What Darwin Didn’t Know

What Darwin Didn’t Know in National Geographic has crystallized my intention to do a mixed-media series on “evolution” or “descent with modification” – I actually like Darwin’s original term.

While I’ve been reading about Darwin (Charles and Emma and The Voyage of the Beagle), Darwin the person has come alive for me. Here are a few quotations I like:

His culinary experiences here on the Pampas, and later in Patagonia, besides being part of his voracious tour of discovery, would eventually play a role in his evolutionary thinking. (eating ostrich & armadillo)

“Like to snails, all their property is on their backs & their food around them,” Darwin wrote, referring to the cowboys, not the armadillos.

the match between fossil and living species was close but not identical

These discoveries, analogies, and juxtapositions went into his memory and imagination,

the very word “paleontologist” hadn’t yet come into use.

His best qualifications for interpreting the fossils were his intense curiosity, his talent for close observation, and his instinctive sense that everything in the natural world is somehow connected with everything else. Also, he wasn’t afraid to speculate boldly—so long as he could do it in private.

The orthodox story, still firmly embraced by European science at the time of the Beagle voyage, was that God had created species independently, in sequential batches (to compensate for extinctions), and had chosen to place them, almost arbitrarily, in their particular locales—kangaroos in Australia, giraffes and zebras in Africa, rheas and sloths and armadillos in South America, extinct and living forms clustered closely in space and time.

“This wonderful relationship in the same continent between the dead and the living,” Darwin wrote, would “throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.”

Alfred Russel Wallace (see “The Man Who Wasn’t Darwin” in National Geographic, December 2008)

Modern Darwins article included the quotation about DNA as scripture, which shifted my ideas around the art series.

Quotations from the feature article:

To understand the story of evolution—both its narrative and its mechanism—modern Darwins don’t have to guess. They consult genetic scripture.

I’m wanting to understand more – and my consult with DNA for Dummies hasn’t done it yet – about sentences such as:

Genes are sequences of DNA letters that when activated by the cell make a particular protein.

activated (scientists use the word “expressed”)

Hopi Hoekstra, also at Harvard, and her colleagues traced the color difference to the change of a single letter in a single gene, which cuts down the production of pigment in the fur.

They soon discovered that the finches in fact evolved from one year to the next, as conditions on the island swung from wet to dry and back again.

The variation seen among the Galápagos finches is a classic example of “adaptive radi­ation,” each species evolving from a common ancestor to exploit a special kind of food.

What better evidence for Darwin’s belief in the commonality of all species than to find the same gene doing the same job in birds and fish, continents apart?

He would be delighted to know that a certain gene, called FOXP2, is critical for the normal development of both speech in people and song in birds.

With fiendish ingenuity, her group infected finches’ brains with a special virus, carrying a mirror-image copy of part of the FOXP2 gene, which stifled the gene’s natural expression. The result was that birds not only sang more variably than usual but also inaccurately imitated the songs of adults—in much the same way as children with mutant FOXP2 genes produce variable and inaccurately copied speech.

If natural selection is survival of the fittest (a phrase coined by the philosopher Herbert Spencer, not by Darwin), then sexual selection is reproduction of the sexiest.

It was, in truth, an idea born of desperation, because useless beauty worried him as an apparent exception to the ruthlessly practical workings of natural selection. He wrote to the American botanist Asa Gray in April 1860 that “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”

females approach the males with the most elaborate displays, and invite them to mate.

bright plumage constitutes what evolutionary biologists call an “honest indicator of fitness.” Substandard peacocks cannot fake it. And peahens, by instinctively picking the best males, thereby unknowingly pass on the best genes to their offspring.

pure blue-eyed people. The mutation is a single letter change, from A to G, on the long arm of chromosome 15, which dampens the expression of a gene called OCA2, involved in the manufacture of the pigment that darkens the eyes. By comparing the DNA of Danes with that of people from Turkey and Jordan, Eiberg calculated that this mutation happened only about 6,000-10,000 years ago, well after the invention of agriculture, in a particular individual somewhere around the Black Sea. So Darwin may have gotten his blue eyes because of a single misspelled letter in the DNA in the baby of a Neolithic farmer.

Evolution works not just by changing genes, but by modifying the way those genes are switched on and off.

so evolution was always going to be about changing the process of growth rather than specifying the end product of that growth. In other words, a giraffe doesn’t have special genes for a long neck. Its neck-growing genes are the same as a mouse’s; they may just be switched on for a longer time, so the giraffe ends up with a longer neck.

They named it Tiktaalik, which means “large freshwater fish” in the local Inuktitut language. Although it was plainly a fish with scales and fins, Tiktaalik had a flat, amphibian-style head with a distinct neck, and bones inside its fins corresponding to the upper and lower arm bones and even the wrists of land animals: a missing link, if ever there was one.

It involved the redeployment of old genetic recipes in new ways.”

particulate nature of inheritance: He never understood, as the humble Moravian monk Gregor Mendel did, that an organism isn’t a blend of its two parents at all, but the composite result of lots and lots of individual traits passed down by its father and mother from their own parents, and their grandparents before them.

Modern Darwins

The father of evolution would be thrilled to see the science his theory has inspired.

By Matt Ridley
Photograph by Lynn Johnson

Just two weeks before he died, Charles Darwin wrote a short paper about a tiny clam found clamped to the leg of a water beetle in a pond in the English Midlands. It was his last publication. The man who sent him the beetle was a young shoemaker and amateur naturalist named Walter Drawbridge Crick. The shoemaker eventually married and had a son named Harry, who himself had a son named Francis. In 1953, Francis Crick, together with a young American named James Watson, would make a discovery that has led inexorably to the triumphant vindication of almost everything Darwin deduced about evolution.

Quiz on Darwin I got 90% and told I’m “an expert on Darwin” – time to create work. The incorrect answer was about what page the finches appear on – later than I thought.

Inspiring photography gallery.

Advertisements
%d bloggers like this: