Our bodies are comprised of a vast array of elements, with oxygen, carbon, hydrogen, and nitrogen remaining the most abundant. But there are many other chemical elements present! The figure above lists each element that has been isolated from the human body in the order of decreasing mass.
This chart is based on the work of Ed Uthman, who derived the data from The Elements, by John Emsley.
Ever wonder why we are made up of the particular ratio of elements that we happen to be made up of? The answer may be very simple. Perhaps we are that way because the universe is that way.
First, head over to Wikipedia to check out the full list of the elements that compose the human body. You can sort each by the percent of all the atoms in the body it makes up, which I think is a better way to look at it. Here’s most of you:
Next, look at this chart of how abundant each element is in the universe, organized by percent (larger here):
We are made of pretty much the same stuff that universe is made up of, and in the pretty much the same proportions. Things like hydrogen and oxygen score highly because we are made up of so much water, of course, while in the universe at large hydrogen exists as the fuel for stars and oxygen is an overreactive nuisance.
There are some exceptions, like there always are. Helium for instance, is abundant in the universe as a product of hydrogen fusion, but its nonreactive chemistry is pretty useless to us. Same with neon, great for lights, useless for biology. And iron, for instance, falls a bit further down the list of “living elements” than it does the “universal list”, mostly because we only have use for its +3 oxidation state in biochemical reactions (sorry 2+!). And many of the low scoring elements in our body are just random tag-alongs from our food and environment, and would be toxic at higher levels.
Our experience with life is limited to one place: Earth. I wonder if the elemental composition of living things would follow this pattern, should we find it elsewhere? I think that it would. Biochemistry seems to write its recipes using what it has on hand, and the pantry of elements is stocked in a very particular way.
Do you agree? Are we that way because the universe is that way?