Friday, January 20, 2012

Ants, atavisms and bad science journalism

Some of you may have heard about a study investigating an inducible atavism in ants which was published earlier this month in Science. An atavism can be thought of as the reappearence of an ancestral trait in derived species (ie: a species that has evolved more recently). There are actually quite a few examples of this kind of thing happening. Some cetaceans have been documented with marginal rear limb development.  In fact, we have known about chickens that develop teeth for over 50 years. In the case of the chickens, the mutations in nature are lethal which prevents the birds from even hatching but they survive long enough to grow teeth. Some human examples of atavsisms include development of a dorsal cutaneous appendage (tail) and supernumerary nipples. Atavisms shouldn't be confused with vestigeal organs, though. Atavisms tend to re-emerge suddenly due to some sort of mutation that changes the way genes are expressed. Vestigeal organs are ancestral traits that are still present in the population but in a greatly reduced form.

Atavisms are particularly cool because they provide some excellent proof of evolution. A lot of people tend to think that the fossil record is the cornerstone of evolution. That may have been true in the past, but now the vast majority of our understanding of evolution is being generated by molecular genetics. It is possible to examine the ancient past by investigating genes that once played a role in the development of ancient traits. For a more indepth look at how atavisms relate to evolution (and how they cause issues for creationism), this is a good post to read.

In the case of the study on ants, the discovery of an inducible atavism in the genus Pheidole has changed the way we look at how that genus evolved. The atavism, in this case, is the development of the supersoldier ant subcaste. Previously, it was thought that supersoldiers evolved independently a number of times. The most striking difference between regular worker ants and supersoldier ants is size. The head is particularly large when the two are compared. 

The study revealed that some species without supersoldiers in the genus Pheidole could have them induced by introducing a chemical called methoprene (an insect hormone analog). This is some pretty compelling evidence that the supersoldier subcaste is actually an ancestral trait which has been lost multiple times. This is very different from the previous hypothesis that supersoldier subcastes are derived/new traits that have evolved multiple times more recently.

As I alluded to earlier, the ability to chemically induce atavisms isn't exactly new. Axolotls are a paedomorphic (they retain juvenile traits into adulthood) species of salamander that are closely related to Tiger Salamanders. If you expose them to iodine, they will undergo metamorphosis and develop traits that more closely resemble the adults of related salamanders and their ancestors.

So, how do you think the general media reacted when this study was published?  MSNBC decided to introduce the story like this:
Apparently, everything I told you about the study earlier was entirely wrong since, according to MSNBC, the real purpose was just to see what supersoldier ants do. Also, it seems supersoldiers  in Pheidole don't exist at all anymore. Who knew?

The Daily Mail decided to introduce the story with this headline:
Yeah... I'm not even going to comment on this one.

I really shouldn't be surprised at this point. This isn't the first time that atavisms have been butchered in the media, particularly by the Daily Mail. Check out what they had to say when scientists were able to induce teeth in otherwise normal chickens:
...sigh.

2 comments:

  1. Wow and yet again I feel like crap

    ReplyDelete
    Replies
    1. D: Why? That's definitely not what I'm trying to do!

      Delete