Charles Darwin

Wallace’s manuscript was titled “On the Tendency of Varieties to Depart Indefinitely from the Original Type”. It comprised about twenty pages of lucid, easy prose, written out in the author’s hand. Its cardinal point, signaled in the title, was that the difference between species (as a category) and variety (as a category) is merely a difference of degree. That is, the amount of variation seen between varieties within a species is not inherently limited; rather, those increments can accumulate boundlessly until a variety splits away, becoming a distinct species unto itself. The manuscript posited “a general principle in nature” causing many varieties to do exactly that. And they don’t just split from the parent species, Wallace asserted; they compete against it, sometimes outlive it, and eventually give rise to still other varieties differing more and more from the original type. Wallace, unlike Darwin, had coined no name for this “general principle.” But his manuscript built a case for it with logic very similar to Darwin’s own. ~ Page 154

The manuscript was datelined “Ternate, February 1858.” Wallace had mailed it from a tiny volcanic island in the northern Moluccas. As the story goes, he got his inspiration during an attack of malarial fever, while forced to lie bedridden suffering alternate cold and hot fits and unable to do anything but think. One thing he thought about, as he’d been doing for years, was how species come into existence. Having seen such a spectrum of variation in the wild, having charted the suspicious distribution of closely allied species, Wallace had become ever more persuaded of the reality of transmutation. But what was the causal mechanism? During his bout of fever, he happened to remember Malthus, whom he’d read more than a dozen years earlier. He recalled the geometric rates of population increase, the slower increase in available food, the consequent “checks” to human population growth. Suddenly it occurred to Wallace, just as it had to Darwin, that such checks also regulate animal populations in the wild. Pondering all that adversity and mortality, he asked himself why some individuals survive while so many others die. “And the answer,” as he recollected long afterward, was that “on the whole the best fitted live.” Accidental variation plus the imperatives of struggle result in differential survival; differential survival leads to adaptation; divergent adaptation over vast stretches of time leads to fleet antelopes, strong-winged pigeons, and tall giraffes. Bingo. “The more I thought over it the more I became convinced that I had at length found the long-sought-for law of nature that solves the problem of the origin of species.” ~ Page 156

……. Hooker chose an excerpt from Darwin’s 1844 essay and inserted that, along with the Gray summary and Wallace’s manuscript, into an already full agenda for the Linnean Society meeting. These three statements were ordered alphabetically by author – Darwin’s two, followed by Wallace’s. On the evening of July 1, 1858, the Darwin-Wallace material and five other papers were read to an audience of about thirty people. Hooker and Lyell attended. By coincidence, so did Samuel Stevens, who may have wondered how this Wallace paper got to London without passing through his hands. ~ Page 162

The most remarkable thing about Darwin-Wallace night at the Linnean Society is how little immediately came of it. No general discussion followed the reading of papers. No one stood up in response to what Darwin and Wallace proposed and said, ‘That’s brilliant!’ or ‘That’s outrageous!’ Tea was served, probably. There was some private chat. And then the Linnean fellows went home. The foundations of science had shifted beneath their feet but they didn’t notice.

Why not? This hard to know. Possibly it was because the excerpts from Darwin and the papers from Wallace focused on the circumstances and details of the mechanism, natural selection, not on its larger significance. The word “transmutation’ wasn’t mentioned by either author, let alone the word ‘evolution’ (though Darwin did allude to “the Origin of species”). In the ears of a careless listener, on a hot July night, during an overlong meeting, the Darwin-Wallace readings with their roundabout logic may have seemed to involve merely varieties and variation. Another reason that the audience missed the point may have been those Linnean fellows generally weren’t asking themselves the question – ‘How do species change, one into another?’ – that Darwin and Wallace were answering. ~ Page 163

……. At least a few scientists recognized that this was weighty stuff, for better or worse, though some only condescended to disparage it. The president of the Geological Society of Dublin declared to an audience, early the next year, that Darwin and Wallace’s paper “would not e worthy of notice” if Lyell and Hooker hadn’t acted as sponsors. “if it means what it says, it is truism,” according to this man; “if it means anything more, it is contrary to fact.” Darwin heard about that criticism and savored it as “a taste of the future.” He was right. ~ Page 164

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