Myth Busting Monday: Darwin’s Eureka

It’s been a while since I churned one of these out, so what better time than when I’m avoiding other assignments?

Photo by Alun Salt @ Flickr

Let me throw out some names for you: Darwin’s Finches. Giant Tortoises.

Anyone who has studied biology at even a basic level is probably familiar with these two concepts. The finches and giant tortoises Darwin found on the Galapagos islands were his eureka moment in discovering Natural Selection. In a nut (tortoise?) shell: In the finches he discovered how, on each island, the beaks of the resident species were perfectly tailored to match the size of the seed they needed to eat. Similarly, the tortoises shells differed based on the island they were from.

In fact, this not only was not Darwin’s eureka moment, he didn’t even hit upon the realisation until much later when he was back home in London. He had put all the finches into a singular bag without properly labeling them. He lamented, “Unfortunately most of the specimens of the finch tribe were mingled together.” It was instead supposed likely that they had come from different islands. The tortoise story is another one of a similar vein: the tortoises were simply caught for food, and it was not until later that analysis of the shells triggered the idea that they may have been from different islands.

It was instead the Galapagos mocking bird that first raised Darwin’s doubts as to the fixity of species. The finches themselves aren’t even mentioned in On The Origin of Species, only mentioned later in passing in his Journal. But they do make a much prettier story, which is why they are all over every biology book you see.

And what of Darwin’s other apparent eureka moment: Malthus?

As the story goes, Darwin was reading Thomas Malthus’ essay ‘An Essay on the Principle of Population‘. The Ecologists out there will be more than familiar with the theory. Every ecosystem has what is called a ‘carrying capacity’. When a population exceeds beyond this limit, the environment will no longer have enough resources to sustain it. But ‘checks’ stop a population from reaching such a point: death, disease, famine, poverty, war, and so forth.

Darwin read this essay, and said, “Aha!”

Well, Darwin did not exclaim, “Aha”. At least not in response to this essay, anyway (or perhaps he did, I was not there, but I digress…).

In actuality, Darwin had the full theory for natural selection written down in his notebooks many months before the publication of the essay. What Malthus did was offer support for the mechanism behind natural selection. It was one of many pieces that fell into place for Darwin as he continued to flesh out his idea.

Great ideas seldom blossom in an instant. The mechanism of Natural Selection took many years of slogging it out over a desk before it bloomed into what was published in Origin.

So why do you think there is such a focus by people on significant events in the theory’s conception? Why are people so focused on trying to find these ‘eureka moments’?

Is this a product of trying to over-simplify the story to make it more easily digestible, or is there some other motivation at work here?