Natural and Unnatural History VII

I’m traveling in the Galapagos currently.  Hopefully I’m having fun and seeing great birds and other species!  In the meantime here’s a little of what I will hopefully be seeing!

The Galapagos’s Natural and Unnatural History: Darwin’s Finches Today

I probably have been aware of the Galapagos as a place of ecological and evolutionary importance since I took up ecology in college.   I took a wonderful evolutionary class, but it wasn’t until one summer years ago I stumbled across a copy of “The Beak of the Finch” that the enchantment fell upon me. I read it at the shore, I think.  I don’t think I saw much of the beach that vacation.

The “The Beak of the Finch” juxtaposes current research on Darwin’s finches, with Darwin’s development of his theory, with related work on microevolution (essentially evolution that occurs in measurable time; which are generally very small changes).   In the previous post on evolution, the example of strong selection for chess players over athletes for a generation is an example of microevolution.

Many people – even biologists, even today – find the power of slight variations hard to believe.  “Once just as I was beginning a lecture, a biologist in the audience interrupted me: ‘ How much difference do you claim to see,’ he asked me, ‘between the beak of a finch that survives and the beak of a finch that dies?’
‘One half millimeter,’ I told him.
‘I don’t believe it!’ the man said. ‘I don’t believe a half millimeter really matters so much.’
‘Well that’s the fact,’ I said. ‘Watch my data and then ask questions.’ And he asked no questions.”
– Peter Grant, The Beak of the Finch

But I digress, you’re probably more interested in the finches than data and theory.  In the late 1970s, Rosemary and Peter Grant, of Princeton University, embarked on a study of the finches of Daphne Major, a small island in the archipelago.  What was meant to be a couple year study has blossomed into a lifetime’s worth of work from the wealth of information they’ve gleaned that has transformed our understanding of evolution.  The Grants were the first to witness evolution in action.  From the time of Darwin we could find evidence that evolution had occurred but no one could say “Here, now is evolution. I saw it!” It was a big thorn in the on-process of convincing skeptics, in fact it even gave Darwin doubt.

Scientists have looked for it.  By no means were Peter and Rosemary the first. In fact, scientists even returned to the Galapagos, the holy grail, to find evidence there.  It was during David Lack’s time there that he coined “Darwin’s Finches”.

The Grants arrived in 1973, just after El Nino had finished so food was bountiful.  They observed, measured, counted. For season after season.

“No one had ever subjected Darwin’s finches  to so many different measurements and indignities, and no one had ever measured so many finches. Over the years, in fact, the Grant team’s measurement of live Darwin’s finches have far surpassed the number of specimens in the world’s museums.”
–  Beak of the Finch

Eventually, they got to where the veterans could identify each individual finch by sight (they band them).  Then, in 1977, as mentioned in the climate discussion, La Nina occurred and no rains fell.  That’s when the evolution became truly apparent.  That particular event is considered the strongest directional selection known in science.  Despite the heartbreak, the scientists persevered, collecting and recording.  When they were back in Princeton, between visits, they analyzed.  Then they headed out to the field again.

By geologic time, the Galapagos are new islands.  Colonization is an ongoing battle.    It’s location with its dramatically shifting climate frequently rewrites the rules for survival.  It’s ripe for watching evolution in action.  Which the Grants have done since the 1970s  and I suspect, they’re just arriving now, for the 40th season.

The work of the Grants has launched an entire sub-discipline in the study of evolution.  Scientists now scour the world in search of further evidence of microevolution.  They’re finding it in the Guppies of Trinidad, in the Sparrows off the coast of British Columbia, to the cotton pests of the American South, and in our war against bacteria and viruses.

“What a trifling difference must often determine which shall survive and which perish!”
– Darwin

Sources:

  • “Beak of the Finch”. Jonathan Weiner. 1995.
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