On Alleged Lamarckism

There are some biologists who claim that non-evolutionary processes explain something or other about biology. Evolution works like this. There are pieces of information instantiated in DNA or RNA called genes. Biological systems such as the cells in you body or bacteria use the information in these genes to solve biological problems, such as extracting energy from the environment, or fighting off infection or whatever. The genes are copied to produce new cells and offspring. Variations are produced on these genes by various mechanisms, such as chemicals changing the DNA copying mistakes and so on. Some variations get copied and others don’t. So evolution involves the production of variations of genes and selection among those variations. The bodies of organisms like animals and plants are emergent results of variation and selection of genes (Dawkins, The Extended Phenotype, Chapter 1):

Genes manipulate the world and shape it to assist their replication. It happens that they have ‘chosen’ to do so largely by moulding matter into large multicellular chunks which we call organisms, but this might not have been so. Fundamentally, what is going on is that replicating molecules ensure their survival by means of phenotypic effects on the world. It is only incidentally true that those phenotypic effects happen to be packaged up into units called individual organisms.

What is required for evolution is (1) a means of information storage that can store an unbounded amount of information, (2) a mechanism for copying that information, (3) mechanisms that produce variations of that information and (4) a mechanism that selects among the variations. Whether that information is contained in DNA or RNA isn’t the relevant issue. The logic of the explanation works regardless of how the information is stored. So if we’re going to claim that a non-evolutionary process produces biological complexity there has to be a bit more to it than some minor change in what chemicals do the transmission.

Some biologists think that there are examples of a non-evolutionary kind of process called Lamarckism in which the environment modifies genes directly. So giraffes would have long necks because previous giraffes stretched their necks, this somehow modified their genes and then the modified genes would be passed on.  Lamarckism doesn’t make much sense because the environment doesn’t have the knowledge required to rewrite genes, see The Beginning of Infinity by David Deutsch, Chapter 4.

Let’s look at some alleged examples of Lamarckism. Epigenetic Change: Lamarck, Wake Up, You’re Wanted in the Conference Room! by Denyse O’Leary claims that horizontal gene transfer refutes Darwinism. Sometimes genes move from one bacterium to another and manage to insert themselves in the genome of the bacterium to which it has moved. Since evolution is fundamentally about variation and selection of genes and this is an example of variation and selection of genes, so horizontal gene transfer doesn’t refute evolution. Note also that horizontal gene transfer involves genes manipulating genetic material, not the environment, so it doesn’t fit the definition of Lamarckism.

Another alleged example of Lamarckism involves epigenesis: changes to gene expression as a result of interactions between genes and the environment. Genes changing how they are expressed is a normal part of development (Dawkins, The Extended Phenotype, Glossary): 

epigenesis A word with a long history of controversy in embryology. As opposed to preformationism (q.v.) it is the doctrine that bodily complexity emerges by a developmental process of gene/environment interaction from a relatively simple zygote, rather than being totally mapped out in the egg. In this book it is used for the idea, which I favour, that the genetic code is more like a recipe than a blueprint. It is sometimes said that the epigenesis/preformationism distinction has been made irrelevant by modern molecular biology. I disagree, and have made much of the distinction in Chapter 9, where I claim that epigenesis, but not preformationism, implies that embryonic development is fundamentally, and in principle, irreversible (see central dogma).

This doesn’t count as the environment rewriting genes anymore than setting the temperature on your thermostat is equivalent to changing the design of your boiler. Some of these modifications involve a process called methylation in which a carbon atom bonded to three hydrogen atoms (a methyl group) is attached to a base. Methylating DNA can change how it is expressed. Some researchers have claimed that methylated genes can be passed on from one generation to the next. If this copying continues indefinitely down the generations, then methylation is effectively like a new kind of base in DNA. It is a variation on the information recorded in the non-methylated gene. The methylated gene is selected if it manages to get itself copied and otherwise it is eliminated.

People who want to claim they have examples of Lamarckism and that this somehow refutes evolution will have to do a lot better than the examples above. They should learn about the details of the arguments they’re trying to refute before they claim victory.

About conjecturesandrefutations
My name is Alan Forrester. I am interested in science and philosophy: especially David Deutsch, Ayn Rand, Karl Popper and William Godwin.

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