane, with catalysts present, and a replenishing flow that is balanced out by possibility for concentration of ingredients.
If we accept these ideas, and granted many will not or will find them too speculative, then life requires nothing extra in order to be passed on from one being to another. In the simplest terms, cells divide and the daughter cells go on to become other individuals. What is passed on in modern living cells is a copy of the mother-cell's genes, some of her metabolic equipment, and a section of her enclosing membrane. Nothing supernatural occurs during this process. What occurs is certainly incredibly, almost unimaginably complex and at best incompletely understood. But the broad outlines of it are clear.
I have previously argued that any afterlife is by necessity vitalistic and dualistic. The afterlife exists primarily to fulfil the longing for continued existence and as a mechanism for sustaining the Myth of a Just World. Vitalism and Dualism are the price we pay for fulfilling these longings. If the manner in which we lived is important to an afterlife theory, then that theory demands that information about how lived must survive our physical death in some coherent form. This information is then used to determine our post-mortem fate. Thermodynamics precludes the possibility of this information being preserved because, in our living bodies, the information is encoded in arrangements of atoms. Those atoms become disordered almost as soon as life ends. Nor is there a credible way of transmitting this information from one being to another, even if they were in physical contact. The many Buddhist attempts to explain this information transfer, e.g. a mind-made body (manomaya kāya) or gandharva, do not meet modern standards for theories that make accurate, testable predictions. At best they are myths, at worst they are post hoc rationalisations of something we want to believe despite the evidence.
If we eliminate all forms of Vitalism and Dualism with respect to life, it makes these medieval afterlife views considerably less plausible. If nothing is required to spark matter into life, if there really is no matter/spirit duality, then the idea of something immaterial surviving death is considerably less plausible. Buddhism without the inherent matter/spirit duality, without the supernatural elements changes radically. Karma and rebirth go out the window. The focus becomes how we understand experience and how we can explain the experiences we have during the religious exercises associated with Buddhism.
Because of thermodynamics, religion is basically finished. The death throes are certainly taking a long time, but the world is slowly moving away from seeing life through a religious lens. Buddhism, as a religion in the traditional sense of being concerned with continuity, justice, disembodied spirits, and the afterlife, is finished. We have Hamlet's choice: either embrace the situation and take an active role in shaping the future; or hesitate and allow events to overrun us. But we are not Hamlet, we know how the play ends.
~~oOo~~
Bibliography
Hutchison, C. A. (2016) Design and synthesis of a minimal bacterial genome. Science, 351 (6280) DOI: 10.1126/science.aad6253
Keller, MA. et al. (2016) Conditional iron and pH-dependent activity of a non-enzymatic glycolysis and pentose phosphate pathway. Science Advances 2(1) DOI: 10.1126/sciadv.1501235
Lane, N. (2009) Life Ascending: The Ten Greatest Inventions of Evolution. W.W. Norton. [While it lasts there is a YouTube video with Nick Lane reading his own chapter on the origin of life accompanied by relevant graphics https://youtu.be/UGxAB4Weq0U]
Russell, M. J., Nitschke, W., Branscomb, E. (2013) The inevitable journey to being. Phil Trans Roy Soc Lond B. DOI: 10.1098/rstb.2012.0254
Update 26 Jul 2016
A recent study (by Bill Martin and others) in Nature Microbiology suggests that LUCA was a hydrogen metabolising thermophile. Based on analysis of the common genes in bacteria and archaea it identifies 355 genes as ancestral - i.e. belonging to LUCA.
Weiss, M. C., Sousa, F. L., Mrnjavac, N., Neukirchen, S., Roettger, M., Nelson-Sathi, S. & Martin, W. F. (2016). The physiology and habitat of the last universal common ancestor. Nature Microbiology 1, Article number: 16116. doi:10.1038/nmicrobiol.2016.116.
18 Feb 2017 In Daniel C. Dennett's new book From Bacteria to Bach and Back he references a paper which shows how ribo-nucleotides can be synthesised bypassing the phase of having ribose and an amino acid, which in some cases are very difficult to stick together.
Szostak, J.W. (2009) Origins of life: Systems chemistry on early Earth. Nature. 2009 May. Available from the authors website.
I was reading through Rune Johansson's Pāli Buddhist Texts and came across this little verse [1].
accayanti ahorattā jīvatam uparujjhati āyu khīyati maccānam kunnadīnam va odakaṃ
Days and nights elapse Vitality declines Mortal life is exhausted Like water in streams
We are used to using rivers as metaphors. We understand the idea of the ever changing stream of the river, flowing from head waters to the sea, especially if we come from moist temperate climates. But in North India there is another phenomena which may not be so familiar.
In Feb 2009 I was in Bodhgaya for the convention of the Triratna Buddhist Order. One day I took the time to walk a little out of town to cross the long bridge over the River Falgu (called the Nirañjana in the Buddha's day) to the little village of Senani (also called Sujata in association with the young women who is said to have offered the Bodhisatta some milk-rice after he gave up self-torture). In Senani the farmers still pull a wooden plough behind bullocks despite the fact the iron age began about three millennia ago and resulted in the original clearing of this land. However the fields looked green and productive on this side of the river, where there was only brown dry fields around Bodhgaya. On the edge of the village is a stūpa which was built to commemorate Sujata.
The accompanying image from Google earth [2] shows Bodhgaya and the Falgu/Narañjana, the Mahabodhi Temple complex, the bridge and Suajata's stūpa. Although the bridge is about 600 meters wide, as I walked accompanied by one of the ubiquitous 'school children' [3] of Bodhgaya, I saw only sand. The mighty river had completely dried up, and this was not even the hot season, this was during the coolish winter. This is what this image shows - the brown colour is sand, not water. At higher magnifications one can see the patterns and cart tracks in the sand, as well as the little hut next to the bridge that Śaiva sadhus occupy when it is dry. Pulling back even more one sees that the river peters out in both directions, though I think it probably forms a tributary of the Ganges during the monsoon. There is even a word for this phenomena in Sanskrit: vārṣikodaka 'having water only during the rainy season [varṣa]'.
Certainly I am not used to such contrasts. It occurred to me that the verse above had to be understood in this context - this cyclic flooding and then complete drying up of even substantial rivers. I could not have imagined life becoming exhausted like a small stream because I've (more or less) always lived on islands with abundant rainfall all year round. But in this region when even a large river can completely dry up, what chance does a small stream have? And the verse is saying that life is like a small stream in this region - it may flood, but soon is will disappear. The verse is much more compelling when seen in this context.
The use of the word jīvata is interesting. It begins as a past-participle of jīvati and therefore means 'lived', but comes to mean the life-span, or 'vitality' (itself from Latin vita'life' and probably cognate with jīvata). The noun jīva is an important technical term in Jainism where it denotes a kind of soul which moves from life to life. The verse makes a contrast by choosing another word for life: ayu (Sanskrit āyus). We find this word in āyurveda which means something like the 'knowledge of life' i.e. a literal rending in English would be biology (though they do not quite mean the same thing!). Āyus is related to the Greek word æon, and to English 'eternal, always'. So buried in the history of these words is the notion of eternity, the belief or wish that life will go on and on.
The Canon records that these words were spoken to Māra in the Squirrel Sanctuary near Rājagaha in the heart land of the samaṇa movement. I've noted before that Johannes Bronkhorst has argued that the idea of rebirth came from this region from amongst the samaṇa groups of whom the Jains were pre-eminent in the Buddha's time [Rethinking Indian History]. Māra here argues that the jīvata rolls along like the chariot's wheel, he literally denies that days and nights pass and that life ends. The verse above is the Buddha's rely. The status of Māra is a long story - was he 'real', allegorical, metaphorical? One way we could take this story is as a psychodrama with Māra representing that part of our psyche which coined these words for life which has 'eternal' as a connotation. Māra is our refusal to face up to our own impending death. The refusal to face death is quite a common theme and I have dealth with it at least once before in my essay: From the Beloved.
However we read the verses I find it very helpful to have walked in that landscape when trying to get into the mindset I find in the Pāli texts.
References
The reference is Saṃyutta Nikāya i.109 - pg 201-202 of the single vol ed. of Bhikkhu Bodhi's translation. [I'm tempted to offer a prize for anyone who knows what a 'felly' is without looking it up!]
If you want a closer look at Bodhgaya on Google then the coordinates are: Latitude: N 24° 41.75, Longitude: E 84° 59.49
The 'students' scam money out of tourists and pilgrims by asking them to buy school books for them, which they immediately sell back to the shop. This scam has a second level in which the dupe is invited to visit the school where the headmaster informs them that the child is out of school because they haven't paid their fees, which the generous dupe pays for them - 0nly to see them on the street again the next day. (It happened to a friend of mine!)
I was reading through Rune Johansson's 
