Aliens have got nothing on us
Scientists say the movies don’t go far enough. Ben Guarino reports.
said Tommy Leung, a parasite ecologist at the University of New England in Australia. ‘‘Oh, burst out of the host’s chest – pfff, is that all they do? They don’t make the host become its surrogate parent and care for it like its own brood? They don’t multiply within the host’s body and turn it into some kind of flesh marionette? ‘‘Lame,’’ he concluded. When barnacles of the group Rhizocephala infect crabs, the parasites force the crabs to become doting parents. Some barnacles tweak the crab’s body shape, castrating male crabs to act like mothers. Others grow their roots into crabs’ guts and steal nutrients. Or they grow into brains so the crabs will tend to a barnacle brood. ‘‘That’s the kind of thing you don’t seen on screen,’’ Leung said.
As for ‘‘flesh marionettes,’’ Leung described a type of parasitic wasp: the emerald jewel wasp, which turns cockroaches into bug puppets. The female wasp hunts down a roach three times her size. She paralyses it but doesn’t kill it. Instead she inserts the end of her tail into the cockroach brain.
She begins to feel her way around. ‘‘The tip has all these tactile and chemoreceptors, the equivalent of taste buds, to find the sweet spot on the cockroach brain,’’ Leung said. The wasp tastes and feels its way to just the right nerves, where it delivers a mind-controlling venom.
The roach ‘‘becomes a subservient lap dog,’’ said Leung. The enslaved bug crawls into the wasp’s burrow, where the roach will spend the rest of its life being eaten.
The idea that a parasite could become a hybrid of host and original organism, as seen in Alien sequels, has some scientific merit, too, said Leung. ‘‘There are reallife parasites, particularly parasitic plants, which have been known to pick up some genes from their hosts,’’ he said. ‘‘I think the plants are actually better at how they use their stolen genes.’’
In October, researchers at Penn State reported that a broomrape plant had absorbed its host’s genes 52 times. ‘‘We think this is because of their very intimate connection with their host,’’ Penn State biologist Claude depamphilis explained at the time. The stolen genes allowed the broomrape to undermine the host plant’s defensive efforts, the scientists said.
The process of stealing genes is called horizontal gene transfer. Researchers have uncovered examples of this transfer with increasing frequency, Smout said.
‘‘It’s going literally across species,’’ he said. ‘‘It’s amped up for sci-fi, but crossing between species isn’t as crazy as it sounds.’’
Aliens could learn a trick or two from these gene-stealing plants. (Despite their fangs and acid blood, the aliens keep losing to the human defences of ingenuity and flamethrowers.) That the aliens don’t undermine or change our behaviour is their biggest failing, in Leung’s view.
The Alien monster isn’t simply outclassed by real-life brainbending Earthling parasites. It has a few imperfections in which parasite logic was sacrificed for horror-action narrative.
In The Science of Monsters book, journalist Matt Kaplan critiqued the creatures depicted in the 1986 sequel Aliens.
The monsters slaughter us too easily, he said. It is an ‘‘evolutionary quandary,’’ Kaplan wrote, that ‘‘borders on being a story flaw ... It makes no sense for the aliens to be such capable human-killing machines. Instead they should be masterful human kidnappers that are adept at feeding on some other species when they reach adulthood.’’
Each dismembered space marine, he noted, is one fewer warm body for incubating a chestburster.
Leung argued that the chestbuster cycle was inefficient, as well. Some parasites grow to huge proportions inside their hosts. But they stay put, turning the host into a ‘‘parasite factory’’.
One fish-dwelling crustacean gets so big it would be like having a rabbit in your chest, he said. The crustaceans poke a tiny hole in the side of the fish to spew, over time, thousands of baby parasites into the ocean.
Smout offered a gentle critique of the critiques. The monsters in Alien have only been infecting humans for a few generations, he noted, whereas on Earth parasites have evolved alongside hosts for far longer. Of course extraterrestrials wouldn’t be expert human parasites – yet.
There is one final place where the animal logic of Alien holds up: the human approach to parasites. It’s revealed, toward the end of the movie, that a shadowy space conglomerate wishes to capture the parasite for entrepreneurial purposes.
Parasitologists like Smout are doing the same thing, although Smout’s designs for his parasites are more humanitarian.
He is working on turning the spit from the parasitic liver fluke into wound-healing medicine, having discovered that it encourages cells to multiply faster. ‘‘It’s ultra-potent and causes cells to hyper-proliferate,’’ he said.
He envisions using the substance to close wounds suffered by diabetics or other people who heal more slowly than average.
‘‘The worm crawls along your liver, munching away,’’ he said, ‘‘but it wants to keep you healthy.’’
Parasitic aliens, take note. – Washington Post