Disease Adaptation Flashcards
What is human ecology?
Human Ecology embraces all the mechanisms
by which humans adjust/react to their
environment to form an interdisciplinary field –
environmental physiology, growth and nutrition,
epidemiology, socio-cultural forces, genetics
and demography
What is disease?
- an impairment of health and well-being
- any condition that causes pain, dysfunction, distress, social problems, or death to the person afflicted
- a maladjustment of the human organism to the environment
What is health?
- absence of illness, pain or injury
- a state of complete physical, mental, and social well-being
What causes disease?
Humoral (hot/cold) Miasma Karma Demonic/Sorcery Punitive Germ Epidemiological Triad Multifactorial causation Web of causation
Anthropology and the study of disease
● We don’t all get the same diseases ● We don’t all get the same symptoms ● There’s a role for understanding of our biotic and social environments (and histories) in explaining some of this ○ Human biological and social variation ○ Impacts of the physical environment
Key concepts and approaches
● Species-level evidence basis for ‘normal’
○ Combatting ethnocentrism with data
● Need for both group- and individual-level explanations
● Our relationship with disease is dynamic not static
● Constraints due to our evolutionary past (evolutionary medicine)
● Trade-offs
○ Adaptability and accommodation (rather than just adaptation)
What is stress?
What are we talking about?
Nutritional/Energetic stress
Severe trauma
Psycho-social stress
Short term? Long term? - Seem to be different
Hard to pin down but seemingly important for health outcomes
(Pre)Historic perspectives/Evo Med
● We’ve always had contact with infectious life forms
○ Those might have mostly been parasites
● We’ve not always had this much disease
○ We can’t be sure but it seems likely
● Group sizes and mode of subsistence play important roles
○ cities (high population density, sedentarisation), livestock, land clearing
● A lot of what negatively affects our health is to do with changes that have occurred in our environments (broadly defined)
Trade offs?
An evolutionary concept
Basically, sometimes we can’t have it all growth vs survival vs reproduction it’s situation-specific, it could be…
● current survival vs future survival
● current reproduction vs future survival
● current survival vs future growth, etc.
Trade offs in Ethiopia
Problem: poor access to clean water leads to poor health outcomes (infant mortality) and huge time spent on carrying water
Solution: build wells!
Effect: reduction in infant mortality, shorter birth intervals (both of which mean more children and more competition for food in already impoverished families), thus poorer child health
Evolution and infectious disease
Disease is a powerful pathway for natural selection to act
The human immune system
Depends on the ability of the body to distinguish self from non-self. Is extraordinarily complex
Shared histories with parasites
Parasites and humans have co-evolved
•Natural selection has reduced the virulence of many pathogens (only a small % of microorganisms living in the body cause infectious diseases)
•Some pathogens are specific (have a lifestyle adapted entirely to one host) indicating a long evolutionary history e.g. gonorrhoea
•Humans, however, are constantly changing their environment, and thereby exposing ourselves to new pathogens
Schistosomiasis and Humans
First mentioned in Egyptian papyrus dating 1900BC - very specific relationship between Schistosoma, its intermediate Bulinus snail and human hosts
Pathogen evolution: strategy
- If a parasite is very virulent it can kill its host quickly, but it will be successful if it has managed to reproduce
- A benign parasite may reproduce more slowly, and leave fewer descendants
- The best strategy depends on the lifespan, and ecology of the host, the symptoms produced and the reproduction of the parasite
- Sometimes parasites are virulent, sometimes they become mutualists
