Genes: Blueprints or Recipes?

Scientists are often asked whether genes act as blueprints, or instead as recipes, for human development.  According to NYU Professor Gary Marcus, genes are not blueprints, because there are simply not enough genes to describe exactly how each of our billions of cells should fit together.  Rather, he says, genes are part of "self-regulating recipes" whereby gene activity is designed to respond to environmental cues in the course of natural development.

Whereas I'm sympathetic to this line of reasoning, I still like the blueprint analogy, because it provides fewer and simpler variables for:

1. Transmission of discrete traits
2. Evolutionary selection

Human society is filled with specialized actors.  Some are brave, some are smart, some are leaders, some are followers.  The distribution of these traits is unevenly balanced, in order for society to run "smoothly".  (Smoothness and fairness are, of course, two different things).  In order for these traits to be balanced, bravery, intelligence, and leadership ability must be regulated by simple on-off switches in the genome, otherwise it would be too complicated to allocate and distribute these traits in specified proportions across society.

In other words, while there may be thousands of genes involved in specifying the "recipe" for a leader (how s/he reacts, responds, displays emotions, etc), there must be a fairly small number of genes that act as the blueprint or master switch, to enable one recipe over another.  One only need to do an online search for "single gene responsible for" and "scientists shocked/perplexed/amazed" to find genes like Bax that act as master switches.

Also, evolution of species would be more rapid (in the face of changing environments) if selection were made among a small number of variables.  For example, the genes responsible for the development of beaks on Darwin's finches may act as recipes, but behind these must exist master genes for selection pressure to quickly act upon.

Comments

[Craig]

Couldn't the model also be maximum variablity which allows for maximum chance of survival in the face of environmental change? Perhaps with fewer genes needed for change thus increasing chances of survival under massive change. This could explain how/why we have segments of genes from other species past and present and how they may contribute when we currently think they don't.

Think of these variables as expressed by a bell curve, with the current functional norm the middle of the bell and the current not so functional to non-functional expressions/possibilities on either side.

Think of sexuality (a polygenetic expression with maximum functionality in the middle of the bell)with variables on either end but not so functional in regards to reproduction. So we get the middle which is what we currently regard as "normal" heterosexuality, and then we have variations on either side which are a sliding variation or mixture of both with variable reproductive possibilities. IE: Very strong male or female traits in the middle (thickest portion)of the curve and then a falling off on either end both physically and psychologically. So we end up with hetero as the functional reproductive model and then variation on either end which may be men with more/less female characters and women with more/less male characters and also hermaphrodites expressing both, also variably.

Clearly we aren't simply male or female, there is a sliding variable on either side we can easily observe.

So beaks in the middle are currently the functional model and longer/shorter are on either side of the bell. Under environmental load the edges of the bell move closer to the center and the center either recedes (dies off due to the *new* lack of functionality) or if still viable it also may contribute to either side (like threshhold traits) of the new paradigm. This would depend on if the new paradigm is due to a new opportunity in the environment which leaves the current beak still functonal or if it is a more massive change making the current paradigm dysfunctional leaving only new one to reproduce. A lot depends on the rate of change in the environment.

Massive changes call upon the edges of the bell (variables) more than gradual change.