Which is more realistic, Alien or Predator?

In the current issue of SciFi Weekly, columnist Wil McCarthy gives a big thumbs down to the Christmas flick, Alien vs. Preditor: Requiem. Among other problems, like the plot, the biology is bad.

Worse still, this latest movie plays fast and loose with the known biology of both the xenomorphs (aliens) and the Yautja (predators). We know from previous films, among other sources, that the predators like it hot. Indeed, they visit Earth mainly in the tropics, and only then during the hottest years. Apparently, temperatures below about 40 degrees Celsius (104 degrees Fahrenheit) are uncomfortable to them. They also like humidity, preferring to hunt their prey in rain forests. In a pinch they'll drop down in Los Angeles, where the average nighttime summer humidity runs about 55 percent, but it's clearly not their preferred range.

This makes Gunnison, Colo., a particularly unlikely place for a trophy-hunting expedition; it's a dry, frigid mountain village where the highest recorded temperature—ever!—was 36 C (98 F), and typical midsummer days peak closer to 26 C, barely above room temperature. Now, I can maybe believe a pissed-off Yautja could patrol the area in its high-tech chameleon spacesuit, but would it really strip off that armor for a mere display of machismo? Especially during a rainstorm, at night, in the middle of October? At least I assume it's October; the movie opens with a father and son hunting deer with a rifle, the legal dates for which are available to anyone with a telephone, a library card or an Internet connection. I'm going out on a limb here by assuming that between directors Greg and Colin Strause and screenwriter Shane Slaerno (Armageddon), someone bothered to look this up! This of course begs the question of why the trees still have their leaves and no one has their Halloween decorations out, but never mind about that.

That isn't the only bio faux pas. There is also their amazing (and inconsistent) ability to survive in so many different environments, including oxygen or methane atmospheres - and even the vacuum of space.

The alien, in its original H.R. Giger incarnation and its later queen, dog and predalien forms, is known to retreat from fire and superheated steam, and while it's not affected by Antarctic cold, it does freeze solid at liquid-nitrogen temperatures. Xenomorphs are cold-blooded, but the nests generate their own internal microclimate, which again is fairly warm and wet by human standards. Still, all the evidence suggests that the xenomorphs are not related to the Yautja. Their homeworld likely experiences large swings in temperature—from well below freezing to just below the boiling point of water. More puzzling is the alien's ability to tolerate vacuum. How and why would it evolve an adaptation like that? I'm guessing the planet's air pressure varies along with its temperature, so that mountaintops—warm and habitable in the hot season—periodically find themselves in a Mars-like environment for a few hours or days. Then again, it seems the entire ecosystem sometimes dies off, or dies way back, and takes thousands of years to recover.

You should check out the whole column for more speculation on the physiology and evolution of these pesky aliens.

Here's my own creative Alien-Predator hybrid:



Tags:science fiction, biology, Alien vs. Predator: Requiem, evolution