The understanding that we are essentially collective intelligences – real Selves, but composed of smaller competent agents (not passive parts) has many implications for the notions of “life” and “death”. Some of these are covered in this paper. Here, I wanted to draw some connections between an interesting development in cell biology and recent work in synthetic morphoengineering.
An exciting new research area is emerging – the thanatotranscriptome. In brief, cells from a human or non-human animal, at death, start to turn on expression of specific new genes. Why do cells turn on new genes? Why these specific genes? What, if anything, do they do? What is the evolutionary significance of this? Is it adaptive, or a side-effect of some other aspect of animal biology? There is an excellent team of scientists studying these and other questions; find their work here:
I have an idea about why this occurs. I think the cells are preparing for a new life – in another world, at another scale. In the case of aquatic animals, this expectation is not at all crazy. For mammals and birds, it’s quixotic, with realistic expectations not having caught up yet with their change of environment. To understand the idea, consider the following.
Imagine yourself on an interplanetary expedition, investigating an aqueous world that harbors life. There are multicellular creatures, and amoeba-like ones. Eventually you learn to sequence their hereditary information, and are stunned to find out that some of the single-cell life forms have precisely the same genomes as some of the complex vertebrate-like animals, which also matches that of a set of primitive multicellular forms with diverse blob-like anatomies. How can that be? Upon further study you discover an aquatic animal with a surprising life cycle. They develop from an egg and undergo embryogenesis to become a complex multicellular body. They live a full life, moving and reproducing through their ecosystem. However, upon death, something remarkable happens: as the body falls apart, many of the individual cells disband, dispersing to move out into the environment to continue their life as amoebas. You find that these amoebas can eventually also merge together (having recombined with others they encounter, like slime molds do) and form a new kind of primitive multi-cellular aggregate. At the same time, some others activate reprogramming factors to become oocytes, eventually becoming fertilized and initiating embryogenesis of the complex anatomical form.
I don’t know if this cycle occurs naturally with any life form on Earth, but the pieces of it exist and it’s interesting to think about what it means for the concept of “death”. While an organism dies, the individual cells could live on. While initially surprising, there is nothing inherently impossible about such a life history. Vertebrate bodies already contain a number of amoeba-like cells (immune cells for example), and we culture explanted cells in liquid media (ex vivo) all the time. One can easily imagine an evolutionary advantage to lineages with cells that, although capable of cooperating in a multicellular form factor, continue their journey through the world as unicellular organisms when the body is no longer viable as a whole. Perhaps they turn on some oncogenes (becoming partially “transformed”, like some cell lines), and turn off adhesion factors and gap junction proteins, to become solitary beings with unlimited proliferation potential. More generally they may revert to a more ancient unicellular transcriptional program, as cancer cells do. The unicellulars in the story above exploit the kind of niches in which amoebas flourish on Earth, but can also reboot their multicellularity by aggregation into novel functional, anatomical forms.
We actually do have two real examples of relevant phenomena. The first is the Xenobots: synthetic living proto-organisms made from frog epithelial cells; you can see them at our Institute web page. Xenobots can be created from a dissociation of cells in an early frog blastula. In that case, the original organism is no more. The individual cells live on, and eventually can get back together into a multicellular form that swims, reacts to stimuli, builds copies of itself from loose epithelial cells provided to it, and has other behaviors. They can live for weeks, if fed, undergoing changes in body structure.
The second are the Anthrobots, discussed in a previous post. These are made from lung epithelial cells of human adult donors – about as far from amphibian, embryonic sources as possible. They too result in spherical, self-motile little creatures with several discrete behavior types and the ability to heal neural wounds. In this case, they can be made from tissue from living patient biopsies, or from donated tissues post-mortem. In the latter case, it is again an interesting example of a (in this case, human) organism living on through its cells when the original embodiment has dissolved.
There is one key difference between Xenobots and Anthrobots. Xenopus cells, could, with minimal changes, complete the transformation on their own (after the death of a tadpole for example). But the human lung epithelium cells cannot – there is no way they will survive in the non-aqueous environment of their mammalian host, once the body dies. They require a death doula, in the form of a bioengineer, to transfer them from their former embodiment to their new world. The problems they will solve – physiological, transcriptional, metabolic, behavioral – will be different than their former lives. And the scale of organization of the cells, and then the bots, is different than their prior embodiment. But they do live on.
Continuing the vignette above… You decide to test these animals’ cognitive capacities and notice that they can learn in associative and instrumental training assays. Using simple surgical transplants, and exploiting these animals’ Axolotl-like regenerative capacity, you then find that you can transfer their memories (e.g., association of specific colors with food) from a trained donor to a naïve host by transplanting brain tissue or even extracts (both of which has been done, see references 24-27 in this paper). Likewise, you find that the individual amoebas can learn in simple assays, as has been shown for slime molds on Earth.
You wonder: would amoebas resulting from a trained body’s death retain the information as individuals? Conversely, would an assemblage of such individually-trained amoebas result in an organism that remembered the in- formation? Could learning be propagated between cells, and could the information transcend levels of organization between single cells and a whole organism? Could a collective synthesize individual, simple memories of their cells into a compound, complex memory for the whole? Whose memories would they be? What happens if two cells with different memories (say, positive and negative associations with a specific stimulus) joined into a single body – what is it like to be a creature whose parts have distinct views of the past and thus of their world? Could some human somatic disease and psychological disorders be due to something like this? Should true memories of an associatively-trained animal be considered false memories in the host that inherits them via transplantation or aggregation, since that Subject has never actually experienced the association they now remember? Could genetically-engineered lines of fish or frogs be made with circuits that cause cells to disengage from each other and turn off replication limits, once they detect the cessation of heartbeat or brain signals in the host – resulting in a weird kind of immortality for these animals? These are all questions that we can now address experimentally, to track the flow of information – both morphological and behavioral – as it flows through the impermanent, plastic, fluid constructs we call bodies. Planaria are especially a great model because fragments of planaria are viable and immortal; planarian tissues can be transplanted and the worms can be trained to form memories. So much to do.
There are way more questions than answers about these fundamental issues of embodied minds and the active information that animates them. But one thing is clear – there can be life after death, it just takes on new forms.
Featured image by GPT-4. Life cycle figure image by Jeremy Guay of Peregrine Creative.
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