Evolution and Human Health

I. Motivation

Evolutionary principles can contribute to understanding of origin and treatment of human disease

Evolutionary perspective can supply the WHY of diseaseto complement the HOW of disease

II. Influenza A virus

Hemagglutinin

The five antigenic sites, regions recognized by the immune system, are highlighted with colors.

A phylogenetic analysis of frozen flu samples

Neutral evolution??(deleterious muations eliminated)(neutral fixed)

A phylogenetic analysis of frozen flu samples (1968-1987) From Fitch et al. (1991).

Amino Acid Replacements In antigenic sites In nonantigenic sites

Surviving lineages 33 10 (into 1980’s)

Extinct lineages 31 35

Drift vs. Selection 331 nucleotide substitutions 58% silent 42% replacement

18 codons in hemagglutinin gene majority were replacement

Predicting which lineages of flu will survive

to cause future epidemics

Next flu strain: one with the most mutations in the 18 codons

Batting average: 9 of 11 = 0.818

Origin of the Pandemic Flue strains

A phylogeny of flu viruses, based on the nucleoprotein genes

A phylogeny of flu virus hemagglutinin genes:The 1968 human flu appears to have acquired its

hemagglutinin gene from a bird flu strain

Branches from the nucleoprotein phylogeny revealing

cross-species transmissions

Human flu can infect pigs

Bird flu can infect pigs

Pig flu can infect people.

Evolutionary analysis of the

nucleoprotein gene from the 1918 flu

Founder of clade??

III. Antibiotic resistance

An assessment of the costs of antibiotic resistance to bacteria, over the short term and over the long term

Conclusions: Be very careful with use of antibiotics

IV. Virulence

Virulence??

1. Coincidental2. Short-sighted3. Trade-off

A trade-off between the virulence and transmission to new hosts

The virulence of vectorborne versus directly transmitted diseases

The virulence of intestinal bacteria, as a function of

tendency toward waterborne transmission

V. Fever as an adaptation to the host or to the pathogen-

determining the proper treatment

Fraction surviving over time (infected)

Live Bacteria

Does the antifever medicine acetaminophen

have any effect on the course of chickenpox?

Do antifever medicines have any effect on the course

of the common cold?

Do antifever medicines have any effect on the course

of the common cold? Antibodies

VI. Parental care, step children and stress (the princess and the evil stepFATHER):

Darwinian Psychoanalysis

Stress, cortisol levels, illness, and reproductive success for stepchildren versus genetic children in Dominica

Biological children have higher reproductive success during early adulthood (ages 18-28 for women, 20-30 for men)than do stepchildren

Homicides in Canada

Summary

• Flu

• Antibiotic resistance

• Virulence

• Fever

• Parental care, stress and illness, & reproductive success

Monocytes