Convergent Evolution: Limited Forms Most Beautiful

Chapter 6. Convergent Minds

6 Discussions of the evolution of intelligence have focused on monkeys and apes because of their close evolutionary relationships to humans. Other large-brained social animals, such as corvids, also understand their physical and social worlds. . . . Because corvids and apes share these cognitive tools, we argue that complex cognitive abilities evolved multiple times in distantly related species with vastly different brain structures in order to solve similar socioecological problems. . . . [T]his convergent evolution of cognition has not been built on a convergent evolution of brains. —Emery and Clayton (2004, 1903) Convergent Minds? How can minds be said to converge? We consider our mental states to be a function of our brain structures and sensory inputs. At first glance, then, organisms with radically different brain structures would be expected to have radically different minds. Take, for example, the brains of a magpie and a human. One is a bird brain, possessed by an avian dinosaur in the sauropsid clade of amniotes, and the other is a primate brain, possessed by a placental mammal in the synapsid clade of amniotes . The sauropsid and synapsid lineages diverged back in the Carboniferous ,and have evolved along independent pathways ever since.Magpie brains and human brains are structurally very different, separated by a vast chasm of 340 million years of independent evolution. Yet it can be demonstrated that, in many ways, magpies think like humans (Emery and Clayton 2004; Prior et al. 2008). Our minds have converged. Problem-Solving Behavior It was long thought that the tool was the unique invention of the human mind. Only the human mind had the ability to understand the limits to Convergent Minds 210 Chapter 6 accomplishing a task using the body alone, and thus to conceive of extending those limits by using an external object to accomplish that task. We now know that this long-held belief is not true; other minds have made that conceptual leap as well. Quite a few other minds—no less than 12 independent lineages of animals use tools (table 6.1). Within our own lineage, we can trace the manufacture of stone tools back some 2.6 million years ago to our ancestor Homo habilis, aptly named the “handyman” (evidence of tool usage in our lineage goes as far back as Australopithecus afarensis, some 3.39 million years ago, but it is not clear if A. afarensis manufactured stone tools or simply used naturally occurring sharp stones as tools; see McPherron et al. 2010). Table 6.1 Convergent evolution of tool-using and tool-making behavior 1 Convergent behavior and function:TOOL USAGE (using an existing external object as a tool to attain an immediate goal) Convergent lineages: 1.1 Black-and-yellow mud wasp (Bilateria: Protostomia: Ecdysozoa: Arthropoda: Mandibulata:Hexapoda:Hymenoptera:Vespoidea:Sphecidae;Sceliphroncaementarium) 1.2 Forest ant (Arthropoda: Mandibulata: Hexapoda: Hymenoptera: Formicidae: Myrmicinae; Aphaenogaster rudis) 1.3 Woodpecker finch (Bilateria:Deuterostomia:Chordata:Osteichthyes:Sarcopterygii: Reptiliomorpha: Amniota: Sauropsida: Archosauromorpha: Dinosauria: Saurischia: Theropoda: Maniraptora: Aves: Neognathae: Neoaves: Passeriformes: Emberizidae; Cactospiza pallida) 1.4 Egyptian vulture (Aves: Neognathae: Neoaves: Falconiformes: Accipitridae; Neophron percnopterus) 1.5 Asian elephant (Amniota: Synapsida:Therapsida: Mammalia: Eutheria:Afrotheria: Proboscidea: Elephantidae; Elephas maximus) 1.6 Sea otter (Mammalia: Eutheria: Laurasiatheria: Carnivora: Mustellidae; Enhydra lutris) 1.7 Polar bear (Mammalia: Eutheria: Laurasiatheria: Carnivora: Ursidae; Ursus maritimus) 1.8 Bottlenose dolphin (Mammalia: Eutheria: Laurasiatheria: Cetartiodactyla: Cetacea: Odontoceti: Delphinidae; Tursiops truncatus) 1.9 Black-striped capuchin monkey (Mammalia: Eutheria: Euarchontoglires: Primates: Platyrrhini: Cebidae; Cebus libidinosus) 1.10 Yellow baboon (Mammalia: Eutheria: Euarchontoglires: Primates: Catarrhini: Cercopithecoidea: Cercopithecidae; Papio cynocephalus) 2 Convergent behavior and function: TOOL CONSTRUCTION (modifying an existing external object or objects to create a tool to attain an immediate goal) Convergent lineages: 2.1 New Caledonian crow (Amniota: Sauropsida: Archosauromorpha: Dinosauria: Saurischia: Theropoda: Maniraptora: Aves: Neognathae: Neoaves: Passeriformes: Corvidae; Corvus moneduloides) 2.2 Orangutan(Amniota:Synapsida:Therapsida:Mammalia:Eutheria:Euarchontoglires: Primates: Catarrhini: Hominoidea: Hominoidae: Pongidae; Pongo pygmaeus) Note: For data sources, see text. Convergent Minds 211 Before the invention of these Paleolithic tools, species in the Hominini certainly must have created tools out of wood and other organic matter, tools that decomposed and thus are not preserved in the fossil record. The classic studies of field anthropologists in Africa, beginning with Jane Goodall (Wade 2006), have demonstrated to us that our close Panini cousins, the chimpanzees (Pan troglodytes) and the bonobos (Pan paniscus ), also create and use tools made of wood and other organic matter; thus, tool construction is...