Peter and Rosemary Grant

Peter Raymond Grant
Alma mater
Thesis The significance of some insular characteristics in birds (1964)
Doctoral advisor Ian McTaggart-Cowan
Doctoral students
Known for Darwin's finches
Influences Miklos Udvardy
Spouse Rosemary Grant
Barbara Rosemary Grant
Alma mater
Thesis  (1985)
Doctoral advisor Staffan Ulfstrand
Known for Darwin's finches
Spouse Peter Grant

Peter & Rosemary Grant

Peter Raymond Grant and Barbara Rosemary Grant, a married couple, are both British evolutionary biologists at Princeton University; each holds the position of Emeritus Professor. They are noted for their work concerning Darwin's finches on the Galápagos Island named Daphne Major. The Grants have spent six months of the year each year since 1973 capturing, tagging, and taking blood samples of the finches on the island. It has been their life work to show that natural selection can be seen within one’s lifetime, even within a couple of years. Darwin originally thought that natural selection was a long, drawn out process. The Grants have shown that this is not only incorrect, but that these changes in populations can happen very quickly and can be seen right before our own eyes.

Early Years

As young children, both Rosemary and Peter were fascinated with the world around them and the animals that inhabited their environments. Their curiosities helped shape them into the scientists, and ecologists that they are today.[1]

Peter Raymond Grant was born in 1936 in London, but relocated to the English Countryside to avoid World War II. He attended school at the Surrey-Hampshire border; here he collected insects and studied flowers.[1] He started his college experience at the University of Cambridge and then moved to Canada to see what life in North America was like. He began work on his doctoral degree in Zoology at the University of British Columbia in Vancouver. A few days after beginning his research he met Rosemary; they were married a year later.[1]

Barbara Rosemary Grant, who goes by her middle name, was born in Arnside, England in 1936. She also grew up enjoying the diversity of her surroundings; she would collect plant fossils and compare them to living look-alikes. At the age of 12 she read Darwin’s On the Origin of Species. Despite what teachers told her at school, she was destined to go to the university to get a degree.[2] She graduated from Edinburgh University in Scotland with a degree in Zoology in 1960. For the next year she studied genetics under Conrad Waddington and then devised a dissertation to study isolated populations of fish. This project was put on hold when she accepted a biology teaching job at the University of British Columbia in Vancouver.[2] There she met her soon-to-be husband, Peter Grant.[1]


Peter Grant

Rosemary Grant

Work & Research

Tres Marias Islands, Mexico

For his doctorate degree, Peter Grant studied the relationship between ecology and evolution and how much they are interrelated. The Grants traveled to the Tres Marias Islands of Mexico to conduct field studies of the birds that inhabited the island.[1] They compared the differences of bill length to body size between populations living on the Islands and the nearby mainland. Of the birds studied, 11 species were not significantly different between the mainland and the islands; 4 species were significantly less variable on the islands; and one species was significantly more variable.[3] On average, the islands had larger beaks. The Grants attributed these differences to what foods were available, and what was available was dependent on competitors. The bigger beaks indicated a greater range of foods present in the environment.[1]

McGill University: Montreal, Canada

In 1965, Peter Grant accepted tenure at McGill University in Montreal. He created a method to test the Competition Hypothesis to see if it worked today as it did in the past.[1] This research was done on grassland voles and woodland mice. The study looked at the competitiveness between populations of rodents and among rodent species.[4] In his articles, Interspecific Competition Among Rodents, he concluded that competitive interaction for space is common among many rodent species, not just the species that have been studied in detail.[4] Peter Grant also states that there are many causes for increased competition; reproduction, resources, amount of space, and invasion of other species.[4]

Galapagos Islands

Daphne major was a perfect place to perform experiments and study changes within the birds. It was isolated and not inhabited; any changes that were to occur to the land and environment would be due to natural forces with no human destruction.[5] The island provided the best environment to study natural selection; seasons of heavy rain switched to seasons of extended drought. With these environmental changes brought changes in the types of foods available to the birds. This is what the Grants would study for the next few decades of their lives.

In 1973 the Grants headed out on what they thought would be a 2 year study on the island of Daphne Major in the Galapagos Islands. There they would study evolution and ultimately determine what drives the formation of new species.[5] There are 13 species of finch that live on the island; five of these are tree finch, one warbler finch, one vegetarian finch, and six species of ground finch. These birds provide a great way to study adaptive radiation. Their beaks are specific to the type of diet that they eat; which in turn is reflective of the food available. The finch are easy to catch and provide a good animal to study. The Grants tagged, labeled, measured, and even took blood samples of the birds they were studying. The 2 year study continued through 2012.[5]

During the rainy season of 1977 only 24 millimeters of rain fell. Two of the main finch species were hit exceptionally hard and many of them died.[6] The lack of rain caused major food sources to become scarce, causing the need to find alternative food sources. The smaller, softer seeds ran out, leaving only the larger, tougher seeds. The finch species with smaller beaks struggled to find alternate seeds to eat.[6] The following two years proved that natural selection could happen very rapidly. Because the smaller finch species could not eat on the large seeds, they died off. Finch with larger beaks were able to eat the seeds and reproduce. The population in the years following the drought in 1977, had “measurably larger” beaks than had the previous birds.

In 1981 the Grants came across a bird they had never seen before. It was heavier than the other ground finch, by more than five grams.[7] They called this bird, Big Bird. It had many different characteristics than those of the native finches; a strange call, extra glossy feathers, could eat both large and small seeds, and could also eat the nectar, pollen and seeds of the cacti that grow on the island (9). Big Bird is thought to be a hybrid of the medium-beaked ground finch and the cactus finch.[7] Although hybrids do happen, many of the birds living on the island tend to stick within their own species.[8] Big bird lived for thirteen years, and his descendants have only mated within themselves for the past thirty years, a total of seven generations.[8]

Over the course of 1982-1983, El Nino brought a steady eight months of rain. Daphne Major usually gets two months of rain in the normal rainy season.[9] The excessive rain brought a turnover in the types of vegetation growing on the island. The seeds shifted from large, hard to crack seeds to many different types of small, softer seeds. This gave birds with smaller beaks an advantage when another drought hit the following year.[9] Small-beaked finch could eat all of the small seeds faster than the larger beaked birds could get to them.

In 2003, a drought as bad as the 1977 drought plagued the island. The major difference this time was that large ground finch had become the predominate-size birds. The large ground finch had to compete with the larger-beaked medium ground finch. The large ground finch trumped the medium finch; 90% of the medium ground finch population died due to starvation.[1] Peter Grant said in one paper that the advantage had shifted strongly to the small-beaked members of the medium ground finch population and that evolution by natural selection had occurred again.[1]

Significant Findings

In chapter 8 of Evolution: Making Sense of Life, the takeaway from the Grant’s 40 year study can be broken down into three major lessons. The first is that natural selection is a variable process, it is constantly changing. The fact that they studied the island in both times of excessive rain and drought gives a better picture of what happens to populations over time. The next lesson learned, is that evolution can actually be a fairly rapid process. It does not take millions of years, these processes can be seen in as little as two years. Lastly, and as the author states, most importantly is that selection can change over time. During some years, selection will favor those birds with larger beaks. Other years with substantial amounts of smaller seeds, selection will favor the birds with the smaller beaks.[10]

In their 2003 paper, the Grants wrap up their decades long study by stating that, selection oscillates in a direction. For this reason, neither the medium ground finch or the cactus finch has stayed morphologically the same over the course of the experiment. The average beak and body size are not the same today for either species as they were when the study first began.[11] The Grants also state that these changes in morphology and phenotypes could not have been predicted from the beginning.[12] They were able to directly witness the evolution of the finch species as a result of the inconsistent and harsh environment of Daphne Major.

Awards & Recognition

Peter Grant

Societies and Academies:

Honorary Degrees

Associate Editor of Scientific Journals

Honorary citizen of Puerto Bacquerizo, I. San Cristobal, Galapagos- 2005-

Rosemary Grant

Societies and Academies:

Honorary Degrees:

Honorary citizen of Puerto Bacquerizo, I. San Cristobal, Galapagos- 2005-

Received Jointly

The Balzan Prize citation states:

"Peter and Rosemary Grant are distinguished for their remarkable long-term studies demonstrating evolution in action in Galápagos finches. They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection. They have also elucidated the mechanisms by which new species arise and how genetic diversity is maintained in natural populations. The work of the Grants has had a seminal influence in the fields of population biology, evolution and ecology."



Evolutionary Dynamics of a Natural Population: Large Cactus Finch of the Galapagos

The Beak of a Finch: A Story of Evolution in Our Time - Jonathan Weiner

How and Why Species Multiply: The Radiation of Darwin’s Finches-2008

Most Recent Journal Articles

See also


  1. 1 2 3 4 5 6 7 8 9 Ahmed, F. "Profile of Peter R. Grant." Proceedings of the National Academy of Sciences 107.13 (2010): 5703-705. Web. 1 Nov. 2016.
  2. 1 2 Nair, P. "Profile of B. Rosemary Grant." Proceedings of the National Academy of Sciences 108.30 (2011): 12195-2197. Web. 3 Nov. 2016.
  3. Grant, P. R. "Bill length variability in birds of the Tres Marias Islands, Mexico." Canadian Journal of Zoology 45.5 (1967): 805-815.
  4. 1 2 3 Grant, P. R. Grant, P. R. “Interspecific Competition Among Rodents.” Annual Review of Ecology and Systematics, vol. 3, 1972, pp. 79–106.
  5. 1 2 3 "Watching Evolution Happen in Two Lifetimes." Interview by Emily Singer. Quanta Magazine 22 Sept. 2016: n. pag. Print.
  6. 1 2 Bell, Achenbach, Joel. "The People Who Saw Evolution." Princeton Alumni Weekly 23 Apr. 2014: n. pag. Web. 9 Nov. 2016.
  7. 1 2 Cressey, Daniel. "Darwin's Finches Tracked to Reveal Evolution in Action." Nature (2009): n. pag. Web. 8 Nov. 2016.
  8. 1 2 Daniel. Weiner, Jonathan. "In Darwin’s Footsteps." New York Times 4 Aug. 2014: n. pag. Web. 9 Nov. 2016.
  9. 1 2 Bell, G. "Every Inch a Finch: A Commentary on Grant (1993) 'Hybridization of Darwin's Finches on Isla Daphne Major, Galapagos'" Philosophical Transactions of the Royal Society B: Biological Sciences 370.1666 (2015): 20140287. Web. 9 Nov. 2016.
  10. Zimmer, Carl, and Douglas John Emlen. "Natural Selection: Empirical Studies in the Wild." Evolution: Making Sense of Life. Greenwood Village, CO: Roberts, 2013. 220-23. Print.
  11. Grant, B. Rosemary, and Peter R. Grant. "What Darwin's Finches Can Teach Us about the Evolutionary Origin and Regulation of Biodiversity." BioScience 53.10 (2003): 965. Web. 10 Nov. 2016.
  12. 1 2 "Peter and Rosemary Grant -Bio-bibliography." International Balzan Prize Foundation. Fondazione Internazionale Balzan "Premio", Jan. 2009. Web. 10 Nov. 2016.

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