Lamarckism and Epigenetics – bad news for Darwin or ID?

Every so often you come across a post or article by an Intelligent Design advocate explaining how Lamarckism and Epigenetics are part of the death knell of “Darwinism”.  A recent contribution is this from Robert Sheldon.  Actually the reverse is true.  I am not a biologist so I couldn’t credibly assess the evidence for Lamarckism or Epigenetics – but to the extent they are true, they are bad news for ID.  They are only bad news for “Darwinism” if you define it in a narrow way.

First a couple of reminders. Lamarckism is the theory that organisms can inherit acquired characteristics.  As originally proposed by Lamarck it had two parts:

  • Organisms acquire certain characteristics in their lifetime through usage (e.g. large muscles through exercise)
  • These characteristics are inherited by their offspring

A variant is simply that organisms acquire some characteristics that their parents have acquired in their lifetime – whether these be acquired by usage or any other means.

Lamarck himself famously proposed that giraffes made their necks longer by continually stretching for leaves on tall trees and the next generation of giraffes became taller as a consequence.  Epigenetics is inheritance other than through mutation of the genome.  Epigenetics is often proposed as a mechanism by which Lamarckian inheritance might take place.  As I understand it, while Lamarckism was widely dismissed with the discovery of Mendelian genetics, there is evidence that there is a very limited amount of Lamarckian inheritance – probably through epigenetic methods.

Why would Lamarckism (if widespread) be bad news for ID? The reason is very simple.  The explanatory filter (EF) is at the heart of the argument for ID.  The EF is an argument that goes like this (to quote William Dembski):

Given something we think might be designed, we refer it to the filter. If it successfully passes all three stages of the filter, then we are warranted asserting it is designed. Roughly speaking the filter asks three questions and in the following order: (1) Does a law explain it? (2) Does chance explain it? (3) Does design explain it?

I should add that the answers need to be (1) No (2) No (3) Yes.

Applying the EF to life, e.g. evolution of the bacterial flagellum, the ID proponent argues:

(1) There is no known law that the bacterial flagellum had to evolve. And I think most biologists would agree. There is a chance element to the evolution of anything.

(2) Evolution by chance means random mutation plus natural selection (RM+NS) and RM+NS cannot explain the bacterial flagellum with any reasonable probability.

(3) Design can explain life.  I have never seen an ID proponent argue the case for  this.  They just assume it. A designer of unspecified powers and motives can explain anything.  

In this post I want to concentrate on (2).

Biologists typically respond by demonstrating that RM+NS can explain most things in life.  But you might also ask if there are chance explanations around other than RM+NS. The ID community typically responds by saying the RM+NS is the only game in town.  So knock out RM+NS and then you can conclude design.

But actually there are lots of other chance explanations around and Lamarckism is one of them.  The thing that confuses the issue is that some ID supporters, Sheldon among them, seem to think that Lamarckism is a designed solution not a chance solution.  Sheldon writes:

In contrast, epigenetic effects are purposeful. When food is in short supply, animals grow smaller, and pass that on to their progeny.

This demonstrates a worrying lack of understanding of Lamarckism. All that Lamarckism claims is that in some cases when an organism has acquired a characteristic during its life time there is an increased chance of its offspring having the characteristic.  We may not understand the mechanism but it does not imply design.  This is so basic that I have to wonder if I have misunderstood Sheldon – but I cannot see any other explanation than a severe misunderstanding.

I think there may be three things that lead to this confusion.

(1) Lamarck talks about giraffes acquiring longer necks because they strive to reach higher leaves.  Certainly the giraffes have a purpose. But the purpose is to reach higher leaves, not to have longer necks, and certainly not to give their offspring longer necks.  So the word “purpose” has crept in.  But it is utterly irrelevant to inheritance.  The proposal that by striving to reach higher leaves giraffes may get longer necks is a proposal about the adaptability of giraffes and nothing to do with inheritance.

(2)  If the characteristics are acquired through usage then there is a very good chance they will be useful to the offspring.  So the characteristics could be said to be suiting the purpose of the species as a whole.  But this is not to say that the characteristics were gained through the intention or design of anyone or anything. Just because they suit the purpose of the species it does not mean they were created on purpose.

(3) Even if the characteristics are not acquired through usage they are unlikely to be established in the species unless they are beneficial and thus suit the purposes of the species.  Because natural selection applies to Lamarckian inheritance.  It might be that it is possible to inherit acquired characteristics that are detrimental to the species (Indeed a recent study with rats suggests that this may be true of obesity). But such a characteristic is likely to be eliminated by natural selection before it becomes established in the species. Lamarckism is an alternative source of variation to random mutation.  It substitutes for the RM part of RM+NS.  But NS still inevitably applies.  Unhelpful variations will be eliminated whatever their source. 

Once these confusions are cleared up then I think it becomes obvious that Lamarckism, if true, is a real problem for the design argument (as if there weren’t enough already).


2 Responses to “Lamarckism and Epigenetics – bad news for Darwin or ID?”

  1. 1 uncommondescentdissent November 9, 2010 at 1:04 am

    Hi Mark,
    This Toronto and I’ve started my own blog. Is it okay to make a link to yours?

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