Yes, it is. We identify the individual based on the common descent of two samples from the same individual–crime scene blood vs. sample taken directly from the individual, or based on the common descent of the crime scene sample and a sample taken directly from a relative.
We just use different sets of markers for measuring different relationship distances.
But it is the same. And it doesn’t rely on specific markers at all. There are thousands of different markers that can be used, and only a small number of them are needed for an enormously statistically significant result.
Doesn’t that validate its use for different species and higher taxa?
But it certainly is the case for phylogenetic inference within the species rank, as for different populations. Doesn’t that validate its use for more distant relationships?
Can we agree on the fact that we don’t need to take any DNA from the common ancestor of two humans to determine if they are related?
Do you not see that if the alleged father won’t or isn’t available to provide a sample, that a sample from his brother or sister will be sufficient?
This is a line of reasoning that does not demand the conclusion evolutionists want.
YES we have SUCH like DNA with our parents/cousins etc that DNA can be used to prove relationship.
YET in common design it would be this way too.
We have like dna just because we are so alike in out bodies.
yet this doesn’t suggest a trail back to primates or any biological common descent with any life. Its just a special case.
We have like dna with apes because we have like bodies. Like parts from a common DNA blueprint. Yet we are not related as man was created with Adam/Eve. no primates in our heritage.
so my closeness in DNA to my father is only because of such intimate closeness of body parts. right down to tiny details.
yet its a further line of reasoning to say DNA is a trail .no need to look at it that way.
evolutionism is not proving a trail but presuming one. as usual!
The difficulty with this approach is we never know when the miracles stop, if they ever do, and nothing is learned. Maybe you can be happy with that, but I cannot.
When I was an undergraduate, I studied with evolutionary anthropologist Jeffrey Schwartz, at Pitt, who was famous (or notorious) for arguing that the orangutan, not the chimp, was our closest primate relative. My guess is, if we asked Schwartz into this thread, he would say just what Mung and I are saying: we trust the results of forensic DNA methods (in judging paternity, etc.) because we have independent means of checking our inferences against known lineages.
But the assumptions required to infer relatedness at several orders of magnitude greater genetic distance (roughly, ~60 years for commonly-employed DNA testing to ~6,000,000 years for Homo / Pan last common ancestor) guarantee that someone like Schwartz will dissent – precisely because we have no independent means of testing the assumptions. See, for instance, this paper by Schwartz and Bruno Maresca:
I realize folks here may not want to watch the Jeremy Brown webinar I linked above, but it’s genuinely instructive. Molecular data are NOT the royal road to the history of life. They are just as messy, and uncertain, as other forms of data (e.g., anatomical, paleontological). We do not know the history of species; we infer it.
And any time one infers, one employs assumptions. The greater the distance, the higher the probability the assumptions are wrong.
If all we had to go on was Human DNA and chimp DNA to infer their common ancestry you might have a point. But we have a huge amount more evidence than that. We have sequenced the genomes of thousands of extant creatures and seen the clear branching nested hierarchy signal indicative of common descent. We also have the fossils of hundreds of thousands of extinct species which also show the same clear branching nested hierarchy signal indicative of common descent. The molecular clock may be inaccurate as to the timing of the human-chimp last common ancestor but there is no scientific doubt at all they did share common ancestry.
It’s embarrassing to hear a science professional using the bog standard Creationist tactic of demanding we look at each piece of evidence separately instead of viewing all the data as a consilient whole.
If the nested hierarchy signal from molecular data and fossils is so unambiguous, why does Schwartz argue that the orangutan, not the chimp, represents our closest primate relative? Or maybe I should ask, HOW can Schwartz take that position? (I would be happy to send you the full Schwartz & Maresca paper as background: contact me at nelsonpa@alumni.uchicago.edu)
I live daily in the literature of molecular systematics. Data conflict there is omnipresent, so you will understand why I discount your claim that a “clear branching nested hierarchy signal” exists.
Does Schwartz argue humans and chimps don’t share a common ancestor? Like I said, the timing of the human chimp LCA does not invalidate all the evidence there was a human-chimp LCA.
Because Schwartz is stubborn and doesn’t want to give up on his theory even though all of the evidence is against it. Scientists are human, too.
If by conflict you mean a lack of an absolutely perfect correlation, you would be correct. However, I have yet to publish a paper where I have perfect correlations. In fact, if I see a graph with an r^2 of 1.00000 I tend to distrust it. What you don’t seem to recognize is the statistical significance of the phylogenetic signal. Yes, there is noise. In fact, if what we understand of evolution and biology is correct then there should be noise. This doesn’t change the fact that there is a statistically significant phylogenetic signal.
That is absolutely false. Common descent is the hypothesis that is being tested, not an assumption. If the phylogenetic signal for the distribution of shared DNA and shared morphology is not statistically different from a random distribution then common ancestry is disproven. That’s the test for the hypothesis of common descent.
The question is not the timing; it’s the branching order.
There is only one true history of life. I have six siblings (two sisters, four brothers). I’m the oldest male. There CANNOT be a true history where I’m not the oldest male in my family. Likewise, if Schwartz is right, the (human) chimp)) gorilla))) branching order is false. Now, Schwartz himself may be mistaken – most of his colleagues think he is – but the fact that his human-orang clade can be published indicates that the unequivocal signal you claim isn’t anything like unequivocal.
If one claims, as you do, that a fully consistent nested hierarchy exists, supported by multiple consilient lines of evidence, then the actual published conflicts in molecular data, described by Brown (in the webinar linked above) should not occur.
You forgot to answer the question. Does Schwartz argue humans and chimps don’t share a common ancestor? Does he think the data shows their common ancestry? A simple YES or NO will do.
Found in the Richards et al. paper mentioned above:
" While the relationship between poor model fit and topological conflict between the gene trees and reference tree appears to be complex, we do find several cases where these methods clearly identified systematic bias or other issues in the data. While inspecting PPES results, we noted two cases where a single gene was a large outlier for 1 or more model performance tests relative to all genes (Fig. 5 ). In both cases the PPES outlier was correctly signaling an issue in the analysis. Specifically, phylogenetic analysis of CYTB in the Squamate data set inadvertently included a misaligned region that affected four sequences. This misalignment increased the tree length mean and variance PPES for this gene, which were consequently much larger than these values for all other genes in the data set (Fig. 5 a). The error also drove a spurious phylogenetic result that united a worm lizard with several blind snakes as a clearly erroneous clade. Once we corrected the misalignment, the tree length mean and variance PPES for CYTB were drastically reduced and the position of these taxa in the gene tree returned to their more commonly accepted positions. This result also highlights that other sources of gene tree estimation error beyond those driven by poor model fit, such as alignment errors, can also contribute to non-biological sources of gene tree variation."
A question for those here with the proper skill set - how much of the systemic error (which Paul seems to think would invalidate the entire field) as described in Richards et al. is due to nothing more than sequence error? The numbers of sequences that I believe went into the Richards et al. study was pretty large, and seems to me probable that many percent of the sequences will be erroneous in some way. Does anyone run the same sorts of analyses with deliberate errors to see how often outcomes such as described for the CytB gene actually arise?
My point here is that, if Paul’s argument is reduced to “aha, someone made a mistake in the sequencing”, then it has little or no bearing on the methods themselves, or on the robust conclusions that may be drawn using rigorously-refined sequence collections.
Or maybe this is not an issue. I am not familiar enough with the different statistical approaches to know. Some participants here have the expertise to weigh in on this.
It’s not easy to see what it is that is being offered as a test of common descent or common ancestry and what is being offered as a test of a given branching order assuming common ancestry. i htink we need to separate the two claims.
I’d also like to return to something i raised earlier, because it’s my primary interest (selfish, i know) in this thread.
Are you familiar with the claim that if someone accepts the results of a paternity test they ought to accept the evidence for common descent?
Are people familiar with that claim, has anyone here ever personally made that claim or agree with it?
I am trying to understand the logic/reasoning that undergirds that argument.
Now clearly, to me, when someone makes that claim, when they use the term “common descent” they mean by it something more than a father-daughter relationship.
So to turn it into a specific example, if we accept that we can use DNA to identify that Joe is the father of Mary, then it follows that we can use DNA to identify that some unnamed species is the “parent” of some other unnamed species. But that’s not what phylogenetics does. So I don’t understand the logic.