Politicking about what is taught in schools and fronted in textbooks should start to morph into something more rational as key Darwinian assumptions are quietly abandoned. Get this:
Classic evolutionary theory holds that species separate over time. But it’s fuzzier than that – now we know they also merge…
In that southern California classroom, I told my students that once a species diverged from its ancestor – when it became unable to interbreed and form fertile offspring – those branches were separate, forever isolated. But, even as I spoke the words, I knew something wasn’t exactly right.
I was studying phytoplankton at the time. Single-celled creatures such as phytoplankton reproduce by cell division, which makes the question of what’s an offspring tricky. When you clone yourself, which one is the ancestor?
Graduate students down the hall in a microbiology lab regularly used viruses to transfer genes from one species to another. And gene shuffling wasn’t just happening by manipulation. I’d heard seminars about how different species of bacteria naturally perform a kind of sexual reproduction called conjugation, transferring genes from one to another. How did that kind of gene-hopping fit into the concept of a branching tree?
What I didn’t know then was that, even as I ambivalently placed the overhead film on the projector, the concept of the tree of life had begun to wilt. Four decades on, it’s morphed entirely.
‘That whole abstraction of evolution as being a tree, we always knew was a little inadequate,’ Rasmus Nielsen, a geneticist at the University of California at Berkeley and co-author of the book An Introduction to Population Genetics (2013), told me by video call. ‘But now we know it’s really inadequate.’Juli Berwald, “The web of life” at Aeon (April 5, 2022)
And she can apparently keep her job. Wow.
You may also wish to read: A physicist looks at biology’s problem of “speciation” in humans