Chapter 1: Variation Under Domestication

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Man, this guy didn't know anything.

I don't mean that as an insult. Darwin, as he admits, knew almost nothing about inheritance, about how variation is produced, or about the origins and history of domesticated plants and animals. You'd think that would be a handicap in using domestication as an analogy for evolution.

And yet, in chapter 1 of the Origin, 'Variation Under Domestication', Darwin uses what little knowledge he has so deftly that nowhere do you feel his conclusions are outstripping his data. This, believe me, is quite a skill, both in a scientist and a writer. What, he asks, is the minimum we can infer from what we know?

Well, here's what his readers can be sure of at the end of the chapter:

  • Domestic animals and plants vary - most obviously between different breeds of the same species.
  • Domestic animals and plants have changed through time.
  • This change results from humans breeding selectively from individuals that carry a valuable trait, because offspring tend to look like their parents.

And that's about it -- hard to argue with any of that, then or now. Darwin does speculate about mechanisms: most variation, he suggests, comes from within the organism, by "the conditions of life ... [acting] on the reproductive system". You could see this as analogous to mutation, although I think that would be stretching inference beyond knowledge. There's also a shorter discussion of inheritance, the laws governing which are "quite unknown".

But none of this speculation is load-bearing -- the only essentials are right before our eyes. Darwin begins, with great care, by laying his foundations. Probably because no one else had laid any for him to build on.

If it was down to you to invent biology, where would you begin? Darwin takes the time-honoured path of sacrificing realism for tractability, and studies a simplified and controlled version of nature: farming. He recognized that animal breeders were the biotechnologists of his day, and possessed the nearest thing to a body of experimental biological knowledge.

Once he's latched onto domestic species, Darwin zooms in still further and begins with what is in effect a model organism: "Believing that it is always best to study some special group, I have, after deliberation, taken up domestic pigeons."

I think I can guess how those deliberations went: 'Hmm. I need something that I can keep in reasonably large numbers. It'd also be nice if they bred quickly. (Otherwise it'll take me, like, 20 years to publish.) That rules out sheep, pigs, cattle and so on. Rabbits? They all look pretty much alike -- it'd be nice if they were glaring differences between breeds. I need to be reasonably confident that modern varieties are descended from a single wild species. And I'd really like an excuse to hang around in insalubrious London gin palaces. I know -- pigeons!'

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(This image is taken from Darwin's 'Variation in Animals and Plants under Domestication' of 1868. I found it on Steven Carr's page.)

These deliberations, after all -- speed of breeding, ease of rearing, high variability -- lie behind others' choice of other species as models, such as the fruit fly Drosophila.

A large part of the 'Pigeons' section involves Darwin arguing that the different breeds are all descendents of the rock dove, Columba livia. He spends much of the rest of the chapter arguing that, for most domesticated species, the different varieties of each domestic plant and animal species are usually descended from a single wild ancestor species.

You can see why this is crucial -- it's the evidence that a single ancestor can give rise to many new forms, be they breeds or species (what we now call adaptive radiation). Darwin also notes that breeders create novelties by selecting and breeding within a variety, rather than by crossing varieties -- our first whiff of the equally crucial concept of reproductive isolation.

This belief in common ancestry apparently ran against received opinion: "all the breeders of the various domestic animals and the cultivators of domestic plants, with whom I have ever conversed, or whose treatises I have read, are firmly convinced that the several breeds to which each has attended, are descended from so many aboriginally distinct species".

Again, this shows how little Darwin, or anyone else, had to go on. In this chapter's Darwin-gets-it-wrong moment, he says "I do not believe ... that all our dogs have descended from one wild species." Whereas DNA evidence now points to them all being descended from wolves, and first domesticated in East Asia.

DNA sequencing and archaeology haven't cleared everything up, though. For many domesticated species, the number of domestication events and their timing and location has been controversial. To give one example, the number of times pigs were domesticated has recently been revised upward.

Lacking DNA, or any record of humanity older than ancient Egypt, Darwin has to argue from plausibility. For example, when Britain has "hardly one peculiar [i.e. endemic] mammal", he asks, is it likely that each of the country's sheep breeds is descended from a different wild ancestor?

He is also resourceful in his sources, willing to truffle out evidence from anywhere:

"Savages now sometimes cross their dogs with wild canine animals, to improve the breed, and they formerly did so, as is attested by passages in Pliny."

"The principle of selection I find distinctly given in an ancient Chinese encyclopaedia."

And, as evidence of ancient artificial selection, he mentions that "from passages in Genesis, it is clear that the colour of domestic animals was at that early period attended to."

The. Irony.

Next up, on Wednesday, 'Variation under nature', a chapter that Darwin described as 'short & dry'.

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Thanks James! I'm actually not the first - Adam Rutherford over at the Guardian's comment is free got in there last year (although I didn't know about that when I began, and I've not read his no-doubt-excellent effort in the interests of keeping my own responses fresh).

And I won't be the last - Tom Levenson at the Inverse Square has lined up a terrifyingly well-qualified all-star team to tackle it this year, one chapter per month.

You had stated in your first entry that you wanted to "imagine it's the 24 November 1859" when reading this work. I am having a hard time putting myself in that timeframe. To get the same effect, maybe I should try thinking like a 21st century creationist?

T. Fife: If you did that, you'd miss half the conclusions Darwin comes to, having put the book down half-way through a description in disgust! They do seem - to me, at least - to come long after I'd expect them. But, then, as John says, he is laying a lot of foundation. And laying that foundation takes a long time when you're starting from first principles, as it were.

John: Thanks for your efforts - it's great to read a summary of what I have so recently read. I am currently on chapter 4, but am expecting you to overtake me by the weekend! It is also good to see that some of the things I noted you have also noted - but also a few things that I completely missed, such as the comment about dogs.

As mentioned, you did say you were going to put your 19th century glasses on and appraise the chapter from that perspective. I can't imagine how much a contemporary reader might know about the pigeons Darwin uses - I was certainly at a loss when he mentioned the varieties, but he described the characteristics enough that I could follow along well enough.

Pleased to report, problem sorted, thank-you John. And thank you 'Confused' for your suggestions. I had figured out how to read it doing exactly as you suggested and it worked. Enjoying the post and comments!

Oh, if only Darwin had talked to Mendel...

As one who is chronically unable to get words down (must speak with my shrink), I thought must make an exception and thank you for this excellent commentary.

Thanks for the commentary John. It's much appreciated.

It's really interesting to see him struggling to piece together the mechanisms of heredity, without the benefits of Mendel and later Crick&Watson to give insight to his theories. His theories on recessive traits were fun.

Given his rudimentary knowledge, and our hindsight from 150 years of biological studies, I find it even more ridiculous that one of the biggest anti-evolutionist canards is that somehow Darwin is worshipped or treated as some sacrosanct, infallible authority on the matter. I think a good proportion of laymen today, with a smattering of knowledge of genetics, is more knowledgeable in this area.

On a note of grammatical style, he sure seems to be fond of LOOONG sentences with copious parenthetical statements. Not sure if that was the style of the time, or just his personal style, but I've never seen it used to that extent in any of the 19th century fictional works I've read. :-)

Thanks again for blogging this, and inspiring others to read along, too!

It's really interesting to see him struggling to piece together the mechanisms of heredity, without the benefits of Mendel and later Crick&Watson to give insight to his theories. His theories on recessive traits were fun.

Given his rudimentary knowledge, and our hindsight from 150 years of biological studies, I find it even more ridiculous that one of the biggest anti-evolutionist canards is that somehow Darwin is worshipped or treated as some sacrosanct, infallible authority on the matter. I think a good proportion of laymen today, with a smattering of knowledge of genetics and who has given it much thought, is more knowledgeable in this area.

On a note of grammatical style, he sure seems to be fond of LOOONG sentences with copious parenthetical statements. Not sure if that was the style of the time, or just his personal style, but I've never seen it used to that extent in any of the 19th century fictional works I've read. :-)

Thanks again for blogging this, and inspiring others to read along, too!

I'm really enjoying your blog - I particularly liked your views on Darwin's thoughts on choosing which examples to use.

I suspect that Darwin, although reasonably clever, was not brilliant or a genius. He was dogged, thorough, and persistant however, and this adds charm to the Origin - he made it seem that anyone could have had these ideas.

By DiscoveredJoys (not verified) on 12 Jan 2009 #permalink

Jason: in re: Darwin's long sentences and nested clauses. I am not sure about other contemporaneous science writing, and you are write the contemporaneous fiction writing has much punchier style. However, British philosophers of the time tended toward very complex long sentences. The one that most troubles my students is John Stuart Mill (1806-1873, writing in the early 1860's), as his work is canonical and must be read in ethics as well as in social and political philosophy. By our standards, Mill's writing is circuitous and overly complex. By the standards of the day, it was elegant and considered quite good argumentative prose. Here is an example by way of comparison with Darwin so that you can see the stylistic similarities in their argumentative writing, from the opening passage of Utilitarianism:

THERE ARE few circumstances among those which make up the present condition of human knowledge, more unlike what might have been expected, or more significant of the backward state in which speculation on the most important subjects still lingers, than the little progress which has been made in the decision of the controversy respecting the criterion of right and wrong. From the dawn of philosophy, the question concerning the summum bonum, or, what is the same thing, concerning the foundation of morality, has been accounted the main problem in speculative thought, has occupied the most gifted intellects, and divided them into sects and schools, carrying on a vigorous warfare against one another. And after more than two thousand years the same discussions continue, philosophers are still ranged under the same contending banners, and neither thinkers nor mankind at large seem nearer to being unanimous on the subject, than when the youth Socrates listened to the old Protagoras, and asserted (if Plato's dialogue be grounded on a real conversation) the theory of utilitarianism against the popular morality of the so-called sophist.

By Alison Reiheld (not verified) on 12 Jan 2009 #permalink

Another possible Darwin-got-it-wrong moment in this chapter: Near the end he states:

"To sum up on the origin of our Domestic Races of animals and plants, I believe that the conditions of life, from their action on the reproductive system, are so far of the highest importance as causing variability. I do not believe that variability is an inherent and necessary contingency, under all circumstances, with all organic beings, as some authors have thought."

It's hard for me to imagine what 'all organic beings' are now, let alone darwin's time. I suppose he was aloof to mutations and genetics, so he can be off the hook on this one.

@Alison:

Ah, thank you for your insights on his contemporaries, and the comparison. I admit to not being read into non-fiction of the time.

Darwin isn't insurmountably opaque whatsoever, and most of his parenthetical clauses are very relevant, but it almost comes across as if he were thinking more quickly than he could effectively transcribe. Regardless, it is an enjoyable read.

(Also, ScienceBlogs was throwing an error that appeared fatal, given the recent upgrades; sorry for double-post.)

Darwin may not be all that far off the origins of domestic dogs. There is some evidence that they are descended from gray wolves, yes, but also from Asian singing dogs, with which they are fully interfertile.

On Darwin's use of Mendel - Karl von Nägeli, one of the leading physiologists of his day, failed to appreciate Mendel's ideas, so I doubt that Darwin would have seen the significance. It took at long as 14 years of the Mendelian revolution for anyone to see the implications (William Castle) and 30 years for a mathematical treatment to be given by Fisher and Sewall Wright. But in some respects, Darwin was behind the curve on heredity - Lewes had a piece that was more informed than Darwin in 1856.

"Organic beings" = "Organisms". In Darwin's day, single celled organisms were not well known, and he most likely was referring to the standard distinction, gained from Linnaeus, of Plants and Animals (fungi were at that time thought to be plants).

I was fascinated by the tantalising forshadowings of Mendel's work - less than a decade off publication when the Origin was released, I think - when he talks about how the first offspring of mongrel pigeons are uniform, but the second generation by interbreeding are all different from each other.

Darwin does speculate about mechanisms: most variation, he suggests, comes from within the organism, by "the conditions of life ... [acting] on the reproductive system". You could see this as analogous to mutation, although I think that would be stretching inference beyond knowledge.

This was stretching towards outright Lamarkism, wasn't it?

Confused - I wouldn't call this Lamarckian, because as I read it Darwin thinks such variation happens through inherent failures of the reproductive system (although he does go into environmental influences when he places much weight on the difficulty of getting species to breed in captivity).

Also, there are more frankly Lamarckian bits of ch 1, when Darwin allows that a small proportion of variation comes from "use and disuse". This made me think he had something else in mind when he wrote about variation generated within the reproductive system.

One more thought on Dariwn and Mendel. When Mendel's works where rediscovered in the early twentieth century, many took them as being antithetical to the idea of evolution by natural selection (which was then in the doldrums generally). It took the modern synthesis to stitch them together.

So perhaps it was lucky for Darwin that he didn't know about Mendel.

Some of this Lamarckian vs. not will have to do with which edition you read. And yes I think the "reproductive system" to him was a vague term meaning the whole process, which would or could have included the genetic transmission system had he known about that. Mainly, though, you see Darwin's version of Lemarck in Variation in Plants and Animals ...

....I assume that cells, before their conversion into completely passive or "formed material," throw off minute granules or atoms, which circulate freely throughout the system, and when supplied with proper nutriment multiply by self-division, subsequently becoming developed into cells like those from which they were derived. These granules for the sake of distinctness may be called cell-gemmules, or, as the cellular theory is not fully established, simply gemmules. They are supposed to be transmitted from the parents to the offspring, and are generally developed in the generation which immediately succeeds, but are often transmitted in a dormant state during many generations and are then developed. Their development is supposed to depend on their union with other partially developed cells or gemmules which precede them in the regular course of growth. Why I use the term union, will be seen when we discuss the direct action of pollen on the tissues of the mother-plant. Gemmules are supposed to be thrown off by every cell or unit, not only during the adult state, but during all the stages of development. Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation either into buds or into the sexual elements. Hence, speaking strictly, it is not the reproductive elements, nor the buds, which generate new organisms, but the cells themselves throughout the body. These assumptions constitute the provisional hypothesis which I have called Pangenesis. Nearly

It doesn't matter which edition - it's still not Lamarckism, eith as Lamarck had it, nor as the neo-Lamarckians had it. It's not Weismannian, to be sure, but that isn't the sine qu non for Lamarckism either.

Darwin held only that the "strength" as it were of heredity was determined by the number of gemmules that the organism threw off by using the parts inherited. He did not think that the parts themselves were acquired during life and passed on, which is the "classical" definition of Lamarckism. To call what Darwin roposed as pangenesis Lamarckian is to do all kinds of historical injustice to him and Lamarck. Weismann is not the crucial turning point here - neo-Lamarckians held that acquired traits like calluses were heritable. Weismann showed, or thought he did, that they weren't. But that is not what Darwin believed anyway.

"Use and disuse" is about the variable strength of inheritance, as Darwin held what we might call an "analogue" (or "blending") notion of heredity. It is wrong, but not Lamarckian in any sense other than "non-Mendelian".

I was a bit amused that at the end, he noted that cat were pretty much impossible to selectively breed due to their aloofness.

On the other hand, cats, from their nocturnal rambling habits, cannot be matched, and, although so much valued by women and children, we hardly ever see a distinct breed kept up; such breeds as we do sometimes see are almost always imported from some other country, often from islands.

I know that cat breeding hasn't really been around that long especially when compared to that of dogs, cattle, pigeons, &c. From wiki, "The whole concept of cat breeds is a relatively new one. Two hundred years ago there was no such thing, however today there are almost one hundred cat breeds." Domestic cats don't really vary much in size currently, and most of the variations among the breeds are mixes of color pattern, length and texture of fur, and various differences in body part proportion. There are a few like the polydactyls, the Manx and bobtails, and the Sphynx that have very noticeable differences in body structure that have been bred for. I think if Darwin were alive today, he would marvel at what cat fanciers have done to the ratters of old.

John mentioned Jared Diamond in an earlier post. Maybe it's because I'm Australian that I contrasted Darwin's view with Diamond in this snip:

"If it has taken centuries or thousands of years to improve or modify most of our plants up to their present standard of usefulness to man, we can understand how it is that neither Australia, the Cape of Good Hope, nor any other region inhabited by quite uncivilised man, has afforded us a single plant worth culture. It is not that these countries, so rich in species, do not by a strange chance posess the aboriginal stocks of any useful plants, but that the native plants have not been improved by continued selection up to a standard of perfection comparable with that given to the plants in countries anciently civilised."

In Guns Germs and Steel Diamond argues that in fact it is "strange chance" that gave the fertile crescent the food plants most easily improved by breeding.

Or have I got either Diamond or Darwin wrong (I am not a scientist)?

Thanks for the opportunity to read along with you!!

Rather than supporting Lamarckian evolution, Darwin is refuting the idea here in chapter 1 (see pg 10 - 1st edition). When he discusses the disuse of a feature, he is looking at a relaxation of natural selection on the feature, since the feature would no longer be beneficial to the organism, or the strength of inheritance of the feature would be reduced. Lamarckian evolution would expect an immediate change with the next generation, Darwin seems to suggest time is needed to remove the feature, a property of natural selection.

By Paleoanthro (not verified) on 14 Jan 2009 #permalink

Finally finished chapter 1! Been a bit sloppy with my reading the last week so I'm really lagging behind.

I like your post, only thing I have to add is in regards to the mention of Genesis - the way I understood it, he's not saying that "it's in genesis so it must be true", but means that the Bible was written quite a long time ago, and since it mentions domesticated animals, they must have existed then.

I just realised I'm abusing commas. It's contagious!

You're right - I think he's using Genesis as a historical source to show that artificial selection goes back a long way. I still think this has its ironic side, though.

Its really interesting how darwin was able to gather so much knowledge and evidence for his theory, with so little background information.

I love how Darwin used domestic animals as his jumping-off point. This is how my dad first explained evolution to me when I was a little kid. When you think about selective breeding of farm animals the whole concept seems so logical.

Reading your comments about how it took decades for the Mendelian results to be combined with Darwin's theory to form the modern understanding of evolution is inspiring. It gives me hope that all the confounding scientific puzzles of today, like a unified theory in physics, will work out.