Darwin, Lamarck, and McFadden, Part 1

Can standard Darwinian evolution fully explain the biosphere that we see?

Here are three ideas of how evolution works, which I’ll refer to as Darwinian, Lamarckian, and super-Lamarckian.

• Darwinian: Offspring are just like their parents except for mistakes and DNA copying errors — mutations that are completely random, caused, for example, by stray cosmic rays. All the functionality that evolves is due to natural selection — i.e., some variants are better able to survive or to reproduce.

• Lamarckian: Offspring can be systematically different from their parents based on the parents’ life experience. The parents’ bodies adapted — for example, by strengthening muscles that were used more intensively — and these adaptations were passed along to the offspring. The offspring might need the same muscles during their own lifetimes, and over many generations this (in addition to natural selection) could help direct evolution toward useful adaptations.

• Super-Lamarckian: There is foresight and goal-oriented direction in the ways that offspring are different from their parents. This perspective subsumes the Darwinian and Lamarckian mechanisms — natural selection and inheritance of acquired characteristics, respectively — and goes beyond to posit that evolution has an overall direction, for example, building toward greater complexity and integration, or maybe toward biological forms that are somehow implicit in the deep (non-material) structure of the universe.

The “Lamarckian” model was actually espoused by Darwin 50 years after Lamarck, but that part of Darwin’s legacy has been airbrushed out of history. The super-Lamarckian possibility was theorized 20 years ago in a landmark book by JohnJoe McFadden.

Science that is currently mainstream holds that

• Long-term evolution is governed exclusively by DNA sequence, and this is only Darwinian.

• There are temporary adaptations that are passed along via epigenetics — extra molecular markers attached to the DNA — and this process is Lamarckian.

• There is no such thing as super-Lamarckian

In this series of essays, I will

• Relate the historic background

• Describe evidence that Lamarckian inheritance is happening regularly in bacteria, and reasons to think that it’s also possible in plants and animals

• Propose an experiment to test Lamarckian genetic inheritance definitively

• Speculate about reasons to think that (woo-woo) Super-Lamarckian evolution is also real

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Use it or lose it

Your body is really good at learning. Whatever it is that you persist in trying to do, day after day over a period of time, your body gets better at it, stronger, more coordinated, more flexible, more skilled or versatile. And conversely those potential strengths which you do not exercise will atrophy, and you lose them.

You also know that you can’t pass these strengths and skills on to your children. They have to acquire them anew with their own effort and their own habits. Whatever is innate in your own heritage can be passed along with your genes, but whatever you have acquired or developed must be developed afresh by each new generation.

Wouldn’t it be great if we could get past this limitation? Imagine if you could bust your gut in Pilates class knowing that it wasn’t just your own abs you were strengthening, but a legacy you could pass to future generations? Imagine if your children could pick up where you left off developing their health and their skills and their coordination and reflexes, each generation building on the last to reach for higher and higher goals.

And what a boon for evolution, this would be – if it were real!

Here’s a 1999 article which assumes that there is no such thing as Lamarckian inheritance, and the author creates a mathematical model purporting to show that Lamarckian evolution isn’t noticeably more efficient than straight natural selection. I think that Hayes’s conclusion is wrong, though he’s an engaging writer and talented computer modeler. The beneficial mutations in his model without Lamarckian inheritance are assumed to be unrealistically common.

Since this article came out, the reality of (temporary) Lamarckian epigenetic inheritance has become well-established. Could it be that permanent, Lamarckian modification of the genome is also a reality?

Here’s how the story is still taught to this day:

In 1809, Jean Baptiste Lamarck’s theory of evolution was that the training and habituation that our bodies undergo when we exercise our muscles, when we endure heat and cold, when we use our brains to solve problems – these abilities acquired in a lifetime affect offspring, so that they are born better able to cope with whatever it is that the parents have coped with during their lives. Thus the environment and an individual’s response to it help to shape the character of the next generation, and evolution proceeds efficiently in the directions of those qualities that are required in the environment, and those choices which the parents have made during their lifetimes.

Fifty years later, Darwin’s theory was that offspring differ from their parents in ways that are purely random. The direction of evolution is controlled indirectly, because some of those offspring are better able to survive and to reproduce than others.

The difference is whether genetic variation is random or directed by the environment and life choices of the parents. Darwin said random. Lamarck said directed.

In the 1890s, August Weismann conducted an experiment in which he cut off the tails of rats and then measured the tail lengths of their progeny. He continued, cutting off the tails of 20 generations of rats, and yet each generation was born with tails just as long as the last generation. This was taken to be a definitive refutation of Lamarckian inheritance, and scientists everywhere have developed the theory of Darwin, and reserved the story of Lamarck as a morality tale about discredited science.

If Jean-Baptiste had been alive to defend his theory he might have said that developing a trait by using the neural pathways and strengthening the muscles is quite different from hacking off a body part. What Weismann demonstrated had little to do with the heart of Lamarck’s theory.

But it wasn’t Weismann’s experiments alone that gave Lamarckism a bad name. Beginning in the 1880s, Austrian Paul Kammerrer set out to prove the reality of acquired genetic inheritance, and was caught in scientific fraud. In the 1930s, Trofim Lysenko and the Soviet propaganda machine promoted Lamarckism not so much as a science but a political ideology. Communist social practice was destined to change the core of human nature.

The coffin of Lamarckism was sealed by Francis Crick, who not only discovered DNA as the repository of genetic information, but articulated in 1958 the Central Dogma of Molecular Biology: Information flows from DNA ⇒ Messenger RNA ⇒ Proteins, always in that direction. In 1958, there were no mechanisms known by which proteins could feed back to modify DNA, and Crick boldly speculated that no such mechanisms existed.

Here are some facts that don’t fit with that story:

Random variation is extremely inefficient. The big problem is that two or three or even dozens of genes need to change before a new trait can be acquired. Suppose that a few mutations appear that are steps in the right direction – how are those mutated genes to be preserved while waiting for other mutations that will complete the set and create something that actually offers some selective advantage? Imagine evolving a hand. First, perhaps, the bone structure you need for a hand randomly appears, but without nerves and muscles, it has no use, no functional advantage. So the stepping stone disappears from the gene pool before the rest of the adaptation can appear, by random mutation, and make something that is actually useful.

This problem has been called “irreducible complexity” by the Creationists, Christian critics of Darwinian evolution. Evolutionary scientists, under siege from the Creationists, have decided to “take no prisoners”, and so they deny there is any merit to this criticism, and pretend that Darwin’s theory of evolution works just fine as is. But the honest truth is that the Creationists have hit upon the weakest assumption of evolutionary theory as understood by mainstream scientists today. “Creation science” is in fact not a science at all, but a decision to give up on scientific investigation and accept without question that “that’s the way God made it”. This is not a path I find appealing; nevertheless, Creationist criticism of the version of evolution based on one-mutation-at-a-time is actually quite well-founded.

Evolutionary scientists have always taken it on faith that there is a mechanistic explanation for the origin of every organ, every system, every biological function that we observe. We have hoped and assumed that the more we learn about the workings of the body, the clearer would be the pathway by which it might have evolved one-mutation-at-a-time, with each incremental step offering some selective advantage that would hold it in place while waiting for random mutation to come up with the other steps. But in fact, the more we know, the more puzzling cases we see of “irreducible complexity” which strains our imagination to account for a plausible evolutionary pathway.

Darwin knew this. Even in the first edition of The Origin of Species (1859), he admitted a role for the habits of the parents in determining the traits of the offspring. This idea was coded in the words “use and disuse” in the last paragraph of the book:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms.

Through the development of Darwin’s thought after The Origin, the idea of Lamarckian inheritance gradually gained ground. In 1876 he wrote in a letter (published after his death):

In my opinion, the greatest error which I have committed has been not allowing sufficient weight to the direct action of the environments, i.e. food, climate, etc., independently of natural selection. . . . When I wrote the “Origin,” and for some years afterwards, I could find little good evidence of the direct action of the environment; now there is a large body of evidence.
— From a letter to Moritz Wagner, 1876

Savor the irony that the version of Darwinism that is best accepted today is ultra-orthodox, far more narrow than beliefs and writings of Charles Darwin. If Darwin were submitting his papers to the journal Evolution today, he would receive a patronizing letter of rejection, criticizing his unfocused thinking, and warning him that Lamarckian inheritance is not a credible mechanism, and that he must re-frame his theory in terms of known, validated laws of inheritance.

This kind of censorship in the name of scientific orthodoxy is bad enough when it is well-grounded in empirical science. But in the case of Lamarckian inheritance, it is the mainstream scientists who have missed the boat.

The plausibility of evolution

Is it reasonable to expect that Darwinian evolution by natural selection alone could have produced the variety of robust individuals, species, and entire ecosystems that we see in the incredibly short space of just 4 billion years, with only a billion cubic kilometers for experimentation?

This is a compelling question to which different scientists have very different answers. We might wish that modeling and experiments could resolve the question, but the fact is that it’s hard to get funding for experiments that have a billion-year timeline, and the processes we would wish to model (involving fantastically low probabilities over vast numbers of organisms and huge time periods) require computer resources that we can’t even conceive.

Darwin himself was puzzled by some questions for which he invoked a “Creator” complete with capital “C”. These included

1. The origin of the first living things that are capable of reproducing and evolving

2. Where did sex come from and how is it maintained? Sex has a huge fitness cost, compared to clonal reproduction.

3. The maintenance of diversity — which is needed so selection has something to act upon — in the face of selection which is always acting to collapse toward the fittest variety.

4. Why do most plants and almost all animals age and die on a schedule? Unlimited lifespans would offer a big fitness benefit.

We now know some things that Darwin didn’t know. Question #1 has become more poignant the more we experiment toward a biochemistry of self-reproducing molecules. Today’s evolutionists have given up on Question #2, taking sex as a given, or calling it the Masterpiece of Nature. Question #3 found a partial answer in Mendelian inheritance, but in computer models, (even with sex), diversity collapses faster than what we see in nature. And Question #4 requires group selection, in defiance of contemporary neo-Darwinists, though not necessarily of Darwin himself.

Some biologists see plausibility as a big problem, have described the problem and proposed solutions. The Plausibility of Life by Marc Kirchner and John Gerhart. Evolution in Four Dimensions by Eva Jablonka and Marion Lamb. Others claim that standard neo-Darwinism is all we need. Climbing Mount Improbable by Richard Dawkins. Darwin’s Dangerous Idea, by Daniel Dennett.

These are all serious scientists, applying their intuition to a problem for which scientific methods have no definitive answer. You can read my take on the subject in Parts 2 and 3, forthcoming.