How to Grow a Human by Philip Ball

Author:Philip Ball [Philip Ball]
Language: eng
Format: epub
Publisher: HarperCollinsPublishers
Published: 2019-05-19T16:00:00+00:00

We know these three scenarios already. They are the images, the dreams and nightmares, of legends and fiction: (1) takes us to the Island of Doctor Moreau; (2) shows us King Minos’s wife Pasiphaë, under Poseidon’s enchantment, mating with a bull to spawn the Minotaur; and (3) is the Centaur.

Kobayashi and Nakauchi present this list of possibilities in a paper called “Revisiting the Flight of Icarus”, for they suggest that by designing and fashioning for himself wings “to achieve his ambitious goal of flying”, Icarus was “chimerizing” his own body by adding to it the desired part of another species. I guess they did not really know the myth – for of course the wings were made by Icarus’s father Daedalus, and not simply to be able to fly but in order to escape imprisonment by Minos on Crete. Daedalus was incarcerated by the furious king because he had made the artificial cow-structure within which the enchanted Pasiphaë hid herself to have union with the bull. Researchers in this field are likely to find themselves increasingly grappling with myth and dealing with what myth represents. So it might be wise for them to include among their reading lists not just Cell, Nature and Science, but Homer and Robert Graves.

Now, let me be clear that Kobayashi and Nakauchi immediately followed up their list by saying that they are confident none of these outcomes will ever be realized. There seem to be barriers, they say, that will limit such large contribution of cells, tissues and body parts from the donor in trans-species “xenotransplanation” experiments. Besides, there are various measures one can take to ensure that inadvertent colonization of the host body by the donor tissues doesn’t happen.

Perhaps. But not everyone feels that the limits of the possible (let alone the permissible) are so clear. Take a 2013 study in which the progenitor cells of human brain (glial) cells were grafted into newborn mice. When they had matured, the mice showed better learning and memory, for example in how to navigate mazes. This doesn’t mean that the mice had acquired more human-like cognitive powers – but the researchers suggested that the greater complexity and capabilities of the human glia stimulated neuronal processing in the mouse brain networks. In truth we don’t really know what has gone on in the mouse brains to produce these improvements in performance, but nevertheless it does seem fair to say that the presence of the human brain cells made the mice smarter.

I have seen experts on brain organoids talk with all seriousness about the prospect, although certainly not the desirability, of a brain made from human neurons grown inside a pig: a full-sized brain, blessed with a vascular system like the liver buds that Takanori Takebe has grown in mice. Again, consider it merely a thought experiment. What, then, should we think of it? What would a humanized pig think?

I’m not talking about a research proposal, and if anyone were crazy enough to suggest it, it would be rightly rejected.

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