Like most biologists, I lean to the political left. I support Roe v. Wade and vote accordingly. I have progressive views on medical care, agriculture, conservation, all that life-and-death stuff we call bioethics. But let’s focus on abortion for the moment. Conservatives are often baffled by the liberal politics of scientists, since as they see it the science is on their side. Occasionally, pro-lifers will try to use my own scientific expertise against me. They ask, aren’t you a geneticist? (Yes). Doesn’t a zygote have a different genome than its parents? (Yes). Don’t textbooks show the mammalian life cycle starting at fertilization (Yes). So doesn’t biology prove that life begins at conception?

No.

Life began once. Over three and a half billion years ago. All life since then has been a continuous transmission of that initial spark. This may sound like a cop-out answer, but it’s really not. It drives home the point that, at the biochemical level, life does not end with gametes and then restart with a zygote. Instead, the unbroken molecular dance of life happens throughout the whole process. The reason it sounds like a cop-out is that when most people talk about “life,” they don’t mean the biochemical level. They mean the subjective experience of being a conscious entity. They mean having a mind, feelings, motives, and all that. In that sense, life clearly does not begin at conception. We’ve barely begun to understand consciousness, but what little we can glean from neurobiology shows that it starts later in development. Defining the start of new organism based on genotype is generally convenient, but treating this as an absolute law is nonsensical. For one thing, it would mean identical twins are the same person. For another, it would mean every sperm and egg cell is a unique human being, since each one differs genetically from its parent. Even your white blood cells have their own personal genome. Is skinning your knee tantamount to manslaughter?

Decade after decade, we go round and round again on this abortion question. New generations keep asking biologists to confirm that life begins at conception. The answer is still no. American opinion on this issue has barely budged in 40 years. And that has sobering implications. Abortion is the quintessential poster child of bioethics. The most discussed, debated, and challenged. The case should have been closed long ago. Clearly the influence of conservative religious organizations keeps the pro-life movement alive, but there’s no particular reason for that. It’s not like the Bible stresses the sin of abortion. Prenatal development simply touches something deep and visceral for many people. It shouldn’t be that hard to convince everyone that a microscopic bit of tissue is not the same as a baby. Yet no one has been able to do that.

What on Earth have the bioethicists been up to? If they had one job during the last half-century, it should have been to resolve this grandparent of all bioethical qualms. Their failure doesn’t bode well. As biotechnology develops, we are about to get hit with a host of similar issues. Our ability to genetically modify crops, wildlife, even humans, is blossoming. These techniques could improve the environment and human health, but first society needs to reach an agreement about what is okay. It goes further. We may soon be able to resurrect extinct species, produce both sperm and eggs from the same biological parent, or estimate anyone’s psychological profile and medical risks from a few discarded skin cells. Farther down the road, we might be dealing with the moral status of nonhumans to which we have granted human-like cognition. All of these possibilities can evoke a strong emotional response. But there is no reason to think that making decisions based on our gut reactions will usually be wise.

The way we’re doing bioethics now isn’t very effective or convincing. How can we be better? A good start might be to target our innate biases about biological systems. For example, we’re inclined to assign things to distinct categories even though biological borders are fuzzy. Our brains really want there to be impenetrable boundaries between parent and offspring, male and female, human and ape, life and death, alive and inanimate. But there aren’t. The spaces between these categories form uncanny valleys that make people uncomfortable. This term was originally coined to describe the creepiness of lifelike robots, but the same concept applies to anything that doesn’t quite fit into our preconceived pigeonholes. Rather than accept them as is, people pretend that these transitional entities are fully on one side or the other. That embryos are children, for example. What can we do about that? Social activists have had some success combating similar classification errors along racial and geographic lines. Though racism still exists, most Americans now accept that someone can be both Chinese (by birth) and American (by citizenship), a duality that was not only preposterous but legally impossible just 75 years ago. The valley between exotic foreigner and trusty compatriot was bridged in part because white Americans grew accustomed to their immigrant neighbors. We can fill biological valleys with familiarity, too. The religious right has co-opted the imagery of embryology; it’s a safe bet that a billboard featuring a fetus is promoting a pro-life agenda. Let’s take it back. Maybe folks would be more comfortable with the idea of the blastula as an intermediate step if pictures of it were more commonplace. In that uncanny valley that we all crossed before birth, a cell can be human without being a person.

Let’s keep working on this. After all, we’re going to be spending a lot of time at the intersection of biology and morality. If we don’t get better at navigating it, there will be trouble.