Path: ...!uucp.uio.no!fnord.no!news.eyrie.org!beagle.ediacara.org!.POSTED.beagle.ediacara.org!not-for-mail From: DB Cates Newsgroups: talk.origins Subject: Re: Why all apes including humans do not have tails Date: Sat, 6 Apr 2024 21:10:53 -0500 Organization: University of Ediacara Sender: to%beagle.ediacara.org Approved: moderator@beagle.ediacara.org Message-ID: References: <208515e3-b646-40c9-aa0e-e4954ecf595e@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: beagle.ediacara.org; posting-host="beagle.ediacara.org:3.132.105.89"; logging-data="77077"; mail-complaints-to="usenet@beagle.ediacara.org" User-Agent: Mozilla Thunderbird To: talk-origins@moderators.isc.org Cancel-Lock: sha1:1VFRijRjOYdB0j2UeWl/r+4BBk8= Return-Path: X-Original-To: talk-origins@ediacara.org Delivered-To: talk-origins@ediacara.org id 3CF1A22976C; Sat, 6 Apr 2024 22:10:52 -0400 (EDT) by beagle.ediacara.org (Postfix) with ESMTP id 25A0E229758 for ; Sat, 6 Apr 2024 22:10:50 -0400 (EDT) id 1A6B77D11E; Sun, 7 Apr 2024 02:10:56 +0000 (UTC) Delivered-To: talk-origins@moderators.isc.org by mod-relay.zaccari.net (Postfix) with ESMTP id EFA7B7D009 for ; Sun, 7 Apr 2024 02:10:55 +0000 (UTC) by pmx.weretis.net (Postfix) with ESMTP id 3C2C83E8AE for ; Sun, 7 Apr 2024 04:10:53 +0200 (CEST) id E22D13E8C3; Sun, 7 Apr 2024 04:10:52 +0200 (CEST) Content-Language: en-CA X-User-ID: eJwNyMkBwDAIA7CZUtsc40Ah+4/Q6inBjr1Ok1FXtxOlXj/hK/5lx5Hs1sMtVo7XNFAzGYP4ABlVEUA= In-Reply-To: Bytes: 13952 Lines: 258 On 2024-04-06 7:37 PM, Arkalen wrote: > On 07/04/2024 00:16, DB Cates wrote: >> On 2024-04-06 2:55 AM, Arkalen wrote: >>> On 05/04/2024 23:07, DB Cates wrote: >>>> On 2024-04-05 3:56 AM, Arkalen wrote: >>>>> On 01/03/2024 05:31, DB Cates wrote: >>>>>> On 2024-02-29 1:17 PM, Bob Casanova wrote: >>>>>>> On Thu, 29 Feb 2024 08:05:05 -0800, the following appeared >>>>>>> in talk.origins, posted by erik simpson >>>>>>> : >>>>>>> >>>>>>>> On 2/29/24 3:55 AM, RonO wrote: >>>>>>>>> On 2/28/2024 5:41 PM, erik simpson wrote: >>>>>>>>>> On 2/28/24 3:21 PM, RonO wrote: >>>>>>>>>>> It turns out that the common ancestor that between gibbons >>>>>>>>>>> and the >>>>>>>>>>> great apes had an ALU transposon jump into the intron between >>>>>>>>>>> exon 6 >>>>>>>>>>> and exon 7 of the TBXT gene.  There was already an transposon >>>>>>>>>>> between >>>>>>>>>>> exon 5 and exon 6.  Monkeys and apes have the ALU insertion >>>>>>>>>>> in the >>>>>>>>>>> intron between exon 5 and exon 6, but the apes have the >>>>>>>>>>> second ALU >>>>>>>>>>> insertion in the intron between exons 6 and 7.  So it turns >>>>>>>>>>> out that >>>>>>>>>>> apes still have the exon 6 sequence in the TBXT gene, but the >>>>>>>>>>> two ALU >>>>>>>>>>> transposon sequences form a stem loop structure in the RNA >>>>>>>>>>> transcript >>>>>>>>>>> that messes up processing so exon 6 is skipped and exon 5 is >>>>>>>>>>> stuck to >>>>>>>>>>> exon 7 in the final ape mRNA.  So part of what makes us human >>>>>>>>>>> is due >>>>>>>>>>> to a transposon insertion mutation into the TBXT gene. >>>>>>>>>>> >>>>>>>>>>> The insertion happened in the common ancestor of all extant >>>>>>>>>>> apes, and >>>>>>>>>>> has been retained by the extant ape lineages. >>>>>>>>>>> >>>>>>>>>>> https://www.nature.com/articles/s41586-024-07095-8 >>>>>>>>>>> >>>>>>>>>>> The article is open access. >>>>>>>>>>> >>>>>>>>>>> Ron Okimoto >>>>>>>>>>> >>>>>>>>>> Another effect of this modification is also "Moreover, mice >>>>>>>>>> expressing >>>>>>>>>> the exon-skipped Tbxt isoform develop neural tube defects, a >>>>>>>>>> condition >>>>>>>>>> that affects approximately 1 in 1,000 neonates in humans10. Thus, >>>>>>>>>> tail-loss evolution may have been associated with an adaptive >>>>>>>>>> cost of >>>>>>>>>> the potential for neural tube defects, which continue to >>>>>>>>>> affect human >>>>>>>>>> health today." >>>>>>>>>> >>>>>>>>>> Evidently, the advantages of losing the tail outweigh the >>>>>>>>>> disadvantage >>>>>>>>>> of the neural tube defects. >>>>>>>>>> >>>>>>>>> >>>>>>>>> What were the advantages? >>>>>>>>> >>>>>>>>> Some other simian lineages have lost their tails, but what is the >>>>>>>>> advantage? >>>>>>>>> >>>>>>>>> Apes did become brachiators, but other simian lineages did not, >>>>>>>>> and some >>>>>>>>> simian lineages that adopted a similar lifestyle for supporting >>>>>>>>> themselves in the trees, actually developed prehensile tails as >>>>>>>>> a fifth >>>>>>>>> limb for supporting themselves hanging from branches. >>>>>>>>> >>>>>>>>> For birds there was a selective advantage in terms of weight, >>>>>>>>> and the >>>>>>>>> tailbones degenerated and fused into a small nub.  The tail was >>>>>>>>> not >>>>>>>>> lost, and birds still have a nub that they call a pygostyle >>>>>>>>> that still >>>>>>>>> supports the muscles that control the tail movements and so the >>>>>>>>> feathers >>>>>>>>> associated with the tail. >>>>>>>>> >>>>>>>>> Ron Okimoto >>>>>>>>> >>>>>>>> I believe the article mentions that bipedalism is speculated to >>>>>>>> have >>>>>>>> made bipedalism easier. >>>>>>>> >>>>>>> No causal link there... ;-) >>>>>>>> >>>>>>>> That could be a just-so story, but mutations >>>>>>>> that are adopted and fixed within a population must have >>>>>>>> advantages that >>>>>>>> outweigh potential advantages. >>>>>>>> >>>>>>> Indubitably. >>>>>>>> >>>>>> Really? Drift is out? >>>>>> >>>>> >>>>> I don't know if drift is ever out but is it particularly plausible >>>>> in the case of tail loss, something that seems really rare in >>>>> tetrapods? Like, what lineages actually lost their tails - like, >>>>> really lost, not "reduced" or "replaced by a non-bony appendage >>>>> that serves a taily function": frogs, apes, manx cats... bears are >>>>> maybe on their way... who else? >>>>> >>>> Well, my reply was not specific to the 'tailless' idea but rather to >>>> the >>>> more general statement "mutations that are adopted and fixed within >>>> a population must have advantages that outweigh potential >>>> advantages." and >>>> the "Indubitably." reply. >>> >>> Fair enough, I'd missed that context and I agree it was a reasonable >>> response to that sentence in isolation. >>> >>>> However, you seem to making the claim that 'rare' fixed mutations are >>>> less likely to be due to drift. It would seem to me that common >>>> (over many lineages) fixed mutations, even if not identical but >>>> responsible >>>> for very similar morphology, are almost certainly due to selection. >>>> Rare >>>> fixed mutations that have not been *demonstrated* to be associated with >>>> enhanced reproductive success are more likely to be due to drift. >>>> >>> >>> I'm not sure whether by "rare" mutation you mean "rarely found" or >>> "rarely occurs". >> >> We have a miscommunication. I was referring to *fixed* mutations only, >> not mutations in general. I don't think there are such things as "rare >> mutations". There are some biases and special circumstances, but I >> think it can be stated that mutations occur randomly without too much >> violation of reality. The total number of mutations extant in a given >> population depends on mutation rate, genome size, and population size >> in any cases meaning that every possible mutation happens regularly >> over time. The *really* bad ones are eliminated early and are never >> observed. Most are neutral or near neutral and are, at a very low >> probability, randomly (biased by things like proximity to highly >> conserved areas) fixed by drift. A significant number are deleterious >> and are eliminated before fixation by selection and a small number are >> useful in the extant environment and are positively selected and have >> a higher rate of fixation. >> >> So my argument is that any *particular* mutation that becomes fixed in >> one or a few populations is more likely to be due to drift while one >> that becomes fixed in many diverse populations is much more likely to >> be due to selection. This also applies to different mutations that >> have the same or similar phenotypic effects. >> > > I'm not sure I completely follow/agree but I might be being biased by > the fact I came into this talking about a phenotypic trait not a ========== REMAINDER OF ARTICLE TRUNCATED ==========