From Engineered Stem Cells to Consciousness

Network diagram of neural nodesToday’s brave new word is Sheefs – an acronym for “synthetic human entities with embryolike features” – that appears in a new Harvard Medical School report on the ethics of experiments with human stem cells. For the first time, biotechnologists now can engineer human stem cells so that they organize themselves into structures resembling the early stages of the spinal cord. It’s only a matter of time before they’re able to engineer these cells into tissues, functional organs, and more.

In “Addressing the ethical issues raised by synthetic human entities with embryo-like features”, lead author John Aach and his colleagues urge the research and bioethics communities to undertake a wide-ranging inquiry to address the ethical problems raised by these new capabilities.

For the past 40 years, human embryo research has been constrained by the “14-day rule”: scientists around the world have agreed that research with intact human embryos would not allow them to develop beyond 14 days (or the appearance of the “primitive streak”, a precursor of the spinal cord). They’ve followed the 14-day rule in part because they were unable to keep embryos alive for longer, but new techniques have emerged that could maintain the embryo for 20 days, well after the development of the primitive streak and other crucial anatomical features.

For Aach and others, Sheefs raise a host of ethical issues, in part because rules based on the time elapsed since fertilization don’t apply to embryos that weren’t formed via fertilization. For instance, earlier this month biologists at the University of Cambridge reported that they had injected two different types of mouse stem cells into a microscopic scaffolding, where the cells quickly began signaling, then organized themselves into the same structures found in an early mouse embryo. To start, they recommend that certain capabilities remain off-limits: no scientist should create Sheefs that might experience pain. They conclude that, “addressing the issues raised by SHEEFs will require research limits that are based as directly as possible on the presence of early forms of embryonic features that signify moral status.”

Coincidentally, this week’s issue of The New Yorker features a profile by Joshua Rothman of Daniel Dennett, co-director of the Center for Cognitive Studies at Tufts and the author of a dozen books on consciousness and the human mind. Dennett is firmly in the camp of the physicalists, who believe that science can explain consciousness in purely physical terms, as opposed to the dualists, who believe there is a non-physical aspect to human subjective experience.

Dennett starts with biology; molecules in the Earth’s primordial soup evolved the ability to make self-replicating copies of themselves, some with protective membranes, and life had begun. Rothman expresses it beautifully: “The tree of life grew, its branches stretching toward complexity. Organisms developed systems, subsystems, and sub-subsystems, layered in ever-deepening regression. They used these systems to anticipate their future and to change it. When they looked within, some found that they had selves—constellations of memories, ideas, and purposes that emerged from the systems inside. They experienced being alive and had thoughts about that experience. They developed language and used it to know themselves; they began to ask how they had been made.”

In this view, consciousness isn’t a binary capability that humans possess but other organisms lack. Rather, as we’ve evolved the brain has aggregated layers upon layers of systems that “sort of” feel, know, learn, decide and think. Human brains have more layers than animal brains, and in particular we have language, which endows unprecedented cognition and communication. We even have souls, but in Dennett’s view they originate in molecular processes that ultimately can be described by science. The unique experience of being you is generated by neurons.

Dennett talks about the various stances we take when describing different ways in which matter becomes functional. We move fluidly between taking a “physicalist stance” when talking about water flowing, a “design stance” when explaining how a bicycle works, and an “intentional stance” when interacting with software that seems to anticipate our moves. Crucially, we experience ourselves as intentional beings – creating thoughts, intentions and identity itself, while simultaneously remaining unaware of the physical machinery generating those higher-order properties.

We live amidst the overlap of these two worlds: the development of Sheefs rattles prior conceptions of our biological foundations, while Dennett and his colleagues assert there is no divine spark required for consciousness, even human consciousness.



Addressing the ethical issues raised by synthetic human entities with embryo-like features, John Aach et al, eLife, 21 March 2017

Daniel Dennett’s Science of the Soul: A philosopher’s lifelong quest to understand the making of the mind, The New Yorker, 27 March 2017

A New Form of Stem-Cell Engineering Raises Ethical Questions, Carl Zimmer, The New York Times, 21 March 2017