Sunday, April 27, 2008

Show me the metabolism! Part Three.

Kauffman is chiefly concerned with reproduction as the defining feature of life. He makes only a superficial discussion of metabolism that does not consider its central thermodynamic requirements. But ultimately, metabolism is what is most important. Without petrol, the most splendidly engineered automobile will just sit there. Without a plausible metabolism, the most elegant net of autocatalytic reactions is an empty exercise in symbol manipulation.

Kauffman’s network and Eigen's hypercycles are susceptible to the well-known ‘747 Argument’ of Fred Hoyle et al. and can only plausibly have arisen in two ways:

(1) Through a long and complicated process of prebiotic development containing all the most interesting parts of the story of the origin of life.

(2) As a system created by someone or something.

I don’t intend this as an argument in favour of intelligent design [see definition 1], still less of Intelligent Design [see definition 2]. Ockham’s razor suggests we should stick with explanation (1) unless we should find some very compelling evidence for (2). At any rate, the essential requirements of the pre-biotic processes leading to life based on the chemistry we know are going to be the same as the requirements of pre-biotic processes leading to life based on different chemistry.

What I am arguing is that both the ‘RNA world’ and the ‘Protein world’ are historically late phenomena, and that the critical events for the origin of life lie much deeper. There is no reason to expect that living systems today preserve the same chemistry of the first living systems. It makes much more sense that we have pulled ourselves up by our own bootstraps, as one phase of pre-biotic evolution succeeded another, perhaps as one phase of pre-DNA-life succeeded another. At each stage, we have doubtless destroyed our history more effectively than any Red Guards- for all less successful implementations of life qualify as food. Looking at RNA and Protein is the equivalent of looking under the streetlight for the keys we dropped out in the darkness.

It is as though we are trying to reconstruct the invention of the telegraph, knowing only the mobile phone. Arguing about whether RNA or Protein came first is something like arguing: Which came first, the handset, or the system of towers dotting the landscape?

As far as the ultimate origin of life is concerned, it is useless to try and work backwards. We need to work forwards, by considering the necessary requirements for a CSCP to arise and where and how such a system might realistically arise. If we want to understand where chemicals came from, chemistry is useless to us. We need to use physics. If we are researching the origins of culture, anthropology itself is little help. We need to use evolutionary biology. If we are researching the origins of life, then biochemistry- with its specific, fragile, optimised reactions, the product of ever-so-many years of pre-biotic and biotic evolution- is not the place to start. We need to plant ourselves on a solid base of physical chemistry, stop worrying about designing elaborate systems for allowing pre-biotic reproduction, and concentrate on nutting out a possible proto-proto-metabolism simple enough to arise spontaneously.

Definition 1: ‘intelligent design’ = ‘life as we know it was created by entities based on some different sort of chemistry’

Definition 2: ‘Intelligent Design’ = ‘life as we know it was created by God in some ‘supernatural’ fashion’

1 comment:

Marco said...

Bugger Ockham's razor. Comet amoeba created single cell microbial life in their own image to colonise large planets.