BIOB 272 1st Edition Lecture 31 Outline of Last Lecture SpeciationI. How Sympatric Speciation Occursa. Instant Genetic Barriersb. If Cause Disruptive Selection and Assortative MatingII. Host Shift Example: Hawthorn to AppleIII. Speciation by StepIV. Evolution of Reproductive Barriersa. Types of Reproductive Barriersi. Prezygotic Barrierso Premating:a. Example 1: Sexual Isolation in Firefliesb. Example 2: Mismatched Genital Morphologyo Postmating Barriersii. Postzygotic Barrierso Hybridsa. Example: Horse/Donkeyo How Postzygotic Isolation Evolves- Drosphila ExampleV. Haldane RuleThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VI. Other Genetic Insights into Postzygotic IsolationVII. Summary of Reproductive BarriersVIII. Secondary ContactIX. When Can Hybrid Zones?a. ReinforcementX. Hybridization Leading to New SpeciesXI. Allopolyploidy Can Lead to Extremely Rapid Hybrid SpeciationXII. Homoploid Hybrid SpeciationXIII. Speciation Key PointsOutline of Current Lecture Human EvolutionI. Speciation Wrap-Up- Key PointsII. Human Evolution- A Speciation Case Study- Hominid vs. Hominin- Earliest Hominin Fossils Found- Speciation vs. AnagenesisIII. Earliest Hominin Ancestor? - Ardi- LucyIV. BipedalismV. Emergence of Large BrainsVI. Out of Africa Migration (3 waves)i. First Wave=1.8 MYA: Homo Erectusii. 2nd Wave= 400K-30K Neandertalsiii. 3rd Wave= 100K Anatomically Modern Humansiv. Others?- The Flores HomininVII. Differing Hypotheses to Represent the Genetic History of Anatomically Modern Humansi. Candelabraii. Multiregional Evolutioniii. Replacementiv. AssimililationVIII. Mitochondrial DNA to Base Molecular Clock on the Migration of Hominins- Neandertal Genome SequencingCurrent LectureHuman EvolutionI. Speciation Wrap-Up- Key Points- Speciation (for many taxa) is the process of genetic divergence leading to complete reproductive isolation between populations. - Diverse geographical, ecological and genetic mechanisms underlie formation of new species - Geographic modes of speciation may be sympatric or allopatric speciation - Reproductive isolation may manifest through diverse isolating barriers that act before or after mating - The evolution of genic incompatibilities is generally thought to involve epistatic interactions (D-M incompatibilities) - Hybridization between species can promote or impede specia(onII. Human Evolution- A Speciation Case Study- Humans share their MCRA with chimps and bonobos- Hominid vs. Hominino Hominid: Any member of the monophyletic “great apes”. -Orangutans-Gorillas-Humans-Chimps-Bonobosii. Hominin: Any member of the human lingeage, since the MCRA shared with the chimps/bonobo lineage- Earliest Hominin Fossils Foundo Earliest found in Africa (6.5 to 1.8 mya)= not really very long ago= extensive phenotypic diversity during 6 MY of hominin evolution Huge changes in skulls, pelvis, teeth, how walk, brain size, etc.- Speciation vs. Anagenesiso Speciation: dividing from one branch into two separate – also each branchincludes evolutionary change along themo Anagenesis: evolutionary change (phenotypic) of a lineage over time- no branching off a lineageo Really different anagenesis forms of hominin skullso Co-occurring in time and space= transition to bipedalism (from knuckle walking to upright walking), brain size, skull morphologyIII. Earliest Hominin Ancestor?- Ardi (ArdipithecusRamidus): 4.4 MYAo 50 kg (110 Ib) femaleo Small braino Facultative bipedal- in trees a lot, but could walk somewhato Ethiopia, Afar deserto Found fossils in 2009- Lucy (Australopithecus Afarensis): 3.2 MYAo Fully bipedal- evidence according to pelvis and skull shape and found fossilized foot prints in Laetoli, Tanzania from 3.7 MYAIV. Bipedalism: Knuckle walking to bipedal walking to running- Span of 2 MYA= very rapid- Lucy is the oldest fossil record found of fully bipedalism (walking)- Body Characteristics of bipedalism:o Lumbar curveo Large femoral head and neck (in the femur area)o Reinforced kneeo Large heel boneo Partial foot arch- Homo Ergaster (2MYA) is the oldest fossil record of walking/running- Body Characteristics of Running:o Balanced Heado Reduced neck muscleso Narrow waisto Enlarged hind limb jointso Long legso Short toeso Strong longitudinal archV. Emergence of Large Brains- Possible selective forces: social evolution, language, diet-may have started cooking which allows for new/more nutrients to the body and brainVI. Out of Africa Migration (3 waves)o First Wave=1.8 MYA: Homo Erectus Migrated from Africa to Asia, China, Europe= traveled a long way but couldn’t go very far north due to colder weathero 2nd Wave= 400K-30K Neanderthals Tons of fossils Europe to central Asia Larger cranial capacities=bigger brain Brow ridge, no forehead=expansion of back of skull, very robust, larger rib cage, more muscle mass, slightly differentpelvis bone= all of these factors caused them to need a lot of calories (protein) in dieto 3rd Wave= 100K Anatomically Modern Humans South Africa, East and west world, Australia, New World Overlapped with Neandertals and maybe homo erectus?o Others?- The Flores Hominin (“the hobits”)- 18K Very tiny- about 2 to 3 feet tall Lived on islands where probably interacted with other homo forms= relationship unclear Early offshoot of homo? Likely not a pygmy or diseased population of homo sapiens “Jungle People”?VII. Differing Hypotheses to Represent the Genetic History of Anatomically Modern Humans- rapid evolution (anagenesis) and speciation complicates the reconstruction of the hominin phylogenyo Candelabrao Multiregional Evolutiono Replacemento Assimililation- probably the most true= all modern humans share a common ancestor with both 1.5 MYA Africa and 50,000 years ago ancestors Studies strongly support a model of recent migration out of Africa All populations very closely related All OOA diversity a subset of African diversityVIII. Mitochondrial DNA to Base Molecular Clock on the Migration of Hominins- This evidence also fits fossil evidence= independent evidence- Neandertal Genome Sequencing:o Neandertals disappeared about 30,000 years agoo DNA highly degraded-short and damaged, very difficult to studyo Human contamination (when find fossils) a challenge= skin cells from human handso Use a dentist drill to get to core of bones (often use long bones)- found