Genes That Rise Like Dough

Mutation Is Not the Sole Evolutionary Mechanism

When we think of genome evolution, we typically think of the accumulation of mutations and variants within a gene that renders its function to be improved or altered and allows the individual to be better adapted to the environment and more likely to thrive. The outcome in ancient Humans (or I guess any other species for that matter) is that individual would be stronger and more likely to reproduce, and perhaps even produce more offspring that would ultimately carry the beneficial traits forward. We also know that this process can backfire and lead to weakening the genome and that individual historically would be less likely to thrive.  There are a number of circumstances in which mutation has not been the best way to “improve” the viability of the organism.

Gene Duplication Offers an Alternative Adaptive Strategy

One mechanism that frequently gets overlooked is gene duplication. If there is a gene that needs to be more abundant, that can be achieved by mutations in the regulation system to allow for the gene to be expressed at a higher level or for a longer duration (or all the time, something we refer to as constitutive expression), but the same result can be accomplished by having more than one copy of the gene.  The duplication of genes has happened throughout evolution in many organisms, and is a rather simple way of increasing the output of a single protein.

AMY1 Expansion Highlights Dietary Evolutionary Pressures

A recent example has shown that the increase in the amylose gene (AMY1), that is responsible for breaking down starches to generate sugars to be used for energy, was duplicated over 800,000 years ago and is found in multiple copies in Neanderthals and other ancient genomes.  In fact, the AMY1 gene has been demonstrated to have as many as 11 copies in the genome and a similar gene expressed in the pancreas up to 4 times.  That is quite a bit of genomic real estate to be devoted to breaking down starch.  This demonstrates the historical importance of starch as an energy source during evolution and how the increased ability to capture that energy was beneficial to survival.

Evolution Favored Starch Before Farming Began

One thing I find very interesting about this, is that the earliest record of duplication of the AMY1 gene pre-dates agriculture and the production of yams, potatoes, wheat and other starchy foods.  There does seem to be a coincident expansion of the number of AMY1 genes upon the development of agriculture, so perhaps this answers that age old question “which came first: the enzyme or the bread?”.  It certainly explains my absolute love of bread, so as I am enjoying my warm bagel with a side of hash browns tomorrow morning, I will give thanks for the expansion of my AMY1 genes, and then perhaps take a nap.