Charles and Emma by Deborah Heiligman

themselves? The novelist Charles Dickens felt Malthus depicted poor people as less than human; in novels such as
Oliver Twist,
he sought to remedy that, making poor people well-rounded main characters. Charles, Erasmus, and their London friends discussed these problems over dinner. What might Malthus’s ideas mean—for better or for worse—to society?
    But Charles was even more interested in what Malthus’s theory might mean for nature and for the origin of species. As Charles read the essay, he thought more about animals and plants than about people. He believed there was a directanalogy, a way into the species problem. Reading Malthus and thinking about the natural world, Charles realized that nature was not happy and peaceful, as Paley had described in his natural theology books. The lion did not lie down with the lamb. Life in nature was a struggle, just as in the crowded, poverty-ridden neighborhoods of London. In human society there were not enough jobs for the growing numbers of people; in nature—on a desert island or on top of a mountain—there was also a struggle for existence when there was not enough food for the growing number of birds, beasts, or bugs. Charles reasoned that if too many individuals of a species are born in the same place and try to live off a limited supply of food, there is a fight for survival. The weaker ones die. The ones that are strongest, best adapted to the conditions of the area and most able to get the food, survive. Those who survive pass on their traits to their offspring. This was true of cockroaches, sheep, bees, and beetles.
    And birds.
    While on his voyage, Charles had usually been careful to label every bird, every fossil, every plant. He would write down where he found it and what he thought (or knew) it was. But leaving the Galapagos Islands, he uncharacteristically had thrown birds from different islands into one bag. He regretted this later when he realized that the mockingbirds and the finches would have been wonderful evidence for his theory. On the journey home, he thought about how the mockingbirds from the Galapagos Islands of San Cristóbal and Isabela looked the same, but the ones from Floreana and Santiago seemed different. And each kind was found only on its own island. Were they just varieties, or were they evidence of new species? Had the birds been blown over from the coast of South America and then diverged as they lived and died,generation after generation, on the islands? he wondered. And if they had, what did that mean about the creation of new species?
    When he got back to England, he had given his mockingbird and finch specimens to John Gould, an ornithologist. Gould was especially excited about the finches: There seemed to be more than a dozen species of finches never seen anywhere else before. Gould told Charles that he had brought back birds that seemed to live only in the Galapagos. Charles’s inkling was confirmed: Species were not stable. They were not created in one fell swoop by God, never to change, as the Bible said and most people believed.
    As Charles looked at the beaks of the finches, he began to see evidence of the fight for survival that precipitated the change. He began to see that beaks adapted to the kinds of seeds available on the island. Big beaks could crack open big, hard seeds; small beaks were better for hard-to-get-at seeds. This was not God’s design; it was design brought about by the need for food. His birds and Malthus’s theory had given him the mechanism for the transmutation of species.
    In his notebooks, Charles began to write about his idea of how it all happened. He thought about how traits get passed down, over and over again. He surmised that traits that are passed on change and adapt according to what is needed for survival. These changes—very small ones—add up over time to make bigger changes. These bigger changes result in the creation of new species. He called his idea