Why I’m growing a second brain

Philip Ball in Prospect:

We’re used to thinking of ourselves as a finished product. The finish might not always be quite what we’d like, but it’s what we’re stuck with. From a single fertilised egg, we unfold in a progressive elaboration of cells and tissues until we come mewling and puking into the world. From there it’s a linear story that ends sans teeth, sans eyes, sans taste, sans everything.

But Shakespeare’s age-old narrative of decay, decrepitude and ultimately oblivion no longer works. We have the means to rebuild and replace failing tissues. I speak from personal experience. Over the past several months I have seen a piece of my flesh that was cut from my arm develop into a structure called an “organoid,” a miniature organ. In my case it has become a structure that some call a mini-brain: the size of a frozen pea, it displays many of the distinct features of a real brain that grows in a foetus. I’ve seen evidence that the neurons in such tissue can fire, signalling one another. It would be too poetic to call these signals thoughts, but they are the stuff of thought.

My flesh could have become something else, had the scientists so chosen. It could have become a kidney organoid, or one resembling a piece of heart or pancreas. It could have developed into light-sensitive tissue like that of the retina. And here’s the ultimate fact: it could have become an egg, or sperm, or something like an actual embryo, the beginnings of a being. It could have become any part of “me,” or every part. Here, then, is technology to stir tempting thoughts of cheating death, by replenishing the ailing body or even making a new, lab-grown self to “replace” the old.

More here.