This is a great article! And this is beautiful:<p>> According to Gage’s theory, transposons may make such transformations possible; they may generate novelty, and therefore complexity, in a way that our genes alone cannot. If this is, indeed, why they are unsilenced during neural development, then our brains can be thought of as hosting a kind of evolution in miniature. Just as the beaks of Darwin’s finches are suited to different food sources, each neuron may develop its own specialty in the ecosystem of the brain. (Immune cells make use of transposons for similar reasons, exploiting them in order to generate a large range of antibodies to tag new intruders.)<p>But there's a key bit of missing context, selection via programmed cell death:[0]<p>> The importance of programmed cell death (PCD) during vertebrate development has been well established. During the development of the nervous system in particular, neurotrophic cell death in innervating neurons matches the number of neurons to the size of their target field. However, PCD also occurs during earlier stages of neural development, within populations of proliferating neural precursors and newly postmitotic neuroblasts, all of which are not yet fully differentiated.<p>[0] <a href="https://www.sciencedirect.com/science/article/pii/S0012160604005020" rel="nofollow">https://www.sciencedirect.com/science/article/pii/S001216060...</a>