Personhood movement, chimeras: How biology complicates politics.

How Biology Undercuts the Personhood Movement

How Biology Undercuts the Personhood Movement

The citizen’s guide to the future.
June 10 2014 8:11 AM

Politics in Your DNA

How the realities of biology complicate the “personhood movement.”

from the first US textbook on midwifery, An Abridgement of the Practice of Midwifery, by W. Smellie, 1786.
Twins in the womb

Photo illustration by Juliana Jiménez Jaramillo. Image courtesy U.S. National Library of Medicine/National Institutes of Health.

What if at the very beginning stages of development you absorbed your twin’s cells? You’d be twins—a phenomenon called a chimera. Would you suddenly feel extra special because you are really more than just one person? Threatened and confused about your identity? These are not just hypothetical questions. Some people are chimeras. Probably not many, but certainly a lot more than we know about since most never realize it. Chimerism happens even when we don’t see it.

There’s another kind of genetic mosaic, too, one in which your body is made up of cells from different organisms, usually from different people (occasionally from other animals). This might happen if you have a transfusion or a transplantation, for example, or when mothers absorb some cells from their offspring, or twins absorb cells from each other. Technically, every female is a kind of mosaic of two different X-chromosomes.

News of chimerism and genetic mosaicism is not completely new, nor are the ethical and practical questions associated with them. Yet as a society, we often take a heads-in-the-sand approach to addressing what such developmental complexities mean. Bioethical and policy discussions have instead largely focused on responses to laboratory creations of cross-species combinations that lead to chimeras, hybrids, or genetics mosaics. But they miss the fact that people and politicians care deeply about what it means to them to be human and how we can protect “life.” The personhood movement, and proposed legislation discussed below, show the urgent need to understand what we are really talking about. As the political season for congressional and local campaigns heats up, some candidates will surely make promises or proposals about embryos and reproduction that do not fit the facts. Last campaign season we got claims about “legitimate rape” and whether rape can lead to pregnancy, for example, and we heard Paul Ryan’s claims about personhood. The personhood movement is not going away soon and remains active through, for example. Now is the time to get ready for whatever comes up this round.


Most people didn’t care deeply in the 1960s when Beatrice Mintz combined embryos from two different mice to create a chimera, nor in the 1980s, when Nicole Le Douarin combined chick and quail embryos. The result was taken as intriguing and a little science fictionlike, and it generated discussion of what it would mean if somebody could create human or human-animal chimeras. In the mid-1990s, researchers did just that and provoked public interest. What if researchers introduced human nerve cells into a mouse? (Stanford law professor Hank Greely liked to phrase the question in a different way: What if Mickey Mouse suddenly started talking?)

Debates about this kind of laboratory combination led to legal and regulatory responses in some countries, such as the U.K., which had also led the way in regulating embryo research and in vitro fertilization. The United States didn’t enact any new policies, though bioethics consultants in the U.S. report that people often feel queasy about creating “unnatural” laboratory human chimeras, for a mix of practical and ethical reasons.

But it’s different when the chimera occurs naturally. Does a chimeric person combined from two fertilized eggs get two votes? According to some proposed legislation, he or she should. The discussion matters. As candidates position themselves for the dash to the next congressional and then presidential election, let’s understand what is at issue here.

Rep. Paul Ryan of Wisconsin—the failed Republican vice presidential candidate in 2012—was one of many to co-sponsor the House Sanctity of Human Life Act of 2013. (He was a co-sponsor on earlier, similar legislation as well.) The summary of H.R. 23:

Declares that: (1) the right to life guaranteed by the Constitution is vested in each human and is the person's paramount and most fundamental right; (2) each human life begins with fertilization, cloning, or its functional equivalent, at which time every human has all legal and constitutional attributes and privileges of personhood; and (3) Congress, each state, the District of Columbia, and all U.S. territories have the authority to protect all human lives.” The proposed bill asserts further that “(B) the life of each human being begins with fertilization, cloning, or its functional equivalent, irrespective of sex, health, function or disability, defect, stage of biological development, or condition of dependency, at which time every human being shall have all the legal and constitutional attributes and privileges of personhood.

The impulse is clear. The sponsors, including Ryan, want to protect what they see as human life. They want to prohibit abortions. Unfortunately, they may love life, but they do not understand its earliest developmental stages. Their proposed legislation and the personhood movement ignore the existence of chimeras, among other developmental phenomena.