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DNA is the genetic blueprint of all creatures –- it contains the operating instructions for everyday life and for making the next generation. Recently, an important new dimension of DNA has been revealed –- it contains a vast and detailed record of how species adapt and change. Thus DNA is a living chronicle of evolution. We can now pinpoint the precise changes in DNA that have enabled the marvelous creatures that inhabit our planet to adapt to its many shifting and sometimes extreme environments, from the freezing waters of the Antarctic to the lush canopy of the rain forest. We finally understand not just how the fittest survive but also how they are made. In this book, leading biologist and writer Carroll takes us on as exhilarating tour of this exquisite new record.
Every change or new trait, from the gaudy colors of tropical birds to our color vision through which we admire nature’s artworks, is due to stepwise changes in DNA that we can now trace. Some steps are tiny, just a single change in one letter of a gene’s code. Others are more dramatic and involve the birth and death of many genes. Though the DNA record has resoundingly confirmed Darwin’s main principles, several major surprises have been revealed.
The first surprise is that there is a set of “immortal” genes in the DNA of nearly every creature, from bacteria to whales, These genes first emerged three billion years ago and have survived the constant onslaught of mutations that woukld have erased them eons ago were it not for natural selection.
The second surprise is the discovery of fossil genes. These are bits of DNA text that were once intact and used by ancestors but have fallen into disuse and decay. These relics are an entirely new source of insights into traits and capabilities that have been abandoned as species, including humans, evolved new lifestyles.
Perhaps the most profound surprise is how the DNA record proves that evolution can and does repeat itself. Similar or identical adaptations have occurred in the same way in species as different as butterflies and humans. This repetition overthrows the notion that if we rewound and replayed the history of life, all of the outcomes would be different.
There is grandeur in this new knowledge of how changing one or a few letters in simple code can dramatically change the form or physiology of complex organisms. The ability to see into the machinery of evolution transforms how we look at the process. For more than a century, we were largely restricted to looking only at the outside of evolution. We observed change through the fossil record and could only gaze at the differences among living species “as a savage stares at a passing ship.” No longer. The Making of the Fittest is a treasure trove of completely new information about how evolution actually works and why it matters, and how this remarkable process has shaped humans, the world we now inhabit, and the marvelous creatures with whom we share it.
Sean B. Carroll is an investigator at the Howard Hughes Medical Institute and professor of genetics at the University of Wisconsin-Madison. He is the author of Endless Forms Most Beautiful: The New Science of Evo Devo, which was a finalist for the 2005 Los Angeles Times Book Prize (Science & Technology). He is one of the leading biologists of his generation, and his seminal scientific discoveries have been featured in Time, U.S. News & World Report, Discover, the New York Times, and other publications.
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