Evolutionary Thinking

• We have not evolved from apes, we only share recent common ancestors
• We are not the most 'evolved' species as all species have been evolving for the same amount of time, and we are continuing to evolve
• "Survival of the Fittest" can promote extreme masculinity and right wing ideology - natural selection favours organisms best suited to their environment
• Previously thought that humans were the pinnacle - Great Chain of Being, Haekel's Tree of Life
• Mental Continuity


  Many characteristics found in other species
• Design without a designer


  Our biology has been refined over millions of years
• Evolution can be used to justify eugenic, racist, and extreme beliefs
• Before Darwin


  • Lamark, passing on characteristic developed for survival
  • Chambers, animals developing from each other
  • Islamic scholars creating natural selection ~1000 years before Darwin
• Darwin's works


  • Origin of Species (1859) - evolution by natural selection, how and why we adapt
  • Descent of Man (1871) - applying evolutionary theory to humans and introduction of the theory of sexual selection
• Artificial selection can cause dramatic change over a short period. Major natural changes cannot be observed in our lifetimes, but minor changes can be ie Darwin's finches and a drought meaning only large seeds were available, leading to an average increase in beak size
• Evolutionary Arms Race


  Red Queen Hypothesis (Van Valen) - constant cycle of adaptation and counter-adaptation with constantly evolving diseases
• Sexual selection


  Traits that appear to not be beneficial for survival
• Adaptive radiation


  One species varying into many others
• Adaptive radiation


  • Galapagos finches have different breeds due to gradual diversification over 1m years
  • Lake Victoria's >700 species of cichlid
• Speciation


  • Allopatric - populations isolated by environment
  • Sympatric - subpopulation becomes reproductively isolated
• Hybridisation


  • Kipunji - look like mangabeys but genetically similar to baboons
  • H. sapiens - interbreeding with neanderthals and denisovans - permeability of species boundaries?
• Looking at existing species, we can see how complex features may have evolved ie the eye - light-sensitive cells
• Darwin's model of inheritance

  Gemmules - organic particles containing inheritable information, meaning modified gemmules would be inherited
• Weismann Barrier


  Only information in germ cells (gametes/sex cells) is inherited, changes in somatic cells not passed on
• Blending Inheritance is incorrect as organisms would become increasingly average overtime
• Darwinian Evolution and Mendelian Inheritance

  The Modern Synthesis
• Sources of variation in genes

  • Mutation (copying errors)
  • Recombination (shuffling)
  • Mitosis (cell division during growth and repair)
  • Meiosis (cell division during reproduction)
• Little evidence for Epigenetic inheritance - Meaney (05), maternal behaviour in rats, children inheriting behaviour of adoptive parents. Epigenetic changes do not last for many generations and they are reversible. Genetic transmission is much more stable.
• Phyletic Gradualism


  Constant changes and how gradual changes causes speciation (reproductive isolation)
• Punctuated Equalibria


  Fossil records suggest intermittent stasis and then rapid change. Changes have complex patterns and vary widely. Variation at macro-scale is driven by micro-scale process such as variation in mutation rate and the strength on natural selection.
• Recent African Origin of Human Evolution


  • Oldest H. sapien remains found in Morocco
  • Gradual expansion to ~29-9kya where every habitable area was occupied by humans
• 'Mitochondrial Eve'


  A hypothetical person who is our most common female ancestor from which all modern mitochondrial DNA comes from. From ~100-200kya. The most genetically diverse populations are in Africa and the least diverse are in the Americas, due to repeated migrations causing population bottlenecks
• Hybridisation between modern H. sapiens

  • Denisovans (6% in Papua New Guinea)
  • Neanderthals (1-4% in non-Africans)
• Humans are still subject to natural selection
• Natural selection in humans

  • Cape Verde islands and Portuguese colonisers and West African slaves. High prevalence of Malaria means that the population now are more likely to be of West African origin and have the gene allele DARC which allows for resistance against malaria.
  • H2 inversion, lactace persistence, sickle celle alleles, EPAS1 in high altitudes, CCR5 in HIV and smallpox resistance
• Adjustments


  Phenotypic plasticity - behaviour, acclimatisation, development
• Adaptations


  • Skin colour - a polygenetic trait (MCR1, MFSD12)
  • Body size - Bergann's rule, Allen's rule
  • High Altitudes - mutation of EPAS1 gene, preventing negative effects of long-term haemoglobin elevation
• Cultural innovation has allowed for expansion at a rate, range, and speed near impossible with genetic adaptation alone
• Darwin - Descent of Man - 'curious parallel'


  Natural selection can act on entities other than organisms in similar ways ie preservation of certain words
• Cultural evolution


  • Cultural microevolution - variation, competition, inheritance ie changes in emotional valence in popular song lyrics in last 50 years, increase in hate, decrease in love
  • Cultural macroevolution - changes in populations/cultures
• Cultural transmission and inheritance


  • Content of information - humans trade in publicly accessible symbols, further distinctions among types of symbol systems ie airplane doesn't look or sound like what it is, but iconic symbolism of an airplane means an airport. Symbolically stored info can be searched, annotated, and edited to add to their power and versatility, allowing knowledge to accumulate
  • Mechanisms in the channel of transmission - focus on the channel in which info moves, identifying cultural inheritance with info carried by mechanisms of social learning. An individual learns both socially and individually, but most individual learning has been impacted the activities of our ancestors.
• Gene-culture co-evolution


  • Lactase persistence, only in ~30-40% of adult mammals and associated with LCT gene, so variable in humans due to recent domestication of animals
  • Sickle-cell disease - caused by a recessive mutation of HbS gene, common in areas with high malaria risk as the plasmodium parasite is unable to replicate effectively in sickle-shaped cells
• Supposed universals


  • Potentially due to shared biological characteristics
  • Universals could occur from shared patterns of thought due to convergent evolution
  • Universals may have adaptive features such as social bonding and cohesion
  • Social bonding hypothesis - universals like music may have allowed us to form relationships and cooperate
  • Auditory cheesecake - a pleasant by-product of the processes of evolutionary selection that are not essential, music is just a consequence of adaptive features such as language, pattern recognition, and emotion