"about the idea being retracted "
It bothered me that they brought up the frog DNA and, to my recollection – and I stand by this – it wasn’t brought up in the screenplay at all. There isn’t any reason for them to bring up the frog connection if they don’t tie it into either effect, but I don’t believe they ever do so. “Life will find a Way” quoth Sam Neill’s character, and there’s an end to it.
Crichton is backing and filling to try and make up for his earlier errors. Sir John Roxton is a character in the original Sir Arthur Conan Doyle The Lost World. And there’s no doubt in my mind that Crichton clearly meant to imply that the T. Rex motion-sensitive vision was derived from Frog DNA. Why make a point of using as unlikely a thing as frog DNA in reconstituting a dinosaur otherwise? And why (as we see from Darwin’s Finch’s quote) make a point of the T. Rex having frog DNA otherwise?
Ha! That’s obviously a little in-joke by Crichton. It’s a reference to Lord John Roxton, the gentleman hunter in Arthur Conan Doyle’s original The Lost World (1912). I’m pretty certain no such research exists.
Colibri, are you me, only slightly time-shifted?
I don’t remember the source, but I recall learning that frogs are in an unconscious state unless their eyes detect motion. Unlike our time-linear perception of the world, a frog’s worldview is intermittent. I can see some evolutionary benefit in such a model from a conservation of energy standpoint, but I’m not sure how reliable my source was. Anyone else?
Or maybe Darwin’s Finch is.
(Scene of CalMeacham pricking finger, and drawing blood. “Oh, Cal – that hurt!” And suddenly he’s surrounded by two versions of himself. They all look like Richard Attenborough.)
[QUOTE=Colibri, are you me, only slightly time-shifted?
[/QUOTE]
You without previewing. 
Regarding sex determination, there was really no reason to invoke frog DNA for an explanation in the first place. Most amphibians have chromosomal-based sex determination, although apparently there can be some environmental influence in some species. (I am not aware of this in any frog, although it does occur in some newts.) However, temperature-based sex determination is well known in reptiles, including turtles and crocodilians; the latter are the closest living relatives of dinosaurs besides birds. It would not be a great stretch to imagine sex reversal being possible in dinosaurs even without foreign DNA. In fact, some scientists have proposed that increased temperatures could have contributed to the extinction of the dinosaurs due to changes in sex ration. (Very implausible, IMO.)
Yeah, I did a cursory Google search, and found nothing regarding tyrannosaur brains being likened to frogs’ brains. It’s interesting that he would have attributed the faux paper to Roxton, though, instead of Grant, who seems to have kicked off the whole thing initially anyway. I, like Cal, recall it being at least implied in Jurassic Park that the vision thing was a consequence of the frog DNA (and I recall thinking it was monumentally stupid at the time), but, as I mentioned I can’t actually find any supporting evidence in the book. I’ll have to re-read it a bit more carefully…
Well, I stand by my recollection, too. So which one of us is going to watch it to find out for sure? I think I have the video at home (the hard part will be digging up a VCR to play it on).
I’ve got the video and the VCR. If I can, I’ll look at it tonight.
Well, this is all very interesting. Let me see if I can sum up:
-
If the consensus that TRex hunted live prey is correct, it may have had somewhat heightened motion sensitivity, like any modern predator.
-
But the idea of complete insensitivity to a nonmoving object is nonsense, and has never been advanced by any scientist. It was introduced in the book as an impicit consequence of patching in frog DNA . . .
-
. . . and got transmuted in the movie into a general statement about TRex’es, thereby negating its status as a frog-DNA consequence . . .
-
. . . and is now entering the vernacular as a fictitious “fact”, parroted by no less an authority than Dora the Explorer.
No wonder it’s taking longer than we thought.
Freddie the Pig – that’s my take on it, precisely. I think even those who disagree with parts of it in this thread still think Dora’s assertion isn’t justified.
So is it a fact that a frog’s vision is based on movement? If so, I have the same question about frogs that I had about T-Rex: how do frogs keep from hopping into trees or off cliffs, since trees and cliffs are motionless?
See post#20.
Most frogs of my acquaintance could see large stationary objects well. I used to keep them in terraria and aquaria, and it’s amazing to see how well and rapidly they could hide under existing cover.
I’ve heard and read that frogs are wired for motion-ensitive vision (couldn’t give you cites, though), and this must operate in conjunction with ability to see stationary objects. In other words, it doesn’t see,m possible that frogs are "blind’ to nonmoving objects, but evidently they “tune them out” and don’t notice them until they move.
If that sounds off-the-wall and extemporized, then I have to add that, to some degree, human vision acts the same way. I only learned this last weekend at the Boston Museum of Science. They have an interactive exhibit there in which you place an object just beyond the limits of your peripheral vision, so it’s effectively invisible. You push a button, and part of the object turns, and it becomes visible. Objects beyond the edge of peripheral vision, then, evidently still register on your retina and are detected, yet they’re ignored until they move.
Being at home today, I have decided to re-watch the movie. Gotta give the point here to DCMShirley. Here’s the dialog, at the point where Grant first stumbles upon the nest with Lex and Tim:
Grant: Oh, God. You know what this is? It’s a dinosaur egg. The dinosaurs…are breeding.
Tim: But, my grandpa said all the dinosaurs were girls.
Grant: Amphibian DNA.
Lex: What’s that?
Grant: Well, on the tour, the film said they used frog DNA to fill in the gene sequence gaps. They mutated the dinosaur genetic code and blended it with that of frogs. Now, some West African frogs have been known to spontaneously change sex from male to female in a single sex environment. Malcolm was right. Look. [see several baby footprints leading away from the nest] Life found a way.
Sorry Cal, you’re mistaken.
In the movie, when Alan and the kids find the nest full of fractured egg shells, Timmy asks how this could be if all the dinosaurs are girls. Then Alan says, paraphrasing, “The scientists said they used frog dna to fill in the gaps. Now, some ____ frogs have been known to change genders in a single sex environment. Ian was right…life found a way!” Then the camera dramatically pans down to the little baby dino foot prints leading away from the nest.
The blank was something exotic. West African? South American? I don’t remember.
I can’t locate a final script online. The closest I can find to a hard cite is on [url=]http://en.wikipedia.org/wiki/Biological_issues_in_Jurassic_Park Wiki page.
Darn you, Darwin’s Finch.
Well well well. To my surprise, there actually is support in the literature for this. The West African Reed Frog Hyperolius viridiflavus has been found to undergo spontaneous sex reversal, though it was from female to male. Otherwise such sequential hermaphroditism is known in vertebrates only in fish. So there actually is a small amount of logic to this one.
However, as I’ve already mentioned, there are easier ways to get a reproductive dinosaur population from a unisexual one than splicing in frog DNA. There are a number of parthenogenetic lizard species, and crocodilians have a heat-sensitive system of sex determination. Combine reptile DNA with a little hand waving, and you have a more plausible scenario.