After Charles Darwin, Galapagos finches are still evolving

When Charles Darwin watched his famous finches flit about the craggy cliffs and lush forests of the Galapagos, he observed that something essential was at work in this remote part of the Pacific — some force of nature that, over the course of millennia, pushed each type of bird to become perfectly suited to its environmental niche.

“We see nothing of these slow changes in progress, until the hand of time has marked the long lapse of ages,” he wrote in the “On the Origin of Species.” “… We only see that the forms of life are now different from what they formerly were.”

Perhaps Darwin just didn’t linger in the Galapagos long enough. Married biologists Peter and Rosemary Grant have worked on the islands for more than 40 years, and they’ve witnessed evolution unfolding right before their eyes.

A decade ago, they saw a drought devastate Daphne Major Island, a scrubby volcanic cinder cone home to little more than some cacti and two species of bird: the medium ground finch and the large ground finch. Because of the resulting food shortage, the smaller-beaked medium ground finches — who didn’t try to compete with the bigger birds for large seeds — were outliving their larger-beaked brethren. Within a year, average beak size among medium ground finches had shrunk noticeably.

And unlike Darwin, who developed his theory of natural selection without the benefit of knowing about modern genetics, the Grants were able to figure out exactly how this evolution happened.

In a study published Thursday in the journal Science, they reported that they’ve pinpointed the bit of finch DNA behind the swift transition: a gene called HMGA2.

In finches, HMGA2 seems to be the primary factor in beak size — like a really good group project leader, it orchestrates the expression of a number of other genes, each of which tweaks the size of the bird’s beak. The same gene also appears in dogs, horses, even humans, holding sway over body size and stature.

Looking at the DNA of medium ground finches who lived (and died) during the drought, they found that the birds who starved to death were more likely to have a version of the gene that leads to big beaks. Those who survived were saved by their small-beak variation.

The exact mechanism by which HMGA2 influences a finch’s beak or a human’s height remains unknown. But it’s clearly very powerful — the Grants believe that the shift from bigger to smaller beaks they witnessed during the Daphne Major drought is one of the most dramatic examples of natural selection ever recorded.

The location of HMGA2 adds to work that the Grants (both emeritus professors at Princeton University) and colleagues at Uppsala University in Sweden have already done on Galapagos finches. In a study published last year, the team sequenced the DNA of 120 birds — including members of all known species of Darwin’s finches and two closely related species — to study the variation among them.

They found that the birds have been evolving, interbreeding and specializing in response to their environment ever since their common ancestors first arrived on the islands 2 million years ago. Sometimes the traits that make them so distinctive are a result of selection, other times they’re a result of hybridization — two species interbreeding to produce something slightly new.

The Grants even witnessed an example of hybridization during their time on Daphne Major: In the early ’80s an immigrant to the island named Big Bird mated with a medium ground finch, producing a new lineage that is now some seven generations strong. The Grants are reluctant to say whether they actually witnessed the origin of a new species — the hybrid (can we call it “medium Bird?”) is largely the result of inbreeding, they said two years ago, and could ultimately die out from the resulting “fitness problems.”

Another find from the 2015 study was the gene responsible for beak shape, a bit of genetic code involved in the facial development of vertebrates called ALX1. Depending on which variation of the gene a finch has, its beak may be narrow and pointed for spearing insects or broad and blunt for cracking seeds.

“There are multiple genes that contribute,” Leif Andersson, an animal geneticist who worked on the study from Uppsala University, said at the time. “But we think that ALX1 is one of the most important, if not the most important factor that has changed on the island.”

Combine that with the latest study of HMGA2, and biologists have a pretty thorough blueprint of how these famous finches evolve. Dolph Schluter, a biologist at the University of British Columbia, said the discovery allows scientists to ask a whole new set of questions about how species split and how new gene variants arise.

“On the one hand it doesn’t change anything, in that we already knew there was an evolutionary response to competition during that drought,” he said. “But on the other hand, it changes everything, because we can point to a physical, material basis for that change.”

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Local News

Trader Joe’s customers walk in and out of the store on Monday, Nov. 20, 2023 in Everett, Washington. (Olivia Vanni / The Herald)
New Trader Joe’s opens this week at Everett Mall

It’s a short move from a longtime location, essentially across the street, where parking was often an adventure.

Ian Bramel-Allen enters a guilty plea to second-degree murder during a plea and sentencing hearing on Wednesday, March 6, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
‘Deep remorse’: Man gets 17 years for friend’s fatal stabbing in Edmonds

Ian Bramel-Allen, 44, pleaded guilty Wednesday to second-degree murder for killing Bret Northcutt last year at a WinCo.

Firefighters respond to a small RV and a motorhome fire on Tuesday afternoon in Marysville. (Provided by Snohomish County Fire Distrct 22)
1 injured after RV fire, explosion near Marysville

The cause of the fire in the 11600 block of 81st Avenue NE had not been determined, fire officials said.

Ashton Dedmon appears in court during his sentencing hearing on Tuesday, March 5, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
Everett Navy sailor sentenced to 90 days for fatal hit and run

Ashton Dedmon crashed into Joshua Kollman and drove away. Dedmon, a petty officer on the USS Kidd, reported he had a panic attack.

A kindergarten student works on a computer at Emerson Elementary School on Wednesday, Feb. 28, 2024, in Everett, Washington. (Ryan Berry / The Herald)
‘¡Una erupción!’: Dual language programs expanding to 10 local schools

A new bill aims to support 10 new programs each year statewide. In Snohomish County, most follow a 90-10 model of Spanish and English.

Cassie Franklin, Mayor of Everett, delivers the annual state of the city address Thursday morning in the Edward D. Hansen Conference Center in Everett, Washington on March 31, 2022.  (Kevin Clark / The Herald)
At Everett mayor’s keynote speech: $35 entry, Boeing sponsorship

The city won’t make any money from the event, city spokesperson Simone Tarver said. Still, it’s part of a trend making open government advocates wary.

Logo for news use featuring the Tulalip Indian Reservation in Snohomish County, Washington. 220118
Woman drives off cliff, dies on Tulalip Reservation

The woman fell 70 to 80 feet after driving off Priest Point Drive NW on Sunday afternoon.

Everett
Boy, 4, survives fall from Everett fourth-story apartment window

The child was being treated at Seattle Children’s. The city has a limited supply of window stops for low-income residents.

People head out to the water at low tide during an unseasonably warm day on Saturday, March 16, 2024, at Lighthouse Park in Mukilteo, Washington. (Ryan Berry / The Herald)
Everett shatters record high temperature by 11 degrees

On Saturday, it hit 73 degrees, breaking the previous record of 62 set in 2007.

Snohomish County Fire District #4 and Snohomish Regional Fire & Rescue respond to a motor vehicle collision for a car and pole. The driver was pronounced dead at the scene, near Triangle Bait & Tackle in Snohomish. (Snohomish County Sheriff’s Office)
Police: Troopers tried to stop driver before deadly crash in Snohomish

The man, 31, was driving at “a high rate of speed” when he crashed into a traffic light pole and died, investigators said.

Alan Dean, who is accused of the 1993 strangulation murder of 15-year-old Bothell girl Melissa Lee, appears in court during opening statements of his trial on Monday, March 18, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
31 years later, trial opens in Bothell teen’s brutal killing

In April 1993, Melissa Lee’s body was found below Edgewater Creek Bridge. It would take 27 years to arrest Alan Dean in her death.

Logo for news use featuring the municipality of Snohomish in Snohomish County, Washington. 220118
Man dies after crashing into pole in Snohomish

Just before 1 a.m., the driver crashed into a traffic light pole at the intersection of 2nd Street and Maple Avenue.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.