Evolution and Human Health – Chapter 14

- Flu virus evolution

- Antibiotic resistance

- Cancer as set of evolving population

- Adaptative reasoning and humans

- Pathogens and dietary/lifestyle choices cause disease

- Immune systems of hosts select for resistant pathogens

- Humans further select for resistant pathogens via drug development and use

- Physiological traits and behaviors can be understood by considering evolutionary concepts and evolutionary history

Key Concepts

Antigenic sites:

Sites that the hostimmune systemrecognizes toform a memory and design antibodies.

Viruses from the freezer: Hemagglutinin evolution

Flu strains with novel antigenic sites enjoy a selective advantage

Evolutionary history of influenza A is surprisingly linear!

Phylogeny of Influenza viruses based on nucleoprotein DNA sequences

Nucleoprotein enables a virus to infecta particular host and therefore is mostlikely to ‘capture’ the history of particularstrains.

However, some strains within clades havealleles at other loci (hemagglutinin or neuraminidase) that were obtainedfrom unrelated strains.

Flu strains trade genes

Prior to 1968 Flu EpidemicThere was no human strainWith H3…..where did it come from?

Cross-Species Transmissions (tree based on nucleoprotein)

Bird to Pig

The source of the 1918 pandemic flu remains unknown.

Reid et al., 2004

Humans further select for resistant pathogens via drug development

BacterialResistance

ToAntibiotics

Time

Societal change in antibiotic use

Based on Austin et al., 1999

The cost ofresistance can be

overcome byselection.

Schrag et al., 1997

Evolutionary History of Cancer

Shibata et al., 1996

Colorectal adenocarcinoma

from 43 yr patient

Adenoma samples are older and show higher levels of genetic diversity

What is the Evolutionary Significance of Fever?

Fever represents a condition that is induced by a pathogen for the benefit of the pathogen.

Higher temperature of host would increase reproduction/growth of the pathogen.

Fever represents a condition that is induced by a pathogen for the benefit of the host.

Higher temperature of host would allow the immune response to be more effective.

Behavioral feverIncreases survivalof iguanids afterInjection ofAeromonas

What happens if you prescribe aspirin?

Should Patient’s Allow Fevers to Run their Course?

- Fever may be adaptive against some but not all pathogens.

- Fever may carry significant costs in some cases, but lowcosts in other cases

Evolution and Parenthood: Parents Invest in Ways to Increase Their Fitness

Flinn and England, 1997

Stress, cortisol levels, illness, and reproductive success

Stepchildren vs Genetic Offspring

Stepparents kill stepchildren at a higher rate than biological parents kill biological children

Daly and Wilson, 1988a,b