Lecture 4 - human origins and review 2017.pdf

Timescales of change and mechanisms of adaptability

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Timescales of change and mechanisms of adaptability
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Genetic determinism: A common perspective that assumes that genes determine our fates. Downplays the influence of the environment on the phenotype.
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collagen
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collagen Ehlers-Danlos Syndrome
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What about a more common trait like obesity? insights from Genome-wide association studies (GWAS)
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Systems involved in obesity? Examples: Energy metabolism Tissue growth and development Stress physiology Reproductive hormones Appetite regulation Physical activity Heat production (e.g. after meal)
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Mechanisms of epigenetic memory Source: NIH Epigenomics roadmap 2) methylation 1) histone modification 3) non-coding RNA
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Control PR 0 20 40 60 80 100 120 140 160 180 200 220 * Maternal dietary group Relative to control (%) Control PR 0 20 40 60 80 100 120 * Maternal dietary group Relative to control (%) Control PR 0 20 40 60 80 100 120 * Maternal dietary group Relative to control (%) Target gene: PEPCK Gene Expression Methylation Lillycrop et al J Nutr. 2005 Jun;135(6):1382-6. (Slide: Mark Hanson) protein restriction (pregnant mother) glucose (adult offspring) Prenatal protein restriction (rats): effects on liver glucocorticoid receptor in adult offspring
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Weaver et al (2004) Nature Neuroscience, 7(8)847-54 Heavy licking and grooming rats Increased GR expression (reduced anxiety) Epigenetic model of stress hormone (HPA) physiology
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Maternal transgenerational epigenetic inheritance Drake & Liu (2009), Trends Endocrinology Metab 21(4) Also applies to fathers! epigenetic changes
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Shock conditioning to an odor is inherited by at least 2 generations of offspring image:
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Germ line epigenetic inheritance: micro RNA
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Adaptability as a unifying principle in biology
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0.00000001 seconds 0.0001 hours 0.001 days 0.1 months 1 years 10 decades 100 centuries 1000 millenia 1000000 millions Years Cycle duration How do bodies cope?
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Bodies must cope with change on multiple timescales Different adaptive “modes” are required to cope with change on each timescale: Homeostasis Fastest Developmental plasticity Natural selection Slowest Human adaptability
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Frisancho (1977), Int’l J Biometeor 21(2):135 Plasticity example # 1: Low oxygen at high altitude influences lung growth
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Beyond genetic determinism “The genome is a map of how we’re hard-wired from DNA we receive from both our parents.” Dr. Sanjay Gupta, CNN story on Craig Venter, “Scientist maps his own DNA”, Aired September 5, 2007 -
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Day 3: Evolutionary and life history theory
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Life history theory Theory that explains variation in reproductive and developmental strategies across species – How evolutionary history shapes variation in development and life cycle. – Treats the entire lifecycle as an adaptation shaped by natural selection
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Key life history traits Growth rate: how fast or slow Maturity: what age growth ceases Æ adulthood Adult body size: growth X age maturity Æ adult size • Reproduction: – Litters or singleton?
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