Wednesday, February 4, 2009

D. melanogaster, We Hardly Knew Ye

I get the most adorable dominance displays from people with modest scientific backgrounds who assume I’m “just a dog handler.”

The incident of the day had started out mutually respectful, at least. The individual in question — an animal behaviorist [1] who’d come to a SAR conference to lecture to us on drives — had actually given me a lot of interesting new ideas to think about and employ. Mostly it took the form of an expanded list of instinctual drives that, in their combination, help decide an animal’s reaction to different situations and stimuli — prey drive, social drive, defensive drive, etc. Heather later told me it was pretty standard fare in dog training terms, but it had been new enough for me.

The changeover came after the talk, when I approached the lecturer to ask a question. I asked, got my answer, and then, perpetual optimist I am, offered a philosophical observation:

“Of course, we’re prisoners of our terminology, aren’t we?” I said. “We can’t be sure if any of these drives actually exist.”

I think I read a mix of emotions on her face: amazement at my temerity, engaging her as if I could grasp the material at her level; anger at what she perceived was a challenge to her entire career; pity at the possibility anybody could be so ignorant.

“These are the drives,” she said. “Of course they exist.” Then she got herself the hell away from me.

Of course, my statement was a bit over-reaching. The drives do exist, as a statistically valid entity; as a concept that can help us aim and craft our training goals; and I’d never disparage the power of metaphor for understanding the world. But on the day that we can put a portable combined PET/MR scanner on a dog’s head and actually see what her brain is doing when she is defending her litter, or cuddling with her pups, or chasing a ball, I’ll lay a bet that what we see is not three different brain states but a murky amalgam of subtle shifts in activity and unexpected overlaps that offer no neurological justification for what we thought were the basic modules of behavior.

My animal behaviorist couldn’t see that possibility, because her own training had been limited to just her craft. She’d never stepped outside the paradigm, and so could not see the ways in which the terminology she was using — the names she had been given by her teachers to use — had taken on a reality that might not be entirely, well, real.

Names are the crux of a brouhaha, recently reported by Rex Dalton in Nature, that’s, well, brewing among species taxonomists over the not-so-humble common fruit fly, Drosophila melanogaster. More data have been generated from this tiny beast and how its genes govern its development, anatomy, and behavior than possibly any other.

Thing is, it may have the wrong name.

It all has to do with how species are defined in the first place. When a scientist thinks she’s discovered a new species — whether it’s a live critter or fossilized bones — she needs to produce a type specimen. This is an example of the species that will serve as the benchmark for any other critters found. If the newcomer is too different from the type specimen, e voilà, chances are it’s a different species.

Just as species — in the fruit fly’s case, that’s its second name, melanogaster — are defined by a type specimen, the genus — the first name, Drosophila — has a type species. All candidates for membership in the genus are judged against that species. If you’re too different, again, you may wind up in a different genus.

You might think that D. melanogaster, having the high-powered, monkey-navigated support that it does, would be the type species for Drosophila. But genuses and species are defined historically, first come first served, and in this case another fruit fly, D. funebris, has precedence, having been identified by a dude with the suspicious-sounding name of Johann Fabricius in 1787.

Well, on second look, D. melanogaster doesn’t look as much like D. funebris as it ought. [2] It’s different enough, in fact, that some taxonomists are seriously thinking of renaming it Sophophora melanogaster, promoting what had been a subgenus to the status of a full genus. [3]

As I said, D. melanogaster has friends in the kinds of places where opposable thumbs can do a lot for you. The heresy of renaming one of the most important research species on the cinder was too much for some researchers, who’ve proposed that the type species for Drosophila be changed from funebris to melanogaster.

It isn’t clear what changing such an important animal’s name would do to the scientific literature. In the early Pleistocene, when I went to grad school and you had to look up articles in paper reference books, it would have meant utter chaos. Modern electronic referencing systems may make the switchover relatively invisible. But ya gotta love any science story that quotes a researcher — in this case, Therese Markow of UC San Diego — as saying:

“If this were some obscure beetle, you could rename it Godzilla and it wouldn’t make much difference.”

Well, at the time of publication, the International Commission on Zoological Nomenclature had not yet ruled on the issue, and had even suggested they might just leave it up to the researchers to sort out without an official nod. So maybe a fly is a fly is a fly after all.

For more discussion on the concept of species, and how it’s getting a little wear-worn, check out some interesting back-and-forth on Stephen Bodio’s blog. But please, remember: There is no such thing as “just a dog handler.”

[1] Yeah, the title itself loses any real meaning, ranging from Skinnerian operant conditioning technicians to ethologists -- interestingly, the Wikipedia entry is almost entirely ethological and hasn’t garnered a peep of protest from the Skinnerites.
[2] Or rather, their genes don’t look enough alike — the new relationships have been coming out of studies of the species’ DNA sequences.
[3] Taxonomists — don’t get me started.


Anonymous said...

Ken, what you're saying about drives is what I (and Stephen Jay Gould) have been saying about Spearman's g. All the studies that purport to show that there's a generalized intelligence or problem-solving ability start with the assumption that there's such an ability, and don't consider that what they're measuring may not be "real" in the sense required. Remember Thurston's multiple axes, which accounted for the same data as Spearman's g, but with a completely different interpretation.

Ken Chiacchia said...

Sure, I can see that -- though the analogy (if not the argument) doesn't rule out the potential use of instruments that measure g, such as IQ tests, if you can demonstrate statistical usefulness. Not to open that can of worms!

kabbage said...

I freaked out a math teacher (high school level, I think) last weekend by commenting that in the real world adding zero or multiplying by one really didn't have any significance. Yes, I hold a master's degree in engineering, so I have done a bit of higher math. Yes, I agree that the constructs of multiplying by one or adding zero can be necessary to describe physical things in mathematical terms. I just don't feel the need to add zero tablets of a supplement if the dog doesn't get the supplement at a given meal.

The word verification word is "comolest" which is eerie coming after the post above this one.

Anonymous said...

Well, as to comolesting... there are apparently a number of criminals--mostly women, but not always--who might not ever have done anything violent had they not been hooked up with violent criminals. Caril Fugate, Debra Denise Brown, Christine Gallego, that poor sap who was executed in Christie's place and who probably did kill his wife after all. Though in Brown's case I suspect she really was just as vicious as her boyfriend; certainly her comments in interviews sound that way. Reminds me that we may be liable, in God's eyes, not only for the people that we hurt directly, but for the ones we mislead and anger and tempt as well.

Just another cheerful thought from yours truly.