Glossary
Sickle cell trait
Carrying one copy of the sickle hemoglobin allele protects against severe malaria; two copies cause sickle cell disease. It is the standard example of a trade-off rather than a mismatch.
Published Updated
Where this comes from
In the reference topic that owns this term
Reference topic 37, The Individual Variable, states the mismatch as a card: what the system evolved to expect, what it gets instead, and what happens in the gap.
Mismatch card
- What it expects
The diet, altitude, sunlight and pathogens of the place where your recent ancestors lived and reproduced.
- What it gets
Global food supply, air travel, latitude changes within a single lifetime, and a consumer test that reports ancestry as if it reported physiology.
- What happens in the gap
Mostly small mismatches (the dairy that disagrees, the flush after one glass), occasionally serious ones (sickle trait far from malaria, vitamin D deficiency far from the equator), and a steady traffic in genetic advice that outruns the evidence.
What that chapter recommends
3 of the 4 graded recommendations in Reference topic 37, strongest evidence first. How the grades work.
Settle the dairy question by trial, not by haplogroup
StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.If milk reliably brings bloating, gas or cramping, the likely explanation is lactase non-persistence, the default state for most of the world's adults.
Treat the alcohol flush as information
ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.Facial flushing, racing heart or nausea after a drink, most common in people of East Asian descent, signals reduced ALDH2 activity and, with continued drinking, substantially raised risk of esophageal cancer.
Match vitamin D to skin and latitude
ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.How much vitamin D your skin makes from a given dose of sun depends on its pigment and on your distance from the equator. Chapter 19 carries the doses, the trial evidence and the cautions.
Related terms
The argument behind this term, its studies and its notes are in Reference topic 37 of the reference library. The book gives the practical version. Get the book.