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11/28/2011: Notes on The Selfish Gene by Richard Dawkins

[pages refer to the 30th anniversary paperback edition]

The first step toward understanding life: chemical (Van der Walls) forces

[B]efore the coming of life on earth, some rudimentary evolution of molecules could have occurred by ordinary processes of physics and chemistry. There is no need to think of design or purpose or directedness. If a group of atoms in the presence of energy falls into a stable pattern it will tend to stay that way. The earliest form of natural selection was imply a slection of stable forms and a rejection of unstable ones. There is no mystery about this. It has to happen by definition.

[Chapter 2, p. 13]

The additional principle needed for life to start is that these stable molecules have to replicate. This explanation points also to an elimination of the conflict that seems to exist between what life has achieved on one hand and the second law of thermodynamics. Once a force is in presence, the most probable state of the system is no more a state of randomness but a state of orderness imposed by the force. In the traditional example of a ideal gas in a box, without forces, the most probable state is a state where the atoms of gas are uniformly distributed inside the box; if the atoms have weight and gravity is present, however, all the molecules will fall at the bottom of the box, a much improbable state in the previous case! This is also why there are planets and galaxies and matter is not uniformly distributed inside the Universe. Parallely, this is why there are organized and replicating molecules (DNA), and life, and not nothing instead. In all cases, the second law of thermodynamics is not violated but the state that is the most probable is different depending on the configuration of the system.

A universal definition of life:

All life evolves by the differential survival of [slightly inaccurate self-]replicating entities.

[Chapter 11, p. 192 and the note of p. 322]

Selection has favoured genes that cooperate with others. In the fierce competition for scarce resources, in the relentless struggle to eat other survival machines, and to avoid begin eaten, there must have been a premium on central coordination rather than anarchy within the communal body. Nowadays the intricate mutual co-evolution of genes has proceeded to such an extent that the communal nature of an individual survival machine is virtually unrecognizable.

[Chapter 4, p. 47]

Why Gaian traits cannot be selected:

Genes can have an effect on the body but, as Dawkins argues, genes can also affect the environment outside the body (the so-called extended phenotype). Dawkins gives the example of the form and shape of shelters built by some insects and, most interestingly for us here, the case of a gene controlling the behavior of organisms other than the one that shelters it. If natural selection has selected the gene in the second case, we are in presence of a case where natural selection has fitted the environment to the organism instead of the other way around as it is conceived traditionnally. If this is true, then, is there a reason to stop at this stage; why not thinking that natural selection could also select for genes that modify the ecosystem where the vehicle lives? If we cannot think that way, what is then the fundamental difference between modifying the control of other animal behavior and the conditions of life inside an ecosystem?

I find that the fundamental difference is a quantitative one, not a qualitative one. In the case of a gene controlling other animal’s behavior, a single vehicle where the gene appears will benefit right away from the gene’s activity. The vehicle will have larger chance to survive and the gene in this vehicle will be able to invade the gene pool. In the case of a gene “improving” the ecosystem, a single vehicle is most likely insufficient to modify the ecosystem so that it will not benefit right away from the gene’s activity, its chance of survival is not increased and the genes does not necessarily invade the gene pool. In other words, natural selection can select among the environment-improving genes, only those that affect the environment enough that if the gene appears in a single vehicle, the chances of survival of that vehicle have increased. Ecosystem-improving genes can appear only because they have been part of the vehicle along the way, not because they have been selected; with the same token, ecosystem-deterioring genes can appear as well. This is the argument that Kirchner gives against Gaia theory.

This conclusion is embodied in the following comment by Dawkins on how an organism, a vehicle, ought to be defined:

‘Single’ individual organisms such as ourselves are the ultimate embodiment of many such mergers. The group of organisms — the flock of birds, the pack of wolves — does not merge into a single vehicle, precisely because the genes in the flock or the pack do not share a common method of leaving the present vehicle. To be sure, packs may bud off daughter packs. But the genes in the parent pack don’t pass to the daughter pack in a single vessel in which all have an equal share. The genes in a pack of wolves don’t all stand to gain from the same set of events in the future. A gene can foster its own future welfare by favouring its own individual wolf, at the expense of other individual wolves. An individual wolf, therefore, is a vehicle worthy of the name. A pack of wolves is not.

Read Whitman et al. (2006) and references therein, for a recent discussion on genes and ecosystem. Read Grafen (1984).