How would you come up with this estimation ? Do we have fossils of the last common ancestor of humans and chimps?
That is an important question independent of the other topic.
This is a good resource for someone at my level of understanding of paleoanthropology, which I assume is at about your level as well:
I wasn’t able to find in the resource you offered the answer to my question as to whether we have fossils of the last common ancestor of chimps and humans.
Some guy wrote a book that has a pretty good explanation of what it means to be the MRCA and how it can be determined when it existed even if you don’t know who it is. The book is called “The Genealogical Adam & Eve”. I just wish I could remember the name of the author…
How would we even know if we did?
And why would we need to know it?
Do we have the fossils of Adam and Eve?
You are the one who said that the fossil record offers us a good estimate of when the MRCA of humans and chimps existed, aren’t you? So I assumed you would know or bother whether we have fossils of this MRCA.
The earliest fossils that have a mixture of ape and human features appear around 3-7 million years ago.
Why would you assume that?
Maybe ponder the questions I asked, and you’ll understand better why that is irrelevant.
That’s a serious misunderstanding of how fossils can be used to determine the ages of ancestral nodes. Most simply, a fossil that’s more closely related to humans than chimps or to chimps than humans establishes that the common ancestor lived before the age of that fossil. One can try to estimate the completeness of the fossil record to put limits on how much older the ancestor could be. There’s no need to find the actual ancestor, nor as has been mentioned are we capable of recognizing ancestors and distinguishing them from collateral relatives.
You don’t need the fossil of the MRCA to do that
I am wandering how you could determine the age of ancestral nodes given that according to paleo-experts, the hominin fossil record looks like a tangled messy bush rather than a tree. Here is what Rupe and Sanford say in Contested Bones: « Paleo-experts attribute the messiness of the bush to luxuriant diversity. Every new species that is discovered has added more branches and twigs to the hominin tree making it even bushier. From the paleo-community’s perspective, this newfound diversity has totally obscured the fossil trail leading to man. They freely confess that no part of the hominin bush reveals an ape-to-man progression, with one hominin species evolving into the other.
Ah, yes. Two guys who know nothing about paleoanthropology cannot figure out how paleoanthropology is done. Well, that settles it then.
BTW, do these two guys who you just quoted as saying there is a “luxuriant diversity” of hominin species in the fossil record also say there is no evidence for human evolution in the fossil record? Just wondering.
But to try answer your question, though I’m also no expert: It seems to me a fairly simple thing to see where all the hominim fossils are temporally located, see where no such examples are found, and conclude that the MRCA is located somewhere in between. The more fossils you have, the more narrowly you can define that “somewhere”. A “luxuriant diversity” of fossils, then, allows one to define it fairly accurately.
That much is true. Try to stick to some coherent point and wander no more.
Why should anyone care what those fellows say? You have to stop relying on creationist literature. Haven’t you been paying attention to anything I said, including — astonishingly — even the bit you quoted just now? There is no way to recognize ancestors and thus no way to discern any linear progression. (There’s hardly even a way to recognize separate species, which is a concept hat can’t really be extended over evolutionary time anyway.) What we can do is put fossils into a tree. The age of any ancestral node must be at least as great as that of any descendent fossil. Will you read that this time?
You certainly are.
Why should we care what two people with no relevant expertise say? Shouldn’t we care about the evidence?
BTW, Derek Lowe has addressed your latest stab at spreading vaccine misinformation in great detail:
Why do you equate my concern about ADE with vaccine misinformation? Even Derek Lowe recognizes that « we most certainly need to keep an eye on them (the variants) ».
And here is a recent report that may support my concern.
Usually, when appealing to authority, one goes for a quote from an expert source.
If there is no way to recognize ancestors, how can we recognize that some fossils are descendent from an ancestral node?
By the nature of phylogenetic trees, ancestral nodes do not hold known fossils. Real taxa are at the tips of the tree, the terminal nodes. The terminal nodes are descended from ancestral nodes because that’s how trees are structured. Now, it’s possible that a fossil really does belong at that ancestral node, but again there’s no way to tell. Even if its characters are identical with the inferred state of the ancestral node.
By there being tree structure in the data. That is to say, by there being patterns in the data you expect if common descent was true and you do not expect if common descent is not true. It’s just another sort of indirect evidence. Like you can expect footprints in mud if a large animal walked across that mud. You don’t need the animal itself to have the expected evidence: footprints.
If common descent is true, you expect there to be certain evidence that otherwise should not exist if common descent is not true. So if you find this evidence you then have reason to think common descent is true. If common descent is true (which we think because we have the expected evidence: tree structure in the data), then fossil organisms must have descended from common ancestors.
Thus we can know that organisms we find as fossils(or are part of the extant biosphere) must have descended from “nodes” on the tree even if we can’t know that any particular fossil we find constitutes one such node.