November 20, 2008
How To Start Life Without Miracles Or Huge Improbabilities
I’ve been wondering about the origin of life on Earth for a while now. We all know that there are many theories, including some that are pretty far-fetched if you ask me (things like panspermia or creationism.)
One of the things that always bothered me about creationist arguments is that they always need to point out how improbable life is. They like to say things like: “you can put all the ingredients for a living cell in a jar, but no matter how long you shake the jar you will never get a living cell.” (An example from a popular youtube video) Well, that would indeed be pretty improbable! But the first lifeforms weren’t single-celled organisms. They couldn’t have been, because even the most basic simple-celled organisms found on Earth today are still amazingly complex, as creationists correctly point out. In fact, I’d like to take this one step further and say that even the simplest DNA-strand is still too complex to have come about by chance- let alone the amazingly intricate mechanisms that surround the strand.
So what’s my idea on how life started? Since I am a materialist, in my opinion there can’t have been any form of “miracle” like a deity or aliens involved. I don’t think we need that to explain the origin of life. I don’t think the first form of life came about in an event of staggering improbability (though calling it “commonplace” would be an exaggeration too, I think.)
All that was needed were the correct ingredients in the right place and time, plus an external factor inserting a healthy dose of energy to get things kick started.
… Ok, I think this needs some further explanation, doesn’t it?
Here’s how I think it might have went:
Phase 1: Grandma’s Organic Soup.
It’s one of the oldest takes on the origin of life, and I think it still holds merit. Simple and complex organic molecules are found everywhere mankind looks, whether it’s on Earth (duh!), deep space or planets in our solar system- especially planets (and moons) that are geologically and/or atmospherically active. Titan, one of the many moons of Saturn, got big headlines in 2005 when the Huygens probe landed on it and detected enormous quantities of organic molecules. It was amazing that so far out from the Sun there could be a heavenly body with an active atmosphere, let alone contain such a rich amount of organic chemicals as well.
Now to clarify: ‘organic’ in this context doesn’t mean strands of DNA or RNA, or haemoglobin, or insulin. It means many kinds of carbohydrates, proteins and lipids, including forms of sugars, alcohol and fats. These are still pretty complex, however, and it was somewhat of a surprise to scientists at first to find them outside of the Earth’s biosphere, let alone in so many different places in such quantities.
In this context, it is only logical for them to have been on the early Earth too. If they are found everywhere else, it only makes sense they were here too. However, the main difference between Earth and the rest of the solar system was that here there was water in liquid form, which is perfect for dissolving all manner of substances, including organic ones- and what would not dissolve would still be moving around with the flow of water. Downpour, rivers and glaciers would supply a steady dose of organic substances to the oceans which were formerly stuck on dry land or in the atmosphere, et voilà, one big bowl of organic soup pour Vous.
Phase 2: Grandma’s Pressure Cooker
The next step was to get the soup stirred up so that the ingredients for future life could interact and end up concentrated at what I will conveniently call ‘hotspots.’ Ocean flows are essential for shaping these ‘hotspots.’ A modern parable for this might be the Sargasso Sea, which is a patch of ocean in the middle of the Atlantic with almost no flow of water but which houses a huge concentration of biomass. Columbus encountered the Sargasso which slowed down his journey so much as to almost inspire mutiny. I am not saying life came to be in a Sargasso Sea-like environment per se, rather I am saying that you can have concentrations of biomatter in a larger body of water, including on the ocean floor, which I think is a better environment for the start of life than the ocean’s surface.
The next ingredient would be applying a high concentration of energy to the ‘soup.’ The popular image here is a jolt of lightning, however I think this can be safely dismissed. There are many more reasonable ways to apply energy. One of them might be a big asteroid impact. This is somewhat more reasonable, but it’s still quite improbable. Remember that I don’t like too many “improbabilities” in the theory of the origin of life.
Likelier sources of energy might actually have been pressure, whether on the bottom of the deep sea, in the fissures underneath an underwater volcano or perhaps deep in the Earth’s crust close to the upper reaches of the Earth’s molten magma mantle. An added advantage is that with pressure usually comes heat, which keeps the ‘soup’ warm and the substances dissolved in it reacting. This is where I have to claim some ignorance though, and I’d like people to correct me if I am talking jibberish, but it seems to me that simply applying heat to a container of biological molecules (like pea soup actually, or when cooking whatever), these molecules will immediately start reacting and forming new bonds. Now, normally, when you’re cooking the amount of heat you apply is very great, but I am proposing a situation where the heat is well below the boiling point of water, but still fairly warm.
Actually, I think I need to digress a little more at this point and explain why I think energy from pressure is important in the formation of life. The first lifeform would have been a reasonably complex molecule formed from a combining of less complicated molecules. The manner in which combining of elements and molecules usually happens in the natural world, apart from applying heat, is by applying pressure. A good parable of this might be the ways in which helium and nitrogen – simple molecules – are forced to fuse into more complex molecules in the depths underneath the surfaces of stars. Not only is there a lot of pressure from the sheer weight of a star’s mantles, there is also immense heat from the chain reaction of nuclear fusion that occurs in the interior of stars. Furthermore, when a star goes into supernova, the pressure and heat from the explosion are so immense even more complex molecules form. This accounts for a lot of elements on the periodic table, even though the really heavy ones cannot be explained by supernovae. Eek, geeky tangent alert!
The point I try to make is that in order to fuse simpler molecules into complexer ones, it would be a safe bet to argue that pressure and heat had some role to play in it. That’s why I propose water-filled fissures in the deep ocean floor, slowly filling up with organic substances trickling down from the surface, close to the heat of the inner Earth, might be a good candidate for generating the first life form.
Anyway, whether it was a sudden event or a long, gradual process (more likely in my opinion), something caused the brine of organic and inorganic molecules to collapse in on itself, forcing them to fuse into increasingly more complex combinations. And out of all the many trillions of molecules that interacted and fused, all it took was one of them to behave like a self-replicator.
Phase 3: A bug in grandma’s soup
Now, if you are skeptical, you should think at this point: “ok… now that last sentence was kind of off-hand, but I think you just described a chance event to forget all other chance events.”
Well, you would be almost right, but I think we are are playing a game of large numbers here. Remember that ‘grandma’s pressure cooker’ contained an insanely huge amount of molecules, and that it had the luxury of ‘cooking’ for possibly many hundreds of millions of years on end without worrying about running out of water or ingredients. I think if you look at the problem at that scale, chances for forming a self-replicating molecule increase dramatically.
And this is what I think the first life-form looked like: compared to DNA or even RNA, this molecule was extremely simple and small. All it did was stick to molecules it happened to bounce into, until it got too big for its own good, lost structural integrity, and broke into two or more pieces. Said pieces then would combine again with suitable molecules they would chance into, at which point they broke into pieces again, etc. This must have been an extremely sloppy process in my opinion, and I’d say that there must have been many kinds of molecules suitable for attraction available to these first forms of life, including ones that would pollute and damage their ability to replicate after a certain number of these divisions.Since I am talking about a place where the first lifeform might have been formed, and that this might have been a gradual process, I think it’s fair to assume that their habitat contained all manner of molecules, from the simplest naturally occurring, all the way through the intermediary stages to the first self-replicator. A veritable jungle of different kinds of organic molecules.
I don’t think it’s wrong to assume that in their sloppy ways, maybe more than 99% – a number I have no way of verifying, of course, but please play along and theorize with me – of these self-replicators would have died off within several generations. But even after, say, 50 successful replications, there would still have been an impressive amount of self-replicators in the ‘soup.’ So much, I’d argue, that even that 1% of survivors would constitute a very large numbers of creatures. Remember that we’re still playing a game of large numbers.
Phase 4: the pot boils over!
This would have been the start of natural selection and evolution. As simple as the self-replicators would have been compared to today’s lifeforms, due to their untidy game of attracting and dividing, the first differences in form would have came to be almost immediately- which as said for the majority of them meant certain death, but a few of them might have chanced upon patches in the ‘soup’ with particularly suitable molecules to attract.
The next step might have been direct competition amongst themselves, as some of the lesser polluted self-replicators might have had a better chance at getting at ‘food’ than the more polluted ones. Then again, a more polluted self-replicator might have had the luck of being polluted in such a way that it could actually grow larger than the competition before breaking up into pieces, which meant it could ‘eat’ more molecules than the competition, thereby effectively out competing them.
Again, it’s all relative to the game of large numbers we’re playing. At this stage in the history of life, there would be chance and numbers, and that only. Since we’re talking molecules, there was still no conscious behavior to them. The only thing to even identify them as ‘life’ was their crude form of heredity. They had no senses of any kind, no means of moving around other than external forces (water flow, for example) and no ways of communicating. Yet already they would have started competing amongst themselves for resources, something which would have intensified when many millions of years later, the soup began to run thinner.
By this time, chance and big numbers might have transformed the lucky few (compared to the 99% of individuals that ever lived and that never made it) into something comparable to simple RNA today. They would still be naked molecules, but they would have been shaped by the slow process of evolution into ever more complex little ‘eating’ and dividing machines. They would have become less and less sloppy in their ‘diet,’ becoming increasingly efficient in choosing what was good for their long-term survival and what was detriment.
Perhaps they began to form crude colonies, thereby shutting out competition from outside, but which further concentrated competition from within: now they had to compete against close cousins for resources. The arms race had started in earnest, which would result in an ever increasing complexity in form.
In this way, after an incredible long time and a number of generations for which there is no word in the human language, the first true DNA strands might have formed, and then the first protective fatty outer layers, then the first membranes… all the way to the first true, yet primitive cells. And all this through the ruthless, unthinking force of the law of large numbers combined with a steady supply of nutrients from their habitat.
A long story, with maybe many logical or factual errors. Anyway, this is my idea of how life might have started. I really encourage some feedback on this, so if you spotted mistakes or patches of general ignorance, please point them out to me. I hope I managed to convince you that there’s no need to imagine either huge improbabilities or miracles to theorize about the generation of life here on Earth.
That, or you will never look at your soup the same way ever again.