The Emergence of Complex Life on Earth

1. The Emergence of Complex Life on Earth THE SCOPES TRIAL A plaque that commemorates the trial stands in front of the courthouse that states: 2B 23 Here, from July 10 to 21, 1925 John Thomas Scopes, a County High School teacher, was tried for teaching that a man descended from a lower order of animals in violation of a lately passed state law. William Jennings Bryan assisted the prosecution; Clarence Darrow, Arthur Garfield Hays, and Dudley Field Malone the defense. Scopes was convicted. Rhea County Courthouse, Dayton, Tennessee.

2. The Cambrian Explosion No new phyla have appeared since Cambrian explosion! The divergence of life was well underway before the‘Cambrian Explosion’ Divergence of life during Precambrian period. The hierarchy of biological classification's eight major taxonomic ranks.

3. Snowball Earths ~ 750 - 580 Mya • If enough cooling occurs such that glaciation moves to low latitudes, process could ‘runaway’… more ice causes more solar reflectivity which causes more cooling, etc. Snowball Earth • Recovery occurs when CO2 builds up in atmosphere due to volcanic outgassing and can’t be reabsorbed because of ice cover. • Recovery triggered Cambrian Explosion?

4. 635─542 Mya The Ediacarans • Round, disc-shaped forms that resembled jellyfish. Others resembled worms, arthropods, or even stranger things. • First appearance of large, architecturally complex multicellular organisms in Earth’s history! • Succumbed to changing environmental conditions? • …breakup of supercontinents, rising sea levels, nutrient crises, fluctuations in atmospheric composition, changes in ocean chemistry. • There is evidence that they did not completely disappear. Possibly, they are ancestors of some organisms that emerged during the Cambrian period. DickinsoniaCostata, an iconic Ediacaran organism, displays the characteristic quilted appearance of Ediacaran enigmata

5. Early Cambrian Life Only five of thirty-six modern animal phyla emerged before the Cambrian Explosion. Within ~10 Myr, the rest emerged, such as the arthropods and chordates. At the time of Darwin, it seemed as though all animal life had suddenly appeared literally out of thin air! Trilobite fossil Biomineralization—the ability to use calcium, silicon and phosphorous to make shells, skeletons, exoskeletons and other hard body parts emerged during the Cambrian Explosion. The simultaneous appearance of many phyla that did this argues for its strong evolutionary advantage—probably as a response for protection of ‘prey’ from newly emerging ‘predators.’

6. The Cambrian Explosion • Why was the Cambrian explosion the only known such diversification of life on Earth? • Oxygen is necessary for large scale life; levels were too low beforehand. • As eukaryotes evolved, they developed more and more genetic variation in their DNA: variation begets variation. As new body plans emerged, new avenues for other new body plans became available. • Climate change (eg, recoveries from Snowball Earth). Ice ages beforehand applied evolutionary stress which resulted in a diversification of life. • An early absence of efficient predators would allow untested body plans to survive longer than they might today. • Ultimately, diversification would continue, allowing life to slowly spread to land. While microbes would flourish easily, multicellular life would take more time.

7. Pannotia Supercontinent~600 Mya Pannotia breaks up in shallow oceans increasing shoreline and trapping inland ‘seas’ ‘Trapped’ life forms find themselves in a new environment along coastal regions and inland seas increasing likelihood of evolution of land-based life.

8. Microbial Mat–Yellowstone Fossilized Microbial Mats found in South Africa date back 2.6 Gya ─ prokaryotic life existed on land before the Great Oxidation Event

9. Requirements for ‘Landlubbers’ • Proper cell function requires regulation of water content. • Respiration and gas exchange systems had to change. • Reproductive systems cannot depend on water to carry eggs and sperm towards each other. • Large, multicellular organisms do not float in air. • Air temperatures have more variance and fluctuate more rapidly than water temperature does. • Soil, a combination of mineral particles and decomposed organic matter, did not exist before the colonization of land.

10. Life on Land • ‘Big life’ requires energetic reactions using oxygen as well as a protective ozone layer. Both built up during the Cambrian explosion. • Atmospheric ozone would need to build up first to protect life from UV rays. • Cyanobacteria likely produced copious oxygen over ~2 billion years, but first it was ‘gobbled up’ by geochemical oxidation reactions (e.g., rust), before finally saturating the geochemistry and building oxygen and ozone in the atmosphere. • Plants (lichens) had to have established on land first (about 475 Mya)…and then evolved likely due to stress from havingto adapt to survive without water for prolonged periods. • Some 75 million years later, animals and insects followed plants onto the land.

11. Moving Onto Land Lichens ─ symbiotic combinations of a fungus and photosynthesizers ─ colonize lifeless environments ─ break down rocks to form soil ─ appeared 470 Mya. Aconthostega, among the first vertebrates with four limbs (tetrapods) evolved from fish during the Late Devonian ~ 360 Mya. Aconthostega had lungs and gills!

12. Carboniferous Period 350 Mya Vast forests, primitive amphibians, reptiles and insects thrived on land. Their death led to coal, oil and gas These environmental conditions never existed again after this period ended 300 Mya!

13. A Doomsday Scenario It would soon prove to be a day unlike any other for the dinosaurs and other species that roamed the Earth 65 million years ago. A tiny bright point of light not unlike that of a bright star suddenly appeared in the daytime sky. The bright spot was a 10-km wide asteroid headed towards a point in Earth’s orbit where unfortunately it would arrive at the same time as the Earth! Upon entering the atmosphere, observers would have only 10 seconds left to live before it struck the ground. The explosion caused by the impact released an energy equivalent to that of a 100 million megaton thermonuclear blast—equivalent to 100,000 times the explosive energy store in the combined U.S.—Russia nuclear arsenal!

14. A Doomsday Scenario

15. KT Mass Extinction • Temperatures soared to over a million degrees K — completely vaporizing everything within hundreds of kilometers. • A huge fireball exploded out of the sea and spread outward faster than the speed of sound leaving death and destruction in its wake. • The shock it generated left a crater 200 km wide. Earth’s Cretaceous period had ended abruptly! The Tertiary period had begun!

16. Evidence ─ First Hint Evidence ─ First Hint • Walter discovered a distinct sequence of rock layers marking the 65 million year old boundary between the Cretaceous and Tertiary periods—the ‘KT’ boundary ─ made up of : • a lower layer of sedimen­tary rock rich with a wide variety of marine fossils • a centimeter-thick layer of clay stone devoid of all fos­sils • an upper layer of sedimentary rock contain­ing a much reduced variety of marine fossils • The K comes from Kreidezeit, the German word for Cretaceous. Walter & Luis Alvarez at Gubbio, Umbria, Italy

17. Iridium Concentration Iridium Concentration The ‘thin’ clay layer is devoid of fossils … and rich in the element Iridium! The ‘thin’ clay layer is devoid of fossils … and rich in the element Iridium!

18. World Wide Iridium Anomalies

19. The ‘Smoking Gun’

20. Question What is the most compelling piece of evidence that suggests that the extinction of dinosaurs was “triggered” by the impact of an asteroid 65 million years ago? A layer of sediment laid down at that time which is littered with dinosaur fossils whose heads had obviously been squashed. Dinosaur fossils are found in rock layers older than 65 million years but not younger than 65 million years. A layer of sediment laid down at that time which is rich in the element Iridium (Ir), an element common in asteroids but less common on the Earth. The crater from this impact can still be seen in the Arizona desert. No dinosaur fossils have ever been found because the dinosaurs were completely vaporized by the impact.

21. Other Mass Extinctions

22. The Largest Mass Extinction ‘The Great Killing’─ R.J. Poreda of the science team that discovered that the Bedout High was site of a Chicxulub-sized impact— “There have been five mass extinctions throughout the Earth’s history. Now we have very strong evidence that massive meteor impacts happened precisely at two of those extinctions.”

23. Chelyabinsk, Russia — Feb 15, 2013

24. Tunguska Event 1908 Stony Asteroid or comet ‘exploded’ 3─6 km above ground zero! Size: 10’s of meters Mass: 100 Kilotons Speed: 22 km/sec Energy:10 ─ 20 Megatons

25. Leonid Kulik’s Photograph —1927 Leonid Kulik’s Photograph —1927 No crater! At ground zero — an 8 km zone of trees scorched and devoid of branches, but standing upright. Those farther away had been partly scorched and knocked down in a direction away from the center. Area of leveled forest ~2,150 square kilometers! No crater! At ground zero — an 8 km zone of trees scorched and devoid of branches, but standing upright. Those farther away had been partly scorched and knocked down in a direction away from the center. Area of leveled forest ~2,150 square kilometers!

26. Meteor Crater - Arizona 1.2 km 50,000 yrs ago … 20 – 40 Mtons (size of impactor ~ 50 meter)

27. Comet Shoemaker––Levy 9 Strikes Jupiter 1994 As David Levy stated—“The giggle factor disappeared after Shoemaker-Levy 9.”

28. Impact Frequency 20 m 90 m 4 m 400 m 2 km Chelyabinsk 2013 Meteor Crater World Nuclear Arsenal KT Event

29. Includes the infamous asteroid, 1997XF11, which made a major impact on the world's headlines in March 1997 when observations indicated that it had a good chance of colliding with the Earth in 2028! NEO’s An up to date map of the inner solar system displaying the orbits of the terrestrial planets and the estimated position of thousands of known asteroids. This diagram is missing comets, space probes and the undiscovered asteroids. It is estimated that there are perhaps 100,000 to 1,000,000 undiscovered asteroids on similar Earth crossing orbits. Have a Nice Day!

30. Probability of Death… Odds of Winning Powerball 1 in 195,249,054

31. Question An ET that emerged in a solar system like ours might go extinct before living beyond the stage of operational intelligence longer than 1 - 100 million years most likely because _______. • its Sun might explode as a supernova. • it might get wiped out in an attack by hostile aliens. • its home planet might get swallowed up by a black hole. • its Sun might turn into a white dwarf. • it might undergo global catastrophe initiated by impact of a large (>10 km) comet or asteroid.

32. I didn’t Come From No Monkey! PUBLIC ACTS OF THE STATE OF TENNESSEE PASSED BY THE SIXTY - FOURTH GENERAL ASSEMBLY 1925 AN ACT prohibiting the teaching of the Evolution Theory in all the Universities, Normals and all other public schools of Tennessee, which are supported in whole or in part by the public school funds of the State, and to provide penalties for the violations thereof. Section 1.Be it enacted by the General Assembly of theState of Tennessee, That it shall be unlawful for any teacher in any of the Universities, Normals and all other public schools of the State which are supported in whole or in part by the public school funds of the State, to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals. Section 2.Be it further enacted, That any teacher found guilty of the violation of this Act, Shall be guilty of a misdemeanor and upon conviction, shall be fined not less than One Hundred $ (100.00) Dollars nor more than Five Hundred ($ 500.00) Dollars for each offense.

33. …From Monkeys Evolution of Humans Monkeys and Humans have a common ancestor!

34. The Ancestor of Mammals ~ 65 Mya Scientists have identified and reconstructed the most likely common ancestor (Protungulatumdonnae) of the many species on the most abundant and diverse branch of the mammalian family tree — the branch of creatures that nourish their young in utero through a placenta. The work supports the view that in the global extinctions some 66 million years ago, all non-avian dinosaurs had to die for mammals to flourish. It’s not a monkey — it’s a big, hairy rat! Rendering of Protungulatumdonnae.

35. Phylogenetic Tree Ardi 4.4 Mya Orrorin 6 Mya Toumai 6.3 Mya

36. Evolution of Homo Sapiens The evolution of hominids showing some of the likely ancestors of Homo sapiens dating back 7 million years—starting with S. tchadensis (‘Toumai’ ─ perhaps the most recent ancestor of all hominins).

37. Lucy in the Sky With Diamonds 3.2 Mya ‘Lucy’ ─ first Australopithecus Afarensis skeleton found—in 1974. During the celebration of her discovery, the Beatles ‘Lucy in the Sky With Diamonds’ was played on a tape recorder in camp—hence her name. A mixture of ape and human features—including long dangling arms for swinging in trees—her pelvic, spine, foot, and leg bones left no doubt that she walked upright. Lucy stood three and a half feet tall and her brain size was somewhere between 375–500 cm3. Lucy’s anatomy thus offered overwhelming evidence that the evolution of bipedalism preceded that of large brain size.

38. Homo Habilis─ 2.33 – 1.7 Mya Homo habilis stood 4’ 3” tall and had a Cranial capacity ~ 600 cm3 Homo habilis is thought to have mastered the ‘Olduwan era (Lower Paleolithic) tool case’ which utilized stone flakes. These stone flakes were more advanced than any tools previously used, and gave H. habilis the edge it needed to prosper in hostile environments previously too formidable for primates.

39. Homo Erectus ─ 1.8 – 1.3 Mya Cranial Capacity ~ 850 – 1100 cm3 First Hominid to control fire and live in hunter-gatherer society. Homo Erectus ─ one of most successful and long-lived species of Homo

40. Homo Neanderthalensis 400 – 30 Kya Sapiens 66” tall ─ cranial capacity human size or larger (1500 cm3) 1-4% of our genome is Neanderthal! • Went extinct ~ 30 Kya • Interaction with Homo sapiens sapiens? • Climate change?

41. Question The earliest homo sapiens appeared about ______. • 25 million years ago. • 6 to 8 million years ago. • 300,000 years ago. • 545 million years ago. • 6000 years ago.

43. Where Are the Missing Links? • Number one—they would be difficult to find even if they existed, since their existence would be at best transitory on the scale of geologic time—it’s difficult enough to find fossils of life that flourished for millions years—millions of years ago—let alone some ‘link’ that existed for no more than tens of thousands of years. • Number two—there is no ‘link’!Life changes and evolves slowly—at least on timescales experienced by humans. One life form changes slowly over time starting from another. Which stage in this slow progression represents ‘the link’? There are many ‘links’ that ultimately lead to a new relatively stable species.

44. Transitional Hominids • Pan troglodytes, chimpanzee, modern • Australopithecus africanus, STS 5, 2.6 My • Australopithecus africanus, STS 71, 2.5 My • Homo habilis, KNM-ER 1813, 1.9 My • Homo habilis, OH24, 1.8 My • Homo rudolfensis, KNM-ER 1470, 1.8 My • Homo erectus, Dmanisi cranium D2700, 1.75 My • Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My • Homo heidelbergensis, "Rhodesia man," 300,000 - 125,000 y • Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y • Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y • Homo sapiens neanderthalensis, Le Moustier, 45,000 y • Homo sapiens sapiens, Cro-Magnon I, 30,000 y • Homo sapiens sapiens, modern