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Lecture 1.docx

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Shawn Lehman

ANT 333: Lecture #1 – Patterns in Primate Evolution Introduction to Evolutionary Theories  What to “Get”  What is adaptation & natural selection.  How history impacts above concepts.  Darwin’s role in this debate.  Phylogenetics & biological adaptations. Concept of Adaptation  Adaptation is at core of modern evolutionary biology.  Natural selection is 1st and foremost an explanation of adaptation.  Hard to detect, test, and define adaptation  Dangerous concept, a lot of stories made up Natural Selection Defined  Process whereby any heritable features, anatomical or behavioral, that enhance the fitness of an organism relative to its peers, increase in frequency in the population in succeeding generations.  Units of selection in natural selection only pertain to one individual  Doesn’t have to result in biological evolution, and not all biological evolution is due to natural selction. Adaptation “Defined” (For Now)  An adaptation is a characteristic that allows an organism to live and reproduce in an environment where it probably could not otherwise exist (Vermeij, 1978).  Also refers to process whereby organisms obtain their adaptive characteristics.  Depends on process. What is an Adaptation?  Evolutionary biologists refer to an adaptation as a trait that evolved as the result of natural selection.  Physiologists use “adaptation” when they mean “acclimatization” --A nerve “adapts” to a continual stimulus or our eyes “adapt” to darkness. Does not involve genetic change! Two Different Kinds of Adaptation 1). Non-hereditary adaptation o Acclimatization - e.g., humans living at high altitudes can avoid a lack of oxygen by increasing the number of red blood cells as oxygen pressure decreases. If they move to lower altitudes, the number of red blood cells decreases. –short term 2). Hereditary adaptation o Inherited structures that are said to "make a better fit" of an organism to its environment - e.g., flight in birds: Archaeopteryx had wings but couldn't fly; its descendants today can fly well.  Adaptation can be simultaneously a state and a process. o State – what an adaptation is: wings are an adaptation for flying & o Process – what led to the adaptation forearms have transformed to wings by the process of adaptation. History of Research on Biological Adaptation Aristotle defined four causes in a “biological” process: 1). Final 2). Efficient 3). Formal 4). Material Lucretius noted in 2nd Century A.D. that: “We should avoid the mistake of supposing. ..that the forearms were slung to the stout upper arms and the ministering hands given us on each side, that we might be able to discharge the needful duties of life. Other explanations of like sort which men give, one and all put effect for cause through wrongheaded reasoning; since nothing was born in the body that we might use it, but that which is born begets for itself a use: thus seeing did not exist before the eyes were born, nor the employment of speech ere the tongue was made." - People will make up stories when something they can’t explain is put in front of them. Sir Isaac Newton  Saw evidence for adaptive final causation.  Scientific differences between Pattern (astronomy) and Purpose (biology) clearly spelled out, then benefits of Purpose became apparent.  18th and 19th century scientists saw less proof for divine life in stars.  Astronomy not best medium through which to prove agency of an intelligent creator.  Talked about cause and effect. Two Categories of Evolutionary Scientists Before Darwin’s  Origin of Species. 1). Adaptationists: structure simply followed functional need. 2). Structuralists: function was merely putting to use of the products of structural laws. - concerned with identifying, naming, and categorizing things. Don’t ask “why” 18th & 19th Century Scientists  Cataloging of homologous body parts done by European ‘structuralists.’ Voluminous descriptions of structure, almost no explanatory information on structures.  Functionalists concerned with explanations. Darwin’s Origin of Species  Part I (Chapters I-XIII) introduced principle of natural selection; presented evidence that the conditions necessary for its operation present in both wild and domestic species.  Part II (Chpts. IX-XIII) presented evidence that evolutionary change had occurred—that distinct species were descended from common ancestors. Origin & Evolution  Darwin tinkered with ideas & theory of natural selection, constantly revised.  Multiple editions produced: Some adopting ideas of others, later editions dropping these ideas (e.g., survival of fittest).  Only used “evolve” once, at very end of 1st edition: “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” Darwin & Structure/Function  Established priority of function over structure.  Darwin not an extremist on adaptation. He never insisted in its ubiquity.  Darwin named only 6 or 7 putative adaptations in Origins of Species, and then dismissed 4.  Darwin implied that non-adaptive (that is, never-adaptive) traits could also be inherited.  Adaptations only really need to be a bit better than another individual. Perfection Adaptations?  Darwin o “Natural selection tends only to make each organic being as perfect as, or slightly more perfect than the other inhabitants of the same country with which it comes into competition,” so that “natural selection will not produce absolute perfections...” (On the Origin of 6). Darwin’s Descriptions of Illusory Adaptations  Darwin only willing to label traits as adaptations when they shaped by selection to do task being attributed to them. Sexual selection, “... depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.” Darwin Provided us with new Ability to Determine Direction of Adaptation  Natural theology had no way to determine polarity of adaptation. God could have just as easily adapted either phenomenon to other.  Darwin explained how org
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