Dwindling justification for pessimism about front-loading

To front-load evolution is an attempt to design future states through the present. To accomplish this, future evolutionary events would be dependent on the originally designed state that “expressed” itself across deep time. This original state would thus function to facilitate and provide some guidance to subsequent evolution (illustrative examples are provided here and here and here and here). While one might be tempted to believe that millions or billions of years of evolutionary noise would drown out the design signal from the past, research in developmental and evolutionary biology indicates there is a dwindling justification for such pessimism.

Carol Kaesuk Yoon provides a useful summary of this research entitled From a Few Genes, Life’s Myriad Shapes. There are several excerpts from this story that can be used to highlight the growing plausibility of designing through evolution.

1. For starters, evo-devo researchers are finding that the evolution of complex new forms, rather than requiring many new mutations or many new genes as had long been thought, can instead be accomplished by a much simpler process requiring no more than tweaks to already existing genes and developmental plans.

Note that conventional non-teleological views of evolution came with an expectation – new forms would require many new mutations or many new genes. Yet what we now find is that because of the architecture of life, evolution instead tweaks and reshuffles what it was handed. If novel forms can be spawned by making minor modifications in already existing genes and developmental plans, then front-loading is clearly plausible.

Yet this need not be the case. The original thinking could have turned out to be correct, where novel forms required the spawning of an array of novel genes. Unless those novel genes were somehow front-loaded to appear, the thesis of front-loading would be fatally wounded.

This illustrates the simple fact that front-loading is a viable hypothesis not only because it increasingly fits the data, but because older, non-teleological views of evolution don’t.

2. Stranger still, researchers are finding that the genes that can be tweaked to create new shapes and body parts are surprisingly few. The same DNA sequences are turning out to be the spark inciting one evolutionary flowering after another. “Do these discoveries blow people’s minds? Yes,” said Dr. Sean B. Carroll, biologist at the Howard Hughes Medical Institute at the University of Wisconsin, Madison. “The first response is ‘Huh?’ and the second response is ‘Far out.’ ”

Once again, we see the non-teleological perspective did not prepare scientists for our deeper understanding of evolution. Evolution is largely about exploiting and tweaking what it was handed. As I write in The Design Matrix:

Despite the hundreds of millions of years of evolutionary tinkering in the three lineages that led to humans, flies, and worms, much commonality remains. In fact, when the mouse genome was sequenced and compared to the human genome, Eric Lander, Director of the Whitehead Center for Genome Research at MIT, commented, “as far as I can tell, [there’s] no significant difference between mouse and human. . . it’s basically the same set of genes, just tinkered with in little ways.”

In other words, we can think of humans, flies, and worms, all being built from the same genes, only that they are expressed and used differently. It’s almost as if you could take a mouse genome, reformat it, and make a human.

3. The development of an organism — how one end gets designated as the head or the tail, how feet are enticed to grow at the end of a leg rather than at the wrist — is controlled by a hierarchy of genes, with master genes at the top controlling a next tier of genes, controlling a next and so on. But the real interest for evolutionary biologists is that these hierarchies not only favor the evolution of certain forms but also disallow the growth of others, determining what can and cannot arise not only in the course of the growth of an embryo, but also over the history of life itself.

Here is an important theme to grasp. Evolution is not only constrained by the architecture of life, but it is this very architecture that suggests significant aspects of evolution might be under intrinsic control, as the arrangement of these hierarchies bias the variations that the blind watchmaker will see.

4. “It’s been said that classical evolutionary theory looks at survival of the fittest,” said Dr. Scott F. Gilbert, a developmental biologist at Swarthmore College. By looking at what sorts of organisms are most likely or impossible to develop, he explained, “evo-devo looks at the arrival of the fittest.”

Again, the arrival of the fittest speaks to intrinsic aspects providing the range of possibilities the blind watchmaker will see. In essence, the blind watchmaker can be guided, whereby the intrinsic features play the role of a seeing-eye dog.

5. Evo-devo has also begun to shine a light on a phenomenon with which evolutionary biologists have long been familiar, the way in which different species will come up with sometimes jaw-droppingly similar solutions when confronted with the same challenges.

Among the placental mammals of the Americas and the marsupials of Australia, for example, have evolved the same sorts of animals independently: beasts that burrowed, loping critters that grazed, creatures that had long snouts for eating ants, and versions of wolf.

Yet another piece of the puzzle falls into place. The commonality of convergent evolution not only supports the plausibility of front-loading, but may be a consequence of front-loading. It supports the plausibility of front-loading in showing the options available to the blind watchmaker are actually quite limited. It may be a consequence of front-loading because the biases introduced by the front-loaded state may indeed be a component of those limited outcomes.

So what might we have here? The structure of life facilitates evolution, evolution may be under some form and degree of intrinsic control, evolution merely tweaks what it is handed largely by reformatting genomes, and evolution draws similar solutions when confronted by similar challenges. Sounds like fertile ground for front-loading.

More reading

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