One of the key elements of my novel the Tau Ceti Diversion was the unique setting I imagined for the story. Specifically, an alien planet where the top evolutionary niche was filled by an intelligent insect race. So I needed to think about insect evolution, and how that evolution was affected by the amount of oxygen those insects could take in from the planet’s atmosphere to fuel their metabolism.
Now, it wasn’t going to be too much fun to have my human crew menaced by determined ladybugs or extremely intelligent grasshoppers two inches long, so I needed big insects! I needed a world where the entire biosphere – every single evolutionary niche, both large and small – was filled with insectoid life.
You think people shudder when they have to shoo an insect out of the living room window with a rolled up newspaper, how about having to face a three metre tall intelligent being, staring back at you with multi-faceted insect eyes? Creepy? Stay calm space-explorers!
On Earth, insects are small, and a variety of other life has evolved to claim the top evolutionary spots in the food chain.
The size of insects on Earth has been constrained by two main factors, the way they take oxygen into their bodies, and the amount of oxygen in the atmosphere. Change those two things, and everything changes. Insects were here first. If not for those two constraints, our little furry ancestors would probably never have made it out of their burrows, let alone up the primate tree.
Earth’s insects don’t actually breathe in the way that mammals do. Our insects take oxygen into their bodies through the process of diffusion, the precious oxygen passing across membranes directly into their cells, with waste gases passing out of the cell walls in the other direction. Our insects have a series of holes in their abdomen, called spiracles, that allow air to enter their bodies. From there, incoming air moves into a network of tiny tubes called tracheae. The biggest bugs have the longest tracheae, to allow them to get the most oxygen into their bodies.
Insects have a very limited ability to use their oxygen absorption equipment. They can open or close the spiracles by muscle contraction, and they can also pump muscles inside their body to try and increase the amount of air passing through the tracheal system, but to limited effect. The amount of oxygen they can extract from the air is always going to be limited by the tracheae shape and the rate of oxygen diffusion through the cell walls.
In the Tau Ceti Diversion, human explorers come face-to-face with evolved life dominated by insects, thanks in part to the planet’s high oxygen atmosphere, and an evolutionary adaption of the alien insects that has given them true lungs.
That’s not to say Earth didn’t have some big insects. At the moment our atmosphere has around 21% oxygen (by volume). The concentration of oxygen in the air has gone up and down throughout Earth’s history, mostly in response to what was happening in the biosphere. Toward the end of the Carboniferous periods (300 million years ago), oxygen peaked at a maximum of 35%. At this time there were some pretty impressive insects – like dragonflies with wingspans of over a metre in length. That’ s one hell of an insect, and all with basic air diffusion to get the oxygen into its body.
On my fictional planet of Cru, orbiting Tau Ceti, the oxygen concentration in the atmosphere is more than 30 percent, which certainly makes things fun for the explorers. They not only have to deal with huge insect life, but also have to deliberately moderate their breathing to prevent hyperventilation, and they have to be careful how all that extra oxygen makes any sort of combustion in the atmosphere more aggressive.
My novel, The Tau Ceti Diversion, is a story about our search for new planets to colonise outside our solar system. Much of the action takes place on planet tidally locked to Tau Ceti that has some rather unique life forms. The novel is due to be launched on September 1st 2016 – not long now! – and pre-order is available on Amazon! Read more about what happens in the story here!
Stay tuned for a free chapter download, coming soon!