【英语时差8,16】向癌症进化（在线收听）

Evolving Toward Cancer Is it possible that humans evolved to get cancer? That’s what scientists at Ben Gurion University in Israel claim in a study. They found that the same genetic mutations involved in the evolution of modern humans also gave rise to the evolution of cancer. But why would we have evolved to be at risk for diseases, like cancer, that make our survival more perilous? Isn’t evolution about the survival of the fittest? Sort of. Because what it means to be “fittest” is complicated. Evolution basically describes how organisms–humans included–respond to environmental change. Thanks to random genetic mutations, some members of a group or species live to have babies and pass on their genes. Others–those less fit–die off. After several generations, the mutations that enabled survival spread more broadly through the gene pool. But those same mutations can have other, less desirable effects. Like giving rise to new diseases. And that’s what the Israeli researchers found when they looked at the record of mutations in the DNA of human mitochondria–tiny cellular engines necessary for a cell’s survival. Ancient mutations in mitochondrial DNA are the same as those found in the cells of many tumors. So it appears that those mutations that helped our prehistoric ancestors survive have a dark side–they’ve made us vulnerable to cancer and maybe other diseases. Now, the causes of cancer are complex. Genetic mutations are only one factor. But this research is important, the scientists say, because it strengthens the idea that cancer is linked to our genes. And knowing more about how diseases form and evolve can lead to new treatments and cures.