A robot-in-the-world and software-in-the-world can both be built as primary representations of an extinct-fish-in-the-world. In that sense they are equivalent as model simulations. What differs is how they represent behavior. As part of its representation of an extinct-fish-in-the-world, software-in-the-world must represent the physical interactions of the agent and its environment. This is a hidden or implicit level of representation (let’s call it 0°) that increases the conceptual “distance” between the target and the model that represents it.
As physically embodied biorobots, we’ve already established that ETs aren’t Evolvabots: they don’t evolve and, hence, they can’t directly test hypotheses of evolutionary process. However, as suggested by our list of the seven reasons to use embodied robots (page 178), ETs can test hypotheses about how extinct animals functioned and behaved. Because we’ve taken a page from cognitive science and defined behavior as the interaction of an autonomous agent with its environment, testing the behavior of ETs allows us to examine what Robert Brandon, back in Chapter 2, called “function in the ecological situation”—one of the six pieces of physical evidence needed for explaining adaptation.
Thus ETs, as primary representations, inform our evolutionary investigations by testing behavioral hypotheses of extinct or nonexistent animals. Behavior, as we’ve shown with our Evolvabots, is what selection “sees,” the action in the game of life that we judge using the fitness function. However, because behavior doesn’t fossilize, recon structing it with ETs is a great way to remember the past.
As I promised at the end of the last chapter, I’m not going to use Tadros, at first, to look at what we can learn by using ETs to study the biology of extinct organisms. I’m not going to look at fish nor am I even going to discuss backbones (at least not very much). Instead, our magical mystery tour of lost behaviors in the evolutionary landscape continues with the ET known as Robot Madeleine (Figure 7.4). Madeleine, scallop-shell shaped like the petit madeleine cake, is the first robotic creation named after a French pastry (Figure 7.5). Launched in 2004, Madeleine the robot served, just like Proust’s tea-soaked madeleine the pastry, as the catalyst for explorations into things past,[149] lost vertebrates known as plesiosaurs who, with their four propulsive flippers, were the giant top-level predators of the Jurassic seas over two hundred million years ago.
FIGURE 7.4. Robot Madeleine, a four-flippered Evolutionary Trekker. Madeleine helped launch a new scientific journal, Bioinspiration & Biomimetics, in 2006. Madeleine is designed to represent aquatic tetrapods, descendents of the four-footed vertebrates that evolved on land and then evolved back to the water (see Figure 7.7). By varying the pattern of how she uses her flippers, we can test the hypothesis that four flippers, compared to two, produced swimming behavior with faster top speeds, quicker acceleration, and better braking. The cover image is used with permission of the Institute of Physics. I took the picture of Madeleine while she was going through her first shake-down cruise in the outdoor pool of my friend John Keller.
FIGURE 7.5. A petit madeleine, chocolate, left lateral view, showing its streamlined scallop shape as seen just prior to consumption. Robot Madeleine is the first robot named after a French pastry. We recognize that petite madeleines don’t have flippers and don’t swim. However, the chocolate petit madeleines, in particular, are very tasty, like little moist cakes.
Well, perhaps not quite remembrance: we know of plesiosaurs only because they’ve left us their skeletons as fossils, not because we were around to see them when they still lived. The first plesiosaur was discovered by twenty-two-year-old Mary Anning in 1821 as she scoured the cliffs of Lyme Regis, a West Dorset coastal town on the English Channel. Anning’s sea dragon was clearly a vertebrate—with its many vertebrae forming the great chain of bones along its axis—but was otherwise odd, with four large paddles instead of legs and a girdle of bones instead of gracile ribs amidships.[150] The Reverend Conybeare named it for science in 1824 as Plesiosaurus, from the Greek plesio (= close or near) and saurus (= lizard), and described it as a “comparison with the paddles of the sea turtle will exhibit such fresh analogies as to indicate that in respect of the various forms of animal extremities, the Plesiosaurus holds as it were a middle place between it and the Ichthyosaurus; for we may remark in the first carpal series of the turtle three bones not unlike those of the Plesiosaurus.”[151]
FIGURE 7.6. Plesiosaurus dolichodeirus, cast of fossil. Note the strangeness: a tiny head on a long neck, short body reinforced with robust bone, and, best of all, four large flippers of a form that appears to be shaped for doing the hydrodynamic work of an underwater wing. This cast, about two meters long, is from the Warthin Museum of Geology and Natural History at Vassar College. It was purchased in the nineteenth century by the college and was listed as Item 225 in the Wards Scientific catalogue of 1866. Photo by Rick Jones.
Richard Ellis, in his book Sea Dragons, notes that Conybeare’s scientific description was followed by Dean Buckland’s more famous 1836 construction: “To the head of a lizard, it united the teeth of a crocodile; a neck of enormous length, resembling the body of a serpent; a trunk and tail having the proportions of any ordinary quadruped, the ribs of a chameleon and the paddles of a whale.”
Strangest of all is the fact that these descriptions are not flights of fancy. The darn things look pretty much as described in Figure 7.6.[152]
Although their utter strangeness makes plesiosaurs so compelling, in an evolutionary sense they were pedestrian. Plesiosaurs[153] are just one example of what Carl Zimmer has described as a repeated series of past and ongoing evolutionary experiments in which sea creatures descend from four-legged terrestrial vertebrates known as tetrapods.[154] From land to sea they go. Because of their heritage as terrestrial tetrapods, any vertebrate lineage that has crawled back to the sea, evolutionarily speaking, is called an aquatic tetrapod. Living aquatic tetrapods that you might recognize include whales and dolphins, sea turtles, penguins, otters, and seals and sea lions. And there are more!
Not even including amphibians, it’s simply stunning how many times terrestrial tetrapods have spawned species that have returned to the sea and adapted to aquatic locomotion. Analyzing a beautifully preserved Late Cretaceous mosasaur (mosasaurs are yet another group of giant, extinct aquatic tetrapods), Johan Lindgren, a researcher at Lund University in Sweden, and his colleagues have shown how selection for enhanced swimming performance has apparently and repeatedly built streamlined bodies, vertebral columns reshaped to enhance and regionally control bending stiffness, and caudal fins with increased span.[155] Keep in mind that any pattern of convergent evolution (see Chapter 2) is excellent circumstantial evidence that a strong and steady selection pressure has been at work.
149
Marcel Proust,
150
Christopher McGowan,
151
H. T. de la Beche and W. D. Conybeare, “Notice of the Discovery of a New Animal, Forming a Link Between the
152
Richard Forrest has created and maintains an excellent site on plesiosaurs that you should visit: \plesiosaur.com/. Dr. Adam Stuart Smith also has an excellent site that features his own research: www.plesiosauria.com/index.html.
153
The term “plesiosaur” can be confusing. For example, within the Order Plesiosauria, we’ve got the short-necked Pliosauroidea and the long-necked Plesiosauroidea as Suborders. When I use the term plesiosaur here, I include all members of the Order, after Adam Stuart Smith (www.plesiosauria.com/classification.html). Just keep in mind that some folks prefer to talk about “true plesiosaurs” as just the long-necked forms, leaving pliosaurs to the side.
154
Carl Zimmer,
155
J. Lindgren, M. W. Caldwell, T. Konishi, and L. M. Chiappe, “Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur,”