Comparative and Evolutionary Perspectives on Cognition
Darwinian Insights and the Theory of Evolution
Foundational Principles of Natural Selection: Charles Darwin established three primary insights that form the basis of the theory of evolution by natural selection:
Individual Variation: No two individuals are identical. Whether observing humans (including twins), monkeys, spiders, dogs, or tomatoes, inherent differences always exist.
Differential Reproductive Success: Certain variants within a population possess traits that allow them to leave more offspring in the subsequent generation than others.
Changing Composition: Because specific variants reproduce more successfully, the composition of the next generation shifts slightly from the previous one. This process, over vast periods, leads to organisms becoming "fit to function," aligning with environmental demands.
Speciation: Over very long durations, consistent acquisition of different traits—often facilitated by geographic isolation, such as on different islands—results in the emergence of new species.
Scientific Standing: Darwinian evolution is described as the "only game in town" for biology; all biological reasoning is built upon this foundation without viable scientific alternatives.
The Relationship Between Humans and Other Primates
The "Monkeys vs. Apes" Clarification: While popular media often refers to humans as "monkeys," humans are biologically classified as apes.
Morphological Differences: Apes (including humans) do not have tails, whereas monkeys do.
Shoulder Anatomy: All Great Apes possess a shoulder apparatus that allows for a -degree range of arm motion; monkeys do not have this capacity.
Phylogenetic Tree of Primates:
Strepsirrhini (Wet Noses): Includes lemurs and lorises (left side of the tree).
Haplorhini (Dry Noses):
Tarsiers: These are night-adapted primates with notably large eyes.
New World Monkeys: Found in Central and South America.
Old World Monkeys: Found in Africa and Asia.
Apes (Old World subgroup): Divided into Small Apes (Gibbons found in Southeast Asia) and Great Apes (Orangutans, Gorillas, and Chimpanzees).
Great Ape Subspecies: There are two species each of Gorillas, Orangutans, and Chimpanzees. The second chimpanzee species is the Bonobo.
Defining Primate Characteristics:
Sensory Shift: Primates rely on vision rather than olfaction (smell). Most other mammals use whiskers and wet noses for olfactory input.
Vision: Primates have lost whiskers and wet noses, possessing a smaller olfactory brain, color vision, and stereoscopic (3D) vision. Color vision is essential for identifying ripe fruit in trees.
Arboreal Adaptation: The transition to vision and the development of grasping hands (with fingernails instead of claws and opposable thumbs) were evolutionary responses to life in trees. Failure to see or grasp correctly in an arboreal environment leads to death via natural selection.
Diet: Most primates are omnivores. While they eat fruit and leaves, some, like chimpanzees, hunt other monkeys for animal protein.
Genetic and Physical Continuity
Genetics: Charles Darwin correctly posited that African apes are our closest relatives despite lacking DNA evidence. Modern genetics shows the closest match to humans is the two species of chimpanzee (Bonobo and Common Chimp).
The " Overlap" Misconception: While often cited, the percentage is misleading.
DNA consists of only four proteins: Adenine (), Cytosine (), Guanine (), and Thymine ().
A random string of one molecule compared to human DNA would still yield a match by pure chance.
Humans share approximately of their DNA with bananas due to basic cell functioning.
The significance lies in the relative match: Chimpanzees are more closely related to humans than they are to Gorillas.
Anatomic Continuity: Human anatomy, nervous systems, and vascular systems are remarkably similar to other animals. This justifies medical research; for example, a pig's heart valve can be successfully implanted into a human body.
Psychological Continuity and Methodological Biases
The "Gap" Problem: While physical continuity is established, humans often perceive a "vast gap" in mental capacities (language, reason, technology, etc.).
Darwin's The Descent of Man argued that mental powers must also evolve by "gradation" (accumulated small differences).
Many psychologists hold biases that ignore this. Some emphasize discontinuity due to religious beliefs or pragmatic reasons (to justify the poor treatment of animals in the food industry). Others emphasize continuity and may overstate animal successes to support Darwinian theory.
Technical Challenges: In comparative cognition, "absence of evidence is not evidence of absence." It is difficult to prove a species lack an ability because the test might simply be flawed.
Investigating Consciousness and Thinking
Consciousness: Identifying consciousness in animals is difficult because there are over different theories of consciousness in humans.
Pain Research: Rats with chronically inflamed joints (arthritis) will choose water containing an analgesic (painkiller) over plain water, whereas healthy rats prefer plain water. This suggests a subjective experience of pain similar to humans.
Ethics: In Australia, research on mammals and cephalopods (Octopus and Cuttlefish) requires ethical approval because the government assumes they can experience distress or pain.
Lloyd Morgan’s Canon: A principle of parsimony stating that we should never interpret an action as the outcome of higher mental faculties if it can be interpreted as the outcome of one which stands lower on the psychological scale.
The Clever Hans Phenomenon: A horse named Clever Hans appeared to understand German and perform math by stomping his hoof.
Investigation: A student of a Berlin professor found that Hans could only answer if the questioner knew the answer and was visible.
Mechanism: Hans was picking up on subtle, inadvertent physical cues (smiling, relaxing) to know when to stop stomping. This highlighted the danger of "cueing" in animal research.
Reasoning, Tool Use, and Culture
Insight vs. Trial and Error:
Wolfgang Kohler: A German psychologist (and alleged spy) who worked with chimpanzees like Sultan on Tenerife in . He observed "insightful" problem-solving, such as stacking boxes or joining sticks together to reach food.
Trial and Error: Responses learned through reinforcement and chaining (e.g., the dog Pippin in the Spanish TV ad).
Primate Tool Use:
Chimpanzees: Use sticks to "fish" for ants or termites; use leaves as sponges or toilet paper; use stones as hammers and anvils to crack nuts.
Gorillas: Observed using sticks to measure water depth or dig up tubers.
Orangutans: Have been seen using sticks to try and hit fish (imitating humans).
Social Intelligence Hypothesis: Suggested by Nick Humphrey, this posits that primate intelligence evolved to solve social problems rather than physical ones.
Neocortex Ratio: There is a positive correlation between the size of a primate's social group and its neocortex ratio.
Social Dynamics: Primates engage in grooming to build bonds and form complex coalitions to move up the hierarchy (rather than relying on size alone). They track relationships and understand third-party affiliations.
Culture: Socially maintained traditions.
Andy Whiten's Research: Longitudinal studies identified approximately traits (e.g., nut cracking, high-fives während grooming) that vary between chimp groups for non-physical reasons.
Archeological Evidence: A site in the Thai Forest shows chimps have used the same stone tools to crack nuts for over years.
Communication and Language
Historical Failure: Richard Garner tried to use Edison’s phonograph to decode "monkey language" in the late century but was dismissed as a scandal.
Vervet Monkey Alarm Calls: Studied by Marler, Cheney, and Seyfarth, these monkeys have distinct calls for leopards (run up tree), eagles (hide in thicket), and pythons.
Ape Language Projects:
Great apes lack vocal control but can use hands. Successes involve American Sign Language (ASL) and lexigram boards.
Kanzi (Bonobo): The most linguistically capable animal. He reached an understanding level of a human -year-old (approx. accuracy with novel, nonsense commands like "put soap in the fridge").
Limitations: Ape production is limited to commands/requests (e.g., "tickle me") rather than open-ended discourse or complex syntax.
Self-Awareness and Secondary Representation
The Mirror Test: Created by Gordon Gallup.
The Procedure: Animals are marked with red rouge or paint while anesthetized or surreptitiously.
Results: Chimpanzees, Gorillas, and Orangutans pass by using the mirror to touch the mark on their own bodies. Human children pass this test between and months.
Failures: Monkeys and Gibbons (Small Apes) consistently fail. In a study of Small Apes (Siamangs, Common Gibbons), the animals searched behind the mirror rather than recognizing the reflection.
Secondary Representation: This capacity allows for self-recognition and Pretend Play.
Kanzi's Study (): Kanzi engaged in pretend play, such as "drinking" from an empty glass that an experimenter had "poured" water into.
Evolutionary Inference: Using parsimony and homology, it is inferred that the common ancestor of Great Apes and humans evolved the capacity for secondary representation between and million years ago.
The Hominin Gap and Extinction
Extinct Relatives: The gap between humans and apes seems large because bridging species like Homo erectus ( to years ago), Neanderthals, and Homo floresiensis are extinct.
Homo erectus: Had a brain size of approximately (between a chimp's and a human's to ) and made bifacial hand axes.
Human Impact: Current humans are likely responsible for the extinction of other hominins and are currently causing the extinction of Great Apes. If Great Apes disappear, the nearest relatives will be monkeys, making the evolutionary gap appear even larger to future generations.
Questions & Discussion
Working with Apes: The lecturer mentioned working with chimps in Rockhampton and noted that in Australia, there are limited opportunities to work with apes.
Mirror Test Exceptions: A student asked about other animals passing the mirror test.
Elephants: One study claimed success, but the lecturer found it unconvincing because the elephant's trunk control is precise enough that they should have removed the mark immediately if they understood it.
Dolphins: One study made "big noise," but the lack of limbs makes the dependent variable (contingency testing) harder to verify.
Consensus: The lecturer is confident only in Great Apes () while Monkeys and Gibbons consistently fail.