Big Question: Are all people created equal?

Curiosity contributor Susan Sherwood held this question up to genetic and environmental scrutiny and here's what she found.

In the U.S. Declaration of Independence, the founding fathers said it was "…self-evident, that all men are created equal." They were trying to make a political point, but were they accurate? The phrase used was, "created equal" -- not "considered equal." When it comes right down to it, regardless of the descriptor you use: Economically, socially, physically, intellectually, politically -- do we all start out on a level playing field? Are we, from the start, essentially the same?

Of course we're not. We’re talking genetics here, the most basic start for every human. Even identical twins, who, genetically, are the most closely linked of all people, have differences. Contrary to popular belief, they often don’t even have identical DNA, even though they came from the same fertilized egg [source: Scientific American]. They do not share the same fingerprints, and it is not uncommon for one twin to develop a disorder, such as Parkinson’s disease, schizophrenia or obesity, while the other does not. If identical twins are not always created equal, how can people, in general, be assumed to have equivalent early starts?

Environment also comes into play, because that can affect mental and physical health, even before birth. For example, a UCLA study examined the impact of air pollution on fetal development and found that high maternal exposure to environmental toxins can result in brain, respiratory and digestive problems. So if a mom lives in a smoggy city while pregnant, her baby might have difficulties that wouldn’t have arisen if she'd carried her child as a country dweller.

Nature doesn’t make anything the same: from snowflakes, to fingerprints to zebra stripes. Add environmental influences, and that assures humans will vary in intelligence, health, personality and abilities. So are people actually created unequal? Absolutely. You might even say it’s "self-evident."