Joseph Dalton Hooker

In my Darwin post, I characterised Sir Joseph Dalton Hooker (1817- December 10 1911; hereafter Hooker; portrait above from Endersby (2009)) as Darwin’s favourite pen pal. If you ever read Darwin’s letters, you will notice that Hooker was his most active correspondent (although I have not actually done a count). These letters are not unlike the e-mails we modern researchers send to each other: they are always informative, full of advice, and with the occasional mocking of other researchers, as well as little snippets of family life (information on holidays, etc.); on an unrelated note, I would like to remind you that scientists are not the unfeeling Spock robots we are often made out to be. They also contain several famous phrases, including the origin of flowers as an “abominable mystery” and the “warm little pond” scenario for the origin of life. He is most well-known as the long-time Director of the Royal Botanical Gardens, Kew in London, a position inherited from his father, Sir William Hooker.

There is a reason why Hooker is viewed as one of the greatest botanists of the Victorian era. Not only was he productive (among his works are included the first complete guides to the floras of Antarctica and New Zealand), but his scientific achievements are outstanding, as was his way of thinking. For example, he was one of the first to notice just how endemic and diverse the flora of southwest Australia is (Hooker, 1860), and constructed a revolutionary hypothesis. The old view had been that SW Australia originated very recently, as supposedly supported by the geology of the area, which lacked marine fossils. But it being so young clashes with such high endemism and diversity. Instead Hooker found the key to it: the soils there are infertile and the climate was harsh. This leads to plants not producing as many seeds, meaning that many species can coexist. 150 years later, this is still the predominant view on which all our knowledge of the topic is based on.

He also did some palaeobotanical work, exploring coal deposits in the Carboniferous of Lancashire. These had limestone nodules in them, preserving ancient plants down to cellular levels, and it is from these specimens that we were able to reconstruct such iconic plants as Calamites and Lepidodendron.

As with other naturalists and evolutionary biologists of the time, Hooker was fascinated by island biota. He was one of the first to emphasise the different phenomena at work in oceanic islands and continents. For example, he noted that islands had a more polar character, both in climate and flora, as continental landmasses at the same latitude. He wrote of the evolutionary trajectories island plants underwent. For example, in Hooker (1847), he correctly identified that insular floras tend to lose their dispersal abilities, using the example of weeds on the Galápagos.

Related to this, he also did a lot of biogeographical work. For example, in his Flora Antarctica, he successfully predicted that Australia and South America were, at some point in the geological past, connected to each other, due to the similarity of the floras of their floras. This, even though plate tectonics wasn’t even close to being postulated.

His biogeography broke new ground (building on Alexander von Humboldt‘s work), and much of the foundations of our current biogeographical knowledge can be traced back to Hooker. For example, that climate and invasive potential shape plant distributions is Hooker’s idea, as is the stressing of historical and geological factors.

Among the plants he described are the very unqiue Welwitschia and the pitcher plant Nepenthes, also investigating its digestive enzymes (although its status as a carnivorous plant was still rejected). He described the floras of several countries, including Chile, Tasmania, New Zealand, Australia, Antarctica [not a country, but you know what I mean] and Ascension Island (which he proposed to terraform, successfully turning it from a barren landscape to a forest of introduced species of his own choosing; a successful experiment).

He also did a lot of work on the pollination of those rare flower taxa he found. That cycads are insect-pollinated was first found out by Hooker, for example. Same with the gnetaleans.

Hooker is also known as one of Darwin’s best supporters with respect to Darwin’s evolutionary theory. Without Hooker, the Origin would not have been such a great and classic book, as it was Hooker who pushed Darwin to gather more evidence since their correpsondence in 1847, and he also provided much evidence from the botanical side.

Hooker may not have been the first with whom Darwin shared transmutationist ideas (that honour goes to Lyell, of course), but he was the first to know that Darwin had become a full-blown transmutationist (i.e. believed in the changeability of species in time), as we can tell from this 1844 letter: “At last gleams of light have come, & I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.”

And even before he was convinced, Hooker was all for the open spread of ideas in science: it was he, along with Charles Lyell, who first communicated the papers by Darwin and Wallace to the Linnean Society on July 1, 1858. By the time of the Origin‘s publication though, Hooker became one of the main popularisers of Darwin’s theory, and along with Huxley and Lyell, was the major force that led to its acceptance.

This of course included fighting the anti-evolutionists of the time. In the case of Hooker, one prominent example is Sir William Dawson, an excellent geologist and palaeobotanist who nonetheless rejected evolution due to his religious beliefs. While Dawson was clearly on the wrong side of the debate, the escalation rose to unreasonable heights, with Hooker ensuring that Dawson’s seminal and now-classic work on Devonian plants would not get published by the Royal Society. A dick move by any standard – he may have been a flaming creotard (even by Victorian standards), but his work was very, very good. If I may sidetrack a bit, had this happened today, Hooker would be reprimanded, but it would be understandable – anti-evolutionism today is tantamount to being anti-science. But back then, the lines were a bit more blurry, and while I’m not denying Dawson’s extreme stupidity, I would say that given the social context, his monograph deserved publication, despite its source.

Anyway, Darwin and Hooker eventually came to hold many similar views. Hooker subscribed to Darwin’s secpies concept (“Independently of fusion from intercrossing, the complete absence, in a well-investigated region, of varieties linking together any two closely-allied forms, is probably the most important of all the criterions of their specific distinctness”, as Darwin puts it in the Descent, p. 215).

On the origin of life, they also had some correspondence, mostly to take the piss out of Richard Owen. Darwin’s “warm little pond” scenario was outlined in a letter to Hooker. Much to my pleasure, Hooker thought panspermia is ridiculous, writing to Darwin that “the notion of introducing life on Meteors is astounding and very unphilosophical […]. For my part, I would as soon believe in the Phoenix as in the meteoritic import of life”.

Hooker and Darwin’s friendship was not limited to science, and they were friends outside of academia, up to Darwin’s death. Hooker was one of Darwin’s pallbearers at the funeral.

In terms of honours, most noteworthy is Hooker’s Darwin-Wallace medal, a prize given once every fifty years: in 1908, 1958 and 2008 (since 2010, it’s annual). He received a silver one in 1908, along with Francis Galton and Ernst Haeckel and 3 others. There is no snub intended with his being given a silver, not a gold one: only Wallace himself has ever been awarded a gold medal.

For those interested in such matters, Hooker was a freethinker and “agnostic”, quoted in his biography that he “distrusts all theologians”, that whatever force behind the universe is “inscrutable” and that Jesus was just some Essenian monk around whom myths and stories grew.

If you want to know more about him and check out his writings first-hand, click here. The Kew UKOTS blog has a post on him too.

Footnote: This post was supposed to go up yesterday, December 11th, in honour of the centenary of his death. However, I was too beat up after a full-day field trip to Paphos, a 3 hour drive away from where I live, and fell into a deep slumber upon my return. But, well, it’s already been 36525 days, I’m sure you won’t mind one extra day…

References:

Endersby J. 2009. Lumpers and Splitters: Darwin, Hooker, and the Search for Order. Science326, 1496-1499.

Hooker JD. 1847. On the Vegetation of the Galapagos Archipelago, as compared with that of some other Tropical Islands and of the Continent of America. Transactions of the Linnean Society of London20, 235–262.

Hooker JD. 1860. The Botany Of The Antarctic Voyage of H. M. Discovery Ships Erebus and Terror in the years 1839–1843. Part III: Flora Tasmaniae, Vol. I: Dicotyledones.

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