Despite being one of the most influential of the early modern biologists and having crucially paved the way for Darwin, Jean-Baptiste Lamarck has mostly gone down in history for being wrong. His theory of “use and disuse” as a mechanism for evolution was roundly rejected and is often presented in introductory biology textbooks as totally misguided and even silly.
Historian Jessica Riskin, of Stanford University, has written a new book entitled, “The Restless Clock: A History of the Centuries-Long Argument over What Makes Living Things Tick.” In this book, she urges a fresh look at the bold and imaginative ideas of Lamarck and how they inspired the naturalists that followed him.
More provocatively, Professor Riskin shines the same harsh light of historical hindsight that has tormented Lamarck onto Darwin, Huxley, and even the neo-Darwinians of the modern era. Her surprising conclusion is that the modern packaging of evolutionary theory has not fully loosed itself from the theological compromises brokered by the Victorians.
Professor Riskin advances the controversial and intriguing claim that our neo-darwinian understanding of evolution actually robs living things of their agency in devising their own solutions to the challenges of surviving and thriving in a planet teeming with competitors, and surrenders it to the “prime mover,” now thought of as random mutation but originally imagined to be a divine clock-maker.
This may seem like philosophical mumbo-jumbo to scientists steeped in the new evolutionary synthesis, but there is one point that cannot be ignored: we now know that certain biochemically coded information can indeed be passed from one generation to the next beyond the fixed sequence of DNA. Experiences as diverse as stress, diet, injury, and intoxication can leave epigenetic and/or biochemical marks on our gamete cells (sperm and eggs) which can then be passed on to the resulting zygote. (More on that below.)
In sum, we now know of concrete mechanisms by which current conditions can affect the way our genes are inherited. It’s not quite Lamarck’s giraffe passing on a long neck for having stretched her own, but it’s also not the rigid prevailing dogma that the genetic material we pass on to our progeny was strictly fixed before we were even born.
Below, Professor Riskin summarizes her research into how the big ideas of evolutionary theory took shape and reveals the surprising echoes of an early form of theological evolution that can still be heard today. For a more thorough exploration, I recommend her book, The Restless Clock.
Too often, we scientist and science educators overlook how the ideas we hold so dear took shape. -NHL
You’ve heard of Jean-Baptiste Lamarck, the misguided Frenchman who said that when a giraffe sticks out its neck to reach high leaves on a tree, it has longer-necked babies, the Lamarck whose outlandish theory awaited sober refutation by Darwin. But did you know that Lamarck was the first to suggest a separate science of living things and then coined the term “biology?” He was also the first to develop a systematic theory of what we now call evolution. Darwin himself, as well as every major Darwinist until the end of the nineteenth century, was really a Lamarckian.
They were Lamarckians in the sense that they all espoused core principles of Lamarck’s theory of the development of species. In particular, they believed that living forms changed over time in law-like ways, an idea that Lamarck was the first to develop, and that the causes of these changes included the habits, behaviors and willful actions of individual organisms.
Around the turn of the twentieth century, “Lamarckism” became the antithesis, not only of Darwinism, but of all legitimate science. Lamarck was suddenly not just wrong, but absurd, beyond the pale, even dangerous. What happened?
The question would be intriguing even were it not for the fact that a century later, in the 1980’s and ‘90’s, Lamarckism began to move quietly back into the scientific fold. Still, the anti-Lamarckian interpretation of evolution has remained powerful. The philosopher of biology Daniel Dennett has observed that a demonstration of Lamarckian inheritance would be “fatal to Darwinism,” but is “safely discredited,” while the biologist and writer Richard Dawkins has described what he calls a “Lamarckian scare,” confessing, “to be painfully honest,” a return to Lamarckian evolution would “devastate my world view.”
These are extreme terms – “painful,” “scary,” “fatal,” “devastating.” Dennett and Dawkins, and other neo-Darwinists, have clearly seen Lamarckism as a threat, not just to a particular scientific idea or theory, but to an entire worldview, to modern science, to reason itself. Why? I believe this feeling of menace has evolved from an older one, in which it was not science or reason that was being threatened, but rather a kind of limited partnership arrangement between science and theology.
To understand this unspoken arrangement between science and theology, you must first consider that the founding model of modern science, established during the Scientific Revolution of the seventeenth century, assumed and indeed relied upon the existence of a supernatural God. The founders of modern science, including people such as René Descartes, Isaac Newton and Robert Boyle, described the world as a machine, like a great clock, whose parts were made of inert matter, moving only when set in motion by some external (divine) force.
These thinkers insisted that one could not explain the movements of the great clock of nature by ascribing desires or tendencies or willful actions to its parts. That was against the rules. They banished any form of agency – purposeful or willful action – from nature’s machinery and from natural science. In so doing, they gave a monopoly on agency to an external god, leaving behind a fundamentally passive natural world. Henceforth, science would describe the passive machinery of nature, while questions of meaning, purpose and agency would be the province of theology.
In other words, the founding model of nature in modern science, a passive world- machine, arose hand-in-hand with a core tradition in modern theology, the argument from design, which finds evidence of the existence of a rational God in the rational design of nature. Of course, forces and tendencies (gravitational, electrical, magnetic, fluid…) permeated modern physics. The question of whether these forces originated inside or outside the world-machine provoked some debate, but those who argued for an intrinsically active world-machine were not able to hold sway over those, notably Newton and his followers, who argued that natural forces originated outside nature’s machinery in the will of God. The evacuation of purposeful action from a passive world- machine remained entrenched in science.
Lamarck’s theory threatened all this. Instead of appealing to an external source for the agency involved in the creation and transformation of living forms, Lamarck proposed to naturalize that agency, to consider it a natural force like the forces of contemporary experimental physics such as gravity, electricity or magnetism, and to insist that all of these forces originated within the world-machine. For one thing, Lamarck hypothesized a rudimentary, upward-striving pouvoir de la vie that drove all organisms to complexify and elaborate themselves over time.
In addition to this primitive life force, another kind of agency acted in animals as well, according to Lamarck, namely their “habits,” their “ways of life” and acts of will. “When the will determines an animal to perform a given action,” he wrote, “the organs that must execute this action are immediately provoked” to carry it out. Many repetitions of these “acts of organization” would then “fortify, extend, develop and even create the necessary organs.”
Both sorts of Lamarckian living agency, the rudimentary, primitive force of life and the higher force of will, were internal to the works, constitutive of the machinery from within. Lamarck argued that this must be the case, because if each creature instead owed its organization to a force outside itself, then instead of being animate machines, animals would be “totally passive machines.” They would never have had “sensibility or the intimate sentiment of existence that follows from it,” nor the power to act, nor ideas, nor thought, nor intelligence. They would not, in short, have been alive.
The notion that living beings produced themselves by their own agency was controversial. Lamarck’s fellow naturalist and critic, the devout Lutheran zoologist Georges Cuvier, famously rejected it. It was Cuvier who wrote poor Lamarck’s eulogy: rarely can a eulogy have offered fainter praise. Cuvier observed that no one had found Lamarck’s theory worth attacking, since it rested upon the “arbitrary” assumption “that desires [and] efforts, can engender organs,” an idea that might “amuse the imagination of a poet” but could never persuade a true anatomist. The theological implications of Lamarck’s view that living beings created and continually re-made themselves cannot have pleased the pious Cuvier.
Several decades later, Lamarck (or anyway his theory) encountered an even more effective attack at the hands of the German biologist August Weismann, whose interpretation of Darwinian evolution became the standard one in the 20th century (Dawkins and Dennett both describe themselves as neo-Weismannists). The “Darwinism” of Weismann’s redefinition eliminated all Lamarckian inner agencies, which had figured in Darwin’s original theory. Weismann located evolutionary agency decisively outside the organism, insisting that organisms had no role in shaping their evolutionary destiny: no kind of experience or behavior on the part of an individual organism could change the machinery of inheritance.
An unbreachable barrier separated somatic (body) cells from germ (reproductive) cells according to Weismann. He insisted that no changes taking place in the somatic cells could ever be transmitted to the germ cells. This enormously influential idea, eliminating the possibility of “inheritance of acquired characteristics,” became known as the Weismann barrier.
Weismann also had some collateral victims, namely several generations of mice. Although he was not a farmer’s wife, and most likely did not use a carving knife, he did chop the tails off these hapless mice in order to show that their offspring had perfectly healthy, normal-length tails. Weismann presented this as a definitive refutation of Lamarckism, although he himself also quietly acknowledged that it had no real bearing on Lamarck’s theory, since having one’s tail chopped off is not a behavior, habit, or act of will (nor, for that matter, did the experiment disprove Lamarck’s intrinsic upward-tending force of life). But Weismann said his mice would defeat the popular version of belief in inheritance of acquired characteristics.
This was a spoof rather than a refutation, but what it lacked in relevance, it made up in clarity, and it still appears in textbooks as the final disproof of Lamarckian inheritance.
The “Weismann barrier” separating somatic cells from germ cells was in effect a barrier between individual agency and evolutionary transformation. It remained such – a denial of evolutionary agency to organisms – as it became a core principle of neo- Darwinism, when Francis Crick restated it as the “Central Dogma” of molecular biology.
Crick’s “Central Dogma” states that there is no reverse translation from protein to RNA to DNA – the transcription only happens in one direction, from DNA to RNA to protein – which is essentially a translation of the Weismann barrier into the language of genetics. So Weismann’s barrier between individual agency and evolutionary transformation became an axiom of genetics.
In order to truly understand their core axioms, scientists should understanding something about their histories. Never is this more crucial than with the origins of Weismann’s barrier: Weismann was working around the turn of the 20th century within the emerging German model of a research university, in which the science and theology faculties struck a kind of bargain. The science faculties restricted themselves to demonstrations, in ever more specialized detail, of the mechanical complexity of natural forms, while leaving the questions of meaning, will, and agency to the theology faculties.
It was an institutional application of the argument from design, which had banished agency to the province of a supernatural god, leaving behind a mechanical world that was infinitely intricate but essentially passive.
Weismann subscribed to the established scientific axiom that agency was supernatural, operating only outside of nature’s machinery. He described purposefulness, the source of meaning and direction, as lying beyond the mechanism of the universe, in the province of what he called a “spiritual First Cause” or a “teleological Universal Cause” (with capital letters to suggest divinity).
His mechanist approach to biology was overtly teleological, as he himself stressed: “Without teleology, there would be no mechanism” he wrote, and also “without mechanism there would be no teleology.” He emphasized that his conception of the universe was therefore anti-materialist, because it assumed a purposeful divinity. Strange that this is the same Weismann that Dawkins and Dennet so revere.
The ideas of Weismannism were brought to the United States in the middle decades of the 20th century by another product of the German research university, Ernst Mayr. Mayr studied biology at the University of Berlin in the mid-1920’s, receiving his PhD in 1926. His adviser was the ornithologist Erwin Stresemann, who greatly admired Weismann for having vanquished Lamarkcism. Stresemann was a firm subscriber to the passive- mechanical view of living beings. Stresemann wrote, for example, “an animal does not act for itself, but under a higher commission: animal non agit, sed agitur [an animal does not act, but is acted upon],” and he endorsed the view that “[t]he animal does not think, does not reflect, does not establish aims for itself, and if it nevertheless behaves purposively, then someone must have thought for it.”
Notice in both of those expressions how the passive mechanism of the animal implies a higher power, an external Someone.
When Mayr went to New York in 1931, he brought his training and influences with him. By then, the United States had been importing the German model of the research university, particularly in biology, for more than half a century, since the founding of Johns Hopkins in 1876 on the template of the University of Berlin. American biology was a well-prepared soil into which to plant Weismann’s ideas and the model of science they represented.
Now, I don’t mean to ascribe theological motivations to Mayr himself, who reminisced that he had first become interested as a boy in reading the work of naturalists such as Ernst Haeckel “to have ammunition in arguments about the Bible and religion,” and certainly not to Dennett or Dawkins, atheism’s leading missionaries, but rather to point out the hidden and surprising historical origins of the dogma they have all defended with such force and power. In defending it, they are heirs, however ironically, to a theological tradition, the argument from design.
Dawkins takes the Weismann barrier, recast as the Central Dogma, to be the all- important firewall between science and religion, keeping scientific explanation free of teleological appeals to purpose or agency. But a wall has two sides and in historical terms this one was first built to serve the reciprocal function as well: to be a firewall protecting theology from science, ensuring a monopoly on agency to a supernatural God and, to his theologian-interpreters, ownership of the ultimate questions of the meaning and essence of life.
Viewing Lamarck as the founder of our modern view that life can create and shape its own reality begins the rehabilitation of his reputation. However, I think that recent discoveries in molecular biology vindicate him as well.
In the simplest example, it is clear that the physiological state of the womb, and therefore of the woman, have an impact on how genes are expressed in an embryo or even a fully-formed fetus. (I say “woman” and not “mother” because the most convincing research has been done in surrogate pregnancies.) There are a variety of ways in which this happens, but it most often occurs via a phenomenon called epigenetics.
Epigenetics refers to how covalent modification of DNA (or more often, the histone proteins closely associated with DNA) affects how that DNA is expressed. A couple decades ago, biologists assumed that all of the differences and diversity among human beings were captured in subtle differences in our genome sequences, the As and Cs and Gs and Ts. We now know that genetic control of our phenotype (how our bodies look, act, and function) is much deeper than that. The exact same DNA sequence can be expressed very differently in two different cells based on how that DNA is “marked up” by epigenetics.
We should have seen this coming. Scientists have long known that the cells of our liver to do things very differently than the cells of our bones, for example, despite having the exact same genome sequence. Skin cells and neurons couldn’t behave more differently, couldn’t look more distinct, and yet the only differences in their genes are found in the epigenetic modifications.
How does this support Lamarck? For one thing, it demolishes all notions of the Weismann barrier. Events in our lives do effect how the genes in our gametes function when they give rise to our offspring. Identical twins begin their lives with the same genome sequence but differences in gene expression accumulate over time such that everyone who knows them well can easily note their many physical and psychological differences. Not surprisingly, epigenetic differences can be found in their gametes as well.
The most dramatic example of Lamarckian inheritance has recently been reported in cases of surrogate pregnancy. Scientists working at a fertility clinic in Spain have discovered a mechanism by which the genetics of gestational surrogates is passed on to developing fetuses. The vehicle for this genetic transmission is something called micro-RNA, usually abbreviated miRNA, or simply, miR. Doctors found that micro-RNA molecules encoded by the surrogate mother’s genome were expressed and secreted by her endometrium into the uterine fluid and taken up by the developing embryo. These miRNA molecules, which have variations among individuals (which is how the scientists could detect this phenomenon) are capable of changing how genes are expressed and initiating the placement of specific epigenetic marks on DNA that then have further effects on gene expression.
Put simply, the genes of the surrogate mother appear to have affects on the genes of the offspring. While the discovery focused on the possibility of genetic influence from a “non-genetic mother,” the Lamarckian implication is that, in a standard pregnancy, a mother’s physiology can affect how the genes of her offspring are expressed in real-time. The phenotype of the developing child is not simply a function of her gene sequences, but is also influenced by the life history of her mother before and during the pregnancy. That’s a clear molecular manifestation of Lamarck’s ideas.
There are other molecular examples of how phenotype is much more than simply inherited gene sequences. In the phenomenon of RNA editing, a gene sequence is actually altered at the time of expression. DNA methylation can result in dramatic and relatively permanent changes in how genes are turned on and turned off. We are well aware of how stress hormones, and all hormones and signaling factors really, can alter the biochemistry and gene expression machinery of both gametes and developing embryos. Differential splicing, where the same gene can lead to a multitude of slightly different proteins, is well known but poorly understood. All of these phenomena emphasize how gene sequences are just part of the story.
Even something as simple as egg polarity, where gene expression factors are clustered on one side of the egg, can have dramatic long-term effects on the interplay between genotype and phenotype. Not surprisingly, micro-RNAs and epigenetics influence all of these super-genetic phenomena.
The field of genetics has long known that phenotypes are built from much more than just genotypes. DNA sequences are the raw building materials, but they are not the house. It is beyond question that the environment and other physiological conditions profoundly influence how our bodies and minds spring forth from our genes. We also now know that some of that is heritable.
And that’s a positively Lamarckian truth.