The idea,  expressed In “Andrew’s Brain”  by EL Doctorow, that a complete record of past lives is recorded in the genome and that extinct species and even individuals may be brought back,  if one day scientists might figure out how to do this, isn’t as far-fetched as it sounds.  I remember learning about the discovery of the chemical structure of  DNA by Watson and Crick in biology class, and thinking how this could not possibly be true. What bothered me was that all of the instructions for the unraveling of an animal’s complex structure couldn’t exist within the confines of the nuclei of cells. Later, when I became more acquainted  with embryology carrying this informational content in such a small volume seemed more unsettling. Of course, I did convert.  Francis Crick ironically  was mainly writing about brain as the repository of memory over those years.

But it is much worse than I thought.  Now I come to learn that exons, the expressed, protein making lengths of DNA, represent, in highly evolved animals,  a small portion of the genome.  Some animals, humans in particular,  are burdened dark genetic matter (introns)  that isn’t even expressed. There are only maybe 25,000 protein expressing gene exons,  which are more than enough to specify a whole individual.  So much for human complexity. Then what is that other “junk DNA” that is unexpressed and why the effort to reproduce this stuff in every cell? Some of it does serve a function as regulator of gene expression and may be activated to make protein under certain circumstances.

Wonderfully illuminating for me was, “Endless Forms Most Beautiful” by Sean Carroll. You almost have to read it just because of the name. Carroll maintains that different animals and plants are not different by virtue of their genes. Amazingly fruit fly genes are very similar to chimpanzee genes. That was heresy compared to everything I’d been taught. Animals only differ due to having different genes, so I thought. Nope. Animals have much the same genes. Differentiation is by gene expression, which genes are turned on to make proteins and in what quantity. It was all about switches. Even more amazingly, in some cases, vastly larger quantities of DNA was the remnant of past genetic material which was not expressed.

This was revolutionary. When organisms diversify into forms fit for their environments they are not doing so by the standard evolutionary means, depending on mutation for gene diversity and hoping that by chance one or another mutation may make them more fit for a specific habitat.  I’d been taught that mutation was the grist for genetic diversity, but this was not precisely correct.  Organisms already carry the diversity of their ancestors from the past in their genetic material.   Should his environment change, the organism may find it possible to reach into his library or tool box,  ready made and pull something out, from his junk intron compendium, to now use, to adapt himself. This process speeds up evolutionary adaptation by orders of magnitude.  When you think about it, a lot of biological processes work this way. In speaking and writing, we depend on a compendium or toolbox containing words and phrases that we reach into which then help in expression and behavior is composed of these pre made  elements which again we may refer to as memory.  Our immune system, especially B-cells, reach into their own library of unexpressed DNA which may be under the right circumstances of antigen exposure, be recruited to make antibody from immunoglobulin diversity. Immune cells, like whole organisms carry within themselves their own store of inner memory. Stored but unexpressed waiting to be expressed, is incipient potential information, memory, a record of the past.

Recently the plight of the carrier pigeon has been prominent in the news, a species, now extinct, who sleeps with the aurochs. Carrier pigeons until the end of the nineteenth century numbered in the billions in North America. There are no living carrier  pigeons today because people slaughtered them in enormous numbers.  This has happened to many animals. Fear not, it will one day be possible to bring the carrier pigeons and all manner of extinct species back alive a la Jurassic Park.