What’s wrong with New Scientist

[Follows from a previous post]

In one sense, and I am sure this is the sense that New Scientist will use in its defence, the headline is perfectly true. Darwin was wrong. He wrote The Origin of Species in 1859. A small selection of the things he didn’t know about at the time were genetics (Gregor Mendel, 1865/6 but obscure until 1900), germ theory (Robert Koch, 1876), and DNA (first isolated by Freidrich Miescher, 1869, shown to be the molecule of inheritance by Frederick Griffith, 1928, but not really grasped until Crick and Watson described its self-replicating structure, 1953).

Since Darwin did not understand genetics, he made the mistake of assuming that inheritance was mixed like paint rather than discretely like genes. In general, when one looks at the offspring of two adults, the offspring tends to have a mixture of traits from both parents. If a white-skinned person and a black-skinned person mate, their children tend to have light-brown skin. The problem this posed for Darwin was that organisms in a population should mix their heritable characteristics more and more over time. Eventually they should all have much the same heritable features and be virtual clones of each other.

Darwin himself never came up with a solution to this hole in his theory. We know now the answer is that organisms inherit discrete units of inheritance, not mixable traits. Skin colour appears to mix because there are so many genes involved. When traits are determined by very few genes, as in blood type or colour-blindness, then mixing is clearly not a satisfactory explanation. The most dramatic example is sex: if inheritance was mixed, then children of men and women would not be boys and girls but would be mix-gendered instead and after a few generations, we would all be pretty much exactly half-men/half-women. From this single example, it should have been clear for thousands of years that inheritance is not mixed, and yet this did not occur to Darwin nor to anyone else active in science or natural philosophy before him.

In the case of sex in humans, the discrete particles are the X and Y chromosomes. In the case of red-green colour blindness, the discrete particles are two genes on the X chromosome. With blood type, it’s a single gene on chromosome 9. And it’s not just genes that do the discrete inheriting. Eye colour is determined by an interplay of DNA sequences called SNPs (pron. “snips”).

Darwin’s other big problem was that he didn’t know where diversity came from. He would have been happy to push the problem back to Creation, but since he knew that the Earth was at least many millions of years old, he could not explain where new heritable characteristics came from. How could dinosaurs arise from their not-very-dinosaurian ancestors? The answer we now know is mutation. DNA is a very efficient self-replicator, but it is not perfect. Because DNA makes errors when it replicates, new heritable traits are constantly bubbling up in living species.

So did Darwin make mistakes? Of course he did. And these are just his two biggest mistakes; there are many others. But he was right, absolutely right, about what really matters in biology: life evolves, and it does so through descent with modification.

Had New Scientist run an article about Darwin’s errors and what we have learned in the last 150 years, there would be nothing to complain about. Darwin was, after all, trying to practise science and not prophecy, so he expected to make mistakes. But Graham Lawton wasn’t interested in anything as mundane as that. He wanted to create a stir. Unfortunately he did so by making errors of his own that are far more egregious than any Darwin made.

1. Error of fact: Graham Lawton writes, “For much of the past 150 years, biology has largely concerned itself with filling in the details of the tree.” Let’s put this plainly: this is unadulterated bullshit. It would be a fair description of biology before Darwin, which was mostly an exercise in discovering new species on the one hand and trying to fit them into classification systems on the other. But after Darwin, biology exploded — and not just in evolutionary theory. Chemistry became biochemistry. Physics (especially electricity) drove the new science of neurology. Physics and chemistry combined to make physiology. Ecology became a new science. Paleontology boomed. Genetics didn’t even exist until 1900. This statement is about as truthful as saying nothing much happened in engineering between the the Second Industrial Revolution’s steam engines and the release of the iPhone. 

The idea that biology stood motionless under the baleful glare of Darwinism is an invention of Lawton’s intended to make his story appear more revolutionary. He’s not doing journalism, he’s doing side-show spruiking. Roll up! Roll up! Come see the amazing Wolfman! Only when you get into the tent, you find the Wolfman is an alcoholic layabout who hasn’t shaved for ten years and whose only remaining teeth are his canines.

2. Exaggeration and misdirection: Lawton writes as if he’s got hold of a stunning new development. In fact, what he is arguing is that the “Tree of Life” metaphor fails because life doesn’t just branch outwards. Sometimes genes are transferred not by direct descent but by swapping from one organism to another — often from completely different species. This is known as horizontal gene transfer (as opposed to “vertical” gene transfer when you inherit DNA from your parents). We now know that horizontal gene transfer has been a lot more important in evolution than we used to think. Where it was once considered to be a relatively uncommon process, we have now accumulated evidence that it may have been a major force behind evolution. As some writers have put it, the Tree of Life is really more of a web than a tree. But this is not especially controversial.

Despite Lawton’s best efforts to make this look like some internecine feud between scientists, the only ongoing debate is about the degree to which horizontal gene transfer has influenced evolution. HGT (to abbreviate) was first described back in 1959. Like Mendel’s work, this paper was not recognised until much later. It was not until 1984 that HGT became a big research field. But that’s still 25 years ago and Lawton is acting like it’s some extraordinary revelation.

3. Error of fact: “As early as 1993, some were proposing that for bacteria and archaea the tree of life was more like a web,” says Lawton. Rubbish again! The “webbiness” of life was understood a long time before 1993. Not only was HGT (and its ramifications) understood, there is a related concept called endosymbiosis, where one organism becomes symbiotic with another inside it, which was detailed by Lynn Margulis in 1970. She was very sharp in pointing out what this meant for evolution — it wasn’t just about competition; co-operation was just as important. “Life did not take over the globe by combat, but by networking.” She was certainly aware of the “webbiness” this implied, saying (admittedly later) “the tree of life often grows in on itself.” But even 1970 wasn’t the first mention of endosymbiosis — the idea was proposed, with good evidence, by Konstantin Mereschkowski back in 1905! Lawton could have found all this out by checking Wikipedia.

Does this matter? A little pizazz is always welcome in science journalism, but one has to draw the line when the pizazz distracts from important truths rather than drawing light to them. What really, really irks me about this story is that it covers exactly the same ground, and interviews exactly the same people, about exactly the same research paper as a much better article written nearly two years ago by Lisa Zyga.

Ms Zyga was capable of writing a fascinating article without misrepresenting anything and in about a fifth the word-length. Given the remarkable similarities, I wonder if Mr Lawton read Ms Zyga’s piece. I’m not suggesting plagiarism (Lawton might have written a decent article if he had) and in fact I’d suggest Lawton should have read Ms Zyga’s article prior to going to press. If he had done so, he would have been much better equipped to deal with the scientific concept he so clearly fails to understand.

4. Error of Fact: Lawton says,

The tree-of-life concept was absolutely central to Darwin’s thinking, equal in importance to natural selection, according to biologist W. Ford Doolittle of Dalhousie University in Halifax, Nova Scotia, Canada. Without it the theory of evolution would never have happened. The tree also helped carry the day for evolution. Darwin argued successfully that the tree of life was a fact of nature, plain for all to see though in need of explanation. The explanation he came up with was evolution by natural selection.

Ever since Darwin the tree has been the unifying principle for understanding the history of life on Earth. At its base is LUCA, the Last Universal Common Ancestor of all living things, and out of LUCA grows a trunk, which splits again and again to create a vast, bifurcating tree.

But this is completely wrong. For one thing, Lawton is confusing the Darwin with later biologists who expanded the Tree of Life metaphor into areas Darwin himself could not have contemplated. Darwin himself had nothing to say about a Last Universal Common Ancestor because he had no way of knowing anything about the subject. Darwin suggested that modern species had common ancestors, but he made no predictions about whether there was one or many common ancestors. It is also untrue that the theory of evolution would never have arisen without the Tree metaphor. There were many pillars of evidence that Darwin drew on. The common features of related species was only one of them. I understand that Lawton is quoting another scientist here, but to repeat such a quote uncritically does not indicate good research.

In comparison, here’s Zyga’s take:

While parts of evolution certainly are tree-like, other parts may be nets or webs or other complex models. Most importantly, however, there seems to be no “theory of everything” in evolution, no metanarrative to unify all life forms…

As for any blow to Darwin’s ego, the scientists [Doolittle and Baptestse, the same scientists interviewed by Lawton] point out that he never wrote about reconstructing the tree in an attempt to relate every living thing, but rather used the model as a general guide.

“I’d like to think he would adjust,” Doolittle said about Darwin. “After all, his theory was developed before there was any understanding of genetics and when bacteria were still believed to be spontaneously generated.”

Isn’t it amazing? If you actually know the history of Darwinism and you quote scientists in a more reasonable manner, you get a story that is just as interesting without all the puffed-up conflict and inflated sense of revolution. And what’s more, you can do it two years ago!

5. Pandering to the barbarians at the gate: It has been less than a week since New Scientist ran this story and already it has been quoted by creationists trying to push anti-evolutionary material into the Texas school curriculum. [More on this at Panda's Thumb.] You may note, as further evidence of New Scientist’s intransigence, that they reported on this development without mentioning that the creationists were referring to a New Scientist story.

Next: Not dead yet: the Tree of Life as an active metaphor

Tags: darwin, darwin was wrong, lawton, new scientist, tree of life, zyga