GENES & ENVIRONMENT INTERPLAY
Lecture 1
adding genetics in a research study got
easier → saliva from participants
cheaper → costs of genotyping
better statistical tools → like polygenic scores
main questions in field of behavior genetics = what makes us similar?/what makes us different?
in the ancient world it was thought that parents pass on characteristics to offspring
in the Greek perspective ⇒ father supplies essential characteristics and mother supplies material
building blocks (Pythagoras). ⇒ children are made from ‘purified blood from the testes’(semen) and
menstrual blood (Aristotle)
Antonie van Leeuwenhoek and Nicolaas Hartsoeker invented microscope and started in field of
microbiology
Theory of Preformationism: we all come from miniature versions of ourselves, sperm contain
complete performed individuals called ‘homunculus’
flaws with Theory of Preformationism
Francis Galton provided evidence against this theory through twins studies to investigate the
relative influence of heredity (nature) and environment (nurture). He analyzed the tendency of
twin pairs to become more alike over time. He found that development is also influenced by
environment (+ genetic inheritence).
Galton founded psychometrics (= science of measuring mental faculties), differential
psychology, and behavior genetics
Galton : “nature prevails (heerst) enormously over nurture”
flaw with Galton’s theory → studied ‘men of eminence’ (= succesful individuals) and
observed they tended to come from same families. Today, family clustering occurs not just due
to genetics but also environmental factors (social class, education, privilege). His belief in
‘nature’ ignored the inequalities that kept succes within certain families
o he worked before discovery of DNA
o he used biased and selective data
o he ignored influence of environment and social factors
Why was he racist?
, o he believed that intelligence e.g. were genetically determined and that some races
were naturally superior to others
o came with term eugenics (=well-born) and promoted increasing production among
the strong genetic lines while limiting reproductoin among weaker ones
Voyage of the Beagle (1839)
Book by Charles Darwin that details his expedition, in which he collected observations and specimens
(later contributed to his theory of natural selection)
findings
o fossils → suggested extinct species were related to modern ones
o geological observations → supported idea of slow, gradual changes shaping the earth
o Galápagos finches → showed variation in beak shapes, hinting adaptation to different
environments (= KEY IDEA for evolution)
Charles Darwin’s Theory of Pangenesis
proposed this theory to explain how traits were intherited
Darwin suggested that every part of body produces tiny particales called “gemmules” that
carry info about traits. Gemmules circulate through bloodstream and accumulate in
reproductive cells (egg or sperm)
but → there was no proof that gemmules existed and it contradicted Mendel’s experiments
(traits follow a particulate inheritance pattern, not blending)
blending inheritance theories
suggested that offspring inherit a blend of traits from both parents
BUT
o blending implies that traits from both parents mix together, causing any differences
between individuals to gradually diminish over generations
o diversity of traits would be lost, population would become more similar → this would
undermine the natural selection process, which relies on variation in traits to work ⇒
natural selection needs diversity in traits for evolution to occur
Lecture 1
adding genetics in a research study got
easier → saliva from participants
cheaper → costs of genotyping
better statistical tools → like polygenic scores
main questions in field of behavior genetics = what makes us similar?/what makes us different?
in the ancient world it was thought that parents pass on characteristics to offspring
in the Greek perspective ⇒ father supplies essential characteristics and mother supplies material
building blocks (Pythagoras). ⇒ children are made from ‘purified blood from the testes’(semen) and
menstrual blood (Aristotle)
Antonie van Leeuwenhoek and Nicolaas Hartsoeker invented microscope and started in field of
microbiology
Theory of Preformationism: we all come from miniature versions of ourselves, sperm contain
complete performed individuals called ‘homunculus’
flaws with Theory of Preformationism
Francis Galton provided evidence against this theory through twins studies to investigate the
relative influence of heredity (nature) and environment (nurture). He analyzed the tendency of
twin pairs to become more alike over time. He found that development is also influenced by
environment (+ genetic inheritence).
Galton founded psychometrics (= science of measuring mental faculties), differential
psychology, and behavior genetics
Galton : “nature prevails (heerst) enormously over nurture”
flaw with Galton’s theory → studied ‘men of eminence’ (= succesful individuals) and
observed they tended to come from same families. Today, family clustering occurs not just due
to genetics but also environmental factors (social class, education, privilege). His belief in
‘nature’ ignored the inequalities that kept succes within certain families
o he worked before discovery of DNA
o he used biased and selective data
o he ignored influence of environment and social factors
Why was he racist?
, o he believed that intelligence e.g. were genetically determined and that some races
were naturally superior to others
o came with term eugenics (=well-born) and promoted increasing production among
the strong genetic lines while limiting reproductoin among weaker ones
Voyage of the Beagle (1839)
Book by Charles Darwin that details his expedition, in which he collected observations and specimens
(later contributed to his theory of natural selection)
findings
o fossils → suggested extinct species were related to modern ones
o geological observations → supported idea of slow, gradual changes shaping the earth
o Galápagos finches → showed variation in beak shapes, hinting adaptation to different
environments (= KEY IDEA for evolution)
Charles Darwin’s Theory of Pangenesis
proposed this theory to explain how traits were intherited
Darwin suggested that every part of body produces tiny particales called “gemmules” that
carry info about traits. Gemmules circulate through bloodstream and accumulate in
reproductive cells (egg or sperm)
but → there was no proof that gemmules existed and it contradicted Mendel’s experiments
(traits follow a particulate inheritance pattern, not blending)
blending inheritance theories
suggested that offspring inherit a blend of traits from both parents
BUT
o blending implies that traits from both parents mix together, causing any differences
between individuals to gradually diminish over generations
o diversity of traits would be lost, population would become more similar → this would
undermine the natural selection process, which relies on variation in traits to work ⇒
natural selection needs diversity in traits for evolution to occur
