I expressed some scepticism at Massimo Pigliucci’s “One more time: no, epigenetics is not Lamarckism.”
Mary Paniscus also expressed some scepticism at the essay, but the difference is that she knows her genetic biology a lot better than I do. I need to clarify my residual interest in Lamarckism.
Firstly Massimo (and Mary) are correct. Epigenetics is not an opportunity – an excuse – to bring Lamarckism into biological evolution. Genetic or epigenetic, however and whenever the mutation occurs in relation to the environment, inheritance is “atomic” via the cells involved at conception / inception. There is no sense in which the mutation is in any direct sense adaptive in positive response to the environmental situation that may have caused the mutation. They are generally negative (maladaptive) damage to the existing genetic / epigenetic state, and can only turn out to be positive to individuals of the species (phenotype) in the long run. At the direct causal level, the evolutionary change is only randomly related to the mutation.
[Aside – such mutation cannot be inherently “positive”, not until the phenotype can value it as an “affordance” providing an advantageous opportunity to the species. All mutations that don’t wreck the reproductive cycle, and all historically preserved mutations, have that potential, but it’s the behaviour in the phenotype generations that turns the otherwise random – generally maladaptive – mutation into an evolved trait.]
That selection from random variation is the essence of Darwinism, so there is no sense in which it is Lamarckian, even if the mutation arises from environmental exposure. That’s true both genetically (DNA-based) and epigenetically (generic-atomic) anyway.
My scepticism is on two levels beyond biology because (a) Massimo is a philosopher and (b) my interests are epistemological and human. Biology is only part of science and science is only a part of this rational interest.
- Firstly, causation itself. The significance in which it makes any sense to say “this event caused this outcome” when processes operate indirectly across many levels. As Mary says, phenotypic evolution is always indirectly related to genetic (or epigenetic) mutation. (The epigenetic / genetic confusion – opportunity for critics to slip-in spurious agendas – arises only from the “atomic” naming problem – see previous post on this. Words matter.)
- Secondly, in non-biological evolution (in Dennett’s design spaces) dealing with sentient and intelligent beings, not all changes are random, many are intentional and purposeful (if you’re not in denial of free-will, that is)(*). The situation varies from (0,0,0) to (1,1,1) Darwinian. The non-Darwinian end of that vector might usefully be thought of as positively Lamarckian – adaptive learning? Here, it’s just a word, a label. Neither Darwin nor Lamarck was anywhere close to the mechanisms of how all these processes happen, nor were they thinking beyond biological species when they proposed their ideas. No reason to demonise Lamarck just because Darwin was right.
So, neither of these points invalidates Massimo’s headline. Epigenetics is NOT an excuse to slip Lamarkism back into biological evolution. My scepticism simply expresses the fact that philosophically, beyond biology, there is more to this.
[(*) And remember, even genetic (and epigenetic) changes can be engineered by imperfect human intention.]