The Other Legacy of Charles Darwin

February 12, 2009
By: Steve A. Kay

Charles Darwin, 1809 - 1882

On this, the 200th anniversary of Charles Darwin's birthday, much is being said and written about evolution, natural selection and the conflict between religion and science. But Darwin's legacy is much more than the publication 150 years ago of the transformative ideas he put forth in "The Origin of Species."

Darwin set an example for the scientists who followed him on how to observe and make sense of the natural world. He used rigorous experiments to confirm his ideas. And he showed us how to synthesize disparate concepts and data into coherent hypotheses. In other words, Darwin knew it was important that his discoveries generated testable predictions.

Darwin's meticulous methods, emulated by today's most successful researchers, became evident to me more than 20 years ago when, as a graduate student in England, I began investigating the question of how plants alter their growth patterns as light levels change. As it happens, the problem had also intrigued Darwin, who detailed his observations and experiments in "The Power of Movement in Plants."

Published in 1880, the book is one of Darwin's lesser-known works. But it's a fascinating insight into the process by which Darwin unveiled the natural world and formulated new ideas. In it, Darwin describes his observations and experiments on how different types of plants grow and move in response to sunlight, darkness and other kinds of stimuli.

Plants are bursting with rhythm and movement. We just don't see it. When we look at a vase of flowers or field of sunflowers, we imagine them in our mind's eye to be "still life," like the still life paintings of the Dutch masters. But take a time lapse movie of a vase of tulips or a field of sunflower plants and you'll realize that they move in remarkable and often predictable ways. Plants have evolved internal light sensors that position themselves to capture the sun's energy. We don't notice those movements because we live on a different time scale. But Darwin did, and he recorded them with meticulous detail.

Darwin was one of the first to study and measure the movements plants make independent of light. He detailed one set of those daily movements, the circadian rhythm, regulated by an internal biological clock, by ingeniously recording the motions of a tobacco leaf on which he had waxed a pin. Darwin also studied in immense detail the spiral movements that bean and other plants make as they grow taller and determined that they benefited the plants by allowing them to search for something to grow on.

By mapping the daily movements of sunflower plants, which turn to the east like clockwork just before dawn to face the sun, Darwin was able to predict their movements and understand the movements of plants toward light, a process we call "tropism." He also was the first to discover that when two closely related species of plants are genetically crossed, they become larger and more vigorous. This trait, known as "hybrid vigor," is the basis for the way we breed corn and other cereal crops today.

As a plant geneticist and dean of the University of California San Diego's Division of Biological Sciences, it's mind-boggling for me to look at Darwin's "The Power of Movement in Plants" and think that it was merely a footnote in Darwin's life - a sidebar from someone who regarded himself as an amateur naturalist, who didn't have formal scientific training, research grants, graduate students or tenure. Not only did Darwin's study of the growth rhythms in plants represent a significant contribution to plant science, he provided the world with the basic knowledge that has allowed us to employ scientifically based strategies to improve agricultural productivity.

Here was a man who applied his powers of observation and rigorous testing to everything he looked at in great detail, from the movements in plants and barnacles, to how pigeons navigate, to the importance of earthworms in soil health and ecology. His experiments were in many ways more ingenious than those performed in state of the art laboratories today.

We now have the technology in our molecular genetics laboratories to hunt down and sequence the genes that cause many human diseases. But the reason we can do that is because of the basic concepts that Darwin developed and the connections he made about the relatedness between different forms of life. Today we know this is because many of the same genes found in humans are also found in other species, from fruit flies to roundworms and yes, even plants.

As biologists at UC San Diego celebrate Darwin's 200th anniversary with a birthday bash today and a symposium in April where we will bring together the world's leading evolutionary biologists, we should recognize that Darwin's legacy was not only his transformative ideas about evolution, but also the meticulous manner by which he observed and tested the natural world.

We have now entered an age in biology when we will, within our lifetimes, be able to sequence every gene and every nucleotide from practically every known organism on the planet. But how do we put all of that genetic information into context? What do these genes that we study at the molecular level actually do in organisms? How do we relate the variation that we see at the genetic level to the variation we see in living things?

What we biologists have begun to realize is that we've become better at sequencing the genomes of organisms than understanding in detail how they live and interact with their environments. So there is growing recognition that we need to observe organisms in the same meticulous way that Darwin did 200 years ago. In a sense, we've come full circle. And Charles Darwin is once again showing us the way.

Kay is dean of the Division of Biological Sciences at the University of California San Diego.

Originally published in the San Diego Union Tribune