Monday, 28 January 2008

Cosmic Conflation: Evolution, Abiogenesis and the Big Bang

I have now now watched more creationist propaganda - and responses thereto - on the internet than is medically recommended. Doctors now recommend that you aren't exposed to more than 300 mC (milicretins) of creationism per day. Some even consider this level too high as experiments with monkeys have shown that an acute dosage of as little as 600 mC can be fatal to other monkeys in the vicinity. Breaks of at least 24 hours are recommended between repeated doses, although these can be reduced with sufficient exposure to the sceptical literature. Some recent studies even suggest a link between exposure to creationism and autism rates in the US, however they have yet to demonstrate a mechanism to explain their simplistic correlation equals causation arguments.

Anyway, pointlessly length introductions aside, todays story is about one of the most infuriating aspects of the creationism/ID crowd: The conflation of evolution, abiogenesis and the big bang into one big mega-theory against which they then argue. Oddly enough, it's quite easy to shoot down a theory that tries to account for both the early inflation of the Universe following the Big Bang and the development of the bacterial flagellar motor.
I will now attempt to summarise each of these three areas below, relying on little more than a physics degree, an inquiring mind, my undergraduate dissertation and some stuff that I read. If you'd like to try this at home, you can substitute some sticky-backed-plastic and a Styrofoam cup for the physics degree and any issue of New Scientist for the dissertation.
[Disclaimer A: The following huge sections of text can be avoided by anyone who knows this stuff already. Alternatively, those people can read it and point out my fundamental mistakes.]

The body of theories that make up evolutionary science is vast, varied and complex, somewhat like the phenomena it attempts do describe. However, the basic Darwinian model is relatively easy to explain and serves well enough as a demonstration.
[Disclaimer B: There really is a lot more to it than this. Science has had nearly 150 years to modify its theories since On the Origin of Species was published in 1859.]
  • Given infinite resources, populations of organisms tend grow exponentially
  • There are only finite resources on the planet
Under these circumstances, organisms have no choice but to compete for the limited resources available.
  • Organisms reproduce by duplicating their genes in future generations
  • Mutations can be introduced by errors in gene replication or by radiation
The combination of reproduction and mutation leads to variation. Even very infrequent mutations will lead to some degree of variation within a species. We can therefore say that:
  • There is competition amongst organisms for limited resources
  • Variation will occur in a population simply by mutation
Variation plus Competition equals Natural Selection.

Organisms with mutations that are detrimental to their survival are less likely to live long enough to reproduce, whilst those with beneficial mutations will be able to do so, and might even be able to do so more than their counterparts. Thus, beneficial genes will tend to be duplicated more than detrimental ones.

All you need now is time. This process does not need to proceed quickly. It is not in any great hurry. Life has had at least 3.4 billion years (3,400,000,000) in which to develop to its current state.

Importantly, evolutionary theory does not currently make any claims about the initial emergence of life. It only describes its subsequent development. The ultimate origin of life is known as:

Abiogenesis is literally the formation of life from non-life. Theories of this kind describe possible ways for simple common molecules - such as water, methane etc. - to develop into the more complex molecules required for life, and subsequently into life itself.

To begin with, there is no single accepted theory for abiogenesis. Since we have virtually no evidence about what chemical processes were going on in the distant past, we can only speculate as to how life might have started to live. However, we can make models and develop likely ways in which this could have occurred, and we can perform limited experiments in the lab. The problem is that we do know that life had a whole planet and a very very long time in which to develop. These parameters do not lend themselves to lab experiments.
What we do know:
  • Water was liquid on the surface of the earth around 4.4 billion years ago
  • Evidence for biological processes exists as far back as 3.4 billion years
  • Eukaryotes (the lineage from which we descend) existed up to 2.7 billion years ago
This rough estimation gives life a billion years in which to first develop. By anyone's estimation this is a really long time.

Creationists always claim that the chances of life occurring spontaneously are extremely remote. They arbitrarily set the probability at something like 1,000,000,000,000,000,000,000,000,000 (that's 27 zeros) to one, so let's run with that as our base probability for the cosmic lottery shall we?
Let's assume that for the first step of abiogenesis to occur, we need a cubic metre of water and a year. This is probably overly generous. Given the the billion years and the 1.37 billion cubic kilometres of water that we have to play with, that means we get to buy 1,370,000,000,000,000,000,000,000,000 cosmic lottery tickets. Now, this doesn't prove anything but it does serve to illustrate the sheer quantity of time and resources involved. It also demonstrates that any trained monkey can make up stupid probabilities. (ook)

However, whilst probability doesn't stop abiogenesis form occurring in the first place it does make it very difficult to test experimentally. You could make a chamber in which to replicate the conditions of the early Earth and die before you saw anything like abiogenesis. So how do we test the many theories that exist to explain the emergence of life on Earth?

We may not need to. In order to crush the creationist arument, the theory only needs to be plausible enough. In fact, the current body of theory is certainly plausible enough that a little trimming with Ockham's Razor will be all that is required.

For those interested in a more robust test of the theories I think the answer lies in computer simulations. Computer modeling of the world around us is improving every year and computers themselves are getting more powerful every year. I don't think we're at that point yet, but it seems plausible that it will eventually be financially viable to run a simulation of the basic chemical processes involved and just keep tweaking the parameters a little until something exciting happens. We can then check those parameters against what we believe the early Earth was like. If we're really lucky, we might even get a prediction to test by going and looking at some really old rocks.
The formation of life, however, has fairly little do do with the formation of the Universe as explained by:

The Big Bang
I'm not going to go into this at length except to say that the Big Bang model says nothing about the formation of life on Earth. It's like comparing the Milky Way galaxy to a badger. Whilst one couldn't form without the existence of the other, they have very little to say to each other.

Proceeding from some basic assumptions, the Big Bang attempts to explain how the Universe has developed over its 13.7 billion year lifespan. It states that the Universe began as a singularity and that is has been expanding ever since. It describes the timeline over which quarks and gluons formed protons and neutrons, the emergence of electrons and how these various particles subsequently combined to form Hydrogen. The hydrogen collapses to form stars, which turn Hydrogen into heavier elements and then explode, scattering these elements across the Universe. From these building blocks new stars and planets can form.

So, what the Big Bang model can tell us is how the Universe progressed from being very dense and very hot, to being much more tenuous and cool. Within this framework, better understood theories like gravitation do the work of forming the stars and so on. The Big Bang model is just that: a model. A model well supported by observation, but relying more heavily on mathematics nonetheless. The proof or disproof of Big Bang theory bears no relevance to the theories of evolutionary science. If we suddenly discover tomorrow that the Big Bang model is all wrong, evolution will keep plodding along regardless and abiogenesis will still have had to happen for evolution to be there in the first place.

So that's basically it. Three different theories, proceeding from different sets of assumptions. However, the creationists will tend to call all of these evolution. You see, for them "evolution" just means "anything that disagrees with my assumption that god did it."
I do seem to have rambled on a lot and I'm sure many of you (say maybe three out of all four of you) already know all this stuff anyway. That's OK, I think I disclaimered it sufficiently in compliance with blog safety rules.

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