The Red Notebook

See if you can guess who wrote the following:

[A]lthough each species must have passed through numerous transitional stages, it is probable that the periods, during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition.

Gould? Eldredge? Sounds like a textbook description of punctuated equilibrium, doesn’t it?

But no, the awkward comma after the word periods is the real and potentially surprising give-away: our punctuationally challenged punctuationist is none other than Charles Darwin, writing in the fourth edition of On the Origin of Species!

What’s that? Darwin a punctationist? Some mistake, surely! Wasn’t he the one who kept banging on about how Natura non facit saltum (Nature does not make leaps)?

In January 2008, Evolving Thoughts‘ John Wilkins wrote a typically thought-provoking post explaining how Linnaeus‘s phrase Natura non facit saltum doesn’t really mean what you probably thought it meant. The phrase, Wilkins explained, was originally intended to describe how Nature exists in small gradations; not how Nature comes about (i.e. evolves) gradually, in small, continuous steps. The distinction is a subtle one, and the two interpretations of the phrase are not necessarily contradictory—but neither does the fact that living and extinct species can be grouped into a continuum necessarily imply that they must have evolved at a uniform rate.

Upon reading On the Origin of Species for the first time, Darwin’s great ally (and bulldog) Thomas Henry Huxley questioned Darwin’s apparently hard-line gradualism, writing to Darwin:

The only objections that have occurred to me are 1^st that you have loaded yourself with an unnecessary difficulty in adopting ‘Natura non facit saltum’ so unreservedly. I believe she does make small jumps—

Huxley’s comment seems to have put Darwin slightly on the defensive. By the second edition of Origin, published less than a year later, he had inserted a qualifier into his description of Linnaeus’s dictum, describing it as ‘that old, but somewhat exaggerated, canon in natural history of “Natura non facit saltum”‘ (my emphasis added).

Seven months before the publication of Origin, Darwin had tried to clarify his views on this subject to Joseph Dalton Hooker:

I would advise you to be cautious about stating so broadly (I thought that you perhaps knew of distinct cases unknown to me) about species not varying for many generations & then suddenly varying. To a certain extent I quite believe it; ie that a plant will not vary until after some few generations (perhaps dozen or so) & then will begin to vary possibly suddenly, more likely gradually. But even my belief in this is grounded on very few facts.— I believe another & very distinct explanation may be given of a sort of current belief in the doctrine, viz that variations are often not attended to, & till they are attended to & accumulated, they make no show.—

In other words, although Darwin was prepared to believe that some variations could appear relatively suddenly, he also suspected that variations were happening all of the time, but not always being attended to (i.e. selected) and accumulated. Again, these viewpoints are not necessarily incompatible.

But, whereas Darwin seemed to be hedging his bets somewhat in his 1859 letter to Hooker, as we have seen from the passage quoted at the beginning of this article, he was clearly less hesitant of expressing what would now be described as punctuationist views seven years later in the fourth edition of Origin.

Had something happened between the publication of the third and fourth editions of Origin (1861 and 1866 respectively) to cause Darwin to insert the passage? I believe a clue comes earlier in the fourth edition, where Darwin is again describing the punctuated nature of evolution:

It is a more important consideration, clearly leading to the same result, as lately insisted on by Dr. Falconer, namely, that the periods during which species have been undergoing modification, though very long as measured by years, have probably been short in comparison with the periods during which these same species remained without undergoing any change. We may infer that this has been the case, from there being no inherent tendency in organic beings to become modified or to progress in structure, and from all modifications depending, firstly on long-continued variability, and secondly on changes in the physical conditions of life, or on changes in the habits and structure of competing species, or on the immigration of new forms; and such contingencies will supervene in most cases only after long intervals of time and at a slow rate. These changes, moreover, in the organic and inorganic conditions of life will affect only a limited number of the inhabitants of any one area or country.

As in his 1859 letter to Hooker, Darwin is again saying that variations are happening all of the time, but their selection is down to life’s contingencies (a favourite word of punctuationists). The clue I referred to is the name Dr Hugh Falconer. In 1863, Darwin and Falconer had corresponded briefly on the subject of species formation. In one letter, Darwin wrote:

I should rather like to see it rendered highly probable that the process of formation of a new species was short compared to its duration; that is if the process was allowed to be slow and long: the idea is new to me.— Heer’s view that new species are suddenly formed like monsters, I feel a conviction from many reasons is false.

Here, I suspect, we come to the real reason for Darwin’s insertion of the passage quoted at the beginning of this article into the fourth edition of Origin. In a footnote to this letter, the Darwin Correspondence Project explains:

Working mostly with Tertiary plants and insects, the Swiss palaeontologist Oswald Heer maintained that species were generally constant, but that during occasional periods of creation, existing types underwent abrupt variation and gave rise to new species […]. By 1863, Heer’s view of new species formation was being presented in the international literature as a rival to CD’s theory of slow evolution by natural selection.

It seems to me that, by inserting the punctationist passage into the fourth edition of Origin, Darwin was trying to make it quite clear that his own theory of evolution by means of Natural Selection was quite adequate for explaining the apparently punctuated nature of species formation—without recourse to Oswald Heer’s monsters.

As usual, Darwin was correct. He understood that it was perfectly possible for evolution to be punctuated, without the need for Nature to make monstrous leaps.

Postscript (27-Feb-2009): The aforementioned John Wilkins has written again on this subject in a post entitled Myth 4: Darwin was a gradualist.

New Scientist: Languages evolve in sudden leaps, not creeps

Language evolves in sudden leaps, according to a statistical study of three major language groups. The finding challenges the slow-and-steady model held by many linguists and matches evidence that genetic evolution follows a similar path.

SJG would no doubt have written a fantastic essay about this. He is sorely missed.

I appreciate we are supposed to find this amusing, but I find it rather disturbing:

Sunday Times: DNA pioneer James Watson is blacker than he thought

James Watson, the DNA pioneer who claimed Africans are less intelligent than whites, has been found to have 16 times more genes of black origin than the average white European.

An analysis of his genome shows that 16% of his genes are likely to have come from a black ancestor of African descent. By contrast, most people of European descent would have no more than 1%.

Yes, very funny, let’s all laugh at James Watson’s silly, racist views (again). But I think this news report could be misconstrued in a number of ways:

• some people might (bizarrely) interpret the report as supporting the view that Africans are less intelligent than Europeans: silly, old James Watson has more black genes than most Europeans—which explains why he is so silly;
• some people might interpret it as implying that the genetic contribution to human intelligence is measurable, and separable from the environmental contribution;
• some might interpret it as implying that there are ‘black’ (African) genes and ‘white’ (European) genes—almost as if we didn’t all originate in Africa;
• some might interpret it as implying that ‘race’ is a meaningful, genetic concept.

In fact, the report says and implies none of these things. But people need to be incredibly careful when reporting this sort of story—in the same way that James Watson should have been a lot more careful when he was expressing his outdated views.

See also: Books: The Mismeasure of Man

New Scientist: Evolutionary ‘big bang’ gave rise to flowering plants

Flower power had its true heyday not in the 1960s, but 140 million years ago. That was when the ancestors of more than 99 per cent of flowering plants came into being in a “big bang” lasting just a few million years…

[A team from Oberlin College, Ohio] sequenced entire chloroplast genomes for 45 flower species from all major groups, which revealed that five sister groups split off nearly simultaneously. Two groups, the eudicots (including roses, sunflowers and tomatoes) and the monocots (grasses and their relatives), together account for 95 per cent of flowering plants. Magnolias occupy a third group. The two others are less well known (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0708072104).

Larry Moran over at the Sandwalk and PZ Myers at Pharyngula both encourage us to read This Week’s Citation Classic: Gould and Lewontin’s The Spandrels of San Marco and the Panglossian Paradigm: a Critique of the Adaptationist Programme.

I have just re-read the paper, and can confirm that, 28 years after its original publication, it is as relevant as ever. The one-line summary:

One must not confuse the fact that a structure is used in some way […] with the primary evolutionary reason for its existence and conformation.

But don’t trust to one-line summaries; the paper is well worth 20 minutes of your time.

What else are you going to do on a Sunday morning? Everyone else is at church!

It is a source of continuing regret to me that I never got to send any of the fan letters I began writing to the late Stephen Jay Gould. They weren’t good enough, and I didn’t want to waste his time.

One of my unsent letters was on a subject which Gould said was in his top-three for reader feedback. In his essay Left Snails and Right Minds (published in his book Dinosaur in a Haystack), Gould wondered why old engravings of snails often show their shells spiralling the wrong way (the vast majority of snail shells have right-handed spirals; the old engravings often showed them left-handed). Some years after first reading the essay, I came across the following letter in Volume 5 of The Correspondence of Charles Darwin, which caused me to start drafting another unsent letter to Gould:

Charles Darwin to James de Carle Sowerby, 21st January, 1851

My dear Sir

I am much pleased with the Plates.— […] Only one figure will require a weighty alteration, viz P. rigidus. Nevertheless, I hope that you will loook [sic] over your Figures carefully for I saw a good many little blemishes; & the Plate is not very clean.—

The few reversed figures are unfortunate.— […]

Your’s Sincerely
C. Darwin

Sowerby was artist to the Palaeontographical Society and was preparing the engravings for one of Darwin’s barnacle books, Fossil Cirripedia (1851). From earlier letters, it is quite clear that Darwin was extremely frustrated with Sowerby’s slow progress. In contrast, a few reversed figures seemed relatively unimportant—although I thought Gould would have been amused that his great hero also suffered from reversed engravings.

By a strange co-incidence, shortly after reading Gould’s essay, I read a chapter in Richard Dawkins’s (then) latest book, Climbing Mount Improbable, which also dealt with shells. In it, Dawkins explained how the shapes of all shells can be recreated on a computer using just three parameters (or ‘genes’), which he named flare, verm, and spire. This time, I actually did write to the author:

Richard Carter to Richard Dawkins, 8th August, 1996

Dear Prof. Dawkins,

I greatly enjoyed reading your recent, excellent book, Climbing Mount Improbable and, in particular, the chapter on shells. However, I think I may have spotted a small mistake: on page 153, when talking about what you have called the spire parameter, you state:

Spire has no limits: negative values trivially indicate an upside down shell.

Although it is hard to visualise, I reckon that, if you turned this “upside down” shell the right way up, it would actually be spiralling in the opposite direction to a shell with a positive spire (anti-clockwise, as opposed to clockwise). Although this is hardly earth-shattering, I would argue that it is not trivial – after all, your favourite sparring partner, Stephen Jay Gould, dedicated an entire chapter to anti-clockwise snail shells in his recent, equally excellent, Dinosaur in a Haystack. […]

Yours sincerely,
Richard Carter

To my great delight (and my dad’s: he has boasted about it ever since), Dawkins emailed me straight back, confirming the error:

Richard Dawkins to Richard Carter, 15th August, 1996

Dear Mr Carter

Thank you for your letter of 8th August.

Yes, you are correct that the computer shell with a negative spire would beanticlockwise, and it is certainly not trivial. If I had thought of this,it would have saved me the trouble of building in a separate gene forhandedness. Damn! […]

With best wishes

Yours sincerely
Richard Dawkins

(Let it not be said that Richard Dawkins never admitted to making a mistake.)

Then, yesterday, I spotted another interesting example of reversed images, which, bearing in mind the subject matter, I’m sure would also have amused Gould. While re-reading my recent Red Notebook post The Expression of Emotions in Darwin, I suddenly realised that the photograph of Darwin that was the subject of the piece also appears on the covers of two books I have recently read—but in mirror image:

Original image of Darwin

Books showing reversed image

A quick check of the buttons on Darwin’s waistcoat on a higher resolution version of the image confirmed that the photograph of Darwin on the left is shown the correct way round, whereas the photographs appearing on the covers of the two books are shown in mirror image.

Plus ça change, as we say in Yorkshire.

The Berberis dawinii in my garden this morning

The Darwin’s Barberry in my garden is in flower already. It’s supposed to flower from April to May. There’s global warming for you.

Berberis darwinii, to give it its scientific name, was named by William Hooker, after it was first collected in Chiloe, Chile in 1835 by Charles Darwin during the Beagle voyage. The plant later became of interest to Darwin, because it was believed to be self-fertilising (although Darwin correctly dismissed this idea). It is now a very popular garden shrub.

The Berberis darwinii in my garden was a gift from my father, who is a keen gardener. I had asked him for something named after Darwin. The week after my father presented me with the plant, my favourite science writer, Stephen Jay Gould died, so I planted the Berberis darwinii in his memory.

I fully approve of the modern secular practice of planting trees as living memorials to the deceased, but I like to think Gould would have preferred a Berberis darwinii: partly because it is named after his personal hero, but mainly because—thanks partly to my supreme laziness as a gardener—it should soon grow into his favourite evolutionary motif: a straggly bush.

I am sure Gould would have approved.

Stephen Jay Gould would have loved this:

Guardian: Fossil research suggests ‘mass dying’ triggered teeming oceans

A cataclysmic mass extinction that devastated life on Earth millions of years ago is the unlikely reason such a rich variety of life is found in the oceans today, scientists have discovered.

Around 250m years ago at the end of the Permian era the Earth experienced its most dramatic loss of life, when an estimated 95% of marine species and 70% of land animals were wiped out. Scientists are uncertain what caused the extinction, but many suspect rapid environmental upheaval caused by vast volcanic eruptions were at least in part to blame.

Scientists at the Field Museum of Natural History, in Chicago, used a new database of fossil records to study how lifeforms in the oceans changed over 545m years. Instead of finding a gradual rise in different species, they spotted a sudden explosion in marine life shortly after what paleontologists call “the great dying”.

I’ve never understood the objections to apparent bursts of speciation in the fossil record being down to actual bursts of speciation, rather than imperfections in the fossil record. There is no reason to believe that speciation must always be a steady process. There is nothing anti-Darwinian about this: if a large number of ecological niches suddenly become available (following a mass extinction, say), previous constraints are suddenly removed, and evolution is almost bound to fill the niches as quickly as possible.