Some of the most egregious abuses of the English language take place at the hands of real-estate agents. Quasi-poetic crimes typical in the U.K. include "delightfully presented" or "well-proportioned." These phrases mean nothing, because when you're trying to sell a crappy house at an inflated price, you write to confuse, not to inform. Here, I'd like to share my disappointment at the abuse of English in the pages of (arguably) the world's most prominent science magazine.
A news item in this week's issue of Nature describes the research of molecular biologist Kevin Peterson under the heading "Phylogeny: Rewriting evolution." In it, we are told that "tiny molecules called microRNAs are tearing apart traditional ideas about the animal family tree" and that Peterson's work "changes everything about our understanding of mammal evolution."
The substance of these claims is a not-yet-published study of molecules called microRNAs that changes something -- I guess "everything" -- about the family tree of mammals. By "family tree" I mean a representation of how they share evolutionary history. Such trees typically show a number of species connected by lines to indicate what pairs have evolved from a common ancestor. For example, we'd place a chimpanzee and human adjacent to one another, to the exclusion of (in order of decreasing relatedness) gorilla, gibbon, lemur, whale, opossum, bird, salamander, lungfish, tuna, and shark. You might be amazed at the potential number of trees by which you could connect these species. For example, we could have placed the gorilla next to the shark, the human with the bird, or the tuna with the whale. In fact, it would take well over 13 billion rearrangements to exhaust the potential number of rooted, bifurcating trees for these 12 species. With more species, this number grows tremendously; around 60 it exceeds the number of atoms in the visible universe.
Now what do these astronomical numbers have to do with mammals and microRNAs? Not much, except to try and convey when it really is accurate for a popular article to use the superlative. At the core of this news essay is a respected Dartmouth biologist who has published quite a bit on microRNAs, small molecules that help regulate protein synthesis. Like other kinds of heritable information, microRNAs are valuable indicators of one of the core postulates of evolution: common descent. If true, closely related animals should have similar microRNAs, just as they should have similar features of the adult skeleton, embryonic development, and DNA. Their use to help tease apart persistent questions about the evolutionary tree of life is a welcome and valuable scientific endeavor.
The papers on microRNAs published to date have indeed sparked debate. For example, in the case of turtles, microRNAs were consistent with a suggestion made in 1924 by Robert Broom (among others) that turtles are reptiles with a close evolutionary relationship to lizards. In the case of jawless fish, microRNAs supported the 1874 tree of Ernst Haeckel, which showed the two living groups -- hagfish and lamprey -- as each other's nearest relative, outside of a larger group of jawed fish.
So what "traditional ideas" are being "torn apart" regarding mammals? Like I mentioned above, nothing has yet surfaced in the peer-reviewed literature, so I can't really say for sure (and neither can the reporter who wrote this piece). However, the news item does come with a figure that contrasts the "traditional tree" (actually just a decade old) with "Kevin Peterson's analysis." At first glance they seem quite different: "Traditionally," the elephant shows up at the base, whereas, according to Peterson, the first branch is mouse and rat. In reality, these two trees show the same pattern, differing only in terms of the root position. In other words, pretend you've got a bonsai plant on your dining room table. Now pick it up, turn it around, and replace the old root with one of the branches that was formerly pointing upwards. Has the pattern of bifurcating branches in your plant actually changed? Not at all. And this is essentially the difference between the two trees figured in this news article. The pattern in each is the same; the two differ only in terms of the root position.
The reality is that in reconstructing the vertebrate tree of life, molecular data, including microRNAs, are quite consistent with comparative anatomy and genomic DNA. None of these data support a tree showing mice with sharks, elephants with lampreys, or any other of the astronomical number of possibilities that one might assemble at random for a given set of species. Some aspects of the mammalian tree of life have indeed changed over the years. For example, using only comparative anatomy, no one would have surmised that hippos are closer to whales than they are to pigs. The rooting of the placental mammal tree is one such topic within mammalogy that maybe Peterson's data can help resolve, once they're vetted through peer review. And by the way, his data are not the first to suggest a placental root among rodents, although many investigators (including me) think this is probably not a genuine signal.
Regardless, the exaggerated prose about "rewriting textbooks" might have been justified if a group like mouse-shark really was supported as sharing a close common ancestor. But there is no such result from microRNAs, because they're far more consistent with other sources of data than this news item would have you believe. The real tragedy when science writing resembles real-estate speak is that the chance is lost to convey to the public a tremendous consilience between different bodies of data. The embryology familiar to T. H. Huxley in the 1860s didn't have to lead to vertebrate trees similar to those based on DNA. But it does, and that is a truly "delightful" fact, one that is a direct result of the common ancestry shared by living things as Charles Darwin theorized 150 years ago. Science journalists should try to make this extraordinary discovery clear to the public rather than obscuring it with buckets of hyperbole.
Without a tree of life, Darwin’s central doctrine is undermined. The tree of life metaphor represented Darwin’s attempt to unify all of biology into an explanatory framework. If we don’t know who is related to whom, and what came from what, all hope of unifying biology in a law-driven, naturalistic framework is called into doubt. The reality is a web of life. A web has no root. The information is all there; it is just shared. Where did the information come from? Darwin said it all had a common origin in a warm little pond, took root, and branched progressively outward into a glorious tree. If that metaphor is being replaced by a web, where is the designing spider?
The spiritual nature of Darwinism is revealed when questioning this metaphor.
The apologists point out the heresy. The analogous Genesis story has its "tree of life" and classification of animals, just as Darwin has declared with his "tree of life".
A web has inter-connecting links between radiating lines. In evolution this would suggest cross-breeding between distinct species. This does not happen in nature. Some cross breeding occurs (i.e. hybridization) between very closely related species. For example, tigers and lions, species of butterflies, horses and donkeys, and some canine species. However, distinct branches cannot cross (i.e. a horse can not breed with a cow).
Evolutionary lineage is best described as a tree. However, even this is simplistic as it creates distinct nodes, giving rise to the "need" for transition species. In reality there are no nodes. Every species is undergoing evolution, making everything a transition species.
But point taken. Where science is relatively steady and established, especially these days, it is a bad idea to portray it as otherwise.
Nope.
Can new information refine certain ideas about mammalian evolution? Sure can. More information is always welcome. But what never happens is that new information completely contradicts old information. New information almost always "fits."
Think of it like a puzzle. We not only have to put the puzzle together, but we have to find the pieces, too. The more pieces we find the more pieces we can connect. Some pieces don't have a definite place, yet -- we don't have enough pieces to get the picture in that area. But in large areas we not only have pieces that fit, but that put together a consistent picture.
So hyperbole of the "this changes everything" sort is unhelpful. We have these creationists who don't want to know what the picture looks like and won't look at it. They will look at some individual pieces and pretend two things might go together without any evidence for it. They *like* the hyperbole because it allows them to "challenge evolutionary assumptions" with their own "model" (which models nothing and uses no evidence).
The piranhaconda has the be the coolest cheesy abomination to crawl out of the microRNA slime lately.
Lune
Hyperbole sells units and unit sales are what they want.
thanks for the article! I thought the same when I read the headline in Nature. The need to seel your science, and the willingness of journalists to use superlatives (how many times have I been asked if my results "re-write the textbooks"...) are really doing more harm than good at times. It would be great if we were able to make the public understand that science is not about "re-writing the history books" (at least not in one go), but about finding all the pieces to put the puzzle together. Thusm, instead of expecting that all your research is amazing and world-changing, the public might finally understand that there are topics to investigate that, for themselves, seem trifles - but they lead to the next puzzle piece, without which the total picture would not be complete.
Did you read more than the headline in NATURE? If you had, you would know that Asher's critique and your follow-up post are pure poppycock, as regards Dolgin's article. At any rate, how can we take seriously an author (Asher) who sets out to criticize hyperbole but subtitles his article (I assume he did) "How Hyperbole Poisons Everything."
I'm sure he wouldn't exaggerate hyperbolically. Naw, never in a million years.
Lune
The bizarre smorgasbord of animals you listed completely misrepresents the point of the article - to describe a worker who's perhaps better identified strings of common ancestors.
I trust you can do much better in a whole book than you show you can in a short promotional article for that book.
If you want to use if for blurb on your pseudo-creationist tomes, then you should make sure the last line is included too.
"The link" as you say amouts to a different root position for the same topology (see the article's "duelling trees" figure). The trees depicted are not sufficiently different to merit the exaggerated claims in the article. The headline implies that something fundamental has been overturned about mammal phylogeny, moreover from a paper that's not yet been published. That's what I'm complaining about.
The different species I mentioned are relevant because previous microRNA papers have been actually published on them (e.g., turtles & jawless fish), showing topologies largely consistent with previous ideas on vertebrate phylogenetics.
It's an important mission to help translate science in any field into a non-expert account, as this is how the public comes to understand science (since its definitely not through the US's education system) and can be a way of facilitating interfield scientific discourse. Accurate translations of scientific papers rely on a sufficient understanding of the field to provide context for the article. Maybe this should be a dedicated position at every news agency that writes about science (im sure it already is at some like sciencedaily and physorg).