Sthe study of Darwin’s finches was the life’s work of the famous British evolutionary biologists Rosemary and Peter Grant. For several months each year for 40 years, the husband-and-wife team visited the Galápagos Islands in the eastern Pacific Ocean to closely track the fate of thousands of finches on two small islands there. The Grants showed that evolution by natural selection can be observed in nature in real time: they were the first to see and measure it in action in nature. One step sideways, three steps forward is Rosemary Grant’s new memoir. It reflects on her far-from-straight path to becoming a biologist, living with a family on the Galápagos – for 10 years the scientists’ two daughters accompanied them – and the joy of sharing ideas with her partner . Rosemary, 87, is senior research biologist emeritus at Princeton University in New Jersey. The book appears a new edition of 40 years of evolution – the Grants’ classic version of their study of the finches – which will appear later this year.
The Galápagos are known for their unusual and unique species, including giant tortoises, marine iguanas and flightless cormorants. But what is the Charles Darwin compound?
Darwin spent five weeks there on his round-the-world trip in 1835, and the islands were key to solidifying the concept of evolution by natural selection [put forward in On the Origin of Species in 1859]. While there, he collected a variety of specimens of various sizes of songbirds. Later, back in England, he was informed that they were all species of finches. He reasoned that their diversity in terms of body size and bill shape evolved over time as they adapted to feed on different food sources. [which vary by island]. Today we recognize 17 different species of Galápagos finches and there is also one on Cocos Island. We now know that they all evolved in the last one to two million years from a single ancestral species – probably a small flock of finches that came from mainland South America.
Where did the idea to study finches on the Galápagos come from?
We knew about work earlier that the adaptive radiation of Darwin’s finches was very young, and it was just this kind of situation that Darwin suggested would be the place to look for evidence of speciation. Also, many of the islands have never been inhabited by humans (what we saw would be completely natural) and the archipelago is prone to drought (causing food shortages and large numbers of bird deaths and thus possibly natural selection).
We began our fieldwork in 1973 on the very small island of Daphne Major, a steep-sided volcanic crater. We went with two of Peter’s postdocs and our children aged six and eight. We added Genovesa, a larger and flatter island further north, in 1978. We conducted parallel studies on the two islands for a decade before concentrating only on Daphne because, being smaller, it was possible to follow the fate of each individual finch.
We would capture the birds, take their bands and body and bill measurements along with a small blood sample for later DNA analysis. We would also see what they feed on, monitor the amounts of food available and record their songs (which vary between species and are important when it comes time to choose a mate).
What was island life like? How did you keep your kids busy?
We had to take all our research equipment, camping supplies, food and water. The water was critical and often we had a boat deliver new containers at intervals. They were five gallons each and, on Daphne, we had to haul them to our galley – which was a cave in the cliff that we shaded with a canopy to keep cool.
[Our children] Nicola and Thalia loved it and always wanted to come. They would help out a bit and were good at finding nests for us. They also did their own research, and it actually led to publications – Nicola about mockingbirds and Thalia on pigeons. We also took books and they had a violin.
Any scary incidents?
Luckily we didn’t have any serious accidents or illnesses, but Peter was almost attacked by a shark next to Daphne. We didn’t use fresh water for washing – it was too valuable. Instead, we would dive into the ocean, cover ourselves with shampoo, and then dive back in to rinse. The children and I had already washed and Peter came down. He had shampoo on when I saw this shark come up from the depths and go towards his shoulder before suddenly turning away. Later back home we read that sodium lauryl sulfate, which is found in many shampoos, has been found to have shark repellent effects. We looked at our bottle’s ingredients and sure enough, there it was. Afterwards we washed in buckets!
Was Darwin right about how evolution would occur?
While Darwin provided the clue as to where to see evolution, he thought that any observations of change would be few: major changes would take millions of years. We found that change happened much faster. The evolutionary process that Darwin outlined is character displacement (or divergence) caused by competition with another species. Over a period of almost 30 years we were able to see the average bill and body size of the population of one of Daphne’s main finch species, the medium ground finch (Geospiza fortis), became smaller after its larger members were eliminated for food by another invading finch species during a drought.
But we also saw other methods of speciation that Darwin did not anticipate, involving the rare hybridization (or cross-breeding) of species – including the formation of a completely new generation. This remarkable and unexpected process began with the arrival of a single male large cactus finch (Geospiza conirostris) on Daphne from an island in the far south of the archipelago. However, whether the lineage ultimately succeeds or fails remains to be seen.
What is the message for species conservation that has come from your work?
That we must keep populations capable of further natural change, which means you can’t just save one species. A full complement of related species provides the opportunity for genetic input and variation. On both Daphne and Genovesa, if it weren’t for the multiple finch species that occasionally interbreed, we would probably have seen extinctions with the droughts.
Any advice for those juggling parenthood with professional life?
Don’t be in a hurry. Not everything has to go in a straight line. Try to make time to be with your children and introduce them to a variety of experiences. We struggled financially and my PhD seemed elusive, but one of the best times in our lives was being alone as a family on a desert island.
Have you ever resented how easily your husband achieved his career goals, given how much more difficult it was for you?
Never. Peter was unusual among men of his time in that he was very supportive of what I wanted to do (which was to go back to research and do my PhD). The Galápagos work was ours: we did it together, we published together and he would always bring me into the conversation. Most husbands would have said they couldn’t possibly work with their wives!