Comments

  1. nomdeplume says

    Yes, SciManDan is usually excellent, but I’ve often noticed he lacks biological knowledge – hope he takes up PZ’s offer and suggestion.

    On the eye. Another error by Dan is the suggestion that trilobites are somehow on the main pathway of eye evolution to the human eye. Arthropod and vertebrate eyes probably had similar light patch origins, but completely diverged from that point on.

    A creationist point that I always want to scream at the iPad screen about is their notion that (a) human eyes have directly evolved from the light sensitive eyepatch and (b) that human eyes are somehow at the peak of evolutionary development of eyes.

    Of course if you look back through phylogeny the human eye is just a step along a chain through various mammals, reptile, amphibian, fish eye. It doesn’t somehow emerge fully formed. And the human eye is nowhere near the “best” eye – think of raptor eyes, or nocturnal carnivores, or indeed arthropod eyes. Conversely, I’d like to see a creationist attempt to explain how some species “lose” eyes when they live in caves, or burrow, or have them covered by a transparent eyelid, and why are some eyes on the front of the face, some on the sides and some on the top. I guess I’ll keep yelling at the screen!

    Oh, and happy new year PZ, and all who sail on the good ship Pharyngula.

  2. birgerjohansson says

    OT
    RIP Eduard Nikolayevich Artemyev, composer of the film music for Tarkovsky’s films Solaris, Mirror and Stalker. Another sad news item for 2022.

  3. robro says

    nomedplume @ #1 — “human eyes are somehow at the peak of evolutionary development of eyes…” I would not expect creationists to make the point about “evolutionary development” at all. Their position is that nothing evolved. God created everything in 6 days, and because he created humans last then everything about humans must be the best. I understand that this ignores that some animals have capabilities in lots of things that are far superior to humans.

  4. Gerald Squelart says

    Hi! Just a tech detail: In your past few videos, the sound only comes from the left, please check your mic! (Feel free to delete this comment once viewed — Thanks!)

  5. says

    Dan has an unfortunate habit of leaning on a pop sci understanding of areas outside his field. It’s not the first time he’s said things which are obviously incorrect on even cursory examination. To be fair, I’m not sure arguing with creationists actually deserves any more effort.

  6. bcw bcw says

    One of the things that most people get wrong as in Dan’s video and which shows up in far too many school biology texts is the idea that there is a point or goal to evolution. Eyes! Avoiding antibodies! etc. Evolution is a consequence of the way the chemistry of life works not the goal of it. Snowmen go away in the summer because of how their construction interacts with changes in the environment, not because they want to evolve into puddles. Proteins are light-sensitive because they are, and sometimes that produces other chemistry that’s not a bad thing.

  7. hemidactylus says

    I liked the parts about opsins and G-proteins but would be interested in the cooptability involved as stuff used for one thing undergoes functional shifting to contribute to something else obviating an apparent need for from-scratch de novo components. Plus though overly sexed up in the past a gene such as Pax6 undergirds the divergent and convergent (or parallel…) implementation of eyes across phyla. Two eyes comes from a bilaterian common ancestor’s symmetry. We have two pairs of limbs too. It’s right there in the name. Vertebrates were a johnny come lately subbranch. We tend to give an inordinate amount of focus on our branch while God was inordinately fond of beetles (and still dominant bacteria) instead.

    Gotta take care with junk DNA lest Larry Sandwalker takes you to task. His book is coming soon. Holy ENCODE entrails Batman, SciManDan pooped the bed right off the bat. Regulatory upstream noncoding sites where transcription factors control gene expression of transcripts are quite different from pseudogenes that lost their way for instance. ENCODE may have shown a bunch of dead sites that transcribe stuff, but that stuff goes on to do diddly squat. Junk RNA? Panadaptionists read function into stuff as the default.

  8. chrislawson says

    hemidactylus@8–

    I would go so far as to say that the extreme adaptationist take that there’s no such thing as non-functional DNA is both observably wrong and mechanistically incompatible with any workable theory of evolution. If every genetic sequence has a biological function, then evolution can only proceed by tiny mutational basepair-by-basepair gains in function. Which happens and is important, but cannot be the full story.

  9. hemidactylus says

    Hmmm…what had our chordate precursors for eyes or an eye or paired eyes? I don’t take lancelets and tunicates as ancestral of course but each seems to have at best a singular eyespot.

    Of Ciona a tunicate: “The larva has a dorsal nerve cord, running along the tail just above the notochord, and this expands at the front into a very simple brain that includes a light sensor (an ‘eye’) and a tilt detector.” And of amphioxus: *“So even though amphioxus adults have a very simple brain, and simple sense organs (the ‘eye spot’), the genes are shared, and phylogenetic precursors of vertebrate brain regions, eyes, and other organs, are there in amphioxus.” both quoted from Vertebrate palaeontology by Michael Benton

  10. cheerfulcharlie says

    Over at Laurence Moran’s excellent biology site Sandwalk, professor Moran has been posting for quite some time on the subject of junk DNA. There is a lot of bad science out there on that subject. This is a good site to learn more than you ever wanted to know about junk DNA. And a warning about how sometimes science goes off the rails by people who should know better. Moran has bones to pick with Wikipedia on this subject also.

  11. hemidactylus says

    @12- cheerfulcharlie
    Larry’s grapples with the Wikipedia editing process involving dingbats fighting his changes really soured me on that site. Sad stuff. Now he’s dealing with book editors.

  12. StevoR says

    Thanks PZ I hadn’t heard of this guy before here. Minor detail but I wondered and checked and seems the earliest eyes actually evolved in the Ediacaran period :

    The first fossils of eyes found to date are from the Ediacaran period (about 555 million years ago).[8] The lower Cambrian had a burst of apparently rapid evolution, called the “Cambrian explosion”. One of the many hypotheses for “causes” of the Cambrian explosion is the “Light Switch” theory of Andrew Parker: it holds that the evolution of advanced eyes started an arms race that accelerated evolution.[9] Before the Cambrian explosion, animals may have sensed light, but did not use it for fast locomotion or navigation by vision.

    Source : https://en.wikipedia.org/wiki/Evolution_of_the_eye

    Citing :

    McMenamin, Mark A. S. (2016). Dynamic Paleontology: Using Quantification and Other Tools to Decipher the History of Life. Springer. ISBN 978-3-319-22776-4.

    Which is a book I haven’t got – or read – so cannot confirm.

    However, I haven’t been able to find an example of an Ediacaran species with eyes and this article from 2019 :

    https://www.zmescience.com/science/biology/first-eye-fossil/

    Claims the oldest eye fossil is from a trilobite specifically Schmidtiellus reeta and from 530 million years ago in the early Cambrian not 555 million,

    Google search suggests this rather technical academic paper :

    https://royalsocietypublishing.org/doi/10.1098/rspb.2020.3055

    contains this sentence :

    by SD Evans · 2021 · Cited by 6 — The Ediacara Biota preserves the oldest fossil evidence of abundant, … complex bilaterian characters, including appendages, eyes and gut.

    But I cannot seem to find that in there so.. okay, I am confused now. Were there Ediacran fossils with early eyes or did they only start in trilobites from the early Cambrian?

  13. says

    PZ I really appreciate all the educational biological info you provide us. And, the contributions of the commenters here often add so much, too. Though I research what is presented and learn a lot, I must admit I am not as sophisticated in biological science as many of you.

    Happy New Year everyone. I wish you all health and prosperity. But, looking around at the socio-political landscape I say, ‘Hold onto your hats, it’s about to get really crazy’.

    Silly remark #1 for 2023: Does having to wear an eye patch sometimes make me primitive in evolutionary terms?

  14. chrislawson says

    StevoR– yeah, just checked that Evans/Droser/Edwards 2021 paper and you’re right, it does (quite annoyingly imho) make that very broad statement without referencing.

    The best I could find was a fascinating review of eye evolution in Nature (and not behind a paywall!!!) @ https://www.nature.com/articles/eye2017226

    First known eyes

    The fossil record reveals the first known eye was in a trilobite, Olenellus fowleri. Although doubtful it is the first eye, it is the first known eye because of the calcite composition of its ommatidia (the individual units of a compound eyes.) Calcite, a crystal of limestone, is already a form of stone so does not need to fossilize to be preserved. This ancient arthropod probably lived between 600 and 550 mya before the Cambrian explosion and possessed fully formed eyes with multiple individual ommatidia. [27, 28, 29] Classically, though, we currently accept that the oldest Olenellus comes from the middle or early Cambrian.

    This would suggest that eyes were forming well before the Cambrian period but no record of such pre-Cambrian trilobites, or other animals with eyes, exists, at least to date.

    This paper is 5 years old now. (Also note there is an important missing comma in the first para.)

  15. chrislawson says

    Clarification, I mean the first para I’ve quoted, not the first in the paper itself.

  16. nomdeplume says

    @18 I guess this is what fooled Dan. This is just a fluke of preservation becuse of the calcite. None of the earlier eyes would have been fossilised. But also trilobite eyes have nothing to do with the evolution of other eyes (vertebrates, arthropods, molluscs) because the group went almost totally extinct.

  17. StevoR says

    @ chrislawson, nomdeplume & shermanj : thanks.

    So seems no eyes in the Ediacara fuana after all… & yes, Happy New Year to all here.

  18. birgerjohansson says

    Creationist/populist Republican troll:
    “Look, a scientist was wrong about someting. Therefore, you should not trust a scientist about anything “.

    Tory troll: “Never trust an expert. If we listened to experts, we would never have done Brexit, or defunded the NHS”.

    Goebbels: Intuition is better than the tyranny of the intellect.

  19. chrislawson says

    StevoR@21–

    I think it would be better to say no known eyes in the Ediacaran. It is almost certain that there were animals with eyes in that era, just none that left fossil evidence. So far.

    Also, since none of us are afaik paleontologists, it’s quite possible that we’ve missed the published evidence. Search engine algorithms aren’t always efficient at digging out the right papers.

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