Big Picture on Evolution
• This was the famed ‘modern synthesis’.
• Genes may become inactivated but remain in the genome as pseudogenes.
• Charles Darwin,
is remembered as the father of evolutionary thinking.
• Natural selection: Those most suited to their environment survive at the expense of those less ‘fit’.
> organisms produce more
offspring than survive to reproduce.
• One of the strongest cultural systems in language, which shows clear signs of evolutionary change
• A change in DNA might be beneficial but is usually harmful. Often, though, it won’t make a blind bit
of difference. This is known as a neutral change.
Living things fall into three major divisions: Bacteria, Archaea and Eukarya.
Archae: Although single-celled and lacking a nucleus, genetic comparisons suggest they are
closely related to eukaryotes than to bacteria.
Hox genes: These are ‘master control’ genes that coordinate the activity of many other genes.
found throughout the animal world
No sweet tooth: cats are indifferent to sweet things because they cannot taste sugar- a gene coding
for part of the sugar receptor is pseudogene
People were shorter than they are now. We do seem to be getting taller – but that’s due to better
diet rather than any evolutionary change.
Mixing pots: Virus genomes can also swap bits of their genome with one another.
‘primordial soup’ model: Stanley Miller’s famous experiment in the 1950s, where he mixed some
simple chemicals, applied a strong charge, and stood well back; he managed to create complex
‘biological’ compounds such as amino acids.
A popular new idea is that life emerged at hydrothermal vents.
Creationism is a faith- based position that holds that life/people were created by God.
Creation science was a move to position this kind of thinking as legitimate science.
Intelligent design (ID) attempts to raise the same issues but without including a religious
dimension by not specifically saying that God is the intelligent designer.
Darwinian views of evolution imply that all aspects of the biology of organisms must be adaptive –
providing some kind of selective advantage – otherwise they could not have evolved. Applied to
humans and their behaviour, this is known as evolutionary psychology.
Wallace outlined his theory in a letter to Darwin. Darwin feared being scooped, but also did not
want to cheat Wallace. He consulted eminent friends, who suggested that
Darwin then set about describing all his evidence, which he published in On the Origin of Species in
An early influential idea was that animals preferentially help their relatives, who share some of
The more closely related they are, the more likely they would be to collaborate.
Game theory studies, which explore people’s altruistic or selfish decision-making in various
scenarios. So mechanisms may evolve that lead to altruistic behaviour within a species because the long-term
benefits outweigh the short-term advantage of selfishness.
indirect reciprocity – ‘I’ll scratch your back because I know someone will scratch mine’
Life has existed for 3.5 billion years
INHERITENCE OF TRAITS article
Given the current size of the world’s population, the human genome is less diverse than might be
This observation is explained in part by two phenomena — the recent divergence of humans from
other primates and the relatively small size of the human population over most of its history
• In prehistoric times, the human population expanded in size as it migrated into new territory
• Modern humans migrated out of Africa about 100,000 years ago
• Mankind began migrating to America and Australia.
• Famine, war, environmental disruption and infectious disease epidemics can all create POPULATION
• Immigration counteracts the effects of isolation, and can restore diversity quickly if it occurs before the
isolate expands markedly in size
• Genetic drift makes populations more different, but then gene flow can make populations
more similar. As a result, gene flow reduces the effects of genetic drift.
The importance of deographic history: Unfortunately, for most isolates we lack reliable informa-
tion on their initial genetic makeup, their total number of founders, and the extent and duration of
their isola- tion.
More systematic analysis of DNA variation between and within populations is clearly needed. Such
research, which is in its infancy, is a stated goal of the Human Genome Project.
Isolates such as the Lapps of Scandinavia (Saami-populations) and the Basques of southern Europe
are well established (200–400 generations old) and demographically stable
Because of their small size and paucity of recessive dis- eases, these groups have been largely
ignored by geneti- cists.
Of more value in mapping rare diseases are the Finns, Amish, Sardinians and Bedouins. These
isolates also show a high frequency of certain Mendelian disorders and many disease genes have
been identified in them.
For studies of complex traits, geneticists have tended to target younger population isolates (10–20
generations old) that originated from a small number of founders and underwent rapid population
The people in most isolates share a common environment and culture
Small isolated populations also offer unusual opportunities for the standardization of diagnostic
and phenotypic criteria, which increases diagnostic reliability.
One example is Finland, where five medical schools with shared academic traditions train all the
clinicians in the country.
national population registries are available for certain isolated populations.
> the registries record births, deaths, marriages and migrations of individuals, and are of enormous value
for the reconstruction of large pedigrees.
The most extensive example of the systematic use of population history, genealogical records and
nationwide health-care registries in genetic research is the deCode project in Iceland
Some diseases, such as lipid disorders, offer better opportunities for quantification than other d