David P. Mindell at Reason: The conventional narrative for evolution is outdated. I am not casting doubt on the fact of evolution. I am saying that the way most people think of life’s story has not kept pace with new knowledge about evolution’s many and disparate paths.
The short version of the conventional narrative describes life as one big family linked by common ancestry. All of us, from bacteria to kelp, condors, and people, are fellow travelers through time, sharing our deepest and oldest roots. In this narrative, the path of common ancestry is a sprawling series of splitting events. A single species splits to become two, and those two species become four, which become eight, then 16, then 32, and so on, with bifurcating branches for millions of species. In this view, the course of common ancestry is diagrammed as a tree, with dividing branches denoting species, and is linked to the process of natural selection, which favors those individuals and groups enjoying greater reproductive success. As Charles Darwin wrote: “The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth.”
The change in evolution’s narrative that I advance here emphasizes the sharing of genetic materials among different species, and a greater role for the influence of species on their mutual genetic change. I use “horizontal evolution” as a broad umbrella term to cover the various processes for this genetic integration among life forms.
In vertical evolution, genetic material passes from parents to progeny. By contrast, horizontal evolution often entails transfer of genes that is not from parents to progeny. Most of us don’t know much of the copious evidence coming to light for horizontal evolution, even within our own past: It is buried in our genomes, a result of events ranging from ancient horizontal gene transfers from viruses to relatively recent hybridization among different species of Homo. The bias of our experience makes it easy to miss the radical plot twists that horizontal evolution knits into the narrative of change.
By taking both horizontal and vertical evolution into account, we can understand the phylogeny for all of life, the overall pattern of genealogy, as a network. This network resembles the tree familiar to us from the conventional model of evolution, but it adds horizontal connections among branches, as species alternately diverge and integrate.
How Evolution’s Narrative Evolved
Ötzi, also known as the Tyrolean Iceman, was born about 5,300 years ago and died, apparently murdered, at the age of 45. With graying brown hair and a thin beard, his five-foot-four-inch, 110-pound body lay frozen and well-preserved in a glacier for millennia. He was spotted by hikers in 1991 high in the mountains along the Italian and Austrian border, as his icy crypt melted.
More here.
