1. Development of Life George Lebo October 17, 2012 AST 2037 1

2. From Last Time: Then … Life Appears! First fossil cells found in rocks at about T – 3.7 to T – 3.5 Billion Years! Tiny little things Not O 2 breathers like us (none around!) Probably CO 2 breathers Modern cyanobacteria look a lot like these fossils AND they are CO 2 breathers Suggests that the first (fossil) life may have been cyanobacteria (?) 2

3. Summary Earth of Way Back When was different We can tell from chemical and radio-isotope analysis of rocks Water and other volatiles may have come from comet impacts Life formed a long time ago – about 3.5 Billion Yr or so We know from fossils We don’t know exactly how, but … We know we had the right elements Those elements + lightning make amino acids DNA may have originated from these acids in a clay matrix Next question: How did things get from Then to Now?? 3

4. Evolution This time with a capital “E” Reproduction occurs via DNA Any change in the DNA from one generation to the next creates “mutation” Causes of mutation: Radiation (all those rock decays; cosmic rays) Chemical contamination “Transcription errors” Random mutation produces wide range of changes Senescence (Biological Aging) Apoptosis (Programmed Cell Death) Unregulated Cell Division (leading to a tumor or to cancer) 4

5. DNA Mutation Examples 5

6. Natural Selection Some mutations will be competitively “helpful”, some neutral, some disadvantageous Natural selection: those with competitive “edge” more likely to succeed in reproducing; those without are less likely 6

7. Natural Selection: Examples We have seen this in action on even short timescales: Cockroaches and insecticide TB bacteria and antibiotics Light/dark pepper moths in England: Prior to 1800, mostly light-colored with occasional dark ones (collector items) After Industrial Revolution, trees darkened by soot, dark ones camouflaged, light ones easy to see Light ones disappear (eaten by birds!) Population now dominated by dark moths This was a hoax. The moths were planted. See museum of hoaxes 7

8. REQUIREMENTS FOR MUTATIONAL EVOLUTION (ROSS) MANY INDIVIDUALS (AT LEAST ONE QUADRILLION) SMALL BODY SIZE (LESS THAN TWO CM.) SHORT GESTATION PERIOD (LESS THAN THREE MONTHS) LARGE NUMBER OF PROGENY

9. FRED HOYLE’S ANALYSIS According to Hoyle's analysis, the probability of cellular life evolving were about one-in-10 40000. He commented: The chance that higher life forms might have emerged in this way is comparable to the chance that a tornado sweeping through a junkyard might assemble a Boeing 747 from the materials therein. Life as we know it is, among other things, dependent on at least 2000 different enzymes. How could the blind forces of the primal sea manage to put together the correct chemical elements to build enzymes? [4] [4]

10. “A THIRD WAY”, JAMES SHAPIRO NOT CREATIONISM OR EVOLUTIONISM Genomes, asserts Shapiro, are not really the static "beads on a string" envisioned by the Darwinians. Rather, they are fluid and complex. Genes are now seen as multipurpose elements that turn on and off as required for the survival and well-being of the organism they belong to.

11. Back to Early Life Old fossils – like cyanobacteria Then … Stromatolites Lots and lots of stromatolites! 11

12. Stromatolites Large agglomerations of single-celled organisms First they form “microbial mats” (i.e. “pond scum” layer) These layers live, die, get covered by silt Next mat forms, etc. Produces layered fossils 12

13. Modern Stromatolites Stromatolites still alive today Mostly in places where high acidity or salinity in water removes “predators” (i.e. snails and other grazers) 13

14. Atmospheric Bioengineering Remember … atmosphere had no O 2 to start At about 2.5 GYA, O 2 level jumped Why? LOTS of cyanobacteria and other CO 2 breathers! 14

15. Development in the Archaic Era Time span from 3.6 GYA to about 0.6 GYA All single-celled life at this time – LOTS of stromatolites Responsible for the oxygen-enrichment of the atmosphere (liberating O 2 from CO 2 ) Initially prokaryotes – simpler structure, no nucleus Eukaryotic fossils date to ~2 GYA Sterol chemicals begin to show up in rocks about ~2.7 GYA Sterols only known to come from Eukaryotes now (maybe from Eukaryotes or proto-Eukaryotes then) Still single-celled, but far more complex … 15

16. Endosymbiotic Theory Idea that complex eukaryotes formed from symbiotic relationship between simpler prokaryotic cells In other words, big cell “encapsulates” smaller specialized prokaryotes which form mitochondria, chloroplasts, etc. 16

17. Endosymbiotic Theory Evidence for it: Mitochondria have their own DNA, which is unlike nuclear DNA but similar to prokaryote DNA Chloroplasts actually resemble cyanobacteria “Main cell” offered nucleus which stores most of the mitochondria/plastid DNA in a more “protected” environment Laboratory observations of endosymbiotic relationships developing between some algaes and prokaryotes 17

18. Single-Celled Evolution Move from cyanobacteria (simple) to green algae (complex) From prokaryote to eukaryote Eukaryotes have 10x to 1,000x more DNA (information for complex structures) But still … only single-celled life found until ~0.6 GYA In context: Life has been around for 3.5 GY But single-celled for 2.9 GY of it !!! (for college student scale – as if multi-cell only arrived 3 years ago!) 18

19. Early Life: Multi-Cellular Around 600 MYA, start seeing a range of multi-cellular organisms Seen in sites spread across the world at the same time Best examples: The Ediacaran Fauna Small fossils (typically a few mm to a few cm) Ediacaran Period is the last geological period of the Neoproterozoic Era 19

20. Cyclomedusa Common fossil from this period Round symmetry; up to 8-10 inches across (!) 20

21. Tribrachidium Three-fold symmetry, rather than plain round 21

22. Spriggina Later Ediacaran Bilateral symmetry (familiar?) Fossils show clear head, mouth Centralized structure as well First fossil to show “animal” features 22

23. Ediacaran Properties Range of features: Many have round symmetry Others have 3-fold symmetry Later ones show bi-lateral symmetry (like us!) All “soft-bodied” – vaguely reminiscent of jellyfish and anemones For early ones, not sure if the moved around or not – could be “filter feeders” Spriggina sure looks a lot like an “animal” Few, if any, of the Ediacara left recognizable evolutionary “descendants” seen in modern life 23

24. Small Shellies At transition between Edicaran and the upcoming “Cambrian” era, start seeing fossils with hard shells (~550 MYA) Also start seeing more calcium carbonate and phosphates in the rocks 24

25. The Cambrian Explosion Over a period of just a few million years (unresolved in the geological record – meaning it was geologically “instantaneous”) we suddenly see lots of real “animals” Called the “Cambrian Explosion” (530 MYA) 25

26. Cambrian Examples Things that really look like “critters” today (!!) 26

27. The Burgess Shale Fossil deposit in western Canada provided first examples Now many from worldwide 27

28. The Burgess Shale 28

29. The Burgess Shale 29

30. Trilobites A huge variety of these found in the Cambrian Look a lot like Horseshoe Crabs (not actually related though!) Have properties including: Armor Legs Mouth Eyes (!!) 30

31. Trilobites 31

32. Why “Explosion”? Note the rapid growth in size from a cell, to a few cells (~3 GY); from a few cells to animals (~0.05 GY); from animals to large animals (~0.01 GY) Over only a few million years (versus BILLIONS before) every currently recognized phylum of life on Earth developed in the Cambrian explosion (!) Punctuated Equilibrium – Nature remained in a state of “stasis” for long periods of time then, suddenly, a spurt of evolution produced new life forms - Proposed by Steven J. Gould 32

33. The Cambrian Explosion Initially, at least, land was still totally barren No trees, no plants, no critters, no evidence of bacterial life on land either The sea, on the other hand, was teeming with life! 33

34. Nature Red in Tooth & Claw Burgess Shale also provides first conclusive evidence of active predation 34

35. What Enabled the Cambrian Explosion? O 2 levels jumped to nearly “modern” right before the Cambrian explosion All modern animals are O 2 breathers Perhaps the O 2 increase enabled a dramatic increase in diversity/size of animals 35

36. What Next? So far, so good: We got from bacteria to algae in about 3 billion years (slow progress?) From algae to jellyfish-like Ediacara in about 50 million years (faster) From Ediacara to every known phylum and active predators in a few million years (REALLY fast!) How do we go from there to dinosaurs to US ? Answer: not in a straight line! 36

37. Evolutionary Timeline 530 MYa – first footprint fossil found on land 505 Mya – first true fish in the sea 475 MYa – first land plant fossils 360 MYa -- Beginning of the Carboniferous Age (lots of land plants and trees!) 360 MYa – First amphibians, followed quickly by first reptiles; insects on land/air; sharks in the ocean 37

38. Permian Period 285 MYa to about 250 MYa Earth would now have been “recognizable” (if somewhat weird!) Land has immense forests of trees and other plants (but no flowers!) Ocean has lots of fish (including sharks), marine mammals, still trilobites too 38

39. Permian Period Land has insects, amphibians, reptiles Reptiles could reach sizes of 10-20 feet (!) 39

40. Permian Period: Pangaea One of several supercontinents formed over the history of Earth – About one every 500 million years 40

41. End-Permian By the late Permian, things seem to be going very well! Tremendous diversity of life: Plants and animals Sea and Land Then … it all stopped (!) 41

42. Permian Extinction AKA “The Great Dying” 96% of all marine species extinct 70% of land vertebrates extinct Note – not individual critters, but entire species! Overall mortality of living creatures even for “survivor” species might have been >95-99% (!) “Fungal spike”: Large jump in fungal fossils after this Why? lots of dead plant/animal matter! What caused it ??? – Hypotheses are: Glaciation of Gondwana Simultaneous glaciation of the poles Volcanoes Formation of Pangaea 42

44. Mesozoic Era Defined to begin post- Permian Extinction Includes Triassic, Jurassic, Cretaceous 44

45. Mesozoic Era Big “bounce” in the development of life after the Permian Extinction Big developments: Dinosaurs (which come to dominate) Flowering plants (angiosperms) Marine reptiles Flying reptiles First Mammals Etc. 45

46. Mesozoic Dinosaurs 46

47. Mesozoic Angiosperms 47

48. Mesozoic Mammals 48

49. Mesozoic Reptiles 49

50. Late Cretaceous Again, unprecedented diversity of life on land and sea Then (again!) it all ends! The Cretaceous-Tertiary (K-T) extinction 50

51. K-T Boundary Clear geologic signature “break” found worldwide Thin, whitish line in the rock Interestingly, lots of dinosaurs BELOW the line; none ABOVE the line (!!) Many other species also disappear then (pteranodons; many marine reptiles) About 65 Mya … 51

52. K-T Extinction Species extincted included: Almost ALL large vertebrates on land (dinosaurs, etc.) Most species of plankton and reef-dwelling animals Tropical marine invertebrates Many land plant species Again … these are entire species lost! Death toll for individual living beings >90% in many cases The greatest loss of species in the last 100 million years on Earth 52

53. K-T: What caused it? Iridium: Rarely found on Earth’s surface Large concentrations in the K-T Boundary worldwide Found in similar concentration ins METEORS Alvarez & Alvarez developed the KT Impact Theory based on this Initially, many people skeptical But … shocked quartz also found worldwide in K-T Boundary 53

54. K-T: How did that kill everything? Energetics: A meteor about 30 meters across has the energy of a large hydrogen fusion weapon A small asteroid a few miles across would hit with more energy than 1,000 times the world’s entire nuclear arsenal (going off at one time in one place!) But … even that wouldn’t kill critters worldwide, would it? 54

55. K-T: Impact Climate Change That large of an impact would have sent literally tons of dust into the atmosphere We used to worry about “nuclear winter” – this would be MUCH larger, colder, longer Subsequent freezing of food sources and death of many photosynthetic organisms would kill/starve higher animals as well 55

56. K-T Impact: Chicxulub! Site just north of Yucatan peninsula in Mexico Evidence of large impact crater Crater age matches K-T Crater size matches K-T energetics 56

57. Mass Extinctions We have seen the K-T and Permian extinctions Evidence for several others 57

58. Impacts: How often? Depends on the size: 1-ton bomb – EVERYDAY! (Why don’t we notice it?) 58

59. Impacts: Tunguska Atomic bomb size – every 100-200 years (TUNGUSKA) Shattered windows in Moscow (2000 miles away) Heard on the streets of London (3000 miles away) Flattened a forest of trees No crater; center trees still standing; suggests “airburst” (possibly comet?) 59

60. Impacts: Future? Atomic bomb size – every 100-200 years (TUNGUSKA) Extinction-level hit – every ~100-200 MY Aren’t we about due?? 60

61. Later evolution Tertiary – age of mammals Human evolution timeline Note: agriculture and human settlements about 13,000 years ago Writing, etc. about 5,000 years ago or so Pyramids and Ziggurats Transport via boats, etc. Telecommunication Space travel Most signs of “intelligence” limited to the past 50-100 years 61

62. Tertiary & Quarternary Age of mammals Human evolution timeline: Hominids appear about 5 MYr ago “Modern” humans are recent (last 150,000 years) Neanderthal Man co-existed for a while (250,000 to 30,000 years ago), but then went extinct 62

63. Tertiary & Quarternary 63

64. Development of Intelligence Working definition of intelligence: Capable of developing technology for interstellar communication Radio works; so would lasers; still working on “subspace communicators” 64

65. Development of Intelligence Agriculture and human settlements about 13,000 years ago Writing, etc. about 5,000 years ago or so Pyramids and Ziggurats Transport via boats, etc. Telecommunication Space travel Most signs of “intelligence” limited to the past 50-100 years (!) 65

66. Is Intelligence Inevitable? We often think that evolution had the “goal” of producing us, or things a lot like us/ After all, we are the pinnacle of evolution … right? But, nature had LOTS of opportunities to develop intelligence before, and it did not happen 66

67. Is Intelligence Inevitable? Even for hominids, “intelligence” only developed in the last <200,000 years (that is <4% of hominid duration on Earth!) And … it only became obvious (according to our definition) in the last 100 years That’s about 0.002% of hominid duration on Earth Or … about 0.0000025% of the duration of life on Earth!!! 67