Hacker News Reader

Comment by dekhn | Hacker News Reader

Convergent evolution is a thing, it occurs, but it's generally considered super-rare due to the parsimonious assumption.

It's unlikely that the sequences of the two independently evolved proteins would be so similar; you also wouldn't see a chain of progressively similar hemoglobins as you moved down the gene tree to older ancestral organisms.

View on HN

I think even if there were convergent evolution in phenotype, the DNA and underlying proteins would likely be very different.

Well, there are functional constraints on binding iron, right? There would probably be some residues- spread throughout the protein- that in its 3D folded form, would have a similar orientation to allow for heme binding and controlled release.

> Convergent evolution is a thing, it occurs, but it's generally considered super-rare.

Not anymore - though it depends on what precisely you mean by convergence, of course. I highly recommend the new book Improbable Destinies by Jonathan Losos[0]

[0]https://www.amazon.com/Improbable-Destinies-Chance-Future-Ev...

By convergence, I mean in the sense that two independent organisms that did not share a historical character trait (in this case, a specific homologous gene) independently evolved an identical trait (a gene with provably no homology, but identical function) through the process of natural selection, with no information sharing via horizontal gene duplication.

This was argued out a while ago with stick insects that lost and then regained the ability to fly (several independent subspecies did this). A lot of people thought it meant the stick insects "completely lost all the genes associated with wing formation" and then "gained an entirely new set of genes that caused wing formation", but folks in the evo devo world believe- and I agree- that the insect never lost anything except a few regulatory domains that managed the expression of pre-existing components that are depended upon by multiple other subsystems (IE, wings are composed of basis proteins that are used for many body parts).

My interest is in molecular evolution, not full character traits, because those phenotypes are incredibly complex and IMHO beyond our current level of sophistication in analysis.

> By convergence, I mean in the sense that two independent organisms that did not share a historical character trait (in this case, a specific homologous gene) independently evolved an identical trait (a gene with provably no homology, but identical function) through the process of natural selection, with no information sharing via horizontal gene duplication.

I'm no expert and could be wrong but I think this is what Losos is referring to in his book. For example, "New and Old World porcupines do not share a common evolutionary heritage… The two lineages have independently evolved their quills from different, unquilled rodent species." Dozens of stuff like this. He goes into more detail with tropical island anoles, his field of expertise, and orients the whole discussion around Stephen Jay Gould and Simon Conway Morris's competing views on the overall paradigm of convergence.

See this NPR interview for a quick summary[0]. A key quote (which I'm not discerning enough to tell if it challenges your claims or if your claims are actually already in response to these claims): "the flood of molecular DNA data that has come forth in the last two decades or so has in many cases revised our understanding about how species are related to each other. And it has revealed that many species that we thought were similar because they're closely related, that they're not closely related and that their similarity is the result of convergent evolution."

https://www.npr.org/2017/09/07/549250035/biologist-jonathan-...

Sure, I'm not going to complain about things like quills being an example of convergent evolution. those two porcupines aren't the same species- they were ad-hoc clustered together based on phenotypic similarity. But if you investigated, you'd seen huge differences in the sets of genes required to grow quills.

There's nothing surprising or interesting about that- spike shapes are common in nature and probably fall out of basic genetic evo-devo rules naturally.

> Convergent evolution is a thing, it occurs, but it's generally considered super-rare

Not if you're a mossy frog -

http://fuckyeahconvergentevolution.tumblr.com/post/839362577...

do you have a link to an actual article I can read?

Reply on news.ycombinator.com