Three easy science pieces

I can see that book-writing is going to trim my posting here for a while, and that’s as it should be, for the book has a deadline and is something I’ve been researching for several years. But, as Maru the cat says, “I do my best.”

Here are three science-related articles you might (i.e., should) want to peruse:


From the BBC news comes a report on a South American plant about to bloom in a Surrey greenhouse 15 years after it was planted. The plant, Puya chilensis, is called the “sheep-eating plant” because it supposedly esnares sheep and other animals and, after they die, using their rotten carcasses as fertilizer.

I don’t believe that for a minute, though the BBC reports on it without doubt:

In the Andes it uses its sharp spines to snare and trap sheep and other animals, which slowly starve to death.

The animals then decay at the base of the plant, acting as a fertiliser.

The RHS [Royal Horticultural Society] feeds its specimen on liquid fertiliser. . .

. . . I’m really pleased that we’ve finally coaxed our Puya chilensis into flower,” said horticulturalist Cara Smith.

“We keep it well fed with liquid fertiliser as feeding it on its natural diet might prove a bit problematic.

“It’s growing in the arid section of our glasshouse with its deadly spines well out of reach of both children and sheep alike.”

Well, that’s humorous, but not obviously a joke and therefore misleading to readers.

Matthew has found an article on the phylogenetic relationships of this plant, but nothing about its vampiric proclivities. I’m betting the whole “fertilizer” thing is a myth, but I may be wrong. Readers?

Here’s a picture of the plant about to bloom:




At National Geographic you should read “The case of the missing ancestor,” about the Denisovans, a group (indeed, possibly a subspecies) of hominin that lived in Asia roughly 50,000-30,000 years ago. DNA from teeth and finger bones show that the group was not only distinct from both modern humans and Neanderthals, but that they’ve left traces in their DNA in modern humans: up to 5% of the DNA in native Australians and the inhabitants of New Guinea and Melanesia. (Modern humans also contain about 2.5% of Neanderthal DNA.)

The article discusses the possible evolutionary relationships between these three groups, and the questions that remain.  Given that modern humans contain substantial fractions of both Neanderthal and Denisovan DNA, I’d say that these groups would be considered populations or subspecies rather than species, the reason being that there was obviously interbreeding where they met, and the “hybrid” offspring must have been fertile.” Interbreeding and fertile offspring in nature usually indicates that two populations belong to the same species.


Last week’s New York Times has an article on the post-television doings of Bill Nye, the Science Guy: “Firebrand for science, and big man on campus“. It includes a nice three-minute video profile of Nye, who really impresses me, especially because he’s clearly made a huge difference in the lives of many kids. There are people who wouldn’t be scientists if they hadn’t watched his show.

The article includes quotes from Phil Plait and Neil deGrasse Tyson, and you may not know this about Nye’s background:

There was nothing in Mr. Nye’s early days that suggested he might be a firebrand for science. Born in Washington, D.C., he studied mechanical engineering at Cornell, where he got to know a professor named Carl Sagan. He moved out West to do engineering for Boeing, where he spent some three years designing a hydraulic tube for the 747 that served to dampen vibration in the steering mechanism. He refers to it lovingly as “my tube.”

He tried his hand at stand-up comedy — his first time onstage was during a Steve Martin look-alike competition, which he won. He would achieve escape velocity from Boeing with an idea for a television program that would teach science to children in a wacky way. The best-known version of “Bill Nye the Science Guy” ran from 1992 to 1996, and won 18 Emmys in five years.

h/t: Genghis, Grania, Matthew, John, Greg, and others.


  1. Posted June 21, 2013 at 10:52 am | Permalink

    We need more people like Bill Nye.
    I was also wondering, are any of our schools doing any of these?

  2. Posted June 21, 2013 at 11:02 am | Permalink

    A fun anecdote:
    My sister worked at a TV station in Seattle way back when, and she went on a date with Bill Nye. This was during that period when Bill was on meteoric ascent with his science show.

    As my sister related, Bill talked non-stop about himself from the moment the date began. After she was just about filled to overflowing with Nye’s attentions to himself, Nye looked at my sister and said, in so many words:

    “Well, enough about me. What do =you= think about me?”

    ….the “one-and-done” date.

    Certainly I recognize that for a person to succeed in television, it is a prerequisite to have a towering ego. It is a funny story, though.

    • lanceleuven
      Posted June 22, 2013 at 12:23 am | Permalink

      That’s hilarious!

    • ChrisK
      Posted June 22, 2013 at 1:32 pm | Permalink

      I’m glad that I’m not famous. I fear what first date stories could be told about me!

  3. BilBy
    Posted June 21, 2013 at 11:08 am | Permalink

    Is the Puya sheep-eating tree the same as the ‘ya te veo’ tree that allegedly kills and eats humans? There is also the huge plant from southern Madagascar that ate humans. All true, obviously.

  4. Jim Thomerson
    Posted June 21, 2013 at 11:15 am | Permalink

    This is the last (?) of a series of papers about persistant intergeneric hybrids of minnows in a Canadian lake. There are F1 and backcross hybrids. An earlier study found that the hybrid survival in older cohorts is less than the parent species. I don’t know if introgression is documented between the parent species. I wouldn’t be surprised at some mitochondrial introgression.

    It does appear that there is enough introgression among the human groups to permit thinking of them as subgroups of a single species.

  5. eric
    Posted June 21, 2013 at 11:42 am | Permalink

    I’m sure it eats sheep – how could it not? Its just not a predator.

    The whole story seems ludicrous. Its not like we’re lacking an explanation for why there are spines on trees.

  6. Posted June 21, 2013 at 11:50 am | Permalink

    The Puya plant reminds me of the Borometz – the Vegetable-lamb-of-Tartary. The medieval legend of a plant that produces a lamb as its fruit.

  7. lkr
    Posted June 21, 2013 at 12:22 pm | Permalink

    “sheep-eating” — sheep, or even camelids, would be too late-arriving to account for this as an evolved adaptation. My bet is that Puya made its living skewering litopterns and such well before the Great Faunal Exchange.

  8. John Harshman
    Posted June 21, 2013 at 12:47 pm | Permalink

    Interbreeding and fertile offspring in nature usually indicates that two populations belong to the same species.

    Not from where I sit (birds, and ducks in particular). There are in fact relatively few pairs of duck species for which no fertile hybrids are known. At least in birds, you have to make your species definitions a bit more forgiving than that. It’s enough that there is selection against hybrid individuals in most localities. And that allows for a reasonable amount of introgression, at least of genomic segments far away from whatever causes the selection.

    • Posted June 21, 2013 at 5:52 pm | Permalink

      And don’t even get me started on orchids, where intergeneric hybrids are very fertile (and dominate the commercial orchid market). However, there are many strong pre-mating barriers between species and genera of orchids. So although they COULD make fertile intergeneric hybrids, they very rarely actually do so in the wild.

      • John Harshman
        Posted June 21, 2013 at 6:37 pm | Permalink

        And there’s the difference between orchids and ducks (though I’ll grant there may be others): ducks will happily do so in the wild, though rarely enough not to cause undue confusion. Usually; the American black duck may be disappearing as a species, swamped by mallards.

      • lkr
        Posted June 22, 2013 at 9:52 am | Permalink

        not so! In the Mediterranean, at least, hybrid swarms, often intergeneric, are extremely abundant. The false-copulation types like Ophrys are in the midst of this. I suppose depending on a male wasp or male-anything to be a faithful messenger is not always going to work…

        • Posted June 22, 2013 at 10:22 am | Permalink

          Here in South America, it’s uncommon to find hybrid swarms of pseudocopulation orchids. Maybe recent habitat changes in the Mediterranean have led to shifts, and new overlaps, in pollinator or orchid distributions?

  9. GP
    Posted June 21, 2013 at 1:53 pm | Permalink

    That plant reminds me of a century plant at a greenhouse in Toronto, which is blooming now for the first time in 75 years, and has grown so tall so quickly that they had to cut a hole in the glass roof:

    • Posted June 21, 2013 at 2:40 pm | Permalink

      I have dozens of these in my yard, but they don’t live for 75 years in southern Arizona, and are very susceptible to attack by native agave weevils and exotic Strategus beetles. The oldest plants I’ve seen (with a basal rosette about as tall as a one-story house) bloomed at 28-30 years old; those in my neighborhood bloom at 15-20 years and don’t grow as big. This species is native to Mexico but is widely naturalized in the Mediterranean region. Our four common native southern AZ species may bloom in as little as 5-10 years (small low-elevation bajada form of Agave palmeri) or as many as 20-50 years (spectacular Agave parryi var. huachucensis).

      Mary Irish, the botanist quoted in the article, has written a book on gardening with agaves and their relatives; she refers to A. americana somewhat disparagingly as the “Gray Giant” because it’s so ubiquitous in Tucson.

      My Agave webpage has photos of wild agaves and a “sport” A. palmeri that never bloomed, but just kept growing.

  10. Diana MacPherson
    Posted June 21, 2013 at 2:52 pm | Permalink

    That sheep eating bit was probably made up by some guy that stole sheep. The plant ate your sheep…yeah, yeah that’s it, the plant

  11. madscientist
    Posted June 21, 2013 at 4:45 pm | Permalink

    I’m betting the fertilizer thing is a myth too – I’m sure the RHS throw some nasty little kids into the plant. Plants all have their own nutritional requirements; I wouldn’t doubt that they occasionally irrigate the plant with some foul smelling liquid.

  12. Posted June 21, 2013 at 5:59 pm | Permalink

    I live in the land of Puyas, and some (not that species) grow wild in my yard. There are patches of old volcanic lava where they are the dominant plant, and it is hell to have to walk through those patches. They’ve shredded many pairs of my pants, and drawn much blood too. Tomorrow, if I remember, I will take some pictures of their devilish thorns. They are not normal. They are backward-hooked and, if I am not misremembering, some point inward and some point outward. (Granted I may still be traumatized by my encounters with them, so my mind may be making this up. We’ll see tomorrow.) I think there is little reason for my species to be adapted to capture animals (the volcanic sands are nutrient-rich), but I can easily imagine some critters getting hung up on these spines and dying. A woolly sheep could get into real trouble on these.

    • Posted June 22, 2013 at 6:33 am | Permalink

      I remembered to look at the spines. The ones nearest the tips of the leaves are pointing outward, and are straight. Then, closer to the base, they start to get curved, but still pointing outward. Near the base of the leaves, they become irregular (some pointing out, some pointing inward) and then closer to the base they all point inward like hideous fishhooks.

  13. Posted June 21, 2013 at 6:44 pm | Permalink

    After reading many comments, a story with peculiar aspects resurfaced in my mind.

    I owned a house previously owned by a nursery manager. Twenty-thirty various trees and bushes about the yard, including a small Colorado Blue Spruce. Very sharp needles. So sharp in fact, that snails would go out on the branches, but could not reverse and leave (too sharp). The snails would starve and drop to the ground around the tree. Not enough to fertilize, I’m sure.

    And speaking of animals as fertilizer, I understand that salmonids swimming high into the Coast Range of British Columbia have been identified as the source of phosphorous that improves soils and tree cover far inland.

  14. Timothy Hughbanks
    Posted June 21, 2013 at 7:58 pm | Permalink

    The National Geographic article on the Denisovans was very interesting. The details concerning innovations in analyzing single stranded DNA were cool.

  15. Dennis Hansen
    Posted June 22, 2013 at 2:12 am | Permalink

    Puya and ‘carnivory’ — there is one published account that I am aware of:
    Macedoruiz, H. D. 1977. Felis catus caught by Puya raimondii. Mammalia 41:231-232.

    I don’t have the paper here right now, but will check it Monday.

    Probably most likely to have evolved as ‘normal’ antiherbivory spines, but then why do many of the spines point backward/inward?

  16. rayez
    Posted June 22, 2013 at 11:48 pm | Permalink

    What the National Geographic article does not mention (it is not published yet) is that a fourth human subspecies/population has been identified in the Denisovan DNA. It was talked about at a Cold Spring Harbor meeting; for those with access to Science:
    From the Science report: Four percent of the Denisovan genome comes from yet another, more ancient, human—”something unknown,” Pääbo reported.
    John Hawks comments:

  17. kingsofnh
    Posted June 23, 2013 at 5:40 pm | Permalink

    It seems there was indeed a paper that reported the carnivory of the Puya.

    It was a real pain to track down because every damned claim of this only referenced a source that often didn’t give its source. Google Scholar FTW!

    • Dominic
      Posted June 24, 2013 at 7:06 am | Permalink

      In case the link ever fails I am going to be librarianish –
      Puya raimondii (Pitcairnioideae, Bromeliaceae) and birds: an hypothesis on nutrient relationships
      William E. Rees, Nicholas A. Roe
      Canadian Journal of Botany, 1980, 58(11): 1262-1268, 10.1139/b80-157

  18. Dominic
    Posted June 24, 2013 at 7:04 am | Permalink

    We should qualify “Modern humans also contain about 2.5% of Neanderthal DNA” – it depends where the modern humans are from – those with ancient European ancestry in other words rather than Australasians, Americans or Africans.

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