[count-your-change]

An interesting feature of the cladogram in the article is that it depicts organisms splitting into just two lines, the original disappearing. But why would an ancestor of humans and apes for example, not split into humans, apes, and a dozen other creatures instead of just two?

[allmendream]

A cladogram depicts a branch point as a speciation event, where two populations diverged. A speciation event is where a subpopulation branches off, or a species becomes divided and starts to diverge, thus two branches.

And the Ape clade went six different directions at different times and places (six that survived as independent breeding populations); humans, chimps and bonobo-chimps, gorillas, orangutans and gibbons.

[GodGunsGuts]

Good question. I think the evos would crack that up to “purifying selection” or some such.

[metmom]

An interesting feature of the cladogram in the article is that it depicts organisms splitting into just two lines, the original disappearing. But why would an ancestor of humans and apes for example, not split into humans, apes, and a dozen other creatures instead of just two?

And why would the ancestor of humans, or any other creature, not survive along with the differing branches that evolved from it?

Kind of like the answer in the form of a question, *If Americans came from Europeans, then why are there still Europeans?*.

Funny how the evos want to have their cake and eat it to.

[Stultis]

An interesting feature of the cladogram in the article is that it depicts organisms splitting into just two lines, the original disappearing. But why would an ancestor of humans and apes for example, not split into humans, apes, and a dozen other creatures instead of just two?

It is a necessary character of cladistic analysis, and of the cladograms so generated, that all splits must be bifurcating. Three way splits are not allowed.

Also, regarding your comment about "the original disappearing," you are confusing cladograms with traditional phylogenetic trees. In cladograms the nodes, the splitting points, must not be thought of as being occupied by any creature. Cladistics rejects (or at least ignores) the idea of identifying "missing links." Instead it concentrates only on deducing evolutionary relations between contemporary groups of organisms. Another way of putting it is to say that it is impossible, in strict cladistic analysis, to posit or to figure "ancestor-descendent" relationships. You can only look at brother-sister, or cousin-like, relationships.

The nodes in a cladogram represent splits in character states, with the assumption that the given state is "either/or." Or, in any case, cladistic analysis compels you to assign an either/or analysis to the characters under consideration. For instance the split between apes and hominids (including human) is represented by the presence of absence of the trait of bipedalism. If it walks on two legs, it's a hominid. If it doesn't, it's an ape. There is, at least for the formal purpose of cladistic analysis, no in between.

One other factor is that all creatures on one branch of a node constitute a single group, and only those creatures. So, for instance, if you accept that orangutans split off from the other apes before hominids split off from chimps and gorillas, then (in strict cladistic terms) there are no such things as apes, at least as distinct from hominids and humans. (Either that, or you have to say that humans, together with chimps and gorillas, are a type of ape distinct from orangs. IOW humans are apes.)

By the same token there are no such things as "reptiles" for a strict cladist, since some reptiles branched off from other reptiles before mammals branched off from reptiles. Or, in traditional phylogenetic terms, reptiles are not "monophyletic" wrt mammals.

All this means that cladistics is impractical for many purposes, including generally useful classification schemes, were it often makes sense to allow polyphyletic groups, and other groupings which violate strict cladistic principles.