Talk:Basal (phylogenetics)

Examples

"it has had more time to evolve" - that phrase needs reworking. I don't have the time now, but it needed mentioning. I think this is a good start. I came here from the page on Mockingbirds. Your examples relating humans and plants may make perfect sense to a professional, but this layman's mind has to stretch way too far to place plants and humans on the same clade. Couldn't you choose a clade within vertebrates, or synapsids or something? Who's basal in human evolution? I am merely a bird loving artist who stumbled upon this article--but I feel it's an important bit of info that could be better explicated to the layman. And, as a luxury, perhaps having links to creatures that are considered basal would be illuminating.Francis Smith (talk) 01:31, 12 April 2009 (UTC)

Wow, you said that rather nicely. Please, in the future, feel free to just edit out anything you see that is that bad and confusing for the general reader. --KP Botany (talk) 03:33, 12 April 2009 (UTC)

The abuse of "basal"

Okay, so we've all done it (even I've done it), but this notion of a terminal taxon being "basal" in a tree is a common terminological abuse. The base of a tree is its root. None of the terminal species in a cladogram can be said to be basal, that's why they are terminal. The term "basal" simply means towards the root of the tree. Consider the cladogram used in the example:

	Basal group
	Non-basal group Non-basal group Non-basal group Non-basal group

Suppose we simply collapse the "Non-basal" terminals and add an outgroup. We get:

	Outgroup
	Basal group Non-basal group

Which side of the tree is basal now? Neither. That's because all nodes in a cladogram are rotatable. In both cases, the correct way to report the topology is that "Basal group" is the sister group of "Non-basal group". The reason is because we're not actually justified in calling it "basal" any more than we are justified in calling it "primitive". In fact, both terms implie exactly the same thing anyway—that the taxon in question is somehow exhibiting more ancestral features. This is certainly not the case. It simply happens to be a smaller clade and may or may not have a greater number of apomorphic states.

Please see: Krell, F.-T. and Cranston, P. (2004). "Which side of the tree is more basal?". Systematic Entomology 29 (3): 279–281. doi:10.1111/j.0307-6970.2004.00262.x. The Braz (talk) 12:06, 2 November 2009 (UTC)

I totally agree, although I don't see "basal" ever going away. I've yet to see a situation where the meaning of a sentence including "basal" could not be expressed more precisely with "is the sister group to", "is the outgroup to", "is not a member of the clade X + Y", "has the plesiomorphic state of character Z", and so forth.--Curtis Clark (talk) 14:30, 2 November 2009 (UTC)

Indeed, these are all better and more precise alternatives to "basal". I also agree that the terminological abuse is unlikely to go away soon. Perhaps the article could be re-written to explain what "basal" actually means, and the present text used as an addendum to explain what people often mean by it.