On a recent walk with my husband made possible by my mother visiting for Christmas, we started talking about the impact of nature versus nurture. The subject has long fascinated me from a public policy perspective -- can social engineering permanently alter human nature? -- and more personally as a mother of two children, as in, does our parenting really matter?

The topic was in the front of my mind because I had just finished reading the recently released "Steve Jobs" by Walter Isaacson and started 2010's "Unbroken" by Laura Hillenbrand, about Louis Zamperini, a childhood delinquent turned Olympic runner with an incredible World War II survival story.

Both men's personalities explode from the pages and seem unmoored from almost everything their environment forced on them. Reading about Jobs, best known as Apple's co-founder, is like watching a car wreck as often as it is like hearing a symphony.

For all of his genius at churning out beautiful, functional products and imaginative movie masterpieces from Pixar, the man, who died earlier this year, was also mean and selfish to an extreme and practiced what can only be described as incredibly bizarre personal habits, including not showering, eating only one type of food for weeks at a time, and refusing to get license plates.

Nothing in his middle-class background spoke to his singular success, other than the deep love and deference his non-college-educated adoptive parents showed toward their unusual son.

Likewise, Zamperini's parents could not control their son. Hillenbrand writes: "From the moment he could walk, Louie couldn't bear to be corralled."

Most children do not turn out to be world-changing inventors and artists or awe-inspiring athletes with incredible personal courage. But their stories raise questions about the role parents play in their offspring's success, especially in this era where many middle-class parents aspire to "tiger" status, pushing their children incessantly from an early age. And ultimately, their lives raise questions about the impact of genes in shaping who we are and how we turn out.

George Mason University economist Bryan Caplan compiles a hefty ream of evidence on genes' behalf in his 2011 book, "Selfish Reasons to Have More Kids." As he shows, study after study reveals intelligence has very little to do with environment and a lot to do with genes. Likewise, so does happiness, how much money children make when they grow up, and criminal behavior. The list of things parents have little control over extends to character and religious and political "attitudes and behavior" -- even if they do have significant control over the label a child chooses in those categories.

Caplan uses the evidence to try to persuade people to have more children, worry about them less and enjoy them more. Of course, that is easier said than done. And no study is going to make me reprioritize parenting from first place. But it's useful for everyone to know that engineering of all sorts, parental and political included, does not have the potential to change human nature, no matter how diligent the effort.