Let’s reflect for a moment, on what exactly we are made of. The four most abundant atoms  in our bodies are carbon (C), oxygen (O), nitrogen (N) and hydrogen (H) atoms, which together make up 96% of our body mass. Our conscious, self-aware brains allow us to further muse,  where did these atoms come from, and when were they made? In the case of H atoms, all  hydrogen (and most helium) atoms in the known universe were formed just after the big bang  around 14 billion years ago. In cosmological terms, all elements heavier than helium are  called “stardust” (C, O, and N atoms are thus all stardust). They are called stardust because  the atoms of these heavier elements can only be created in the cores of burning stars (suns)  by nuclear fusion processes of hydrogen and helium. These stardust atoms only get  released into interstellar space during the terminal red-giant phase of each sun, or during a final catastrophic supernova explosion. Thus, none of the C, O, and N atoms being produced  in our sun could have been incorporated into our human bodies, as all those atoms are still  part of our sun right now.  

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So how did all these stardust atoms get into our bodies? Well, by about 5 billion years ago,  one particular large gas and dust cloud had been collecting for the proceeding several billion  years. This was our solar nebula. This solar nebula cloud was composed of hydrogen,  helium, and stardust. It is estimated that between 1,000-10,000 older suns, located  throughout the milky way galaxy, had contributed to producing the stardust in this cloud.  Roughly 4.6 billion years ago, the cloud began to collapse under its own gravity and our sun  ignited. The rest of the planets of our solar system formed shortly afterward from the  remaining stardust cloud. Thus Earth, and everything in it and on it, is made from that  stardust. The C, O, N atoms in us right now range from about 5 to 8 billion years old, all  created in the burning cores of many distant stars. In every background image on this  website, you are looking at images of the stardust from which you are made. 

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On earth, by about 1 billion years later (3.5 billion years ago), the environmental conditions  and chemical makeup of earth enabled the first single cell life forms to emerge from this  stardust planet. The basic building blocks of life, such as DNA bases and amino acids, had  long been present, given what we now know about how these building blocks can readily  form from chemical reactions of our C, O, N, H stardust atoms in interstellar space. Natural  selection processes enabled life to become increasingly complex and colonize the water, land, and the air. Our ancient ancestors (small rodent-like nocturnal mammals living in the  shadows of the dinosaurs) caught a break 66 million years ago, when a large asteroid impact  snuffed out the dinosaurs, setting the stage for mammals to dominate the earth. By around 10 million years ago, the mammalian lineage that would give rise to both chimpanzees and  humans diverged from their last common ancestor with gorillas. By about 3 million years ago  genus Homo appeared, and over the next 3 million years about 12 species of genus Homo evolved. Currently, only Homo sapiens (us) remain.  

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What an incredible gift each of us has been given! The gift of intelligent life, made literally  from 5-8-billion-year-old stardust, gathered from thousands of suns throughout our galaxy.  Stardust that first emerged as life 3.5 billion years ago, underwent natural selection  processes, got help from an asteroid, and developed more and more complex brain  structures that finally sparked self-awareness. We can now stand here and look up at the  stars and understand we are made from them, and comprehend our path to where we are  now. What do we do with such a mind-blowing gift?  

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And we are not alone! We now know our solar system is not unique in how it formed. Most  suns have planetary systems. Life’s building blocks we expect everywhere throughout the  universe. There are hundreds of billions of suns in each of several hundred billion galaxies.  The majority of planetary scientists and astrobiologists now believe there is likely to be other  intelligent life in the universe (besides us). They are likely pondering the same gift and wondering how to react to it within their own planetary perspectives. 

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The Gift: What do we do with it? 

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One can choose to take this amazing gift for granted. If you do that you pass your time worried  about myopic day-to-day things that don’t matter much, and you treat people and their  situations with a general indifference. Yawn. On the other hand, if you treat the gift with  respect, and truly reflect on yourself (and others) as self-aware, 5-8-billion-year-old clumps of animated, intergalactic stardust - the world can take on a different feeling. Every day a  miracle. Every person an amazing thing, to be considered with dignity, respect, and wonder — regardless of political, religious or cultural differences between us. We are all... stardust. 

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