'Lamarck's Revenge' Review: Inheriting the Wrong Ideas
Epigenetic changes explain, in part, why even identical twins can differ from each other.
Jean-BaptisteLamarck (1744-1829) formulated the first real theory of biological evolution, in which organisms acquired traits directly from adapting to the environments they faced and passed those new traits on to their offspring. If there's one thing high-school biology students learn, it's that Darwin was right about natural selection. If there's a second thing, it's that Lamarck was wrong.
Recently a few scientific admirers have begun dredging Lamarck from the textbook depths. One of these is Peter Ward, a paleontologist whose earlier works looked at Earth's history of extinctions and the prospects for life on other planets. Mr. Ward's "Lamarck's Revenge: How Epigenetics Is Revolutionizing Our Understanding of Evolution's Past and Present" proposes that Darwin's idea of natural selection is not enough to explain the rapid proliferation of new species after mass extinctions or the rapid response of humans to new environments of the past few thousand years. In his telling, the new science of epigenetics stands ready to replace Darwinian natural selection as the prime explanation of fast evolutionary change.
Lamarck's Revenge
By Peter Ward
Bloomsbury, 273 pages, $28
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Some scientists have hailed epigenetics as the future of biology, while others denounce it as an empty buzzword. Perhaps no other term inspires so much debate among scientists about how to define it.
What is epigenetics, and why has it inspired such intense, sometimes acrimonious, interest? Different types of cells in your body—liver cells, brain cells, skin cells—look and function differently from one another, even though they all carry the same DNA sequence, or genome, that you inherited from your parents. The diversity of your cells dates to when you were an embryo, when molecular processes activated or inhibited different genes in different types of cells. These molecular interactions leave chemical marks on the chromosomes passed on to different lines of cells in the body, explaining why a brain cell cannot be simply reprogrammed into a kidney cell or vice versa. These marks, broadly, are called epigenetic.
Biologists have learned that experiences and environmental insults like chemicals during childhood can leave epigenetic traces. Such traces explain, in part, how identical twins become different from each other. No area of epigenetic research is more controversial than the idea that such marks might be inherited across generations. In "Lamarck's Revenge," Mr. Ward grips this most controversial area of epigenetics and doesn't let go. In his telling, if individuals can pass on to their offspring some trace of new behaviors acquired during their lifetimes, then the offspring can gain a leg up in the survival race. He argues that this new Lamarckian mechanism of inheritance could help explain periods of rapid evolutionary change during the history of life on Earth.
Mr. Ward eloquently describes the scenario at the end of the Permian, roughly 250 million years ago: the greatest mass extinction in the history of Earth, which killed some 95% of species. In the Karoo Beds of South Africa are the remains of the most prolific survivor, a dog-size creature called Lystrosaurus. "Those Lystrosaurus lucky enough to have survived the great extinction ran wild," Mr. Ward writes. In a new world without predators, over hundreds of thousands of years, this creature shrank in body size. Mr. Ward likens Lystrosaurus to the first domesticated animals, which quickly evolved new features and behaviors once humans protected them from predators. In both cases, he argues, epigenetics allowed species to rapidly change their behavior to suit a rapidly changing environment.
But here's the catch. When it comes to the fossil record, paleontologists have a different idea of "fast" from everyday life. Hundreds of thousands of years is plenty of time for Darwinian natural selection to have changed Lystrosaurus. We don't need Lamarckian inheritance or epigenetics to explain it.
Our own species has also been evolving fast for the past 100,000 years. We, along with the species we have domesticated, are among the most prominent examples of rapid evolution. Indeed, Mr. Ward points to humans and our domesticates as support for the role of Lamarckian epigenetics. But there's a problem: Scientists have found no evidence that transgenerational epigenetic inheritance plays a role in a single trait that has changed in humans in the past several thousand years. Some traits, like the gene that enables adults in Europe and some other populations to digest milk effectively, result from new mutations that have rapidly increased within the past few thousand years. Other new traits, like the tolerance of high altitude by the people of Tibet, rely on genes borrowed from ancient human groups. Most of the new traits, like lighter skin pigmentation, are a more complicated blend of the natural selection of genetic variations that have persisted for hundreds of thousands of years and a sprinkling of new ones. As far as we can see, all these traits evolved by Darwinian natural selection on gene sequences, not by children inheriting epigenetic marks on their parents' DNA.
"Lamarck's Revenge" is frustrating. For Mr. Ward, every problem is a nail and epigenetics is the hammer. He lumps together genetic mechanisms like horizontal gene transfer with epigenetics, and every example of epigenetics serves as evidence for the proposition that epigenetic inheritance must matter. This leaves no room for explaining real scientific debates about how epigenetics may shape biology. Not until the fourth chapter does the book discuss any scientific studies of epigenetic inheritance, and the book never presents the views of any scientific detractors of epigenetic inheritance.
One needn't look far to find such detractors. The most famous studies of epigenetic inheritance have examined Dutch men and women born during or shortly after the famine of 1944-45. Deprived of nutrients in utero, the famine survivors carried persistent differences in their epigenetic markers from other adults. Studies of the children of these survivors have also shown effects that might possibly have come from epigenetic inheritance. But those effects are inconsistent. In other words, the evidence for epigenetic inheritance is inconsistent at best—and may not hold up in other human populations beyond this single event.
It's not that there's no evidence for the phenomenon. Experiments in mice have shown the potential, in some circumstances, of inheritance of induced epigenetic changes. But such changes last at most a few generations, and most studies have found no evidence for a directed effect. Instead, the life experiences of the parents exert mostly random effects on their offspring. Such effects may turn out to be important in understanding human health, but they are much more like Darwin's notion of inheritance than Lamarck's.
Still, even if Mr. Ward tells an imperfect and sometimes exaggerated story, this area of science is fascinating. Scientists really are talking about Lamarck again, and while not everyone agrees, there is increasing buzz that in the microbial world, genetics—not epigenetics—sometimes allows organisms to acquire adaptive changes and pass them on.
The highest-profile example is Crispr/Cas, the scientific breakthrough now enabling scientists to edit new sequences directly into genomes, creating novel traits from scratch. Before scientists recognized its engineering applications, Crispr/Cas existed in nature as a way for humble bacteria to fight off viruses. Because it works by assimilating viral DNA directly into a bacterial genome, deploying it as a weapon against the virus itself, the Crispr/Cas mechanism is a form of Lamarckian inheritance. With scientists working to apply these techniques to human genes, we may indeed be able to shape our own evolutionary future.
—Mr. Hawks is a professor of anthropology at the University of Wisconsin-Madison.
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