Posted by: Rob Viens | June 19, 2012

“Cotyledons” of a Theory

On June 19th, the Beagle was getting prepared for it’s big trip to points south.  And even though Brazil may have seemed like it was far away from home, the Beagle was soon to embark on a trip to the truly remote land of Tierra del Fuego. Darwin writes about the preparations, comparing them with the original departure almost 6 months ago:

“Spent the day between the city & being on board.— They are very busy in stowing provisions for sea.— The ship looks in same inextricable confusion which she was in Plymouth.— The Warspite is making sweeps & boarding netting for us.— Our complement of men is increased.— Mr Forsyth is removed from the Flag ship into the Beagle & fills the place of poor little Musters.” (June 19)

“Mr. Forsyth” is Charles Forsyth, the newest midshipman to be added to the crew.  Forsyth actually kept his own journal of the voyage (See more at Charles Darwin Online) – a recently new discovery. Forsyth’s major “claim to fame” after the Beagle voyage was leading one of the first expeditions to look for the lost Franklin Expedition in the arctic.  This was a private expedition sponsored by John Franklin’s wife which seemed to be plagued with problems. (You may recall that Robert McCormick also led a similar expedition.)

On a separate note today…

I know that a lot has been written about exactly when Darwin first started to formulate his theory of evolution by natural selection. At this point, I am no expert on what the scholars have to say about that defining moment.  However, I do know that the observations Darwin made in Brazil were providing him with a big data set to work from. And in the records of these observations we start to see comments that suggest the seeds of the theory had already been planted (if only subconsciously) and may even have been sprouting cotyledons (seed leaves – see yesterday’s post :)).

One such set of observations comes from a June 1832 entry in his Zoological Notebook.  Keep in mind that these was written on the spot, after having been away from home for about 6 months. They are “raw” observations, untarnished by any later observations or influences.

The first comment is more general, but it is sort of a prequel to the second.  As noted in earlier entries, Darwin seems to identify species based on what he knows about familiar species in Britain. But even also realizes that species in Brazil are entirely different from those in Europe.  I’ll let Darwin explain:

“The traveller in a country where every feature wears so totally a different aspect is liable to fall into errors from expecting contrasts & reversed order of things where they do not exist: from this cause a greater degree of caution is necessary in comparing the appearance of Nature in the two zones than would have at first have been expected.” (Zoological Notebook, June 1832)

OK – so it is pretty clear that species in different parts of the world are different.  But Darwin goes a step further a few pages later when he also describes how they seem to “go together”.

“I could not help noticing how exactly the animals & plants in each region are adapted to each other.— Every one must have noticed how Lettuces & Cabbages suffer from the attacks of Caterpillars & Snails.— But when transplanted here in a foreign clime, the leaves remain as entire as if they contained poison.— Nature, when she formed these animals & these plants, knew they must reside together.” (Zoological Notebook, June 1832)

Bat and cactus perfectly adapted to one another (from Murray State Bio 101 site):

bat pollinating a cactus

This is a fairly central concept in ecology  – a field which Darwin helped found. Furthermore, it raises the question, “why?”.  Why are the species in a particular region adapted to each other and not to species in other regions? Knowing a little of how Darwin seemed to think, I have no doubt that he asked himself this very question. If fact, he even goes so far as to answer it (at least in simple terms) – “Nature, when she forms these animals…”. Clearly, he suggests that species are “formed by nature”.  The specific answer to that question (coevolution) is at the heart of the Origin of Species. (RJV)


  1. […] on the slight modifications of tropical species compared to their northern counterparts (see “Cotyledons” of a Theory).  He had become a true naturalist – a path that would ultimately have him returning to England […]

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