In Embryos under the Microscope: The Diverging Meanings of Life, biologist Jane Maienschein gives us a thoughtful and historically contextualized look at embryos so as to better inform conversations that are too often clouded by politics. Scientific knowledge can and should affect our policy and social decisions, she argues, even when the science alone does not tell us what those decisions should be. In the conversation below, Maienschein outlines some of what we now know of embyros, and stresses the importance of allowing that knowledge to supplant conflicting assumptions about the workings and meanings of life.
Q. Since before Aristotle cut open a developing chicken’s egg, scientists and theologians have theorized about embryos they couldn’t see. How does speculation about “invisible embryos” continue to shape contemporary thinking?
Most people have never seen an actual embryo, nor seen one develop from a fertilized egg cell. For them, embryos are largely “invisible” and imagined. Many people imagine a tiny person somehow there inside a woman who has just gotten pregnant, for example, and they imagine it as just growing larger over time. Yet in humans, the fertilized egg becomes an embryo and is called that until it is 8 weeks old; an embryo is not yet formed as a fully formed individual. Only after 8 weeks is it called a fetus, because it has the basic structure, the most important organs, and the very beginnings of the functioning of the human organism. Without knowing these developmental stages, and without actually seeing—through models or under a microscope—we are left to imagine what the invisible embryo looks like and how it behaves.
Q. What do the major advances in embryology over the course of the 20th century suggest about the trajectory of future science?
The case of embryo research shows how science is surprising and exciting in so many ways. Old assumptions give way to new knowledge, which leads to new insights and discoveries. The path is not always linear, and sometimes researchers get stuck in a way of thinking that takes a while to rethink. For example, most 20th-century researchers thought that once a cell becomes differentiated in a certain way, it will be fixed or determined in that way forever. We have learned that it is not that simple and that de-differentiation and re-differentiation is possible—with great potential for regenerative medicine. What history shows is the importance of becoming aware of underlying assumptions and rethinking them.
Q. What has in-vitro fertilization (IVF) revealed about the earliest stages of human development?
The ability to fertilize the egg in a glass dish made it possible to see the developing embryo. Instead of the embryo’s being invisible inside the woman, it is right there to be observed up to the point when it is implanted in the uterus and starts to gain nutrients from the mother. Before that, the human embryo was invisible and largely only imagined or inferred from other organisms. IVF also made the embryo more public, raising questions about whether and how the technology should be regulated and challenging society to reflect on attitudes toward embryos.
Q. How did the issues of cloning and stem-cell research become intertwined in the public imagination, and why is it important to consider them separately?
In 1997, the public heard about the cloning of Dolly the sheep. The media played up the cloning of a mammal as a step on the way to cloning humans. Then it was just the next year, 1998, that we learned of culturing lines of stem cells that came from embryos. These two technologies got mixed up in people’s minds. Cloning involves replacing the nucleus of a cell with another cell, and then development occurs normally. Embryonic stem cell research involves taking the inner cells out of an embryo and culturing them in an artificial cultural medium. These are two very different processes but they were tangled by coming so close to each other.
Q. The Sanctity of Human Life Act, which was proposed but which never came to a vote in the House in 2012, would have endowed a fertilized egg or embryo with “all the legal and constitutional attributes and privileges of personhood.” How was this proposed legislation—and the “personhood” movement more broadly—at odds with what we know about embryos?
Embryos at the earliest stages are really “just a bunch of cells.” They are not differentiated into the organs or tissues that make up an organism. They are not able to exist on their own, and cannot differentiate further without being implanted into a uterus to gain nutrients and remove waste. They have only the most rudimentary structure and function, and they are not in any robust sense yet “formed.” It makes no sense to think of these cells as persons that deserve legal designation as persons with rights.
Q. What new and emerging technologies do you foresee as sources of debate, and why?
Predicting the future is a dangerous thing to do, especially in science where there are so many wonderful surprises. Synthetic biology raises the possibility of “creating” life, and we already synthesize parts of animals and even parts of humans. This technology will no doubt raise ethical questions. It will also likely raise biological questions about whether the engineered parts will serve sufficiently “normal” functions.
Q. Several of the pioneering scientists whom you discuss spent time at the Marine Biological Laboratory (MBL) in Woods Hole, Mass., a research center with which you’re also affiliated. What’s the role of the MBL and of similar research centers in furthering embryonic (and other) science?
Ahhh, I’m glad you asked. The MBL is a magical place that brings together researchers from around the country and the world. Year-round researchers have established research centers with ongoing programs, such as in ecosystems or molecular evolution or regenerative biology. Summer researchers bring new questions and projects, along with a tremendous amount of energy to this seaside laboratory. They work together and talk to experts in fields they would not normally interact with back home. This has led to the feeling of a “national laboratory” with productive results. Today, it’s very difficult for such small independent labs to survive in the increasingly competitive environment with a declining funding base. Fortunately, the MBL has a new collaboration with the University of Chicago that promises great opportunities for the future. Those of us lucky enough to spend time at the MBL or similar places can continue to experience the special creativity there.