No, Scientists in Darwin's Day Did Not Grasp the Complexity of the Cell; Not Even Close - Evolution News & Views

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No, Scientists in Darwin's Day Did Not Grasp the Complexity of the Cell; Not Even Close

Virchow-cell.jpg

Recently a reader of ENV wrote to me asking whether it's true that in Darwin's day, scientists thought that the cell had a simple structure. The reader had argued on an Internet forum that back then, scientists vastly underappreciated the complexity of the cell -- especially compared to what we know today. Some Darwin-defenders responded to him by claiming that Darwin believed the cell was indeed "complex," and quoted Darwin as saying:

A cell is a complex structure, with its investing membrane, nucleus, and nucleolus, a gemmule, as Mr. G. H. Lewes has remarked in his interesting discussion on this subject (Fortnightly Review, Nov. 1, 1868, p. 508), must, perhaps, be a compound one, so as to reproduce all the parts.

This quotation of Darwin was then followed by the customary attacks on ID proponents, calling us ignorant, deceitful, or worse, for claiming that scientists of Darwin's era misunderstood and/or dramatically misunderstimated the complexity of the cell. I suppose that somehow this is supposed to bolster the ability of Darwinism to explain the complexity of the cell.

Well, let's take a closer look at that quote from Darwin. He said that the cell is "complex," in part, because it has a "membrane, nucleus, and nucleolus." It's no surprise that Darwin knew about these cellular components, because they were visible to microscopes of that time. But does this mean he really appreciated or anticipated the complexity of the cell?

The answer is a resounding no. Consider the article that Darwin approvingly cites in that quote, the one by G.H. Lewes in Fortnightly Review. Lewes serves as Darwin's authority for the claim that the cell is "complex," so let's start by looking at what Lewes said about the protoplasm in that very article:

The simplest form of organic life is not -- as commonly stated -- a cell, but a microscopic lump of jelly-like substance, or protoplasm, which has been named sarcode by Dujardin, cytode by Haeckel, and germinal matter by Lionel Beale. This protoplasm, although entirely destitute of texture, and consequently destitute of organs, is nevertheless considered to be an Organism, because it manifests the cardinal phenomena of Life: Nutrition, Reproduction, and Contractility. As examples of this simplest organism we may cite Monads, Vibriones, Protamœbæ, and Polythalamia. Few things are more surprising than the vital activity of these organisms, which puzzle naturalists as to whether they should be called plants or animals. All microscopists are familiar with the spectacle of a formless lump of albuminous matter (a Rhizopod), putting forth a process of its body as a temporary arm or leg, or else slowly wrapping itself round a microscopic plant, or morsel of animal substance, thus making its whole body a mouth and a stomach; but these phenomena are as nothing to those described by Cienkowski, who narrates how one Monad fastens on to a plant and sucks the chlorophyl, first from one cell and then from another; while another Monad, unable to make a hole in the cell-wall, thrusts long processes of its body into the opening already made, and drags out the remains of the chlorophyl left there by its predecessor; while a third Monad leads a predatory life, falling upon other Monads who have filled themselves with food. Here, as he says, we stand on the threshold of that dark region where Animal Will begins; and yet there is here no trace of organisation.

So protoplasm -- which we now call "cytoplasm" and know to be full of cellular organelles, molecular machines, RNA molecules, enzymes, and numerous other crucial biomolecules -- is considered by Darwin's favored authority on the subject to be the "simplest form of organic life," which is a "microscopic lump of jelly-like substance" that is "destitute of texture" and "destitute of organs" with "no trace of organization." This same authority believed a eukaryotic organism like a Rhizopod is little more than a "formless lump of albuminous matter." Not exactly a ringing endorsement or appreciation of the complexity of the cell.

It gets even worse when you read Mr. Lewes's simplistic descriptions of the nucleus or the cell membrane. He writes:

Now let our glance pass on to the second stage -- the Cell. Here we have the first recognised differentiation of structure, in the appearance of a nucleus, or attractive centre, amid the protoplasm. The nucleus is chemically different from the substance which surrounds it; and although perhaps exaggerated importance has been attributed to this nucleus, and mysterious powers have been ascribed to it, yet as an essential constituent of the Cell it commands attention. Indeed, according to the most recent investigations, the definition of a Cell is "a nucleus with surrounding protoplasm." The cell-wall, or delicate investing membrane -- that which makes the Cell a closed sac -- is no longer to be regarded as a necessary constituent, but only as an accessory.

So the nucleus, which we now know to be the information control center of the cell containing chromosomes and much of the genetic information -- billions of bits in some cases -- necessary to form an organism, is of "exaggerated importance," having "mysterious powers." Meanwhile, the membrane is called "only as an accessory" that isn't even necessary to the definition of a cell.

So if we take Lewes's definition of a cell as "a nucleus with surrounding protoplasm," and combine it with his prior description of protoplasm, then we see that a cell is a:structure of "exaggerated importance" with "mysterious powers" surrounded by the "simplest form of organic life," which is a "microscopic lump of jelly-like substance" that is "destitute of texture" and "destitute of organs" with "no trace of organization."This is what Darwin's favored authority on the complexity of the cell said about the complexity of the cell. Not exactly an anticipation of the cell's true complexity.

But what about Darwin's citation of the gemmule? Does this help show he had an accurate understanding of cellular complexity? A gemmule is, of course, a now-discredited concept. Darwin had an inaccurate understanding of inheritance, and believed something similar to Lamarck's long-abandoned view about the inheritance of acquired characteristics. Though I'm generally wary of citing Wikipedia, it correctly explains that "gemmules were imagined particles of inheritance proposed by Charles Darwin as part of his Pangenesis theory." Darwin invented gemmules as a mechanism of explaining blended inheritance. His theory turned out to be wrong: gemmules don't exist. So if someone is trying to claim Darwin had an accurate understanding of the cellular complexity, gemmules aren't a good place to start.

Of course, neither Darwin nor Lewes is to be faulted for getting these things wrong. It's obvious that in their time knowledge of molecular biology and cell structure was extremely primitive compared to 2013.

There are other good examples of Darwin's contemporaries failing to anticipate the complexity of the cell. For example, in his 1979 book The Spontaneous Generation Controversy from Descartes to Oparin (Johns Hopkins University Press, 1979), John Farley observes that Ernst Haeckel called the cell a "simple little lump of albuminous combination of carbon" (p. 73)

Not only did scientists long underestimate the complexity of cells, but they have continued to do so down to recent times, as leading biologists admit. Consider these words from former U.S. National Academy of Sciences president Bruce Alberts:

We have always underestimated cells. Undoubtedly we still do today. But at least we are no longer as naïve as we were when I was a graduate student in the 1960s. Then, most of us viewed cells as containing a giant set of second-order reactions: molecules A and B were thought to diffuse freely, randomly colliding with each other to produce molecule AB -- and likewise for the many other molecules that interact with each other inside a cell. This seemed reasonable because, as we had learned from studying physical chemistry, motions at the scale of molecules are incredibly rapid. Consider an enzyme, for example. If its substrate molecule is present at a concentration of 0.5mM,which is only one substrate molecule for every 105 water molecules, the enzyme's active site will randomly collide with about 500,000 molecules of substrate per second. And a typical globular protein will be spinning to and fro, turning about various axes at rates corresponding to a million rotations per second.

But, as it turns out, we can walk and we can talk because the chemistry that makes life possible is much more elaborate and sophisticated than anything we students had ever considered. Proteins make up most of the dry mass of a cell. But instead of a cell dominated by randomly colliding individual protein molecules, we now know that nearly every major process in a cell is carried out by assemblies of 10 or more protein molecules. And, as it carries out its biological functions, each of these protein assemblies interacts with several other large complexes of proteins. Indeed, the entire cell can be viewed as a factory that contains an elaborate network of interlocking assembly lines, each of which is composed of a set of large protein machines."

(Bruce Alberts, "The Cell as a Collection of Protein Machines: Preparing the Next Generation of Molecular Biologists," Cell, 92 (February 6, 1998): 291-294 (emphases added).)

A strong case, then, can be made that the cell has turned out to be a lot more complicated than Darwin or his contemporaries imagined. Not only did they vastly underestimate the complexity of the cell, but it's probably vastly more complex even than we imagine today.

Image: Rudolf Virchow's cell theory/Wikipedia.