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Evolution and Natural Selection

Natural Selection and Evolution

  • Natural selection is the mechanism by which evolution occurs.

Selective Breeding: Foxes

  • Cats, dogs, horses, pigs, and other animals have been bred for generations to live alongside humans.
  • Exotic pets are hand-raised but are still essentially wild animals.
  • Foxes, the result of a nearly 60-year-long Russian science experiment, are born without fear or aggression towards humans.

The Russian Experiment: Dmitry Belayaev

  • Dmitry Belayaev, a Soviet geneticist, proposed that domesticated animals like dogs are friendly due to genes governing their behavior.

  • The process of wolves evolving into dogs involved "friendliness genes" that were favored as they adapted to live with humans.

  • In 1959, Belayaev's team began selectively breeding foxes at the Institute of Cytology and Genetics in Novosibirsk, Russia.

    • Foxes that showed the least fear or aggression when approached by experimenters were allowed to breed.
    • Less friendly foxes were not allowed to breed (artificial selection).

  • By 2004, nearly 70% of the foxes had reached an elite level of friendliness, effectively domesticating them.

  • It costs around 9,000 to buy and import a fox from Siberia.

Observations and Implications

  • Domesticating a fox does not turn it into a dog, similar to how domesticating a horse does not make it a dog.
  • The foxes represent a behavioral stepping stone in understanding how wolves evolved into dogs.
  • Clive Wynn studies the unique relationship between dogs and people, noting dogs' "hyper sociability" and willingness to form emotional relationships.
  • The Belayaev foxes might offer clues to how hypersocial dogs emerged from wild wolves around 14,000 years ago.
    *A test measured time foxes spent in a one-meter radius circle. Domesticated foxes greet and interact but then move away while wild foxes never relaxed and never crossed the radius. Dogs entered and stayed in the radius for the entire time.
  • The Bassettts and Clive suspect that the foxes' early lives as lab animals, bred for friendliness but barely socialized, may affect their behavior.
  • Domestication involves both genetics and life experiences.
  • Studying fox behavior may provide a roadmap for understanding domestication in other animals.

Genetics Research

  • Anna Few collaborates with the institute in Russia on genetics research, aiming to identify specific genes involved in fox domestication.
  • Comparing genes of wild and domesticated foxes is valuable because friendliness was the primary trait selected for.
  • Identifying the specific genes could help understand domestication across the board.
  • Gene editing tools might potentially be used to domesticate entirely new animals in the lab.

The Foxes' Place

  • The foxes exist in a liminal space between wild animals and companions.
  • They were not created the same way dogs were and are not dogs.
  • When scared, they may seek comfort from humans, highlighting the complex nature of their semi-wild existence.

Evolution: Natural vs. Artificial Selection and The Evidence for it

  • Evolution is change in DNA over time.

Evidence for Evolution

  1. Fossil Record

    • Fossils can be sequenced.
    • Fossils show animals that are no longer alive, indicating change over time.
    • Fossils show similarities to existing animals, suggesting evolution.
    • There are gaps in the fossil record, representing time periods where species are unknown.
    • Fossils are hard to make, requiring specific conditions and time.
    • Patterns based off fossils:
      • Different species lived on Earth at various times in the past.
      • Almost all species living today (99%) were not around a million years ago.
      • The complexity of organisms has increased over time.
      • Generally, the same species are found in the same area.

Carbon Dating

  • Carbon dating is used to estimate the age of fossils.
  • It utilizes the half-life of radioactive carbon in organic materials (bone, wood, charcoal).
  • By measuring the amount of carbon left in a sample, scientists can estimate its age accurately.
  • The less carbon, the older the sample.

  1. Patterns of Distribution

    • Similar species are found in the same areas.
    • Isolated species tend to be similar but different.
    • Charles Darwin's voyage to the Galapagos Islands revealed different finches with similarities to a mainland bird.
    • The mainland bird populated the islands and adapted to different environments, creating new species.
      • This is the basis of Darwin's kick start to the identification of natural selection
    • Evidence from biogeography shows how the movement of continents affects species distribution.
    • Some places have unique (endemic) species found only there, suggesting evolution in isolation. An example of this is Madagascar.

  2. Comparative Anatomy

    • Similar structural similarities exist between different species ex. human, gorilla and chimpanzees.
    • This suggests relatedness or evolution from a common ancestor.
    • Analogous Structures: Serve the same purpose but come from different ancestors ex. dolphin/shark fins vs penguin's fins
    • Homologous Structures: Serve different purposes but have the same structure indicating same ancestor ex. human arm, whale fin, bat wing

  3. Embryology

    • Embryos of different species look very similar at the start of development, indicating a similar ancestor. Example: salamanders, chickens, pigs, and humans

  4. Vestigial Features

    • Structures that are still present in the body but are no longer needed or useful.
      *Examples: appendix, goosebumps, wisdom teeth

  5. Genetics

    • DNA analysis of closely related species reveals how closely related species are.
      • 50 to 70% our DNA is estimated to be shared with a banana.
    • Fungi are genetically more closely related to humans than plants.
    • DNA can track the movement of species around the globe.
    • Artificial selection uses differences in DNA.
    • Ex. cauliflower, broccoli, kale, kalarabi, brussels sprouts, and cabbage all derived from brassica oleracea.