Current Issue

Apr. 23, 2014

Vol. 114, No. 11


The People Who Saw Evolution

After 40 years of research on Darwin’s finches, Peter and Rosemary Grant have written their valediction

By Joel Achenbach ’82
Published in the April 23, 2014, issue

Peter and Rosemary Grant sit in a cave on Daphne Major Island in 2004. The cave generally was used for cooking; here, Peter is shown measuring the beak of a finch.
Lukas Keller/University of Zurich
Peter and Rosemary Grant sit in a cave on Daphne Major Island in 2004. The cave generally was used for cooking; here, Peter is shown measuring the beak of a finch.

Peter and Rosemary Grant are members of a very small scientific tribe: people who have seen evolution happen right before their eyes.

For the Grants, evolution isn’t a theoretical abstraction. It’s gritty and real and immediate and stunningly fast. To witness evolution, they needed cameras, measuring instruments, computer databases, and advanced laboratory techniques for genetic analysis. Most of all, they needed to be there in person ­— in the field, on the ground, enduring baking days and sweltering nights, cooking in a cave, sleeping in tents, and somehow sustaining themselves on a tiny island in the Galápagos that any reasonable person would declare to  be uninhabitable.

The island is a steep-sided volcanic extrusion named Daphne Major. It is so inaccessible that it has no beach, no landing area, just wave-chewed vertical edges plunging into water so deep it might as well be bottomless. Visitors don’t land on the island so much as they leap to it, jumping from a small boat onto a tiny ledge.

In the Galápagos, the Grants studied Charles Darwin’s finches for 40 years. That was not the original plan when they first visited in 1973: They thought they’d be at it for two. Now the research is done — a monumental achievement, and the subject of a valedictory book, 40 Years of Evolution, published this month by Princeton University Press.

The story of Peter and Rosemary Grant is an unusually satisfying tale. Obviously there’s the scientific success: They’re legendary in their field. In their office in Eno Hall they have a blown-up photograph of the two of them receiving the Kyoto Prize — often regarded as the Japanese equivalent of the Nobel — for their lifetime achievements in basic science. They also have achieved renown among the general public, thanks to the Pulitzer Prize-winning 1994 book The Beak of the Finch by Jonathan Weiner.

The Grants have now been married 52 years. They’re both 77 years old. In a practical sense, their work is done. “We feel with the book we’ve written, we’re closing a chapter on our field research,” Peter Grant says. “If we go back at all, it’ll be for short periods, doing interesting things.”

And yet they can’t truly be finished with their research, because evolution never screeches to a halt, or reaches a final, optimizing moment. Evolution isn’t progressive, linear, deterministic, and destination-driven. Evolution never retires.

“We never reached an identifiable point of diminishing returns, or experienced a sense of completion,” the Grants write near the end of their book. “[O]ne conclusion we draw after 40 years is the same as the conclusion we drew after 20 years: Long-term studies in ecology and evolution should be pursued in an open-ended way because for many of them there is no logical end point. Darwin’s finches have much more to teach us.”

The Grants are almost comically warm and fuzzy, and still in great running condition, save a couple of dents in their fenders. They’ve been at Princeton since 1985 and live a couple of miles from campus, not far from Lake Carnegie.

Their relationship reflects the biological principle of fusion: They have not merely adapted to one another, but have merged to a point in which there is little sense in writing about one without immediately discussing the other. They are deferential to one another, never interrupting, and often looking at one another to see if the other wants to go first.

When I ask what Darwin didn’t know when he visited the Galápagos in 1835, they answer in unison: “Genetics.”

Once, when Peter was out of town giving a talk and Rosemary was in Princeton, they independently had the idea of writing a paper discussing the effects of natural selection on a certain plant on the Galápagos island of Española. When Peter returned, he said, “Here’s my paper.” She said: “Well, here’s mine.” They decided to give both papers to their graduate students. One student said, “Both papers are rubbish.” The Grants put their heads together and came up with one paper that was vastly better than the two originals.

She’s from the Lake District in England and attended the University of Edinburgh; he’s from London and attended Cambridge. They met at the University of British Columbia in Vancouver in 1960, where Rosemary was lecturing in embryology, cytology, and genetics, and Peter — still a graduate student in zoology — was her teaching assistant. They married in early 1962. After stints at McGill University and the University of Michigan, the Grants arrived at Princeton in 1985. Among other things, both taught upper-level undergraduate courses in ecology and evolutionary biology, along with a course for first-year graduate students on new developments in ecology, evolution, genetics, and conservation.

“I don’t think we’ve ever competed with each other,” Rosemary says. “We come at things very differently. But it’s always had a synergistic effect.”

It helps to have a sense of humor, she adds.

Rosemary: “We’re not polite to each other.”

Peter: “I’m polite to you!”

The island of Daphne Major is essentially pristine, unaffected by human influence, and largely free of the invasive species commonly found on settled islands. It is young: It rose from the sea only about 15,000 years ago. Daphne is, in effect, a field laboratory.

And Darwin’s finches are ideal subjects for field research in evolutionary biology. They are tame, and thus easily captured for closer study and measurement (“Beak depth was measured with calipers in the plane of the anterior nares at right angles to the commissure, the line at which upper and lower mandibles meet,” the Grants wrote). There are either 13 or 14 species of “Darwin’s finches” — two populations of a warbler finch don’t mix and have genetic differences but look very similar, hence the ambiguity. The finches of the Galápagos represent a relatively recent evolutionary event, descending from a common ancestor that came from the mainland two million to three million years ago.

Post Comments
3 Responses to The People Who Saw Evolution

Peter Roemer '59 Says:

2014-04-21 13:27:48

Great article! It makes the science easy to understand for a layman.

Sandy Kramer '67 Says:

2014-04-28 15:33:56

"A Finch By Any Other Name ..." New Finch Species Shows Conservation, Not Macroevolution by Brian Thomas, M.S. * "Darwin's finches" are a variety of small black birds that were observed and collected by British naturalist Charles Darwin during his famous voyage on the H.M.S. Beagle in the early 1800s. Years later, Darwin argued that subtle variations in their beak sizes supported his concept that all organisms share a common ancestor (a theory known as macroevolution). The finches, whose technical name is Geospiza, have since become classic evolutionary icons. Husband and wife researchers Peter and Rosemary Grant have studied Darwin's finches on the Galapagos Islands for 35 years. In 1981, they noticed a particular finch fly to the island of Daphne Major. It was about five grams heavier, had a larger beak, and sang a slightly different tune than indigenous Daphne Major finches. It interbred with a local finch and left descendants. In the fourth generation, "after a severe drought, the lineage was reduced to a single brother and sister, who bred with each other."1 Their descendants have carried on the family traits. The Grants reported in a study on the birds published in Proceedings of the National Academy of Sciences that "our observations provide new insight into speciation and hence, into the origin of a new species."2 But the details show that this new "species" is just a variation within the finch kind, and is therefore irrelevant to big-picture evolution. Genus Geospiza contains six species, and these are usually distinguished by the songs that the males sing primarily to attract breeding partners. However, if a father bird dies while his chicks are young, and all they hear is the neighboring song of a different species, for example, young birds can learn the wrong songs. When these mature, they sing the song of, and breed with, the foster father's species. Other scenarios result in crossbreeding between Geospiza species. In fact, the founding bird of the "new species" featured in this study was itself a hybrid, mostly from G. fortis, but with some G. scandens in its lineage. None of these fluctuations in traits have added new structures or capabilities, and all the birds studied over the decades remain true to their Geospiza kind. Thus, they are a portrait of hereditary conservation -- not a portrait of macroevolutionary change. Furthermore, the authors listed four reasons why it is unlikely that this new population will remain a distinct species. It is so small that a random fluctuation in breeding rates could wipe it out. The birds might become outcompeted for essential resources by neighboring species. They may interbreed with others, right back into the general Geospiza population. Or, they may implode due to the genetic degradation that comes from inbreeding. Thus, "it is too early to tell" whether this new species will persist.2 It is therefore likely that this speciation event, which had nothing to do with Darwinian competition or neo-Darwinian selection of mutations, will be erased. And if and when that happens, its relevance for demonstrating "evolution" will have been erased -- not that it demonstrated any relevant innovation in the first place. After studying other evolutionarily directionless trends in Darwin's finches, it has become apparent that Charles Darwin used these birds as ad hoc illustrations for his grand but unsupported story.3 Neither his book "On the Origin of Species" nor these later studies have provided any evidence to reasonably explain a step-by-step process whereby nature originates a new living body form -- not even a new family, let alone a new phylum. References: 1. Grant, P.R., and B.R. Grant. 2009. The secondary contact phase of allopatric speciation in Darwin's finches. Proceedings of the National Academy of Sciences. 106 (48): 20141. 2. Ibid 20146. 3. Grant and Grant had their research described by bestselling author Jonathan Weiner in the 1995 book "The Beak of the Finches." It highlighted climate-related rotation in finch beak sizes. Like interbreeding between Geospiza, this fluctuation showed conservation, not innovation. * Mr. Thomas is science writer at the Institute for Creation Research.

Don Utter Says:

2014-04-30 11:21:32

Wow! A post from the Institution for Creation Research from Sandy Kramer. The anti-science crowd keeps going and going. The Scientific American issue from February 2009 calls evolution the most powerful idea in science. Here is some text: Happy 200th Birthday, Charles Darwin. The evolution of the most powerful idea in science, originated by a man who was born in Shrewsbury, England, on February 12, 1809. Here's how Darwin's theory survives, thrives and reshapes the world.
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