tag:blogger.com,1999:blog-4989966954446423670.post6307225531683946071..comments2024-03-02T00:44:55.128-08:00Comments on Pleiotropy: Cladistics does not resolve hobbit controversyBjørn Østmanhttp://www.blogger.com/profile/08859177313382114917noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-4989966954446423670.post-32204937612921219272009-08-19T04:53:09.158-07:002009-08-19T04:53:09.158-07:00For another post, and a day spare with nothing els...For another post, and a day spare with nothing else to do, I will be interested to read your reservations with parsinomy in cladistics. A method you seem to hate given that you let us know you have reservations on every other paragraph.Roberto Kellerhttps://www.blogger.com/profile/15313935930998188137noreply@blogger.comtag:blogger.com,1999:blog-4989966954446423670.post-14057432935689645822009-08-18T17:50:58.684-07:002009-08-18T17:50:58.684-07:00Debbie Argue has just gotten back to me via email,...Debbie Argue has just gotten back to me via email, and says she will check this out next week (she's about to be away from her computer until then).Bjørn Østmanhttps://www.blogger.com/profile/08859177313382114917noreply@blogger.comtag:blogger.com,1999:blog-4989966954446423670.post-11601282260227489502009-08-18T17:48:02.296-07:002009-08-18T17:48:02.296-07:00Is this analysis sufficiently thorough? I don'...<i>Is this analysis sufficiently thorough? I don't have the expertise to venture an opinion. You raise an interesting issue, though--could we look at the characters responsible for floresiensis' position in these trees, and come up with a particular disease or disorder that would account for most of them? The backers of the "hobbits are diseased humans" hypothesis have already listed sets of traits that microcephaly would account for, of course, but AFAIK they haven't done so for a specific set of traits in conjunction with a cladistic phylogeny like this. That might help them narrow down the range of disorders that could be responsible.</i><br /><br />That would be interesting indeed.<br /><br /><i>Only if that disease happened to affect those many traits in the exact way necessary to "fake" an affinity with another part of the tree, no?</i><br /><br />I think that if you take a bunch of traits and "randomize" some of them, then you would expect the taxon to move away from its original position, and then necessarily be placed somewhere else. Cladistics forces one affinity at a time (per tree).<br /><br />I think it has been thoroughly demonstrated that the traits are not of any known disease, and I think that's enough to settle the issue until more evidence appears.Bjørn Østmanhttps://www.blogger.com/profile/08859177313382114917noreply@blogger.comtag:blogger.com,1999:blog-4989966954446423670.post-80846976000841730022009-08-18T15:57:42.826-07:002009-08-18T15:57:42.826-07:00Recall that the opposing view is that the H. flore...<i>Recall that the opposing view is that the H. floresiensis phenotype is caused by disease, and if we were to accept that, then the cladistics don't refute that they are the same. </i><br /><br />It depends on the thoroughness of the analysis, I think. Given enough points of comparison, it could be established as highly unlikely that a disease was responsible for <i>all</i> of the characters placing H. floresiensis at some distance from H. sapiens. <br /><br />Is this analysis sufficiently thorough? I don't have the expertise to venture an opinion. You raise an interesting issue, though--could we look at the characters responsible for floresiensis' position in these trees, and come up with a particular disease or disorder that would account for most of them? The backers of the "hobbits are diseased humans" hypothesis have already listed sets of traits that microcephaly would account for, of course, but AFAIK they haven't done so for a specific set of traits in conjunction with a cladistic phylogeny like this. That might help them narrow down the range of disorders that could be responsible.<br /><br /><i>If they had a disease that affected their morphology in many skeletal traits, then it would not be surprising that the analysis didn't group them with humans.</i><br /><br />Only if that disease happened to affect those many traits in the exact way necessary to "fake" an affinity with another part of the tree, no? If the disease just made them <i>weird</i>, that would not (on average) cause them to be grouped elsewhere. Cladistics ignores unique apomorphies, and they'd still be closer to H. sapiens than to anything else.<br /><br />And if the disease messed with so many of their characters so badly that they lost all (skeletal) trace of affinity to H. sapiens, is it likely that they'd be relatively well-localized on the optimal trees at all? <br /><br />I guess the best way to answer it would be to add H. sapiens skeletons with microcephaly, Laron syndrome, etc. to the analysis, and see if they all cluster together but the floresiensis material still shows up elsewhere.Anton Matesnoreply@blogger.comtag:blogger.com,1999:blog-4989966954446423670.post-50592034600516572672009-08-18T15:23:27.248-07:002009-08-18T15:23:27.248-07:00Anton, good points. I see what you mean about taxa...Anton, good points. I see what you mean about taxa/species.<br /><br /><i>Now it's true that an analysis like this couldn't confirm that H. sapiens and H. floresiensis were the same species, but it can certainly refute that claim.</i><br /><br />Recall that the opposing view is that the H. floresiensis phenotype is caused by disease, and if we were to accept that, then the cladistics don't refute that they are the same. If they had a disease that affected their morphology in many skeletal traits, then it would not be surprising that the analysis didn't group them with humans.<br /><br />Again, my quip with this paper is really only how the authors phrase their conclusion. Assuming that the morphological differences aren't pathological, I find the cladistic analysis interesting (with reservations about parsimony).Bjørn Østmanhttps://www.blogger.com/profile/08859177313382114917noreply@blogger.comtag:blogger.com,1999:blog-4989966954446423670.post-49230739200835283212009-08-18T15:06:58.743-07:002009-08-18T15:06:58.743-07:00The fishy part is that in order to construct clado...<i>The fishy part is that in order to construct cladograms like the ones above, the authors assumed that H. floresiensis and H. sapiens are different species. Once that is done, no other conclusion can be reached. </i><br /><br />I don't think this is the case. The authors assumed that H. floresiensis and their sampled H. sapiens population(s) can be treated as separate <i>taxa</i>, but made no assumption about whether they're different <i>species</i>. After all, cladistics is fine with taxa below the species level.<br /><br />Now it's true that an analysis like this couldn't <i>confirm</i> that H. sapiens and H. floresiensis were the same species, but it can certainly <i>refute</i> that claim. If they are the same species, then they should fall out as sister taxa on the trees. If they're different but very closely related species, then they should <i>also</i> fall out as sister taxa--that's why the trees couldn't unambiguously confirm the former case. But if they consistently <i>don't</i> fall out as sister taxa--which seems to be the case in this analysis--then they must be different and somewhat distantly-related species. (Assuming the parsimony method actually works and all.)<br /><br />There's only one possibility explicitly ruled out by the way the authors set up their analysis: namely, that H. floresiensis falls within the subclade of H. sapiens represented by their sample of eleven humans. And even if that were the case, I suspect their analysis would still return the two groups as sisters, that being the closest result it could actually produce. <br /><br />But if they want to doublecheck that, I suppose they should redo the analysis while scoring each human skeleton separately.Anton Matesnoreply@blogger.com