The Atavism

Sunday, October 2, 2011

Sunday Spinelessness - For aussie beetles, beer bottles are an evolutionary trap

It's Nobel season. Over the next month or so, we'll hear who has received a telegram summoning them to Stockholm and to fame and fortune (the cash part of the prize is worth about 1.5 million dollars). Of course, the Nobels are a big deal. Prizes are given to recognise people who have fundamentally changed the way we think about the world or the way science works. So it's nice that in the week before we start thinking about those huge sicentific acheievements we have the Ig Nobel prizes to remind us that most science is small, and sometimes it's even prettty funny. The Ig Nobels were set up to honour science that "first makes people laugh, then makes them think". This year's winner were announced on Friday and prizes went to researchers who trained a tortoise to yawn on command so they they could find out if yawning was contagious among these animals (it's not), a Japanese team who developed an alarm clock that wakes you up by spraying a fine mist of wasabi across the room and a team who finally provided an answer to that age-old question - "why do discus throwers get dizzy while hammer throwers don't?" (here's that answer). But perhaps the award that's done the most to make people laugh is the one presented  to Darryl Gwynne and David Rentz in recognition of their studies into male Australian beetles that would rather mate with beer bottles than their female counterparts.

The beetles in question are Julodimorpha saundersi, a member of the jewel beetles (Buprestidae) and native to desert habitats in Australia:
BIG beetle 
J. saundersi. Thanks to Jean Hort for sharing this photo as CC2.0
Mating season has probably just finished for these beetles. Adults emerge around August and for next couple of months male J. saundersifly about the place looking for females, which are larger than the males and flightless. So, for millions of years male J. saundersihave spend their springtime looking down hoping to find large (because large females produce more eggs) shiny, amber coloured surfaces covered in dimples like those on the beetles back. And for millions of years I'm sure that worked fine. Then someone invented beer bottles, and because some people suck, beer bottles starting turning up on roadsides in the Australian desert. Apparently, some Australian stubbies* have a series of dimples across the bottom. When a J. saundersimale sees one of these bottles he presumes he's won the reproductive jackpot and found the biggest, most amber, most dimpled female to ever live and... well.. you can see what happens next for yourself:
Image © Darryl Gwynne
Gwyne and Rentz found that they could attract males just by putting beer bottles out, in 30 minutes of observation that managed to lure two of them. Sadly for J. saundersi, this battle with the bottle can have devastating effects. Gwynne observed a beetle being attacked by ants "which were biting at  the soft portions of his everted genitalia" and another dead one being eaten by ants.
I have to admit, the idea of a beetle so madly fixated on a beer bottle that it will give its life in the hope of mating with it is so ridiculous as to be funny. So I'm laughing, but is there anything in this research that fulfills the Ig Nobel's other criterion and makes us think? Well, I'm not sure you and I are so different from a beetle with a pathological sexual attraction to discarded beer bottles.

J. saundersi males had a perfectly sensible approach to finding partners that only broke down when a sudden change in the environment made last generation's strategy look stupid. Any species can fall into that trap because natural selection, the process that makes organisms fit their environment, has no foresight. All that selection can do is adapt the next generation to the last habitat. Usually that's fine, but lately habitats have been changing quickly. The rapid technological change of the last few thousand years has left humans in a few evolutionary traps of our own. The most commonly cited example is about food. Until recently, foods rich in fat and sugar were pretty hard to come by. Since these foods are important for regular running of our body, we have evolved brains that reward us when we eat them. Today, our brains no longer match our environment.  In most western societies fatty and sugary meals are about 10 minutes drive away and, perhaps not surprisingly, the developed world is dealing with a epidemics of obesity and type 2 diabetes. 

I think there is an even more important example of this phenomenon for people that aim to live a skeptical life - our brains developed in a world quite different than the one we live in. The share volume of cognitive biases that psychologists have identified reveal how our intuitions can stray from reality. Not all of those biases arise from a mismatch between our brain and our environment. Brains aren't truth finding machines, because knowing something is true doesn't, in and of itself, provide any survival advantage. But some of these mistaken intuitions really do seem to arise from our evolutionary history. Most of the people that have ever lived have done so in bands of about 50 people. Every piece of news they ever learned about the world came through those people, and maybe a few interactions with other groups. Today, I can open a new browser tab and read one of 50 million twitter streams; or watch, read and hear news from almost anywhere on the planet. But I have still have my brain, which mainly evolved to deal with news from about 50 people, so part of me is amazed when I hear someone won the lottery three times, or someone else has given birth to three children in three different years but each at 7:43. Of course, in a world of 6.7 billion people these things have to happen, but, as much as I know that, it's hard to convince my brain these aren't amazing events. 

I said this fact problem matters for skeptical types, and, indeed, our faulty intuitions can have effects at least as bad as those faced by the amorous beetles that precipitated this post. If you live in a world with 50 contacts, and one of them tells you they got sick after eating a specific sort of food, that's pretty good evidence that you should avoid that food. If you live in a world with billions of potential contacts, and one of them tells you that someone, somewhere got sick after receiving a vaccination or got better after taking a homeopathic remedy that's not evidence for anything. Just like the triple lotto winners, in a world where millions of doses of vaccine given out, someone will get sick after a vaccine whether it causes an illness or not.  Thankfully, we've developed methods that help us, as much as possible, to remove our intuitions from the way we handle evidence. Together, we call those methods science and it's crucial that those methods are the heart of the way our societies develop if we are going to avoid our own evolutionary traps

So, by all means laugh at J. saundersiand his futile, fatal attempts to impregnate a glass bottle, but do try an be aware that similar traps are lurking in our own brains.

Gwynne, D. & Rentz, D. 1983 Beetles on the bottle: male buprestids mistake stubbies for females (Coleoptera). Australian Journal of Entomology, 22, p.79-80. doi: 10.1111/j.1440-6055.1983.tb01846.x
 *For people outside Australiasia, a stubby is a short brown 330 mL bottle which usually contains the caramel fizz that gets called "ale" or "draught" beer down here, but is, in fact, a lager.  

Thanks to Ted, the blogo-sphere's foremost beetle taxonomist for pointing out this species is not called J. saundersi, as it has been shown to be distinct from J. bakewilli the name this population bore when the paper was written

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Posted by David Winter 5:25 PM


Wow - that's fascinating! What beautiful beetles.
It should be noted that the species discussed in the Gwynne & Rentz paper is actually Julodimorpha saundersii, which at the time of their publication was considered a synonym of J. bakewellii. The former occurs throughout SW and Western Australia, while the latter is limited to eastern Australia. Refer to Bellamy & Wier (2008).
Thanks guys,

And especially Ted, always on hand for a taxonomically informed comment on beetles! I don't think a single report on that story got it right!

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