September 13, 2012

A Mechanism for Macroevolution

The recently discovered epigenome is the key to how all evolution has happened, I hypothesize. According to all that we now know, and my proposed theory that the first life on earth contained all the genetic codes for all the kinds of living things today, major evolution would naturally happen without invoking other unknown mysterious mechanisms.

How? Well, first let’s talk briefly about the epigenome. The epigenome is apparently the surrounding chemical environment in which the genome rests. The epigenome influences which genes get activated and which lie dormant. That is, simple chemical changes can influence gene expression. Furthermore, the epigenome gets passed from parent to child, resulting in customized changes to the expression of genes based on the actions and environment of the parent(s). This means that environmental changes influence gene expression for multiple generations. If there is a persistent environmental change, or if there is a persistent behavioral change, there would be a persistent change in the active genetic instructions (genes) for an organism. In other words, there would be some adaptation or evolution based on environment or behavior. We see this adaption all the time today. For example, the beaks of birds on the Galapagos Islands change rapidly in response to the environment. This is an adaption via the epigenome, I believe.

There’s one more important piece of the puzzle. If unexpressed genes remain unexpressed for many generations they can be permanently removed from the genome. Thus, purely environmental changes, causing changes to gene expression as explained above, can result in loss of information to an organism’s genome. An example of this is cave fish that have lost their eyes due to the darkness that renders them useless. The dark environment affected the epigenome which caused the genes for eyes to become unexpressed, and in some cases eventually resulted in the genes being discarded as unneeded.

Now, back to the question of how major evolution would happen naturally through the influence of the epigenome. If the original life on earth had huge amounts of information for all kinds of designs, where something like only 1% was being actively used initially, then the epigenome would result in new gene expression with new designs springing up. A single cell could spontaneously become a multicellular organism because of chemical changes that resulted in new genes becoming activated. If that new multicellular organism remained multicellular for many generations, then it could lose genetic information and its ability to evolve back to a single-celled organism. The change would be a permanent genetic change. The evolutionary leap from single-celled to multi-celled organism then could be explained by the influence of the epigenome—by purely environmental changes. Similarly, if the environment became sufficiently cold, chemical changes in the epigenome might cause a dinosaur to start producing feathers (a previously unexpressed genetic code) for warmth. If the new feathered dinosaur started using those feathers to fly, the behavioral change might result in the feathers becoming a relatively permanent feature. So, the affects of the epigenome could be responsible for the development of the wings of birds.

In fact, genes activated by the epigenome could be self-perpetuating if the genes caused behavioral changes. Those behavioral changes might result in chemical changes that caused the epigenome to remain changed. The persistent change to the epigenome would result in a permanent genetic change if the genome ditched the unexpressed genes.

Finally, it is important to note that these mechanisms for major evolutionary change require sophisticated preexisting information in the genome. It also is important to note that this would be a one-way street: major evolution could only happen for so long before the new genetic information would be exhausted and unused genes would be discarded by organisms. All species would become genetically unique and unable to evolve significant new designs requiring new information. That is why we do not often (if ever) observe macroevolution today. We are only talking about evolution by the loss, reorganization, and selection of already existing information. Complex designs simply should not arise by randomness so frequently as we see in Nature. Some organisms, by the way, would reach this point of genetic exhaustion before others. That is why we see some “living fossils” that haven’t changed significantly in many millions of years. Such organisms have long ago discarded their unused genes and have become relatively unable to evolve.

(That leaves us with several interesting questions. What caused some organisms to ditch their unused genes quicker than others? One possibility is that a more stable environment might cause this to happen quicker. How could the totality of genetic information be preserved for a few billion years before complex life arose? One simple answer to that is that the code for discarding unused genes was not activated until sometime before the Cambrian Explosion.)

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