Free She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity by Carl Zimmer Page A

livers compared to free-ranging breeds. He saw this as the result of pangenesis. Farmers fed these breeds better food and expected less work from them. As a result, they didn’t need to work their lungs or livers, and the organs produced different gemmules as a result.
    To Darwin, cattle and other domesticated animals put pangenesis on an impressive display. In just a few thousand years, humans had altered the heredity of animals and plants in endless ways, producing greyhounds and corgis and Saint Bernards, racehorses and draft horses, apples, wheat, and corn. Breeders such as Bakewell selected individuals to breed, unknowingly choosing which animals could pass their gemmules to future generations. They crossed different strains to combine gemmules in new combinations. Breeders had exploited the same laws of inheritance that had made the evolution of all species—even ourselves—possible.
    “Man, therefore, may besaid to have been trying an experiment on a gigantic scale,” Darwin wrote, “and it is an experiment which nature during the long lapse of time has incessantly tried.”
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    Sitting in Massachusetts, young Luther Burbank read The Variation of Animals and Plants Under Domestication with a rush of marvel and relief. He might be a novice farmer, but now he felt he was part of something far bigger. The same biology that gave rise to all living things—their variation, their selection, and their heredity—now felt like clay he could shape with his hands. Darwin declared that variation emerged from crossbreeding, which mixed gemmules of different origins together in new combinations. By selecting which plants to breed again, Burbank could eventually produce a new variety that reliably passed down its traits to future generations.
    “While I had been struggling along with my experiments, blunderingon half-truths and truths,” Burbank later wrote, “the great master had been reasoning out causes and effects for me and setting them down in orderly fashion, easy to understand.”
    In 1871, Burbank bought a seventeen-acre farm where he could carry out Darwin’s causes and effects. He cross-pollinated beans.His cabbage seeds and sorghum won prizes at the local agricultural fair. And then, at the tender age of twenty-three, Burbank spotted an odd potato that would bring him agricultural immortality.
    One day, as he tended a patch of Early Rose potatoes, Burbank noticed a tiny, tomato-shaped mass dangling from one of the vines. It was, he realized, something wonderfully rare: a seed ball. Farmers typically propagate potatoes by cutting up their tubers and planting the pieces, which can grow into entire new potato plants. Potatoes can also reproduce by having sex. They grow flowers, and once the ovules in the flowers are fertilized by pollen, they develop into seeds. The seeds cling together in a ball-shaped clump.
    Over thousands of years of breeding, domesticated potatoes have mostly lost the ability to make seed balls. If farmers noticed one in a potato field, they usually ignored it. But Burbank had Darwin on his mind, and so, to him, finding a seed ball was like stumbling across a jewel. “Stored in every cherished seed was all the heredity of the variety,” he later said.
    When Burbank spotted the seed ball, it was still immature and thus not yet ready to use for breeding. To make sure he could find it again, Burbank tore a strip of cloth from his shirt and tied it around the plant. When he checked back later, however, the seed ball had dropped to the ground and disappeared from sight. For three straight days, Burbank searched for it. When he finally found it again, he opened it up and found twenty-three potato seeds inside. Burbank carefully stored them away for the winter and then planted them in the spring of 1872.
    From that single seed ball grew a riot of variation. Burbank ended up with potatoes of different colors, shapes, and sizes. When he tasted the tubers, he found that two were unusually