Tuesday, January 27, 2009

Lower Animals and Higher Animals

 
Here's an article from ScienceDaily.
New Tree Of Life Divides All Lower Metazoans From Higher Animals, Molecular Research Confirms

ScienceDaily (Jan. 27, 2009) — A new and comprehensive analysis confirms that the evolutionary relationships among animals are not as simple as previously thought. The traditional idea that animal evolution has followed a trajectory from simple to complex—from sponge to chordate—meets a dramatic exception in the metazoan tree of life.

New work suggests that the so-called "lower" metazoans (including Placozoa, corals, and jellyfish) evolved in parallel to "higher" animals (all other metazoans, from flatworms to chordates). It also appears that Placozoans—large amoeba-shaped, multi-cellular animals—have passed over sponges and other organisms as an animal that most closely mirrors the root of this tree of life.
There's so much wrong with this description that one hardly knows where to begin. Ryan Gregory highlighted the worst parts at Lower and basal.

Do NOT use the words "higher" and "lower" to describe biological species. This is a mistake that many scientists make so we can't blame the journalists1 for this one.


1. I wonder what Graham Lawton thinks about this tree of life?

11 comments :

  1. Wow, that is spectacularly bad, though you're right that way too many of our colleagues talk like that. What's your impression, by the way, of ScienceDaily in general? Mine is so bad (from experiences months ago) that I poked around to see if it was a front for a creationist or other pseudoscientific outfit. Dreck.

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  2. Steve - I have Science Daily in my feed reader (along with Quintessence of Dust, of course.) But it is frustrating to read the full articles because they rarely give the links to the original papers to which they refer. In this case it was to PLoS Biology, so I can find it. One of the issue that I have is that they often just reprint the press release from the institution that is the home of the chief authors.

    I have sent them feedbacks requesting that they link to the original paper's source (if available.)

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  3. Every science journalist should be force-fed a copy of Lovejoy's Great Chain of Being, and a copy of Full House (to choose merely the most prominent of Gould's writings on the theme). Then maybe we wouldn't have to endure any more of this higher/lower BS.

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  4. Well vaguely in defence of the article, the text says "so-called" and refers to lower and higher as "lower" and "higher".

    As for Science Daily, I use it to point me in the direction of interesting new papers. It's quite useful on this front. I regularly check the major, fairly general, journals like Nature and PNAS but obviously there's a lot there that's still flying under my radar. So it serves a purpose for me.

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  5. What's wrong with using the terms 'higher' and 'lower'?

    They are relative terms and refer to geological strata. 'Lower' simply means 'has earlier origins' (and so is found in physically lower layers); 'higher' means 'has later origins' (and so is found in physically higher layers).

    What's the problem?

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  6. Its just a wrong way of thinking about the process. Evolution is not hierarchical, its transcendental.

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  7. What's wrong with using the terms 'higher' and 'lower'?

    They are relative terms and refer to geological strata. 'Lower' simply means 'has earlier origins' (and so is found in physically lower layers); 'higher' means 'has later origins' (and so is found in physically higher layers).


    Because that's not what it means, and because these are modern taxa all extant at the same period.

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  8. anonymous says,

    What's wrong with using the terms 'higher' and 'lower'?

    They are relative terms and refer to geological strata. 'Lower' simply means 'has earlier origins' (and so is found in physically lower layers); 'higher' means 'has later origins' (and so is found in physically higher layers).

    What's the problem?


    Here's a little story to illustrate how wrong you are. I'm making up the story, in case it isn't obvious.

    A paleontologist has graduate students working on two different projects. One of them is studying extremely well preserved bacterial fossils in a slate bed dating to only one million years ago. The other one is studying poorly preserved fossil mammals in an area that dates back to 150 million years ago.

    According to you, our paleontologist could write an article where she says, "The higher bacteria are much better preserved than the lower mammals."

    If you've ever seen such a statement in the scientific literature, I'd appreciate the reference.

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  9. Oh jeez, these are just terms! Terms are conventions. They don't have to be super precise. All that's really required is that the terms are unambiguously understood by those who use them. You know, dragonflies are not flies but mosquitos are flies. Would you be want to start ranting against these terms too?

    So there is nothing wrong with lower and higher animals - everyone immediately knows what they refer too (and, of course, the boundary is blurred).

    Where I went to school, there were, within School of Biology, Department of Higher Plants and Department of Lower Plants. The former dealt with flowering plants and the latter lumped everything else into its lower plants field - algae (all of them), ferns, lichens, and, historically, some protists and fungi (except yeasts :-))

    So what? It did not confuse anyone. *Everyone* still recognized that 1) some/most of these are not even plants and 2) there is little that makes birch higher than laminaria. Using terms is not a problem for scientists. And if non-scientists get confused by scientific terms - well, that's life.

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  10. Being a little disappointed. When I read
    the press release on this elsewhere I expected to see some profound insights on what this means for systematics and the tree of life in the blogosphere. But all I found is this pointless discussion on term :-(

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  11. DK says,

    So there is nothing wrong with lower and higher animals - everyone immediately knows what they refer too (and, of course, the boundary is blurred).

    In my experience, most people who use these terms are confused about evolution. This includes, unfortunately, most scientists. They tend to think of evolution as a form of progress leading from "lower" organisms to "higher" organisms (a ladder of life).

    I've never met anyone who fully understands evolution and all it's implication but continues to refer to some organisms as "higher" and some as "lower." You just can't bring yourself to use such silly terms when they go against your deep understanding of the process. It's sloppy thinking.

    By bringing this to the attention of the general public we can attempt to correct their false notions of evolution as progress toward "higher" species like ourselves. This, in turn, helps them to understand that humans are not special.

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