Wiki describes evolution as "change in the genetic material of a population of organisms from one generation to the next." Natural selection was originally proposed by Charles Darwin to describe how a species effectively adapts to the environment. Not so well known is genetic drift in which random events change the genetic material of individuals in a population. When those survive and propagate those changes forward, genetic drift results.
Neither of the processes infer that evolution necessarily results in a more desirable species. Reverse evolution discovered in Seattle fish explains that Lake Washington was heavily polluted during the 50s and 60s. A small fish, the three-spine stickleback, had adapted to the murky, polluted water. The National Geographic article explains the species had lost bony armor which historically protected them from predators. Now, after successful conservation efforts, the lake has become a beautiful body of water again. But the stickleback were exposed to predators such as lake trout. To survive, they have reverted back in time to their armor.
Reverse evolution in real time provides key insights into basic mechanisms of evolution explains some limitations of going back in time. Researchers adapted Drosophila (fruit flies) over 50 generations, dating back to 1975. (These would have been disco fruit flies. Sorry, my mind wandered.) Returning the current generation of Drosophila to the original environment of 1975, could not completely return the DNA to its original condition. The Science Daily article estimates only about half of the evolutionary changes could be reversed.
By resurrecting ancient proteins, University of Oregon researchers find that evolution can only go forward tells that evolution cannot go backward because paths to previous generations of genes are forever blocked. The Medical News today article explains that researchers studied the evolution of the glucocorticoid receptor (GR) which regulates gene transcription. The researchers identified seven mutations over almost 400 million years that changed its sensitivity from aldosterone to cortisol. With these mutations, they attempted to reverse the DNA back to its original state. They discovered it was impossible because other secondary mutations had occurred which prevented a retracing of the evolutionary path. The resulting protein was inert, or no longer viable. Essentially, they have discovered that evolution burns its bridges.
Mmm. Despite our expanding prowess in genetics, (and perhaps in defense from) seed vaults such as the Svalbard Global Seed Vault could potentially save an ecosystem. It seems we need a similar storage for the animal kingdom.
Comments