THE POWER OF LIFE

The “exhilarating unrest” of evolutionary biology.

Charles Darwin’s theory of natural selection still dominates biology, bolstered by advanced technologies showing that heritable traits are largely driven by our genes. This well-written book by Riskin, a Stanford University historian, does not contest that. But it builds on it in an exciting way. It argues that a contemporary of Darwin’s (Jean-Baptiste Lamarck), with supposedly opposing views, was also right—to a degree. For Lamarck, too, believed that life evolves. Yet he believed living beings can cause evolution to occur faster, over one generation, simply by using a trait a lot. The famous example: Giraffes grow their own necks longer to reach taller trees, then pass on that trait. Lamarck was ridiculed for decades; giraffes cannot do this in one lifetime. But even more advanced technologies show that another monumental process drives evolution: “epigenetics.” And that process has Lamarckian elements. Experiments find that an odor that mice smell in a state of fear—caused by electric shock—can generate fear of that odor in children and grandchildren who never received shocks. That initial fear did not change the structure of any genes. But it did cause the “demethylation” of a smell gene via the attachment of an external chemical methyl group to a region near the gene. This caused a smell gene to be turned on the way that flicking a light switch turns on (but does not alter) a nearby light bulb. That trait was then passed to later generations via sperm. Veterans can pass on PTSD to their children in a similar way. Of course, training can reverse many such inherited epigenetic traits. But all told, epigenetics is profoundly important, the author notes. It affects everything from human health to climate change. “Organisms aren’t just in the environment; they make the environment and they are the environment,” the author concludes. “Science, like living beings, is always changing.”

An intriguing look at the life of a scientist who changed the way we look at life.