Week 4
Our Evolution Over the Past 3 Billion Years
This week focuses on endosymbiosis, the origin of the eukaryotic cell, the origin of multicellularity and the tragic separation of somatic cells from the germline. Are sex and death so fundamentally linked that we should expect them to evolve on other planets?
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13:41
4.1.1 All Eukaryotes
All Eukaryotes. The difference between prokaryotes and eukaryotes. Eukaryotes evolved from Archaea. If prokaryotes are ubiquitous and the transition from prokaryotes to eukaryotes is so important, should we expect ETs to be eukaryotes that evolved from prokaryotes? What does the tree of all eukaryotes look like? -
12:05
4.1.2 We Are Worms. We Are Amoeba
We are worms. We are amoeba. The onion of our many layered identity. ET life is a larger set than ET eukaryotes. ET primates are a larger set than ET apes. The common ancestor of animals and fungi was amoeba-like. Several ways to figure out what a common ancestor was like. -
12:46
4.2.1 Endosymbiosis
Endosymbiosis and Lynn Margulis. The mitochondria, chloroplasts and maybe undulipodia of eukaryotes were once free living alpha proteobacteria, cyanobacteria and spirochaetes (respectively). If endosymbiosis happened repeatedly on Earth, shouldn't we expect it to happen elsewhere? -
09:44
4.2.2 How Big are ETs?
How big are ETs? In the universe how many nested levels of life within life within life can there be? Eukaryotes as matroshka dolls. The Guinness records of life: the largest animal, the largest life form, the most massive life form, the life form with the largest area, the largest single cell. -
12:40
4.2.3 Origins of Multicellularity
Did complex multicellularity evolve independently more than once on Earth? If it did, doesn't that mean we should expect multicellular life elsewhere? What is multicellularity? How can eukaryotic evolutionary paths that were the same for 2 billion years, now be called "independent"? -
03:30
4.2.4 Imagine Slime Mold
Single cells join together and become a multicellular slug before your very eyes. This is analogous to an evolutionary transition in our lineage that probably took a billion years. -
14:19
4.2.5 Reproduction and Sex
How does life on Earth reproduce? Most life forms reproduce by binary fission. They have reproduction without sex and sex without reproduction. Do aliens reproduce sexually or asexually or some other way? How universal is sex? -
12:58
4.2.6 Sex and Death
Humans get old and die. Do aliens get old and die? Is programmed ageing such a fundamental feature of life that we should expect aliens to age? Or might they be immortal? The evolution of sex is the evolution of the distinction between somatic cells and germline cells. -
17:34
4.3.1 Are ETs Multicellular Animals?
Jokin with Jochen. What caused the Cambrian explosion of animal life. Will extraterrestrial life include multicellular animals? As creatures evolve, they accumulate a quirky history -- their features become more entrenched and difficult to change. Thus, early life on Earth might resemble early life elsewhere, but this may not be true for alien life that has evolved for billions of years. -
04:19
4.4.1 Andy Knoll: geobiologist
Knoll uses the geological record to document the early history of Earth and life. MIcrobial mat communites make stromatilites. When the curtain goes up geologically, life is already on stage. Complex multicellularity evolved multiple times. The molecules that make plant and animal cells stick together are very different. Are we alone? Maybe. These really are bar room arguments. -
08:59
4.4.2 Dirk Schulze-Makuch: geobiologist
Dirk Schulze-Makuch (geobiologist) thinks many independent evolutionary paths can lead to complex life. Dirk and Charley politely disagree about the "independent" evolution of invertebrate and vertebrate eyes. Dirk discusses habitability, the definition of life and his answer to the question Where is Everybody? -- space is big and traveling between stars is difficult. -
03:40
4.4.3 Maja Adamska: evolutionary biologist
Maja Adamska (developmental biologist working on sponges) doubts that there are sponges or DNA-based life forms on other planets. Complex multicellularity would evolve again because of mutation and selection. Sponges have sex all the time. She doesn't know whether we are alone or not because she's a scientist and she doesn't know everything and is not afraid to admit to that. -
07:03
4.4.4 Dorion Sagan: science writer/eclectic dilettante
Sagan is the Arlo Guthrie of astrobiology. Microbes forming higher levels of organization through natural processes may be a universal feature of life everywhere. When asked "Are we alone?" Dorian gives a Boolean answer: yes, no, and yes-and-no. Gadfly and mystic, he says that yes, we are alone because there is only one of us -- the all. -
05:06
4.4.5 David Schwartzman: geobiologist
David Schwartzman (geobiologist). The root of the tree of life is hyperthermophilic. David's position is that we are not alone and his solution to the Fermi paradox is: the credentials committee of the galactic club is making their evaluation based on observations of the pathetic state of our primitive civilization...and we're not yet worthy of being members. -
19:09
4.5.1 Student Discussion
Bec asks about choanoflagellates and volvox. What are opisthokonts? Did Venus flytraps evolve digestive enzymes independently of heterotrophs? Riley wants a compromise between Charley's deep homology and Jochen's independent convergence. How similar do prokaryotes need to be to exchange plasmids? How could senescence be an adaptation? -
07:43
4.5.2 What would you do with 100 billion dollars
What would you do with 100 billion dollars under the caveat that you have to spend it to try to answer the question "Are We Alone?" ? Staying alive is important if you want to find ET. Look for a second form of life on Earth. Sample return missions in our Solar System. Bigger telescopes. Remote sensing. Bury the money. Lynden-Bell (1935-2018) recites "The Microbe" by Hilaire Belloc.
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01:00
Aggregation of slime mold Dictyostelium discoideum
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0:16
E.coli growth and binary fission
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10:02
Where Did Eukaryotic Cells Come From? - A Journey Into Endosymbiotic Theory
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01:05:25
HOMAGE TO DARWIN: Evolution debate with Dawkins, Margulis, Brasier and Bell (2009)
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26:58
Lynn Margulis Interview
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12:26
The Complicated Legacy of Lynn Margulis
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27:59
Lynn Margulis on her life, Symbiogenesis, Gaia Theory, Scienctific Practice and Effects of Money
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43:45
Nick Lane: Origin of the eukaryotic cell
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01:04:14
Why is life the way it is? Michael Faraday Prize Lecture - Dr Nick Lane
Sex and the Origins of Death
by William R. Clark, 1998, Oxford University Press
What is Sex?
by Lynn Margulis and Dorion Sagan
Dazzle Gradually: Reflections on the Nature of Nature
by Lynn Margulis and Dorion Sagan, 2007, Chelsea Green Publishing
Life on a Young Planet: The First Three Billion Years of Evolution on Earth
by Andrew H. Knoll, 2003, Princeton University Press