The Patchwork Human: Two Billion Years of Evolution
McFarland & Co., Jefferson, North Carolina
Tell us about your book.
Like an old quilt that has been put together from scraps of material collected over the years, we humans are a patchwork of old and new parts. We participate in the grand evolutionary story of life on Earth. Being made of cells, having a head with a brain and most of the sense organs at one end, having a body with symmetrical right and left sides—those are evolutionarily very old things, going back a billion years or so; we share these traits with lots of creatures. Somewhat newer, from a few hundred million years ago, is our use of sex for reproduction and our growth from an embryo. Using a placenta, making milk for our offspring, being warm-blooded, and having fur are traits we share only with other mammals; they are newer, having originated about 70 million years ago. Walking upright, losing most of our ancestral fur, using our hands to make weapons and other tools, becoming highly social, altruistic, and cooperative—these are relatively recent traits, from only a few million years ago. Finally, we have language, music, and religion, and we’re divided into races; these features appeared only when our Homo sapiens ancestors became fully human, just two or three hundred thousand years ago. And what about the future of our species—stasis, change, or extinction?
What inspired you to write this book?
The inspiration for this book came from years of teaching and interactions with students—all of us wondering where we came from, why are we the way we are, and how we fit into the whole pattern of life on Earth.
Is there anything socially/economically significant about the overall message of your book?
If there is anything significant about the overall message of this book, it is that our evolutionary origins make us who we are and that we belong to this planet in the same ways as do all other life forms.
What’s next for you as an author?
I’m working on a new book—about how we are more than our genes, that both in our everyday lives and in our evolutionary history, we are shaped by our environment.
The Patchwork Human: Two Billion Years of Evolution Excerpt
Who isn’t interested in that primal question, where did I come from? It would be easy to couch an answer in scientific jargon as if it were inscribed on a stone tablet at the top of some mountain that can only be reached with the help of advanced education and technical training and by way of the narrowest of pathways from the plains below, where most people live. I’ve always preferred living on the plains, not so isolated from everyone else. For me, as for most people, explanations are better when they are simple. Therefore this book, while scientific in content, is as free of scientific jargon as possible. It is nevertheless based on “hard science”—not “hard” as in “difficult,” but “hard” as in “solid,” as the scientific articles and books listed at the ends of the chapters testify.
My grandmother used to make elaborate quilts, sewing together pieces of old worn-out clothing. Some of them would take years to complete. When an old pair of pants was ready to be thrown out, she would cut usable parts of it into squares and put them in a basket with other pieces she had collected. When she was in the mood she would take them out and start stitching them together, putting her work aside when she ran out of material that accorded with her sense of design. When enough old shirts or dresses or jackets or other material had accumulated, she would stitch the new pieces onto her previous work. At some point, she got the idea of making not quilts but clothing that could be worn.
Imagine that such clothing is not something we wear, but represents something woven into the very fabric of our being. We are that clothing, stitched together from old and new pieces by evolution.
It might seem that we are all of a piece, all the parts working together seamlessly to make us human. We could imagine that at some time in the past we were assembled in our present form all in one sewing session: this part from one basket, that part from another, a zipper here, a few molecular buttons there, and you have a human being.
However, this doesn’t describe even metaphorically how the human body came into being. Instead—as with any animal or plant—in early versions of ourselves now long gone, small modifications were made one by one during the course of evolution, until over time there gradually emerged a version different in many details from the original. At every stage during the long transformation, all the parts worked together, as they continue to do in the modern version. Some parts of the original remain more or less intact, while other parts have been transformed beyond recognition. The modern human being is a patchwork of old and new parts.
Our fleshy lips, for example, appeared only relatively recently, and are shared by no other species on our branch of the evolutionary tree. Other features have been around for a longer time and are not exclusively ours—fingernails instead of claws or hoofs are a trait we share with monkeys and other primates. Still, other features are very old indeed, ones we share with a very wide range of other animals—we share the trait of having hair with most other mammals including giraffes and mice, and we have four limbs, a trait we share not only with giraffes and mice but also with frogs and lizards and birds.
Of course, other species on their own branches of the evolutionary tree will have evolved their own sets of traits too, different ones, many of which will not be shared with humans at all, such as laying eggs or having wings. Those species will have to make up their own evolutionary trees for their own traits.