In December, 2011, I read (and enjoyed) Nicholas Wade‘s sweeping summary of what we think we know about our lives from before we learned to write stuff down: Before the Dawn. Wade tracks the 50,000 year global human project using genetics to tie together many threads of ancient historical inquiry. I’m blogging about some of the chapters and ideas that stood out to me. Check out all my posts on this book here.
Before the Dawn: Recovering the Lost History of Our Ancestors
by Nicholas Wade
The title of this chapter could easily have been “Metamorphoses” (plural) because the deep time lineages leading to modern humans are a constellation of progressive refinements.
I use the term “progressive” since, in my own subjective view, I’m sitting here blogging on my laptop as a crowning developmental achievement. I understand that an Australopithecus might choose a different term.
Chapter 2 of Before the Dawn means a lot to me, because in it Wade narrates the long story of how modern humans arose from the long evolution of primates. I crave this sort of concise and clear description, and Wade focuses on the most fascinating aspect: development and changes in ape and early human society.
As readers of this blog should be aware by now, I’m also passionate about finding ways to visually represent parts of the evolutionary story of life on Earth through graphics, illustrations, art, and photography. It helps me understand what I learn, and I enjoy expressing what I learn in ways that might help explain it to others.
Nothing has been harder for me to communicate in a simple visual diagram than the evolution of human beings.
The branching tree of life is a brilliant construction for apprehending the long process of population change through inheritance.
But the tree can’t be “complete” in the way that my personal family genealogy is complete (with every individual identified in a precise genealogical position). The branching limbs on a fully detailed tree could never be perfectly straight and tidy. This is why evolutionary scientists have been saying for some time now that the tree of life is “bushy.”
Here’s my first half hearted attempt at trying to draw a picture of Nicholas Wade’s evolutionary narrative. I sat down with Chapter 2, and tried to visualize in one chart what Wade elucidates in his skillful writing. You can see from the resulting mess why I gave up before I was even half done.
What the... ??
I may take another crack at illustrating Wade’s narrative of evolving early human society. But there’s a reason he chose to communicate it in prose (and beautifully so!) The nuanced complexity of written language is what’s often required to communicate something so nuanced and complex!
If I do try another visual representation, it probably won’t be in a branching diagram of straight lines and connections. What we know from the fossil record of the species-by-species progression through human evolution is that there were many, simultaneous, overlapping lineages. Without DNA to sequence, or many more fossils, we simply don’t yet know the exact evolutionary relationships between all of the individual species. We’ve got a pretty good handle on how one genus may have given rise to another (or not), but the history that produced humans is astoundingly complicated.
18 months ago when I visited the breathtaking Hall of Human Origins at the Smithsonian Institution in Washington, DC, I was struck by the elegant way one exhibit represents our evolutionary past:
photo by Dave Huth
This is still a “tree” of life, but not a clear and simple linear arrangement of clean nodes and unobstructed pathways. The Smithsonian’s tree emphasizes its bushiness, arranging groupings of species by genus, and clustering them around a general timeline, but not attempting more in a single metaphorical diagram.
I’ve also found very useful the kind of “parallel bars” charts that are often used to represent the knowledge we have of which species lived when, without trying to link them all up in direct ancestral lines. Good examples of this are in a fantastic set of summary articles from an ongoing series of blog posts on the Biologos Web site. Biological anthropologist James Kidder, who runs a cool science and religion blog, includes the below chart in a post dealing with the genus Homo, found here: http://biologos.org/blog/the-rise-of-early-homo
© James Kidder, at Biologos.org
Scientists have assembled a thrillingly rich knowledge base about which creatures lived where, and when.
But which of the gracile line of Australopithecines broke out into the genus Homo? Did several interbreeding species give rise to one or more early Homo-like lineages that joined and split any number of times? The tree of life gives way to resembling more of a dynamic, flowing river in the complex, real world of speciation and ancestral populations. The closer you look the more miraculous and beautiful the process becomes. Over and over in the long sweep of time emerge new wonders and surprises, erupting from densely complicated interactions between living organisms and their environments.