Big history
2022-2023
Lecture slides & Chapters “Maps of time” about topics 5-8 + philosophical perspectives:
- Evolution & Complexity – Human History – Modernity – Future
Contents
Lecture 5:...............................................................................................................................................3
Evolution............................................................................................................................................3
DNA....................................................................................................................................................5
Prokaryotes vs. Eukaryotes................................................................................................................6
Biological Big Bang: Cambrian explosion.......................................................................................8
Ecology...............................................................................................................................................9
Speciation........................................................................................................................................12
Lecture 6:.............................................................................................................................................12
Threshold 6: Humans and collective learning..................................................................................12
Threshold 7: Agriculture..................................................................................................................15
What explains success of regions?...................................................................................................20
Lecture 7:.............................................................................................................................................22
Threshold 8: The modern revolution...............................................................................................22
Globalization....................................................................................................................................23
Acceleration.....................................................................................................................................25
Energy..............................................................................................................................................26
Lecture 8:.............................................................................................................................................29
Future..............................................................................................................................................31
Famous futures................................................................................................................................33
Lecture 9: Styles of scientific thinking..................................................................................................35
Styles of Scientific Thinking..............................................................................................................35
Table of thresholds: Complete summary.............................................................................................39
Recap questions tutorials................................................................................................................40
1
,Big history overview:
Recap midterm:
1.Birth of the universe 2.Stars and planets
• Big Bang • Stars and planets
• Fundamental forces and particles • New elements
• H and He (and Li) • Supernovas and black holes
• Entropy and energy • Rare earth elements
3.Earth system 4.Emergence of life
• Earth system • What is life
• Geological era’s • Emergence
• Magnetic field • Abiogenesis
• Planetary boundaries • Biomolecules
• Ozone • Carbohydrates, proteins
• N, P, H2O cycles lipids, nucleic acids
• Gaia hypothesis
2
,Lecture 5:
Evolution
Recap
• Life on Earth probably first appeared about 3.8 billion years ago, and consisted of single-celled
bacteria. Many scientists now favor a deep-sea origin for life.
• DNA, which is the blueprint for every living thing, emerged early on. Photosynthesis was also an
early development. Oxygen, a byproduct of photosynthesis, is “the most important waste product in
the history of the world.” Some bacteria learned to live on oxygen; for others it was toxic and led to
death. In the end, oxygen proved to be a more efficient way to produce energy, and allowed bigger,
more complex life forms to appear.
• Life emerged in the oceans between 3.5 billion and 4 billion years ago. Tiny, single-cell organisms
called prokaryotes lived in the seas and ate chemicals in their surrounding environment.
• A massive prokaryotes die-off is known as the oxygen holocaust occurred 2.5 billions year ago.
• Somewhere between 1.6 and 2 billion years ago, slightly bigger single-celled organisms called
eukaryotes evolved.
• DNA is a double-stranded molecule that contains a list of orders for how it wants a living cell to be
constructed. Once every billion copies or so there is an error. These errors result in a slight mutation.
• If useful, it allows an organism to be more successful and likely to pass on its genes. If not so
useful, things go poorly and the gene does not get passed on. On the scale of millions of years, these
copying errors are the engine of evolution and the origin of new species.
• The Cambrian explosion, about 550 million years ago, was biology’s Big Bang, and resulted in a
huge proliferation of plants and animals. Amphibians moved from the sea to the land. They
developed a new type of egg, one with a hard shell that kept the contents from drying out, which
allowed the eggs to be laid on land.
• Dinosaurs evolved about 250 million years ago, and dominated the Earth for over 150 million
years. Our ancestors, the early mammals, were very small—no bigger than cats— as long as the
dinosaurs were around. The dinosaur extinction made way for bigger mammals like us.
• Primates are mammals that evolved after the extinction of the dinosaurs. They possessed forward-
facing eyes and five-fingered, grasping hands. Our ancestors eventually left the trees and began
walking on two legs, which allowed them to carry things (including babies).
Charles Darwin On the Origin of Species
• The fundamental idea used in modern biology to explain both the development and the origins of
life is that of “evolution” by “natural selection.” The theory was first presented systematically in
Charles Darwin’s book On the Origin of Species, which appeared in 1859
• Darwin argued that species are not fixed entities but constantly changing
• The way they change is governed by some simple rules.
• A species is a large collection of individual organisms that are
similar enough to interbreed, but are not quite identical.
• However, over long periods of time, random variations in the
features of individuals may cause the average features of an
entire species to alter. Such minor changes, accumulating over
thousands of generations, must eventually transform the
average features of the entire species.
3
, • To understand how species change, we therefore must understand how and why the features of
some individuals become more common, while those of others dwindle and disappear.
But what determines which individuals reproduce, and which do not?
• Pure chance may play a role here, of course. But in the long run, Darwin argued, the individuals
most likely to survive and reproduce are those that have had the good luck to inherit from their
parents features that make them slightly better adapted to their environment. They will then pass
these same features on to most of their offspring. Over time, these features will become more and
more common because those individuals that do not possess them will produce fewer healthy
offspring, until their lineages die out.
• So it isn’t really that species adapted; it is the other way around. Those individuals who happened
to be better adapted by pure chance were the ones most likely to survive and shape future
generations of their species.
• Adaptation is such an important notion in modern biology that it is worth defining more carefully.
It refers to the fact that all living organisms seem to be exquisitely fitted for the environments in
which they live.
Adaptation and niches
• Adaptation helps explain the great variety of living organisms, for there is a huge variation in
environments to which organisms can adapt themselves. To describe these different environments,
biologists and ecologists use the notions of habitats and niches. Habitats are simply the geographical
environments in which species live.
• As environments are varied and changeable, organisms have to keep adapting if they are
to survive. This is why evolution never ends. Because there is no fixed standard of perfection
or “progress,” adaptation is an endless process.
• In other words; fitness is contextual!
• The idea of a niche is more complex, as it includes the way they live as well. The word niche is
derived from the Latin word meaning “nest.” In architecture, a niche is a recess or alcove in a wall in
which a statue or other object can be placed. In biology and ecology, a niche is the particular way of
living for which an organism seems to have been sculpted or adapted by evolutionary processes.
Does Altruism Exist? (behaviour of an animal that benefits another at its own expense.)
• Altruism from an evolutionary perspective is in need of explanation: If making the sacrifices
necessary to help others costs an organism without benefitting that organism, why would it take
such actions? Why, for example, would a mother lion feed and care for her offspring?
• For some time, the dominant explanation in evolutionary biology has been the selfish gene theory
popularized by Richard Dawkins, according to which genes are the basis for selection. Thus, while it
may not be in the interest of a particular lion to expend resources to feed and protect her young, it is
in the interest of the mother’s genes that she do so, and so lions, like other animals, have evolved
instincts to feed their young. Genes are really running the show, and they’re using individual
organisms as vehicles for their replication.
Multi level selection
• In contrast, group-level selection theory (also known as multi-level selection) says that natural
selection also operates at the level of the group, and that a group of organisms that coordinate their
activities for a common purpose can be practically conceived of as a superorganism in competition
against other groups.
• It is clear that groups and the pressures they exert play some role in the process of natural
selection. Indeed, Wilson argues that “The theories that claimed to explain altruism without invoking
group selection turned out to invoke group selection after all, in every way except using the name”.
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