The Darwin connection

By LESLIE BRUNETTA

For the Monitor

Last modified: 1/22/2012 12:00:00 AM

Last winter, I was diagnosed with breast cancer. And this winter, like past winters, legislators in various states - including, unexpectedly, New Hampshire - are writing bills designed to undermine the teaching of evolution in public school biology classes. Those events seem unrelated. But these bills are bad for my health and the health of each of the 1.5 million Americans diagnosed with cancer every year.



Although most such bills die in committee, they legitimize the idea that the theory of evolution is just an opinion. It is actually a robust explanation for the diversity of life on earth, supported by thousands of observations and experiments, used to make testable predictions about nature - which includes our bodies.



When I was a child in the 1960s, cancer was usually a death sentence. Today, most of us know cancer survivors. The treatment breakthroughs we patients now turn to for help are products of the scientific method. And the most recent treatment breakthroughs rely on knowledge of the DNA of cancer cells. What most non-biologists don't realize is this: If the theory of evolution hadn't predicted the existence of genes, we might never have understood the importance of DNA. Benefiting from such gene-based cancer treatments as Herceptin or Gleevec but rejecting Darwin's theory of evolution is like jetting from Iowa to New Hampshire but rejecting Newton's theory of gravity.



To understand how the theory of evolution has helped cancer patients, look at how breast cancer treatment has progressed. Until the 1970s, standard treatment in the U.S. was radical mastectomy - and surgery alone. Five-year survival rates hovered about 50 percent, probably an inflated percentage. By the 1980s, randomized trials - a hallmark of the scientific method in medicine - showed that most women could opt for lumpectomy, saving their breasts at no additional risk because new regimens of chemotherapy and radiation killed cancer cells surgery didn't touch. Another randomized trial showed that also taking tamoxifen could deliver even better outcomes to many women.



But radiation and chemotherapy attack normal as well as cancer cells. The Holy Grail of cancer research, therefore, has long been to discover what makes cancer cells vary from the normal cells that have begotten them.



In the 1970s, researchers laid a finger on this Grail, discovering cancer-causing genes. This research led to the first drugs targeting those genes. In the 1990s, Herceptin, which targets breast cancer cells that contain too many copies of the HER2 gene, entered clinical trials. By 2006, trials showed that women with early-stage HER2-positive cancer given Herceptin were 50 percent less likely to suffer recurrence. We now also have gene-based tests that allow some breast cancer patients to forego chemotherapy and women with a



family history of breast cancer to learn their risk. The future of treatment - and perhaps prevention - lies in learning more about normal- and cancer-cell genes.



The theory of evolution started researchers down this promising path. When Charles Darwin published On the Origin of Species in 1859, there was as yet no way to explain two of the three legs upon which his theory stood. Those three legs are inborn variation among the members of a species, the fact that environmental pressures allow only some of those members to leave surviving offspring, and the passing of the favored members' traits to the next generation. How was variation generated? And how were traits passed to offspring? The theory predicted the discovery of material answers.



That material would later be known as genes, stretches of DNA. But in 1859, biologists knew so little about reproduction they didn't even understand the role of sperm. Darwin attempted to answer these questions with a misguided hypothesis he called pangenesis. Other evolutionary theorists, notably August Weismann, put forward alternative hypotheses.



In line with the scientific method, each hypothesis was more than an opinion: It was testable.



As researchers tested these hypotheses over decades, evidence accumulated showing first that the material of inheritance was contained in the cell nucleus, then that it was located on the chromosomes, then that it was composed of DNA. In 1953, James Watson and Francis Crick published their DNA model, which finally explained in physical terms both how variation is generated and how offspring inherit traits from parents.



The hunt for cancer-causing genes is thus just a later phase of the hunt for genes that began with the theory of evolution. Meanwhile, creationists, "intelligent design" advocates, and other "challengers" of evolution theory propose no research program. A recent national survey of public school biology teachers indicated that, cowed by the political climate, fewer than a third explicitly endorse the theory of evolution in class.



High school students are our future researchers. They are also our future voters and politicians. Michele Bachmann, Ron Paul, Rick Perry and Rick Santorum, all with enough popular backing to have qualified for the presidential candidates debates, explicitly reject the theory of evolution. The president nominates the directors of the National Institutes of Health and the National Cancer Institute.



If you're looking for a cure for your cancer, don't look to evolution-deniers for hope. As for me, I give thanks to Darwin and the researchers who have stood on his shoulders.



(Leslie Brunetta of Cambridge, Mass., is co-author, with Catherine L. Craig, of Spider Silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating.)





