Just so….
Wow, Snake-spotting may have helped us evolve-study, serious bullshit. No “study” really, just story telling. This kind of crap makes evolutionary biology look bad.
Update: The full paper is up in the forum as “snakes” (PDF).
Update by Darth Quixote: John Hawks, while critical, does have some nice things to say about this paper.
What’s your problem with this theory? Of course, to say that a single factor was solely responsible for a particular evolutionary development is a little over the top, but regarding it as the main contributor is not (granted, I don’t know how to measure “contribution” in this case). Moreover, what theory of the evolutionary development of *anything* doesn’t involve “story telling”?
Gee Armasus, it’s just free speculation. Without some quantitative link or proposal for test it’s unfalsifiable. As Razib says, just-so story.
Yes, this isn’t science in any ordinary interpretation of the term, whether or not one believes the term confined to empirical evidence or not. As Razib remarks, it’s a “just-so” story or, as I’d call it, a “what if?” conjecture, hardly rising to the “hypothesis” level. It’s just the sort of vague idea that could as well occur to a bright 8-year old as to an established professor.
And, considering the relatively late arrival on the scene of venomous species to complicate the lives of primates who couldn’t have been likely to regard any but the larger snake species as especially fearsome (and hysteria-inducing), the advantages of such development of eyesight and information-processing nicety would seem of far broader importance than an occasional venomous snakebite would suggest. In particular, as most who have much knowledge of reptiles are aware, most species (except in Australia) are non-venomous; even further, for those reasonably able to get beyond whatever their initial revulsion quotient (and leaving aside the instinctive vs. cultural question), in any particular geographical environment, it’s relatively easy to make a distinction (V vs. non-V) based on just the same type of visual information as our gal posits as the basis for an indiscriminate fear.
It’s not “back to the drawing-board” for this one; it hasn’t enough to be put on the drawing-board in the first place.
She should have tossed this around with my old friend and her “neighbor” Ed Dawkins, MD, over 30 years an orthopedic surgeon in Davis and still less than 10 miles away in Winters, where he and his wife (Master’s in Biology or sump’n,
UC, Davis) live on a rural property well-endowed with reptile species, including local “rattlers.”
I’ve got no definitive information except the distillation of many years as an amateur herpetologist and one with substantial experience with peoples’ attitudes (long-ago employed in several reptile exhibits): most of the commonly-observed reactions are nearly entirely culturally-transmitted.
That’s my opinion and I’m stickin’ to it.
Without some quantitative link or proposal for test it’s unfalsifiable. As Razib says, just-so story
Granted. But, then, how would Darwin’s original theory haved differed in this respect? It was only later — with the scientific discoveries of Mendelian genetics and the structure of DNA — that quantitative tests became possible.
Not that I think this particular hypothesis seems especially plausible: keen eyesight was necessary to distinguish between poisonous and non-poisonous fruits, for example, and probably a bunch of other stuff.
Yes. At the same time as we diminish the value of conjecture (especially its worthiness as a topic of publication), we shouldn’t lose sight of its validity as a source of scientific thinking and research. To a great degree, all science originates with various sorts of conjecture. Of course, some conjectures are a good bit less conjectural: see the post (and cited article) by razib on another thread regarding testosterone/breast cancer. In one sense, these things come down to WHO is doing the conjecturing: I’d wager that those with scientific (and quantitative) backgrounds are more qualified to raise conjectures that will “pan out” and yield results.
The abstract is available at http://dx.doi.org/10.1016/j.jhevol.2005.12.012
I’m with Razib… this is absurd story-telling with no evidence or testable hypotheses. We could write a similar paper saying that we evolved such vision in order to determine which rocks were stable and which were not in steep mountain hikes.
This is rubbish!
As I remember Carl Sagan posited a fear of snakes and even a basis for midieval dragon legends in his theory of the “triune brain”. He called our most primitive sub-cortical structures the “snake brain”. Somehow having that residual snake structure in our heads predisposed us to hate them.
Sounds like something only Tom Cruise could believe.
“There’s an evolutionary arms race between the predators and prey. Primates get better at spotting and avoiding snakes, so the snakes get better at concealment, or more venomous, and the primates respond,” Isbell said.
This part is obvious rubbish. Poisonous snakes are not large enough to eat primates, for one. Also, the snakes large enough to eat a human–the anaconda, the African rock python, and the reticulated python–are not arboreal, as they are too large to scale trees. Indeed, the anaconda is so large that an adult supports its mass by living in the water.
Many humans have died over the millenia (still a shockingly high number in India) and its likely that we’ve evolved some traits to deal with this threat, but the cause has been accidental poisonous encounters, not from being hunted. Some of our very distant, smallish ancestors (read: monkeys) would have been hunted by snakes, but any evolved characteristics would have long-since been lost.
some of our very distant, smallish ancestors (read: monkeys) would have been hunted by snakes, but any evolved characteristics would have long-since been lost.
Now this is rubbish. The article clearly talks about the evolution of primate vision (which would then have been passed on to humans) not about the modern human evolution. Why would these evolved characteristics long since have been lost?
|Now this is rubbish. The article clearly talks about the evolution of primate vision (which would then have been passed on to humans) not about the modern human evolution. Why would these evolved characteristics long since have been lost?
I should have clarified that last point. The trait must have some other raison d?être or it would have been lost in the subsequent several million years through genetic drift, if nothing else.
I should have clarified that last point. The trait must have some other raison d?être or it would have been lost in the subsequent several million years through genetic drift, if nothing else.
No, genetic drift is only effective in small and isolated populations. It seems peculiarly ad hoc to invoke it here.
No, genetic drift is only effective in small and isolated populations.
Which is exactly what the ancestral population was for 99% of the time between when the alleged adaptation occurred millions of years ago and when our ancestors spread beyond a few thousand individuals.
Tell me, why do humans have inferior olfactory faculties? Our ancestors were undoubtedly stronger in this department at some point in the past–as are virtually all other mammals–and yet this trait has disappeared. Surely, having a good sense of smell didn’t have a deleterious effect on survival? What must have happened is that due to other human characteristics (superior vision? canine companions?), a strong sense of smell became superfluous. No longer necessary, the effort required to maintain our sense of smell would have been coopted to some other use. One would expect the same thing in humans were a superior sense of sight unnecessary beyond mere snake avoidance.