Evidence for evolution in today’s world

Natural selection at work

Change in frequency of traits in a population over time as a consequence of differential survival and reproduction of individuals.

Illustrations of how rapidly selection can alter morphology, behavior, and physiology: 3 examples

Evolution of

1) Dogs (Canis familiaris) from wolves (C. lupus)

2) Drug-resistant disease organisms

3) Herbicide resistant crops and weeds

From VonHoldt et al. 2010, Nature

1. Highlights of dog evolution

• Derived from wolves (Canis lupus), with
genetic signature of Middle Eastern wolves.

• Ancient breeds (>500 years old), including basenji,
chow, Afghan hound, Akita, samoyed, and Siberian husky,
show more recent interbreeding with wolves

• Modern breeds are a product of the Victorian era (1830-1900), all genetically distinct, reflecting intensive inbreeding.

• Breed groups are genetically distinct, reflecting selective breeding based on particular traits (e.g., retrieving, leg length).

• Selection for particular mutations and crossing of these with existing breeds has led to high morphological diversity.

2. Evolution of resistance to antibiotics

How antibiotic resistance evolves in medicine

• Infected individual receives antibiotics and takes less than recommended treatment, failing to kill all of the pathogen.

• Inappropriate prescription of antibiotics

• Sub-optimal dosage to critically ill people

• Poor hygiene in health-care facilities

3. Herbicide resistance in crops and weeds

Herbicides are chemicals that kill plants selectively or broadly by interfering with critical biochemical pathways.

Genetically-engineered crops in use today feature herbicide-resistance or pesticide in crop itself.

credit: http://blogs.ei.columbia.edu/2011/06/23/climate-ready-crops-the-pros-and-cons/

Evolution as Theory and Fact:

• “Theory” in science: a set of unified concepts, assumptions, and propositions about some aspect of the world (or universe). Contains explanatory principles. Makes testable predictions. Falsifiable.

• “Fact” in science: verifiable observation. Evidence that is repeatable in principle.

• “Theory” of evolution involves the concept of descent with modification, timing of changes over earth history, relationship between genes and phenotype. Includes processes of natural selection, speciation, extinction, genealogical relationships. Makes predictions to test in field or lab.

• “Fact” of evolution: direct evidence for natural selection, gene expression, species formation in nature and experiments.

Evolution Worldview:

• Major claims of theory are well supported.

• Humans are a branch on the tree of life... and still quite unusual.

• Evolution is not for or against any religion.

• Evolutionary processes are not “purposeful”, but our lives are full of purpose.

• Genetic heritage is neither destiny nor basis
for social ethics.

Evidence of Evolution in Today’s Word SELF-TEST