I am sure that many readers have already concluded that I do not understand the role of sex in either organic or biotic evolution. At least I can claim, on the basis of the conflicting views in the recent literature, the consolation of abundant company.– George C. Williams, Sex and Evolution, 1975
What’s sex all about? This question has been exercising biologists since well before Williams’s time, but in the 1970’s, with the rise of ‘gene-centrism’ and the related controversy over group selection, a succession of prominent authors grappled with the problem, trying to fit it with current evolutionary theory to no-one’s particular satisfaction. Males were deemed an impediment to a female’s efforts to maximise her reproductive output, time wasted on these feckless types resulting in her only passing on 50% of her genes per offspring. From the perspective of a ‘selfish gene’, meanwhile, getting into every offspring seems a preferable fate to only getting into half of them. On the basis of these apparent large costs, a cryptic offsetting benefit of corresponding magnitude was assumed. Like Godot, it is yet to appear.
Yet sex is widespread. All eukaryotes either do it now, or possess tell-tale signs that their recent ancestors did. Given that it appears costly to individuals, and genes, how did it evolve and why does it persist?
Brexit – you may have heard of it. For 40 years, since the UK joined the then Common Market, there has been a substantial ‘Eurosceptic’ mood in both main political parties and in the country. This has been influenced by a never-ending stream of misinformation Continue reading
Apparently. This, at least, is the latest incantation. Repeat it often enough, and it is so. So what has actually died? What elements of Darwin’s theory(/ies) of evolution have been buried? I can certainly think of one – his theories of variation were wrong, superseded by Mendel, which simultaneously solved one of his dilemmas. But is that it?
Craig Venter has achieved celebrity status in Creationist circles for little more than a slightly embarrassed smile. In a discussion involving, among others, Richard Dawkins, Lawrence Krauss and Paul Davies, Venter makes the eyebrow-raising statement that he does not regard Mycoplasma as the same ‘life-form’ as other prokaryotes, or eukaryotes. His reasoning was that they have ‘different genetic codes’. Dawkins reasonably points out that their codes are ‘all but identical’ (they differ in just one position, Trp for STOP). Creationist videos of the exchange tend to fade on the aforementioned smile given in response. The videos are presented, breathlessly, as “Venter denies Common Descent in front of Richard Dawkins!”. However … one difference? Is that really enough to justify a claim of separate origins? This would be like claiming that Norwegian and Swedish had separate origins on the strength of the difference between æ and ä or ø and ö. Continue reading
It’s not every day you discover a new (supra) kingdom, but a Facebook friend has done just that. Based on phylogenetic analysis (that thing that doesn’t tell us anything, heh heh), they differ genetically from known protists more than we do from fungi (which are more closely related to us than to plants).
We have been gibbering for many, many pages, at least nominally on the topic ‘Common Design vs Common Descent’. I’d like here to discuss an interesting fact I discovered during the course of this. I mentioned it twice, but readers seemed underwhelmed by what, to me, looks like a genuine scientific discovery (I haven’t searched exhaustively for priority). More importantly for present purposes, it provides a useful test-bed for several concepts that regularly do the rounds.
We are cluttering up a thread that’s not about convergence with discussions about convergence. Here, we can discuss this specific issue.
Several themes have been doing the rounds lately. The origin of organelles, standards of evidence, common descent, the role of phylogenetic analysis, and the meaning of ‘prediction’ in science. Here’s a case study/rambling discourse that links a few themes.
This has long been an interest of mine. It dates back to the old talk.origins days, prompted by a Creationist taunt with familiar tone – “I’d like to see someone explain the evolution of sex …” (with the implicit “hurr, hurr”). I articulated some thoughts, then was rounded on by the ‘mainstream’ community. I got a flavour of the world through Creationist eyes – an equally familiar tone: some very sharply expressed contempt and an invitation to f*** off back to high school and learn meiosis.
I’m really not a fan of doing what I’m about to do.
But anyways, this is WJM @ UD
To be fair, when the proponent of a theory who claims that theory to be scientific fact provides little or nothing in the way of falsifiable predictions and offers largely only sweeping narratives and historical inferences based on ideological assumptions and/or an imagined infinite pool of unqualified possibility, it’s impossible for the opposition to offer specified rebuttals.
Until proponents offer specified, falsifiable predictions, the proper response to such a theory is to “lump everything into a single bucket and dismiss the entire topic.”
We are all too familiar with the schtick of certain posters. I’d like to know what they hope to achieve by pounding their limited collection of nails year in year out.
One could summarise the entire output of some in a dozen or so sentences. They KNOW that no-one will answer their challenges to their satisfaction. They KNOW (rather, they think they know) that this is because their challenges cut right to the heart of the matter, and evolutionary theory (“which evolutionary theory?”, a poster mutters for the thousandth time) is not an arena of explanation that will satisfy them. So, once you have satisfied yourself that this is the case, why keep buzzing against that glass like a trapped house-fly?
One of the densest Creationist tropes has to be ‘Common Design’. It is proposed as a direct competitor to Common Descent – template mediated copying of DNA – as an explanation for the high sequence similarity of two DNA segments. But what is actually held in common? If we look at a particular transposon sequence, and find it is in A and B but not C, and another that is in A but not B, etc, we can generally organise a set of such markers into a ‘tree’ structure, much as would be predicted by Common Descent. But no, we are assured that these apparent markers are in fact part of the ‘design’. If A is a whale, B a pig and C a deer, there is something that is vital for the function of both whale and pig but is definitely not required in deer. Instead, a sequence which, in whale and pig, sits either side of the insertion, runs uninterrupted in the deer. That, too, is functional, supposedly, even though the insert would give a product which was the A/B one with a gap and possibly a frameshift, if it were transcribed.
But this is held to be the case even if the sequence, with and without transposon, is never transcribed. A sequence that does nothing, and organises hierarchically exactly as would be expected of common descent, is nonetheless functional … because?
Certain commentators seem surprisingly agitated about pursuing the idea that there is no ‘theory of evolution’. Some mean there is no single theory, although on examination the things they see as separate are frequently simply different components of the same broad process. Or, alternatively, they are referring to evolution in other senses, or in non-biological contexts. Others say there is no theory at all, as if that against which they argue does not even exist.
A theme has emerged that TSZ is somehow suppressing their concerns. So, in the spirit of suppressive dictatorships everywhere, here is a thread for people to say whatever they want about this vital topic. Hopefully without pasting in vast swathes of something already posted elsewhere – a link will suffice.
Mung, to petrushka, elsewhere:
Everyone does not understand “genetic load” and those that do claim to understand are probably wrong. Why don’t you start an OP on genetic load and the genetic load argument? That would be interesting. Betting you won’t.
This is such an OP. I believe the genetic load argument*** was initially proposed by Susumu Ohno in 1972, whose paper also introduced the then-scare-quoted term “junk”. It’s brief, accessible, and worth a read for anyone who wishes to offer an opinion/understand (not necessarily in that order).
The short version: sequence-related function must be subject to deleterious mutations. Long genomes (such as those of most eukaryotes) contain too many bases for the entire genome to be considered functional in that way, given known mutation rates. The bulk of such genomes must either have functions that are not related to sequence, or no function at all.
Interestingly, the paper is hosted on the site of an anti-junk-er, Andras Pellionisz, a self-promoting double-PhD’d … er … maverick. Also of interest is that, contrary to some ID narratives, the idea was initially resisted by ‘Darwinists’, if that term is understood not as people who simply accept evolution, but as people who place most emphasis on Natural Selection. Perfectionism is not the sole preserve of Creationists.
More recent work has characterised the nonfunctional fraction, and this lends considerable empirical support to Ohno’s contentions.
[eta: link to comment]
***[eta: in relation to genome size, not the first time anyone, ever, discussed genetic load!]
During recent discussions on phylogeny, we saw a distinct failure to communicate, probably felt by both sides. The ‘evos’ attempted to consider the role of molecular data in determining relationship. Given that an obvious cause of common sequence is common descent, due to the significant but not perfect fidelity of the DNA replication process, the phylogenetic inference is that sequence similarity is indicative of common descent. This, critics feel, is a circular argument. Continue reading
There has been much discussion, here and elsewhere, on ‘epigenetics’, broadly understood as the control of gene expression. People who cling to ‘classical’ models are portrayed, by revolutionaries and their cheerleaders, as dinosaurs standing in the way of progress.
I could perhaps explain, to any interested bystander, my own rationale for my position, since I’ve requested that of others. Continue reading
A Facebook friend of mine is a conspiracy nut. She was tagged in a post by a friend of hers, so up in my ‘news’ feed comes a post offering incontrovertible evidence that persistent contrails are in fact chemical spraying of the populace or the planet for nefarious purposes. I was dimly aware of this notion but was taken aback when encountering such people in the (virtual) flesh. Continue reading
Mung has drawn our attention to a post by Kirk Durston at ENV. This is my initial reaction to his method to establish the likelihood of generating a protein with AA permease (amino acid membrane transport) capability.
A perennial topic. The organisms we see cluster around specific, distinct types. We can identify an individual as belonging to that type because it has the distinctive characteristics of that type. We know what the characteristics are because we see a lot of such individuals.
the some Creationists, those types represent essential, immutable forms, perhaps with some post-Ark latitude, and a bit of variation around the ‘norm’. It is as if those forms were cast from a mould, with small manufacturing defects. The mould is eternal, unchanging. Continue reading
Not really, of course, that’s just click-bait – it is merely science. But at least one person has been turned from a dodgy path by, in part, considering the dissonance between his faith and scientific evidence. Non-UK residents won’t be able to hear this, but the essence is contained here.
It’s an issue that cross-references many familiar themes – religion, morality, homosexuality, science – so I thought I’d toss it into the arena.