Consider the complexity of the human genome. Three billion individual DNA "base pairs", 23 chromosomes, 200,000 protein coding genes and a whole lot of mystery. Now visualize a gargantuan encyclopedia of 23 volumes, three billion characters long, with only 1.5% of these characters spelling 200,000 "expressive" words.

With this in mind, it's not difficult to appreciate the level of diversity human genetics allows.

Today sees the airing of Marvel's Agents of S.H.I.E.L.D. - the first television series to take place in the "Marvel Cinematic Universe". This particular world is one of many that sit under Marvel's grand umbrella of comic book existences. Stack Marvel's collection of universes atop the universes of other superhero comic book publishers and the result is a series of complex and often convoluted modern mythologies, each containing myriad characters of varying abilities with their own individual history and lore.

But where does the fiction, the mythology of Marvel's universe start? And where does the truth, the real world inspiration end? Molecular genetics obviously hasn't featured in humanity's greatest myths and legends, but stories of humans performing feats above and beyond the accepted limits of human capability have likely existed since the dawn of language itself.

Every aspect of the human body and mind has some basis in genetics, and it's said that all myths have a basis in truth, so could the human genome allow for individuals with extraordinary powers? If so, what is the genetic basis of these amazing traits, and what do they say about human kind? Could we be heroes?

The ubiquity of "super strength" among fictional heroes is far from surprising. Humanity has celebrated the amazing physical feats of Olympians for millennia and still travel from across the globe to witness them lift immense weights, launch themselves over great distances and travel at incredible speeds. But do these men and women possess an "athletic" genetic profile predispositioning them to the growth of greater and more efficient muscles? Fortunately, the genetic basis of mammalian muscle growth is well understood, taking us to our first target, the gene MSTN.

A perfectly healthy boy with scarce body fat and body builder-like musculature.

Coding for the hormone myostatin, MSTN is responsible for skeletal muscle growth regulation in the embryonic stages of development and beyond. Myostatin itself binds to cellular "receptor" molecules, named activin type II receptors, which initiates a chain of biochemical reactions preventing newly formed muscle cells from maturing.

"Double muscled" cattle containing mutated forms of bovine MSTN have been selectively bred
for centuries for their 40% increase in muscle mass. The speedy whippet harbors a similar canine MSTN mutation and lab mice have been created with defective murine MSTN, resulting in the muscular "mighty mouse" strain. But could an MSTN related mutation lead to a favorable human trait?

Well, just ask Liam Hoekstra.

Born in 2005, Liam experienced a brief moment of stardom for his rare variant of an already
rare condition known as myostatin-related muscle hypertrophy - where a MSTN mutation causes increased muscle bulk. In Liam's case, his MSTN gene is normal, but his activin type II receptors are misshapen, hindering myostatin binding. The result? A perfectly healthy boy with scarce body fat and body builder-like musculature.

Unlike the action-oriented Agents of S.H.I.E.L.D. , Liam's contribution to mankind doesn't come from his actions, but from the insight his body gives on those with less favorable genetic makeups. In fact, research is already underway to create a myostatin inhibiting drug to help delay the effects of various degenerative muscle diseases.

Comments on