Popcorn Biology: Avatar (2009)

Avatar

The Smurfs get an upgrade.

Avatar, the highest grossing film of all time, adorated by legions of fanboys and hated by some intellectuals, especially directors who aren’t as rich as James Cameron. My verdict? In the middle: the story and characters are of course pretty bland and forgettable (and also a rip-off of Pochaontas, as everybody noticed) and the movie was probably too long, but the special effects are of course the most spectacular ever seen, and the action scenes are great. If you want a couple of hours of mindless, stupid, brightly coloured fun then Avatar is for you. Many also praise the supposedly very creative design of the creatures of this fantasy world; while some beasts are indeed cool to watch (especially the flying ones), to me many others seem just a lazy effort to make normal animals look weird only by adding a couple extra limbs and some featherish..things. Also, the color pattern of some animals seems to have been chosen pretty poorly (they look like they have taken part in some wild paintball battle). On the other hand, many people complained that the Na’vi were too human-like, but this didn’t bother me; yes, a weird and improbable example of extreme evolutionary convergence, but I can understand the decision to make the aliens look like us, since they’re the focus of the whole film and we have to empathize with them.And it’s not like the rest of Pandora is much more reality-based anyway.

Speaking of which, I digress. This is Popcorn Biology, I should criticize the biological aspects of this movie: a difficult task, as they are many, and many fanboys of the film have probably analyzed them in detail for years. I’ll do my best.

The first thing, the one that bothers me the most, is that for some reason humans can’t breath Pandora’s atmosphere. Which is incredibly odd since Pandora is largely covered in forests, made of trees with an uncanny resemblance to Earth’s trees (another extreme case of convergent evolution?). They’re green, ergo they have chlorophyll, ergo they do photosynthesis, ergo they produce oxygen. A lot of trees means a lot of oxygen, at least during the day.

Though, to be fair, it’s revealed that, in spite of their appearence, the trees of Pandora are quite different from ours, as they communicate with each other through electric and chemical signals, which means they have an equivalent of neurons, I guess. The trees and the animals of the planet are linked in a gigantic neural net, which of course is a concept inspired by James Lovelock’s Gaia “hypothesis”, which is less of an hypothesis and more of a vague metaphor made to capture the imagination of common people. I think that this SMBC cartoon explains my point perfectly.

Of course people tend to think of plants as a background, and focus on animals. What about the animals of Pandora? Well, as I’ve already said, they’re weirdly colored, as if the evolution on that planet didn’t give a fuck about camouflage, on the contrary of what happens here on Earth (no convergent evolution in this case?). Pandoran animals shown in the movie anyway are pretty big: maybe they don’t care about camouflage,, and on the other hand have evolved a system of communication based on colours and vision. The hypothesis is reinforced by the fact that most of them are also bioluminescent. On a side note, most Pandoran plants are bioluminescent too: do they need it to attract pollinators, or to lure the animals for some other reason? Who knows.

I’ve noticed that many animals on Pandora seem to have a respiratory system based on multiple tracheas that open directly on their chest. Maybe this is an adaptation to make possible their big size: enormous animal, especially erbivores, need to eat constantly enormous quantities of food; if they had to breath through the mouth (they’re not really technical tetrapods, so we’ll just assume that it’s possible that they can’t breath through the nose – do they even have a nose?) they would be forced to regularly interrupt their feeding not to die suffucated. This way, they can eat continuously without interruption, thus being a lot more efficient. It’s interesting to note that snakes have a similar adaptation to solve a different problem: they have to swallow the whole prey, so their mouth is occupied by food for relatively long periods of time; not to suffucate, their trachea is extended in their mouth, under the food, and it’s rigid so it stays open and able to breath even when the mouth is full.

The fact that most vertebrate animals of Pandora (although technically they’re not vertebrates, nor animals: they don’t share any common ancestor with animals, since they’re alien organisms) have six legs puzzles me. As I’ve said before, the creators of the movies designed them to be very similar to real animals (in this case tetrapods, especially mammals) in their shape and movement; so, since they move exactly like four legged animals, what’s the advantage of an additional pair of legs? The answer is: none. On the contrary, there are disadvantages: let’s put aside the fact that it would be more difficult ot coordinate them, every additional limb has a cost in term of energy and resources used to create and feed it: if it’s not useful (and in this case it’s not, since we’ve already estabilished that these six-legged aliens move in the exact same way of their four-legged counterparts on Earth), natural selection will make it “disappear”.

Speaking of legs, one of the nerdy criticisms about the human-like appearence of the Na’vi was that they only have two arms and two legs, while the rest of the fauna have 6 legs. I’ll defend Avatar on this one: first of all, this criticism sounds like “Most mammals have a tail, so humans should have a tail too to be considered mammals” (ironically, Na’vi do have a tail). Most important, the creators of the movie actually show a possible “evolutionary sequence” for the loss of limbs: a group of what are called “Prolemurs”, monkey-like creatures, still have sik legs, but the first two pairs are fused from the shoulder to the elbow. So in the Na’vi, other primate-like creatures, the fusion of the 4 arms to form 2 was complete. Maybe they evolved this way for the reason I explained in the previous paragraph, but it’s kind of strange, considering that they’re probably the only “vertebrates” on Pandora that could actually be advantaged by an extra pair of limbs, seeing how they have hands to grab and manipulate things. Oh, well.

Wow. That was long. Consider it a gift for the end of the year. I’m going to Rome for the holidays, so my blogging for the next seven days may be discontinuous to nonexistent (again). Happy new year folks, see ya in 2012.

December 31st’s Featured Organism: Branchiostoma lanceolatum

Branchiostoma lanceolatum

The origin of all vertebrates, you included, wasn't probably very different from this guy.

Yeah, yeah, late again; this is the last featured organism… of this year. So I wanted to commemorate our origin as vertebrates: it’s true, the lancelet (Branchiostoma lanceolatum) is not exactly the direct ancestor of all vertebrates, as once was thought; it’s part of the Cephalochordata, the sister group of vertebrates (well, unless Urochordata are the sister group of vertebrates, and Cephalochordata are the sister group of both, which lately seems to be a more likely hypothesis – the debate rages on). Still, it’s one of the closest living relatives, if not THE closest living relative, of vertebrates, and its body structure is probably very similar to the real ancestor of vertebrates. This little marine animal that burrows in the sand, filters food particles from the water and is barely able to swim clumsily ondulating its body, reinforced by a notochord, is probably not very different from the species that many millions of years ago started the radiation that would eventually originate sea squirts, hagfishes, great white sharks, goldfishes, giant japanese salamanders, snapping turtles, velociraptors, iguanas, ostriches, porcupines and humans, among the other things with a spine (or just a notochord).