Out of Thin Air
12-19-10
The origin of man is perhaps the most hotly debated topic in history. Over the years religionists, scientists, philosophers, kings, and fools have all participated in the fight, each drawing different conclusions. I believe the answer is reasonably simple, and with only a little effort we can riddle out the source.
The human body is about 89% hydrogen and oxygen (either as water or locked into hydrocarbons/carbohydrates), 9.5% carbon, and 1.5% other trace elements (mostly nitrogen)[1]. The hydrogen, oxygen, carbon, and other elements in our body come from what we consume; hence, “you are what you eat”.
If we set the trace stuff aside for a moment, we can ask, “what the heck are we eating that contains so much carbon, hydrogen, and oxygen?” The answer is incredibly simple. We eat plants and/or animals, and we drink water. Water is H2O, and directly provides a majority of the hydrogen and oxygen mass of our bodies. Plants are also derived almost entirely from the same three elements, mostly in the form of water and carbohydrates. Animals have a similar composition, mostly as water and hydrocarbons.
A lesser man might stop their journey here, and determine that he is a roast beef sandwich. We, however, will rise above our predecessors, and ask “where did our beef and bun get their carbon, hydrogen, and oxygen from?”
A quick look at the food chain simplifies our problem. Every animal, like us, eats plants and/or animals. Eventually, all meat is derived from water and plants. Serendipitously, this means we can ignore the animals entirely, and simply ask where plants get their mass from.
Plants, as it happens, come from the air. It is true. The photosynthesis process uses the energy from the sun to break apart 6 carbon dioxide (CO2) and 6 water (H2O) molecules, then recombine them to form 1 glucose (C6H12O6, a carbohydrate) and 6 oxygen (O2) molecules. After water, basically the entire mass of the plant is either glucose, or a derivative, and the glucose is made from water and the carbon dioxide in the air (by mass, mostly from the air).
At this point we might conclude that since plants come from thin air, so do humans. We would be right, but for the wrong reasons, since we have failed to ask where the water and air came from. This comes back to hydrogen, oxygen, and carbon. Under appropriate conditions, carbon dioxide and water form readily from their component elements. The overwhelming majority of oxygen is a byproduct of helium fusion in massive stars[2]. Carbon is also formed by a similar process, requiring the collision of 3 helium nuclei, which (for all practical purposes) can only occur in large stars[3]. The helium in each case was formed by the fusion of hydrogen in these stars.
In other words, scattered across our universe are many sextilions of stars, each is an incredible factory churning raw hydrogen into the elements from which we derive our flesh. A portion of these stars will end their lives in an incredible explosion, distributing these elements, which eventually coalesce into new stars and planets.
Our bodies are made from the bits of a billion stars, burning balls of gas who ended their lives to begin ours; exploded, reformed, and exploded again, until those bits finally rested here, the essence of the Earth, and essence of every plant and animal that lives on it.
It is difficult to imagine a more impressive origin for man. The religionist will conclude that this is the ultimate proof that we are children of God, who must have understood the inevitability of this when first creating the universe, and who therefore, in effect, clearly created us. The scientist will determine that “The cosmos is full beyond measure of elegant truths; of exquisite interrelationships; of the awesome machinery of nature” (Carl Sagan). Philosophers may conjecture that we are a part of the universe, just as the universe is a part of us. Kings may find a reason to believe in the transcendence of the common man. We need only pity the fool, for whom “alas, it [is] very, very deep, And so he [sits], and [falls] asleep” (Kismet, The Olive Tree).

http://www.xkcd.com/793/
…And Nate concludes that we appeared out of thin air.
Of course, answering the question like this is just as unsatisfying as telling little Billy that he came from New York when the answer to his real question was “sperm meets egg.” The poor kid will grow up thinking “New York” is a magical land of parentless babies.
Of course, this makes the huge assumption that the laws of physics operate in the same manner throughout the universe as they do here on Earth….