So, which of our 3 human clans (A, B and C) is “closest to the common ancestor of both groups”?
“Both groups” meaning the group consisting of A, B and C, and the group consisting of D?
Without a cladogram showing their interrelationships, it is impossible to say. Among reptiles, either turtles (unless they’re archosaurs) or alternately lepidosaurians are the most basal living reptiles.
Are you disputing the use of concepts like derived and basal clades in phylogenetic taxonomy?
I’m not disputing anything. I’m asking you a question.
Let’s use human family groups and see what the relationships are, per your analysis above.
There are two family groups that split off from each other in 1800: Let’s call them the Hatfields and the McCoys..
Within the McCoy clan, there is one group, the McDees, which split off from the rest of the McCoys around 1850. In 1900, the rest of the remaining McCoys split into 2 other groups: the NcFees and and the McGees.
Of the the 3 family groups, the McDees, McFees and McGees, which is more closely related to the Hatfields?
I understand the position that I’m more closely related to my uncle’s grandchildren than to this great-great-grandchildren. For those who are expressing that view, I have a question.
As previously noted in this thread, humans are most closely related to chimps, and the common ancestor of chimps and humans is most closely related to gorillas. Humans tend on average to have longer generations than chimps. Would you say that gorillas are more closely related to humans, because there are fewer generations separating humans from gorillas than there are generations separating chimps from gorillas? Or would you say that gorillas are more closely related to chimps, because gorillas are more similar to chimps?
If your position is simply that gorillas are equally related to both chimps and humans, you need not respond; I do not disagree with that view. However, if your position is that gorillas are not in fact more similar to chimps than to humans, I would be interested in your thoughts.
They’re all equally related. But the McDees are the most basal relative to their common ancestor with the Hatfields. I don’t think we disagree with each other, we’re just arguing across terms.
OK. I didn’t understand your interest in calling the basal group “closer” to the common ancestor. That seems to be the same as “most closely related”.
At this point it’s a question of terminology. Human generations aren’t quite the same as species evolution. Names aren’t biologically inherited characteristics, and of course species are basically ‘incestuous’, but you can use the name changes and marriages as analogies to mutation. Based on that, the closeness of ‘relation’ can be measured by the number of name changes. I had assumed this is what cladistics was doing. Am I wrong about that? My point was that within a clade, all nodes do not have to be equidistant from the root based on the number of changes. The tree of life is unbalanced.
Nodes within a cladogram are named arbitrarily; there’s nothing that says each node requires a name, and most nodes are absent from any given cladogram (that is, all branching events are not - indeed, cannot be - shown).
The thing to remember about cladograms is that each represents a testable hypothesis regarding relationships; they are not phylogenies in and of themselves. Cladograms can be, and often are, rewritten as more data comes to light. They are not always treated that way (including, admittedly, by myself). Further, cladograms are created based on the presence or absence of certain characters; the working assumption is that the more characters that are shared between two groups, the more closely related they are likely to be.
And that brings me to my claims in this thread: because my understanding of “relatedness” stems from this idea of shared characters, I (and others) have claimed that pretty much the whole of Sauropsida is equally related to us. By that, it is meant that each has the same number of characters that are in common with us as does any other member of that branch of amniotes. And, even though turtles are (possibly) the most basal of extant reptiles, they really don’t have any more characters in common with us than do crocodiles, tuataras, Komodo dragons, or peacocks. That is to say, no reptile is more like us than any other.
That certainly makes sense. I was thinking in terms of distance, as the number of changes, from the common ancestor. Clearly we and they (modern reptiles) are quite some distance from the common ancestor.