John, shouldn’t we make an exception when there is a tree of few species and the fossil record has been sampled well enough that we start to have a chance of seeing the actual ancestor population in the fossil record? For example I think we can be reasonably certain that Homo ergaster (the African populations of Homo erectus) is actually ancestral to archaic Homo sapiens. If there were a different ancestor of us back then, we’d have found it by now. So putting H. ergaster at the tip of a side branch is not the right thing to do. I’ve seen people do that, but for the case of the human lineage it strikes me as too dogmatic.
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Yes, but whether that situation ever arises is questionable. I’ve heard it claimed for Ordovician snails, and that may be the best case. It’s been claimed for Caribbean bryozoans, but geographic sampling is questionable. I don’t see how it can reasonably apply to African hominids. Now, if H. ergaster had several specimens, each treated as an individual OTU, and it turned out to be paraphyletic to most of Homo, I would agree. Even a zero-length branch would be suggestive.
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Are there very strong candidates for direct ancestors for the modern human lineage? Yes, but we should be honest about what the science can support. Morphology just can’t get us there. I would strongly suspect that there were many people pushing for Neanderthals as our direct ancestors, but that was strongly rejected by ancient DNA sequencing.
We see ergaster all over the place about 2 million years ago, it’s brain size is halfway to sapiens and there’s nothing else that comes nearly as close morphologically. There are australopithecines, but they are morphologically less like us.
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Honestly, if they were all interbreeding, they would all be direct ancestors, right?
I was considering the direct ancestors of “archaic Homo sapiens”, who have large brain size and were ancestral to Neanderthals, Denisovans, and us. Those latter interbred with each other but that is not part of the story that I am focused on.
I don’t actually know how intensive the sampling has been. But that would be the case in which we could identify ancestors: if we are confident that our sampling of species was complete.
I’m not sure who “they” are in that sentence.
Can you explain why ancient DNA sequencing excludes Neanderthals as our direct ancestors?
DNA recovered from Neanderthals puts our common ancestor at 500,000 years before present.
Homo heidelbergensis is a popular candidate for the common ancestor of humans and Neanderthals, but again we can’t determine that from fossils alone.
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It seems that the current situation in paleoantropology is that the various hominin species can’t be arranged into a coherent ape-to-man progression. The reason for this may simply stem from the fact that man did not evolve from any Australopithecus ape, or any other type of apish like creature. Here is an alternative model proposed by Rupe and Sanford in Contested Bones, based on multiple branching trees rather than a single tree with single common ancestor of ape and man.
It seems to me that you not only aren’t knowledgeable or competent enough to make that assessment, but are also not knowledgeable, competent or skeptical enough not to be fooled by professional charlatans.
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Yes, as would be expected from a branching tree. Similarly, the horse fossil record doesn’t show a clear Eohippus to Equus progression, yet creationists consider horses to be a single “kind”. Creationists are nothing if not inconsistent. And no, it isn’t true that paleontologists agree that “there appears to be a clear seperation [sic] between the ape and human type”.
Sorry, but that’s just a picture they made up without any actual data to back it up. Right? Further, the evidence of common ancestry isn’t by any means confined to fossils; in fact fossils aren’t even the main evidence, and their scenario isn’t compatible with that evidence. You have to stop this selective credulity. Just because a creationist says it doesn’t make it true.
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Glad to see you accept DNA sequences as evidence for or against common ancestry. Ancient and modern DNA sequencing supports Neanderthals as ancestors to a few percent of our genome. In that sense they are (among) our ancestors.
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This response gives @Giltil too much credit. What he actually asked for in the analogy would be an Equidae to Equus progression.
You give him too much credit. He didn’t coherently ask for anything.
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For starters, obviously there can be no such progression by definition since we are apes.
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If he doesn’t like ape, then we can call it primate-to-primate progression.
What I was asking for (maybe not clearly enough) is whether the fossil record is best explained by the Rupe & Sanford’s model (based on multiple branching trees) than by the traditional evolutionary narrative (based on a single tree with single common ancestor of ape and man). And contrary to what you claim, as far as the fossil record is concerned, this is a perfectly coherent question.
A one-off side comment: We always get a better prediction by proposing a more complex model (multiple branching trees is multiplying the degrees of freedom). But more complex models are not always the better explanation. In statistics we have some quantifiable ways of making this sort of judgement. Informally it’s called Occam’s Razor.
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