Summary Oxford University FHS revision notes: Are Humans Still Evolving?
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Course
Genetics and Evolution
Institution
Oxford University (OX)
My Oxford University notes for the FHS exam in Genetics and Evolution. Useful for Biology, Biomedical Sciences and Human Sciences. I achieved a first and multiple academic prizes. Includes descriptions of concepts and key references/experiments.
Are humans still evolving?
Discuss three adaptations that contribute to genetic diversity within and between modern human
populations.
Human Evolution Has Stopped (?)
RINALDI (2017): some have claimed that culture has halted natural selection, buffering human genetic
diversity from evolution and elevating humans above the laws of biology.
The argument that humans are no longer evolving is known as the Human Evolutionary Stasis Argument
(HESA). POWELL (2012) notes that HESAs are self-contradictory – if selection is weak, there is a far greater
chance of genetic drift, resulting in new phenotypes and hence evolution. If selection is strong, it is
essentially impossible for all individuals in a population to have identical genetic traits, therefore selection
must be acting on at least some individuals at any one moment. This is a strong theoretical argument
against HESA.
Human evolution has stopped (?)
Practically every person born into a developed country has a chance of surviving throughout their
entire reproductive life and well beyond (SANIOTIS AND HENNEBERG 2011)
Surely, then, we have elevated ourselves above the laws of biology and escaped the grip of natural
selection (RINALDI 2017)?
Indeed, some have argued that over the past 40,000 to 50,000 years humans have experienced no
biological change, and everything we call culture and civilization has been built with the same body
and brain (RINALDI 2017)
Evolution has the most rapid effect when there is a high and rapid turnover of generations and there is
strong selection on a particular trait, or suite of traits, that favour survival
Implication: selection acting on humans in the contemporary world will be relatively weak
compared to other points in human history
Human Evolution Continues
We have substantial evidence for adaptation of human phenotypes within populations over short
evolutionary time scales within the last 5000 years.
Cheddar Man
Recent analysis of Nuclear DNA from the temporal bone (side of skull) of ≈10,000-year-old fossil of
a male individual
Early Briton
Appears to have had dark, curly hair, lactose intolerance, blue eyes, and very dark skin
pigmentation
Clearly looks nothing like British people today who have no recent family history of immigration ->
shows how much Britons have changed within relatively recent evolutionary history
Evolving how? Consider…
Evolution as genetic demography (role of genes as units of inheritance/transmission for
phenotypes)
Sexual selection and mate choice
Phenotypes as complex polygenic traits
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