This is a comment I left on a review of Avatar on Dark Worlds blog that raises issues with the lousy science in Avatar:
Then there is the subject of evolution on Pandora. All the animals have six limbs. Four up front and two in the back. All of them, including the Pterodactyl like creatures. Four wings and pair of legs. Four eyes as well. One pair above sightly farther out than the inner pair.
Everything except the Terminator Smurfs. Two eyes, and four limbs.
Radically different biology, yet they could mesh their nervous system with the local animals.
Did the Terminator Smurfs braid their hair to protect the nerve bundle or did it grow like that naturally.
Oh, why did the Pterodactyl like creatures naturally develop stirrups for the Terminator Smurfs?
With all the “scientists” they had on that planet, why didn’t any notice that the Terminator Smurfs obviously didn’t evolve there?
Update: One of the comments points out that the story line is remarkably similar to a Poul Anderson short story, “Call Me Joe.” There are also comments about the movie drawing from Ursula K. Le Guin’s “The World for World is Forest.” I would add Alan Dean Foster’s Midworld as well.