In defense of speculative zoology

The attraction of speculative zoology is obvious: cool critters. But there is another reason to play the game. It is natural for us to look at the history of life on earth and wonder how much of it was inevitable and how much was accidental. This is maybe the biggest, baddest question in evolutionary biology, and a lot of ink has been spilled over it. Complex life was inevitable. No it wasn't. If you replayed the Cambrian explosion you'd get the same results. No you wouldn't.

Speculative zoology is a way to sneak up on these questions unannounced and, just possibly, take them (and yourself) by surprise. When I ask, "What would have happened if marsupials had gotten the northern continents and Africa and placentals had been stuck with South America and Australia?" what I'm really asking is, "Would changing the players on the board make any difference after a few rounds (= tens to hundreds of millions of years) of play?" Is evolution completely unpredictable, or are some things bound to happen just because the Earth and life are what they are?

When people ask me about contingency versus determinism in evolution, I usually pimp contingency all the way. But tonight I learned something surprising.

I was playing the God game with Randy (as described in the previous post) and he said he'd like to wipe out all eukaryotes. That's all the amoebas, fungi, plants, and animals, plus a few things you've probably never heard of. Bacteria and archaea would be the only survivors.

This suggestion momentarily discomfited me. I had a vision of the world stuck at the bacteria stage for billions of years. What if it never got past that stage? What if it was just Bacteria World until the sun went nova?

But then I thought, "Hey, wait a minute." The Earth already was Bacteria World for billions of years. But not forever. Complex life eventually got rolling. Things did come out on land. Things did learn to fly. A few things discovered fire and eventually blogging.

Don't get me wrong. I am familiar with the arguments for why all of those events were lucky breaks, one in a zillion long shots that might never be repeated. But I don't believe it anymore. I think they were inevitable. You can say, "Complex life might not evolve again" or "Consciousness might not evolve again". But you would have said the same standing on a Proterozoic beach or wandering through the rubble after Chixulub. It would have been wrong then, and I think it's wrong now. Whatever stage or level you think life might get stuck at, it's already been through once and didn't.

"Of course you think that because you're a product of a world where life never got stuck." Yeah, yeah, take your Anthropic Principle and cram it up your protostome. When I look at the history of life, there are some plateaus, but they don't last forever. Not a one. I don't think it was inevitable that some Miocene primates would come down from the trees and end up splitting the atom, but I think the combination of intelligence, tool use, and communication was bound to come along sooner or later.

I could be wrong. I'd be happy to be wrong. The upshot is that I've thought about this stuff more intensely tonight than I ever have before in my life, and it's mostly thanks to the game.

I also want to explain the effect that speculative zoology has on me. A naive observer might think of it as an escape from the real world, dreaming up phantasms to replace the mundane critters I'm stuck with, an ultimately life-denying exercise in futility. That's exactly backward. Playing the game doesn't make me appreciate life less, it makes me appreciate it more.

Just think about all the totally badass things that have ever lived. Giant pterosaurs. Indricotherium. Conodonts. Glyptodonts. Anomalocaris. Dunkleosteus. Koolasuchus (yes, really). Champsosaurs. Multituberculates. Mihirungs. Ichthyosaurs. Carcharodon megalodon. Sharovipteryx. Drepanosaurs. Effigia. Deinosuchus. Helicoprion. Pelagic trilobites. And yes, freakin' Amphicoelias.

In the immortal words of Tenacious D, that shit came off the top o' my fuckin' head, y'all. That's a ten-second seine haul through my RAM. The tip of the paleobiology iceberg.

Speculative zoology invites you to cast your eye over the whole Dramatis Personae of Earth's history and start rewriting their lines. You can't wish for a monotreme takeover unless you know and love monotremes.

You want to know the real whole total uncensored and unabashed truth? Screw sauropods (sorry, Mike, it had to be said). The coolest stuff that ever lived is alive right now. Whales with heads that wouldn't fit in your living room that live on mile-long swarms of crustaceans the size of boogers. A mammal with an electrosensory nose and poison spurs on its feet that dives for worms and lays eggs. Snapping turtles. Opossums. Peccaries. Poison dart frogs. Hummingbirds, man--the whole saurischian machine, that powered animals six stories tall, crammed into a fun-size package the size of your thumb. And they fly for thousands of miles, drop their bodies into torpor, and lay eggs that are even smaller than they are (not all at once, of course). Naked mole rats. Eagles. Hyenas. Saltwater crocs. Sturgeon. Loosejaws. Arctic terns. Armadillos. Axolotls. Kodiak bears. Velvet worms. Ratites. Hornbills. Sea otters. Manatees. Horseshoe crabs. Moray eels. Nudibranchs. Earthworms 20 feet long. Ruminants that can stand in the palm of your hand. SLIMES.

Ants, people! Crawling all over your bodies!

I cannot contemplate this smorgasbord, this wall-to-wall concentration of coolness, without wanting to run screaming into the street, shouting and laughing and tearing my clothes off. I exult in the facts that (1) these things are alive, (2) I am alive to see them, and (3) this is what I get to do with my life.

That straight-up pedal-to-the-firewall mushroom-cloud-in-the-rearview-mirror ROCKS!!

Further rounds of the God game

Sometimes you kick a rock and all you get is a sore toe. Sometimes you kick a rock and it hits some other rocks and pretty soon half the mountain is coming down.

It's probably too early to tell on this one. I blogged on Brain Candy Topic #117 the other day--or, as some would have it, threw down a gauntlet. Darren Naish picked it up. We'll see where it goes. I've already gotten some good suggestions, and I'm sure Darren will get a lot more.

I've got more ideas. Ideas for speculative zoology, and ideas about speculative zoology. I'm putting the former in this post and the latter in the next.

This evening I grabbed some awesomely cheesy, greasy pizza with my freakishly productive labmate, Randy Irmis, and we took turns coming up with evolutionary experiments.


I would like to see how Actinopterygii (ray-finned fishes) would fare if all the sarcopterygians (lungfish, coelocanths, all vertebrates with legs) suddenly went extinct. I assume they'd invade the land, but how? Their limb musculature is all inside their bodies. Would they be forced to truck around on fins modified into stilts? Maybe they would evolve jointed limbs actuated remotely by freaky long tendons. In gestalt appearance, they might be closer to arthropods than tetrapods.


I would also like to clear out all tetrapods other than bats. I've always been intrigued by the utter absence of flightless bats, and the flightless bats from After Man were wicked cool. What would a world repopulated by flightless bats look like? Would some bats find new uses for their fingers and wing membranes if they were no longer constrained to be airworthy? Would we get penguin bats? Whale bats? Fossorial bats? What if some bats lived in caves and only came out at night? Oh, wait.

I think games like this are a good heuristic for finding out what animals you are possibly more interested in than you realize. I would like to see a world where edentates took over. No, monotremes. No, lissamphibians.

As for Randy, he'd go back to the Triassic and rub out the cynodonts (basal synapsids get to live). Would mammals still evolve, or would reptiles get the whole pie? (My guess: the latter. Mammalian success in the Triassic looks like a fluke to me.) He'd to go the K/T and let the mosasaurs slip through. Do whales, sirenians, and pinnipeds even have a chance to evolve? (My guess: yes. Marine mammals evolved in the presence of sharks, and later in the presence of other marine mammals. You don't have to get there first if you can get there better.)

He would go back to the Cambrian and whack the early chordates. Excellent choice. It is hard to imagine most non-chordates stepping into those shoes. But then they've never had the chance, have they? That's the whole point.

After a while, "kill X" or "kill everything but X" gets a little old. So we started tinkering with the world in more subtle ways.

What if the Earth had no axial tilt? No seasons. That could have some radical implications for ecology. In a classic paper, Hairston, Smith & Slobodkin (1967; free PDF here) posed the question, "Why is the world green?" Why aren't herbivores able to eat up all of the available plant biomass? "Because they'd starve to death" is not a convincing answer. If starvation was all that was holding the herbivores back, we ought to see constant cycles of overgrazing, mass starvation, and recovery. But we don't. Something is keeping the herbivore populations in check. Maybe it's predators, maybe it's plant defenses. I suspect a big part of the answer is seasonality. We may look at the green world and think, "This place could support a lot more herbivores," but the real question is, how many herbivores can a region support when it is dry or brown or covered in snow?


But what if there were no seasons? No dry season, no winter. Without seasonal harshness to hold them down, could herbivores catch up with plants? Maybe the world would become a wasteland, populated by fast-growing plants that could flower within a single day, and prowled by lean, fast-moving herbivores that would range over wide areas eating plants as soon as they appeared and aestivating between rains. Even if herbivores couldn't catch up, something would have to change. Possibly evolutionary arms races would be accelerated. Plants would need more horrendous defenses, and burgeoning populations of herbivores would need some way to fight off the carnivores. Would a world without seasons be a hyperkinetic pressure cooker of biotic destruction? (As a proponent of Predator Theater, I'm not opposed to that.)


What if the collision that created the moon had never happened? (Image courtesy of Nova Celestia.) The Earth would be a little smaller, a little lighter. It would spin faster. Days would be shorter. And with no moon to slow things down, days would stay short for a long time. What would tectonics be like on this smaller, lighter, faster-spinning planet?

Speaking of, what if we could turn the tectonic fires up, down, or off? Say plate tectonics stopped right now. How long would it take for erosion to grind everything down? Presumably the whole world would eventually be under water. How long would it take? What would the topography of this static world be like, as the mountain ranges wore down and the ocean basis filled up? Perhaps the flattening land and the filling, rising seas would meet in huge mud flats, hundreds or thousands of miles across. How would plants and animals adjust to Mudworld? Maybe there would not be empty mud flats, but mangrove forests spanning entire continents.

All of this brain play is not in vain. In the next post, I'm going to take a stab at a big question: why engage in speculative zoology?

-----------

If you like wacky chimaeric critters, check out the photoshopped animal contests at Worth1000, where I stole a couple of the images above.

Playing Darwin's God

Figure 1. The Lesser Tadwee of southern Uqbar.

I don't want to play God.

All I want is the ability to live for billions of years, see and control everything that transpires on Earth, and speed up and slow down time at my leisure.

Why do I want these powers? I blame Dougal Dixon. His book After Man: A Zoology of the Future came out when I was still in grade school. I was freakin' fas-cin-ated. After After Man I was much taken with Dixon's The New Dinosaurs, Wayne Douglas Barlowe's Expedition, the awesome but dead-link-ridden Speculative Dinosaur Project, the creations of Nemo Ramjet, so on and so forth, imaginary zoology without end.

Figure 2. One of Nemo Ramjet's horrors.

I want the powers, obviously, so that I can tinker with evolution. Here are some experiments I have planned, just in case I wake up some morning with the aforementioned abilities. Most of them involve you either dying right now or never coming into existence, so I'll understand if you think they suck.

1. Humans go extinct immediately, and global temperatures rise to Jurassic levels over, say, 20 million years. When will Antarctica lose its ice cap? How fast? How much of the newly exposed land will be under water, and how fast will isostasy bring it back up? What will colonize this empty continent? Birds, obviously, but what else? What terrestrial flora and fauna will colonize Australia? How long will it take? It's a long haul to the nearest sizeable landmasses; on the other hand, transoceanic dispersal is apparently more common than we thought (de Queiroz 2005 Trends in Ecology and Evolution 20:68-73).

2. Another Antarctica experiment. The land bridge connecting Antarctica to South America never breaks. The circumpolar current never forms and Antarctica does not ice over. No polar ice caps, no ice ages. What survives on Antarctica? What happens in the rest of the world? In the warmer, wetter climate, Africa will probably be covered in forest, not savanna. What hominids, if any, evolve? Ooh, ooh, ooh--with the addition of Antarctica, South America ought to have more land area than North America. Maybe South America wins the Great American Interchange. That would be rad!

Figure 3. A truly fantastic image of SpecWorld.

3. Go back to the end of the Cretaceous. I know what you're thinking, but you're dead wrong, foo'. The dinosaurs DO go extinct. Everywhere except Australia. I don't care what the mechanism was, asteroid, or, uh, one of those lame reasons--whatever it is, it skips the Land of Oz. What do these dinosaur do with the Cenozoic? What do the monotremes and marsupials do with them dinosaurs? What happens during the Pleistocene? Do any of those dinAusaurs cross the ole Wallace Line and wreck some Asiatic shop? Or do the Aborigines smoke their asses 'til they ain't no moa? Ha ha hee hee.

4. Go back to the Permian. You know that part where the continents split up? Yeah, not so much this time. Fast forward to the Mesozoic. Any dinosaurs around, or did they lose out to the therapsids? Or did the harsh conditions on the mostly-desert supercontinent favor archosaurs right from the start, so that mammals don't even get a toehold? And what's going on geologically with this unnaturally large and long-lasting landmass? Those hot spots are still going to be burning. Maybe Pangaea is pocked with resurgent calderas. A desert supercontinent stocked with volcanoes and dinosaurs? Sounds like a nice getaway.

5. Starting now, all tetrapods go extinct except turtles. No more mammals, birds, crocs, lizards, snakes, amphibians... Obviously turtles are going to have to step up and take over the world. But how? I mean, they're turtles. Or maybe the turtles don't take over the world. Maybe fish beat them to the punch. Could they get out of the water in time to give the turtles some fight? Maybe not. But think about it, man! Super-tall giraffe turtles. Lean, mean cheetah turtles. Blind cave turtles. Giant whale turtles.

Top THAT.

Seriously. If you had the aforementioned powers, what experiments would you do?