Modern Humans
Are humans still evolving? // Discuss three adaptations that contribute to genetic diversity within and
between modern human populations. // Discuss with examples the role of culture in the biological
evolution of Homo sapiens. // How can cultural evolution change the rate and pattern of biological
evolution? Discuss with examples.
Mind Maps
Are humans still evolving?
Contemporary selective pressures -> genetic diversity
Cultural evolution
Role in the biological evolution of sapiens
Contemporary Evolution
Cultural practices can modify selective pressures acting on human populations. Similarly, they can alter the
degree of gene flow among populations and random mating within populations.
*Population Structure notes are relevant to the influence of culture on evolutionary processes other than
selection (i.e. drift and flow).
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
Coevolution with microbes (pathogens and commensals) (see notes on Host-Pathogen Selective
Pressures)
Coevolution with culture
We have substantial evidence for adaptation of human phenotypes within populations over short
evolutionary time scales within the last 5000 years.
Detection of evolution in human populations during the past 2000 years (FIELD et al. 2016)
Height
Male-specific signal of decreased BMI
Increased infant head circumference and birth weight
Increase in female hip size and in favour of later sexual maturation
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
, Difficult to study natural selection in contemporary populations because it is processual and takes place
over a long time-span
Possible with large-scale, multigenerational, longitudinal studies, many of which were initially
organised to assess the genetic and social determinants of disease risk
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)
I disagree with the suggestion that culture acts as a buffer between human genetic diversity and evolution.
Rather, culture is a key component of our selective environment, and compelling evidence of selection on
several key genes can be directly linked to human cultural practices.
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
Frameworks
Cultural transmission
Culture definition: culture: ideas, behaviours, and artefacts that can be learned and transmitted between
individuals and can change over time (CAVALLI-SFORZA AND FELDMAN 1981).
Transmitted culture can be viewed as an inheritance system
Population-level changes, both random & selected differences
What is transmitted?
Behaviours
Beliefs
‘Memes’ (symbolism)
Transmission of information by:
Imitation/social learning
o Humans capable of high fidelity copying in childhood
Language (teaching)
Are humans still evolving? // Discuss three adaptations that contribute to genetic diversity within and
between modern human populations. // Discuss with examples the role of culture in the biological
evolution of Homo sapiens. // How can cultural evolution change the rate and pattern of biological
evolution? Discuss with examples.
Mind Maps
Are humans still evolving?
Contemporary selective pressures -> genetic diversity
Cultural evolution
Role in the biological evolution of sapiens
Contemporary Evolution
Cultural practices can modify selective pressures acting on human populations. Similarly, they can alter the
degree of gene flow among populations and random mating within populations.
*Population Structure notes are relevant to the influence of culture on evolutionary processes other than
selection (i.e. drift and flow).
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
Coevolution with microbes (pathogens and commensals) (see notes on Host-Pathogen Selective
Pressures)
Coevolution with culture
We have substantial evidence for adaptation of human phenotypes within populations over short
evolutionary time scales within the last 5000 years.
Detection of evolution in human populations during the past 2000 years (FIELD et al. 2016)
Height
Male-specific signal of decreased BMI
Increased infant head circumference and birth weight
Increase in female hip size and in favour of later sexual maturation
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
, Difficult to study natural selection in contemporary populations because it is processual and takes place
over a long time-span
Possible with large-scale, multigenerational, longitudinal studies, many of which were initially
organised to assess the genetic and social determinants of disease risk
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)
I disagree with the suggestion that culture acts as a buffer between human genetic diversity and evolution.
Rather, culture is a key component of our selective environment, and compelling evidence of selection on
several key genes can be directly linked to human cultural practices.
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
Frameworks
Cultural transmission
Culture definition: culture: ideas, behaviours, and artefacts that can be learned and transmitted between
individuals and can change over time (CAVALLI-SFORZA AND FELDMAN 1981).
Transmitted culture can be viewed as an inheritance system
Population-level changes, both random & selected differences
What is transmitted?
Behaviours
Beliefs
‘Memes’ (symbolism)
Transmission of information by:
Imitation/social learning
o Humans capable of high fidelity copying in childhood
Language (teaching)
