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115-418: Since the 1970s, the concept of the triune brain has been subject to criticism in evolutionary and developmental neuroscience and is regarded as a myth. Although it overlaps in some respects with contemporary understanding of the brain, the triune brain hypothesis is no longer espoused by comparative neuroscientists in the post-2000 era due to harsh criticism against it. MacLean originally formulated his model in

230-404: A Pulitzer Prize in 1977, he was asked to write and narrate the show. It was targeted to a general audience of viewers, who Sagan felt had lost interest in science, partly due to a stifled educational system. Each of the 13 episodes was created to focus on a particular subject or person, thereby demonstrating the synergy of the universe. They covered a wide range of scientific subjects including

345-604: A full professor at Cornell in 1970 and directed the Laboratory for Planetary Studies there. From 1972 to 1981, he was associate director of the Center for Radiophysics and Space Research (CRSR) at Cornell. In 1976, he became the David Duncan Professor of Astronomy and Space Sciences, a position he held for the remainder of his life. Sagan was associated with the U.S. space program from its inception. From

460-492: A 'b ' ", in order to distinguish the word from "millions") made him a favorite target of comic performers, including Johnny Carson , Gary Kroeger , Mike Myers , Bronson Pinchot , Penn Jillette , Harry Shearer , and others. Frank Zappa satirized the line in the song "Be in My Video", noting as well "atomic light." Sagan took this all in good humor, and his final book was titled Billions and Billions , which opened with

575-466: A 16-year-old. Its chancellor, Robert Maynard Hutchins , had recently retooled the undergraduate College of the University of Chicago into an "ideal meritocracy" built on Great Books , Socratic dialogue , comprehensive examinations , and early entrance to college with no age requirement. As an honors-program undergraduate , Sagan worked in the laboratory of geneticist H. J. Muller and wrote

690-493: A career goal: "That was a splendid day—when I began to suspect that if I tried hard I could do astronomy full-time, not just part-time." Sagan graduated from Rahway High School in 1951. Before the end of high school, Sagan entered an essay writing contest in which he explored the idea that human contact with advanced life forms from another planet might be as disastrous for people on Earth as Native Americans' first contact with Europeans had been for Native Americans. The subject

805-417: A few hypotheses for the origin of turtles have suggested that they belong to the parareptiles. The clades Recumbirostra and Varanopidae , traditionally thought to be lepospondyls and synapsids respectively, may also be basal sauropsids. The term "Sauropsida" originated in 1864 with Thomas Henry Huxley , who grouped birds with reptiles based on fossil evidence. The term Sauropsida ("lizard faces") has

920-423: A flashlight shining on a photoelectric cell , which created a crackling sound, and another showed how the sound from a tuning fork became a wave on an oscilloscope . He also saw an exhibit of the then-nascent medium known as television. Remembering it, he later wrote: "Plainly, the world held wonders of a kind I had never guessed. How could a tone become a picture and light become a noise?" Sagan also saw one of

1035-686: A growing, man-made danger and likened it to the natural development of Venus into a hot, life-hostile planet through a kind of runaway greenhouse effect . He testified to the US Congress in 1985 that the greenhouse effect would change the Earth's climate system. Sagan and his Cornell colleague Edwin Ernest Salpeter speculated about life in Jupiter's clouds , given the planet's dense atmospheric composition rich in organic molecules. He studied

1150-670: A kind of "inner war" as a result of his close relationship with both his parents, who were in many ways "opposites." He traced his analytical inclinations to his mother, who had been extremely poor as a child in New York City during World War I and the 1920s, and whose later intellectual ambitions were sabotaged by her poverty, status as a woman and wife, and Jewish ethnicity . Davidson suggested she "worshipped her only son, Carl" because "he would fulfill her unfulfilled dreams." Sagan believed that he had inherited his sense of wonder from his father, who spent his free time giving apples to

1265-448: A library card. He wanted to learn what stars were, since none of his friends or their parents could give him a clear answer: "I went to the librarian and asked for a book about stars [...] and the answer was stunning. It was that the Sun was a star, but really close. The stars were suns, but so far away they were just little points of light. The scale of the universe suddenly opened up to me. It

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1380-558: A long history, and hails back to Thomas Henry Huxley , and his opinion that birds had risen from the dinosaurs . He based this chiefly on the fossils of Hesperornis and Archaeopteryx , that were starting to become known at the time. In the Hunterian lectures delivered at the Royal College of Surgeons in 1863, Huxley grouped the vertebrate classes informally into mammals , sauroids, and ichthyoids (the latter containing

1495-643: A modest apartment in Bensonhurst. He later described his family as Reform Jews , the most liberal of Judaism's four main branches. He and his sister agreed that their father was not especially religious, but that their mother "definitely believed in God, and was active in the temple [...] and served only kosher meat." During the worst years of the Depression , his father worked as a movie theater usher. According to biographer Keay Davidson, Sagan experienced

1610-403: A non-threatening object towards Earth, creating an immensely destructive weapon. In a 1994 paper he co-authored, he ridiculed a three-day-long " Near-Earth Object Interception Workshop " held by Los Alamos National Laboratory (LANL) in 1993 that did not, "even in passing" state that such interception and deflection technologies could have these "ancillary dangers." Sagan remained hopeful that

1725-619: A school for gifted children, he has something really remarkable." However, his parents could not afford to do so. Sagan became president of the school's chemistry club, and set up his own laboratory at home. He taught himself about molecules by making cardboard cutouts to help him visualize how they were formed: "I found that about as interesting as doing [chemical] experiments." He was mostly interested in astronomy, learning about it in his spare time. In his junior year of high school, he discovered that professional astronomers were paid for doing something he always enjoyed, and decided on astronomy as

1840-462: A scientific viewpoint, nuclear winter was a low point for Sagan, although, politically speaking, it popularized his image among the public. The adult Sagan remained a fan of science fiction, although disliking stories that were not realistic (such as ignoring the inverse-square law ) or, he said, did not include "thoughtful pursuit of alternative futures." He wrote books to popularize science, such as Cosmos , which reflected and expanded upon some of

1955-482: A subgroup of archosaurian reptiles despite originally being named as a separate class in Linnaean taxonomy . The base of Sauropsida forks into two main groups of "reptiles": Eureptilia ("true reptiles") and Parareptilia ("next to reptiles"). Eureptilia encompasses all living reptiles (including birds), as well as various extinct groups. Parareptilia is typically considered to be an entirely extinct group, though

2070-575: A thesis on the origins of life with physical chemist Harold Urey . He also joined the Ryerson Astronomical Society. In 1954, he was awarded a Bachelor of Arts with general and special honors in what he quipped was "nothing." In 1955, he earned a Bachelor of Science in physics. He went on to do graduate work at the University of Chicago, earning a Master of Science in physics in 1956 and a Doctor of Philosophy in astronomy and astrophysics in 1960. His doctoral thesis, submitted to

2185-412: A tongue-in-cheek discussion of this catchphrase, observing that Carson was an amateur astronomer and that Carson's comic caricature often included real science. As a humorous tribute to Sagan and his association with the catchphrase "billions and billions", a sagan has been defined as a unit of measurement equivalent to a very large number of anything. Sagan's number is the number of stars in

2300-491: A tremendous increase in the respectability of a then-controversial field. Sagan also helped Frank Drake write the Arecibo message , a radio message beamed into space from the Arecibo radio telescope on November 16, 1974, aimed at informing potential extraterrestrials about Earth. Sagan was chief technology officer of the professional planetary research journal Icarus for 12 years. He co-founded The Planetary Society and

2415-412: A variety of fossil and extant organisms, thus there is currently no consensus of the actual definition (and thus content) of Sauropsida as a phylogenetic unit. Some taxonomists, such as Benton (2004), have co-opted the term to fit into traditional rank-based classifications, making Sauropsida and Synapsida class-level taxa to replace the traditional Class Reptilia, while Modesto and Anderson (2004), using

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2530-429: Is a bird species. The cladogram presented here illustrates the "family tree" of sauropsids, and follows a simplified version of the relationships found by M.S. Lee, in 2013. All genetic studies have supported the hypothesis that turtles (formerly categorized together with ancient anapsids ) are diapsid reptiles, despite lacking any skull openings behind their eye sockets; some studies have even placed turtles among

2645-572: Is considered by Modesto a sauropsid group. (mammals and allies) [REDACTED] Mesosauridae [REDACTED] Captorhinidae [REDACTED] Araeoscelidia [REDACTED] Paleothyris Varanopidae [REDACTED] Parareptilia [REDACTED] [REDACTED] Eosuchia [REDACTED] In recent studies, the " microsaur " clade Recumbirostra , historically considered lepospondyl reptiliomorphs, have been recovered as early sauropsids. A 2024 study defines Captorhinidae and Araeoscelidia as sister groups that split off before

2760-565: Is his research on the possibility of extraterrestrial life , including experimental demonstration of the production of amino acids from basic chemicals by exposure to light. He assembled the first physical messages sent into space, the Pioneer plaque and the Voyager Golden Record , which were universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. He argued in favor of

2875-503: Is most evident in the slow decay of substantive content in the enormously influential media, the 30 second sound bites (now down to 10 seconds or less), lowest common denominator programming, credulous presentations on pseudoscience and superstition, but especially a kind of celebration of ignorance. Carl Sagan , from Demon-Haunted World (1995) Long before the ill-fated tenure process, Cornell University astronomer Thomas Gold had courted Sagan to move to Ithaca, New York , and join

2990-408: Is said to be controlled by the neomammalian complex. The model thus suggest that these two (and three depending on the situation) structures are in a perpetual battle to control the body. These interactions between the neocortex and the reptilian brain often seem competitive as the conscious thought generated by the neocortex can suppress the primitive thoughts generated by the reptilian complex. Thus,

3105-406: Is said to control all of the instinctual and impulsive actions, while the neomammalian complex is responsible for keeping the primitive instincts constrained. An example is controlling the impulse of eating. It seems that if one is hungry, then that means the reptilian complex is commanding the body to eat. However, an individual has the rational choice not to eat when hungry, and this rational thought

3220-455: Is the sibling taxon to Synapsida , the other clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles", all synapsids are more closely related to mammals than to any modern reptile. Sauropsids, on the other hand, include all amniotes more closely related to modern reptiles than to mammals. This includes Aves ( birds ), which are recognized as

3335-686: The Voyager Golden Record précis. During World War II , Sagan's parents worried about the fate of their European relatives, but he was generally unaware of the details of the ongoing war. He wrote, "Sure, we had relatives who were caught up in the Holocaust . Hitler was not a popular fellow in our household... but on the other hand, I was fairly insulated from the horrors of the war." His sister, Carol, said that their mother "above all wanted to protect Carl... she had an extraordinarily difficult time dealing with World War II and

3450-541: The Betty and Barney Hill abduction . To mark the tenth anniversary of Sagan's death, David Morrison , a former student of Sagan, recalled "Sagan's immense contributions to planetary research, the public understanding of science, and the skeptical movement" in Skeptical Inquirer . Following Saddam Hussein 's threats to light Kuwait 's oil wells on fire in response to any physical challenge to Iraqi control of

3565-628: The International Astronomical Union 's commission on "Physical Studies of Planets and Satellites" throughout the 1950s. In 1958, Sagan and Kuiper worked on the classified military Project A119 , a secret United States Air Force plan to detonate a nuclear warhead on the Moon and document its effects. Sagan had a Top Secret clearance at the Air Force and a Secret clearance with NASA . In 1999, an article published in

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3680-493: The International Space Station at the expense of further robotic missions. Former student David Morrison described Sagan as "an 'idea person' and a master of intuitive physical arguments and ' back of the envelope ' calculations", and Gerard Kuiper said that "Some persons work best in specializing on a major program in the laboratory; others are best in liaison between sciences. Dr. Sagan belongs in

3795-713: The PhyloCode standard, have suggested replacing the name Sauropsida with their redefinition of Reptilia, arguing that the latter is by far better known and should have priority. Cladistic definitions of Sauropsida include: Sauropsids evolved from basal amniotes approximately 320 million years ago, in the Carboniferous Period of the Paleozoic Era. In the Mesozoic Era (from about 250 million years ago to about 66 million years ago), sauropsids were

3910-580: The Public Welfare Medal , the highest award of the National Academy of Sciences for "distinguished contributions in the application of science to the public welfare." He was denied membership in the academy, reportedly because his media activities made him unpopular with many other scientists. As of 2017 , Sagan is the most cited SETI scientist and one of the most cited planetary scientists. In 1980 Sagan co-wrote and narrated

4025-421: The anamniotes ), based on the gaps in physiological traits and lack of transitional fossils that seemed to exist between the three groups. Early in the following year he proposed the names Sauropsida and Ichthyopsida for the two latter. Huxley did however include groups on the mammalian line ( synapsids ) like Dicynodon among the sauropsids. Thus, under the original definition, Sauropsida contained not only

4140-1649: The archosaurs , though a few have recovered turtles as lepidosauromorphs instead. The cladogram below used a combination of genetic (molecular) and fossil (morphological) data to obtain its results. Synapsida ( mammals and their extinct relatives) [REDACTED] † Millerettidae [REDACTED] † Eunotosaurus † Lanthanosuchidae [REDACTED] † Pareiasauromorpha [REDACTED] † Procolophonoidea [REDACTED] † Captorhinidae [REDACTED] † Paleothyris † Araeoscelidia [REDACTED] † Claudiosaurus [REDACTED] † Younginiformes [REDACTED] † Kuehneosauridae [REDACTED] Rhynchocephalia ( tuatara and their extinct relatives) [REDACTED] Squamata ( lizards and snakes ) [REDACTED] [REDACTED] † Eosauropterygia [REDACTED] † Placodontia [REDACTED] † Sinosaurosphargis † Odontochelys † Proganochelys Testudines ( turtles ) [REDACTED] † Choristodera [REDACTED] † Prolacertiformes [REDACTED] † Rhynchosauria [REDACTED] † Trilophosaurus [REDACTED] Archosauriformes ( crocodiles , birds , dinosaurs and extinct relatives) [REDACTED] [REDACTED] Laurin & Piñeiro (2017) and Modesto (2019) proposed an alternate phylogeny of basal sauropsids. In this tree, parareptiles include turtles and are closely related to non-araeoscelidian diapsids. The family Varanopidae , otherwise included in Synapsida ,

4255-522: The catchphrase "billions and billions", although he never actually used the phrase in the Cosmos series. He rather used the term "billions upon billions." Richard Feynman , a precursor to Sagan, used the phrase "billions and billions" many times in his " red books ." However, Sagan's frequent use of the word billions and distinctive delivery emphasizing the "b" (which he did intentionally, in place of more cumbersome alternatives such as "billions with

4370-482: The observable universe . This number is reasonably well defined, because it is known what stars are and what the observable universe is, but its value is highly uncertain. Sagan's ability to convey his ideas allowed many people to understand the cosmos better—simultaneously emphasizing the value and worthiness of the human race, and the relative insignificance of the Earth in comparison to the Universe . He delivered

4485-465: The origin of life and a perspective of humans' place on Earth. The show won an Emmy , along with a Peabody Award , and transformed Sagan from an obscure astronomer into a pop-culture icon. Time magazine ran a cover story about Sagan soon after the show broadcast, referring to him as "creator, chief writer and host-narrator of the show." In 2000, "Cosmos" was released on a remastered set of DVDs. After Cosmos aired, Sagan became associated with

4600-413: The "limbic brain" refers to those brain structures, wherever located, associated with social and nurturing behaviors, mutual reciprocity, and other behaviors and affects that arose during the age of the mammals; and the "reptilian brain" refers to those brain structures related to territoriality, ritual behavior and other "reptile" behaviors. Howard Bloom , in his book The Lucifer Principle , references

4715-572: The 1950s onward, he worked as an advisor to NASA , where one of his duties included briefing the Apollo astronauts before their flights to the Moon . Sagan contributed to many of the robotic spacecraft missions that explored the Solar System , arranging experiments on many of the expeditions. Sagan assembled the first physical message that was sent into space: a gold-plated plaque , attached to

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4830-464: The 1960s and propounded it at length in his 1990 book The Triune Brain in Evolution . The triune brain hypothesis became familiar to a broad popular audience through Carl Sagan 's Pulitzer prize winning 1977 book The Dragons of Eden . "Reptilian complex" (also known as the "R-complex", "reptilian brain" or "lizard brain") was the name MacLean gave to the basal ganglia , structures derived from

4945-522: The 1977 series of Royal Institution Christmas Lectures in London. Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with radio telescopes for signals from potential intelligent extraterrestrial life-forms . Sagan was so persuasive that by 1982 he was able to get a petition advocating SETI published in the journal Science , signed by 70 scientists, including seven Nobel Prize winners. This signaled

5060-479: The Burroughs novels. That same year, mass hysteria developed about the possibility that extraterrestrial visitors had arrived in flying saucers , and the young Sagan joined in the speculation that the flying "discs" people reported seeing in the sky might be alien spaceships. Sagan attended David A. Boody Junior High School in his native Bensonhurst and had his bar mitzvah when he turned 13. In 1948, when he

5175-584: The Department of Astronomy and Astrophysics, was entitled Physical Studies of the Planets . During his graduate studies , he used the summer months to work with planetary scientist Gerard Kuiper , who was his dissertation director , as well as physicist George Gamow and chemist Melvin Calvin . The title of Sagan's dissertation reflected interests he had in common with Kuiper, who had been president of

5290-406: The Earth but to forestall or postpone developing the technological methods that would be needed to defend against them. He argued that all of the numerous methods proposed to alter the orbit of an asteroid , including the employment of nuclear detonations , created a deflection dilemma : if the ability to deflect an asteroid away from the Earth exists, then one would also have the ability to divert

5405-557: The Holocaust." Sagan's book The Demon-Haunted World (1996) included his memories of this conflicted period, when his family dealt with the realities of the war in Europe, but tried to prevent it from undermining his optimistic spirit. Soon after entering elementary school, Sagan began to express his strong inquisitiveness about nature. He recalled taking his first trips to the public library alone, at age five, when his mother got him

5520-783: The Laboratory for Planetary Studies . Sagan and his works received numerous awards and honors, including the NASA Distinguished Public Service Medal , the National Academy of Sciences Public Welfare Medal , the Pulitzer Prize for General Nonfiction (for his book The Dragons of Eden ), and (for Cosmos: A Personal Voyage ) two Emmy Awards , the Peabody Award , and the Hugo Award . He married three times and had five children. After developing myelodysplasia , Sagan died of pneumonia at

5635-476: The Protosauria ("first lizards"), which included some Paleozoic amphibians as well as early reptiles predating the sauropsid/synapsid split (and thus not true sauropsids). His concept differed from modern classifications in that he considered a modified fifth metatarsal to be an apomorphy of the group, leading him to place Sauropterygia , Mesosauria and possibly Ichthyosauria and Araeoscelida in

5750-862: The Theropsida. In 1956, D. M. S. Watson observed that sauropsids and synapsids diverged very early in the reptilian evolutionary history, and so he divided Goodrich's Protosauria between the two groups. He also reinterpreted the Sauropsida and Theropsida to exclude birds and mammals respectively, making them paraphyletic , unlike Goodrich's definition. Thus his Sauropsida included Procolophonia , Eosuchia , Protorosauria , Millerosauria , Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia , Rhynchosauria , Choristodera , Thalattosauria , Crocodilia , " thecodonts " ( paraphyletic basal Archosauria ), non- avian dinosaurs , pterosaurs and sauropyterygians . However, his concept differed from

5865-517: The Tiger to explain his somatic experiencing approach to healing trauma. In the series of novels written by Lee Child featuring knight-errant figure Jack Reacher , Reacher often experiences messages from what he calls his "lizard brain" that alert him to potential danger. Glynda-Lee Hoffmann, in her book The Secret Dowry of Eve, Women's Role in the Development of Consciousness , references

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5980-504: The ability to maintain constant body temperature but made them unable to save water from evaporation. Moreover, the way synapsids discharge nitrogenous waste is through urea , which is toxic and must be dissolved in water to be secreted. Unfortunately, the upcoming Permian and Triassic periods were arid periods. As a result, only a small percent of early synapsids survived in the land from South Africa to Antarctica in today's geography. Unlike synapsids, sauropsids do not have those glands on

6095-521: The age of 62 on December 20, 1996. Carl Edward Sagan was born on November 9, 1934, in the Bensonhurst neighborhood of New York City's Brooklyn borough. His mother, Rachel Molly Gruber (1906–1982), was a housewife from New York City; his father, Samuel Sagan (1905–1979), was a Ukrainian-born garment worker who had emigrated from Kamianets-Podilskyi (then in the Russian Empire ). Sagan

6210-411: The availability of a variety of new neuroanatomical techniques for charting the circuitry of animal brains. Subsequent findings according to human brain evolution expert Terrence Deacon, have refined the traditional neuroanatomical ideas upon which MacLean based his hypothesis. Deacon mentioned that 'the evolutionary addition of different parts of the brain is simply not realistic. However, all the parts of

6325-469: The award-winning 13-part PBS television series Cosmos: A Personal Voyage , which became the most widely watched series in the history of American public television until 1990. The show has been seen by at least 500 million people across 60 countries. The book, Cosmos , written by Sagan, was published to accompany the series. Because of his earlier popularity as a science writer from his best-selling books, including The Dragons of Eden , which won him

6440-400: The award-winning 1980 television series Cosmos: A Personal Voyage , which became the most widely watched series in the history of American public television : Cosmos has been seen by at least 500 million people in 60 countries. A book, also called Cosmos , was published to accompany the series. Sagan also wrote a science-fiction novel, published in 1985, called Contact , which became

6555-514: The basal ganglia are found in the forebrains of all modern vertebrates, they most likely date to the common evolutionary ancestor of the vertebrates, more than 500 million years ago, rather than to the origin of reptiles. Recent behavioral studies do not support the traditional view of sauropsid behavior as stereotyped and ritualistic (as in MacLean's reptilian complex). Birds have been shown to possess highly sophisticated cognitive abilities, such as

6670-486: The basis for the 1997 film Contact . His papers, comprising 595,000 items, are archived in the Library of Congress . Sagan was a popular public advocate of skeptical scientific inquiry and the scientific method ; he pioneered the field of exobiology and promoted the search for extraterrestrial intelligent life ( SETI ). He spent most of his career as a professor of astronomy at Cornell University, where he directed

6785-692: The book The Cold and the Dark: The World after Nuclear War and in 1990 the book A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race , which explains the nuclear-winter hypothesis and advocates nuclear disarmament . Sagan received a great deal of skepticism and disdain for the use of media to disseminate a very uncertain hypothesis. A personal correspondence with nuclear physicist Edward Teller around 1983 began amicably, with Teller expressing support for continued research to ascertain

6900-628: The book's 1997 motion-picture adaptation , which starred Jodie Foster and won the 1998 Hugo Award for Best Dramatic Presentation. On it, everyone you ever heard of... The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in

7015-490: The brain were already existing, they were just further developed upon as the homosapien species evolved and gained life experiences.' For example, the basal ganglia (structures derived from the floor of the forebrain and making up MacLean's reptilian complex) were shown to take up a much smaller portion of the forebrains of reptiles and birds (together called sauropsids ) than previously supposed, and to exist in amphibians and fish as well as mammals and sauropsids. Because

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7130-476: The concept of the triune brain in his explanations of certain aspects of human behavior. Arthur Koestler made MacLean's concept of the triune brain the centerpiece of much of his later work, notably The Ghost in the Machine . English novelist Julian Barnes quotes MacLean on the triune brain in the foreword to his 1982 novel Before She Met Me . Peter A. Levine uses the triune brain concept in his book Waking

7245-461: The credibility of the winter hypothesis. However, Sagan and Teller's correspondence would ultimately result in Teller writing: "A propagandist is one who uses incomplete information to produce maximum persuasion. I can compliment you on being, indeed, an excellent propagandist, remembering that a propagandist is the better the less he appears to be one." Biographers of Sagan would also comment that from

7360-468: The early amniote tree has split up most of Goodrich's "Protosauria", though definitions of Sauropsida essentially identical to Huxley's (i.e. including the mammal-like reptiles) are also forwarded. Some later cladistic work has used Sauropsida more restrictively, to signify the crown group , i.e. all descendants of the last common ancestor of extant reptiles and birds. A number of phylogenetic stem, node and crown definitions have been published, anchored in

7475-490: The effects of nuclear war , when Paul Crutzen 's "Twilight at Noon" concept suggested that a substantial nuclear exchange could trigger a nuclear twilight and upset the delicate balance of life on Earth by cooling the surface. In 1983 he was one of five authors—the "S"—in the follow-up "TTAPS" model (as the research article came to be known), which contained the first use of the term " nuclear winter ", which his colleague Richard P. Turco had coined. In 1984 he co-authored

7590-513: The evolution of these systems presumably dates to a common vertebrate ancestor. Finally, recent studies based on paleontological data or comparative anatomical evidence strongly suggest that the neocortex was already present in the earliest emerging mammals. In addition, although non-mammals do not have a neocortex in the true sense (that is, a structure comprising part of the forebrain roof, or pallium, consisting of six characteristic layers of neurons), they possess pallial regions, and some parts of

7705-420: The eyes. Since the advent of phylogenetic nomenclature , the term Reptilia has fallen out of favor with many taxonomists, who have used Sauropsida in its place to include a monophyletic group containing the traditional reptiles and the birds. The class Reptilia has been known to be an evolutionary grade rather than a clade for as long as evolution has been recognised. Reclassifying reptiles has been among

7820-461: The fair's most publicized events: the burial at Flushing Meadows of a time capsule , which contained mementos from the 1930s to be recovered by Earth's descendants in a future millennium. Davidson wrote that this "thrilled Carl." As an adult, inspired by his memories of the World's Fair, Sagan and his colleagues would create similar time capsules to be sent out into the galaxy: the Pioneer plaque and

7935-511: The floor of the forebrain during development. The term derives from the idea that comparative neuroanatomists once believed that the forebrains of reptiles and birds were dominated by these structures. MacLean proposed that the reptilian complex was responsible for species-typical instinctual behaviours involved in aggression, dominance, territoriality, and ritual displays. This consists of the septum , amygdalae , hypothalamus , hippocampal complex , and cingulate cortex . MacLean first introduced

8050-492: The formation of crown amniota (synapsids and sauropsids). The same study also considers parareptiles to be polyphyletic, with some groups being closer to the crown group of reptiles than others. The last common ancestor of synapsids and Sauropsida lived at around 320mya during Carboniferous, known as Reptiliomorpha . The early synapsids inherited abundant glands on their skins from their amphibian ancestors. Those glands evolved into sweat glands in synapsids, which granted them

8165-531: The groups usually associated with it today, but also several groups that today are known to be in the mammalian side of the tree. By the early 20th century, the fossils of Permian synapsids from South Africa had become well known, allowing palaeontologists to trace synapsid evolution in much greater detail. The term Sauropsida was taken up by E. S. Goodrich in 1916 much like Huxley's, to include lizards, birds and their relatives. He distinguished them from mammals and their extinct relatives, which he included in

8280-581: The hands of the merchants and the artisans. This tendency found its most effective advocate in a follower of Pythagoras named Plato" and Sauropsids Sauropsida ( Greek for "lizard faces") is a clade of amniotes , broadly equivalent to the class Reptilia , though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinosaurs, are nested within reptiles as more closely related to crocodilians than to lizards or turtles). The most popular definition states that Sauropsida

8395-514: The history of our species, lived there on a mote of dust, suspended in a sunbeam. ... Think of the rivers of blood spilled by all those generals and emperors so that in glory and triumph they could become the momentary masters of a fraction of a dot. Carl Sagan, Cornell lecture in 1994 Sagan wrote a sequel to Cosmos , Pale Blue Dot: A Vision of the Human Future in Space , which

8510-553: The hypothesis, which has since been accepted, that the high surface temperatures of Venus are the result of the greenhouse effect . Initially an assistant professor at Harvard , Sagan later moved to Cornell University , where he spent most of his career. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. He wrote many popular science books, such as The Dragons of Eden , Broca's Brain , Pale Blue Dot and The Demon-Haunted World . He also co-wrote and narrated

8625-436: The idea that the three complexes interact with each other separately rather than a single construct interacting with itself. MacLean originally formulated the triune brain hypothesis in the 1960s, drawing on comparative neuroanatomical work done by Ludwig Edinger , Elizabeth C. Crosby and Charles Judson Herrick early in the twentieth century. The 1980s saw a rebirth of interest in comparative neuroanatomy, motivated in part by

8740-506: The ideas of others for little more than self-promotion. An advisor from his years as an undergraduate student, Harold Urey , wrote a letter to the tenure committee recommending strongly against tenure for Sagan. Science is more than a body of knowledge; it is a way of thinking. I have a foreboding of an America in my children's or grandchildren's time – when the United States is a service and information economy; when nearly all

8855-583: The institution. Sagan instead asked to be made an assistant professor, and eventually Whipple and Menzel were able to convince Harvard to offer Sagan the assistant professor position he requested. Sagan lectured, performed research, and advised graduate students at the institution from 1963 until 1968, as well as working at the Smithsonian Astrophysical Observatory , also located in Cambridge, Massachusetts . In 1968, Sagan

8970-487: The journal Nature revealed that Sagan had included the classified titles of two Project A119 papers in his 1959 application for a scholarship to University of California, Berkeley . A follow-up letter to the journal by project leader Leonard Reiffel confirmed Sagan's security leak. From 1960 to 1962 Sagan was a Miller Fellow at the University of California, Berkeley . Meanwhile, he published an article in 1961 in

9085-488: The journal Science on the atmosphere of Venus, while also working with NASA 's Mariner 2 team, and served as a "Planetary Sciences Consultant" to the RAND Corporation . After the publication of Sagan's Science article, in 1961 Harvard University astronomers Fred Whipple and Donald Menzel offered Sagan the opportunity to give a colloquium at Harvard and subsequently offered him a lecturer position at

9200-419: The key aims of phylogenetic nomenclature . The term Sauropsida had from the mid 20th century been used to denote a branch-based clade containing all amniote species which are not on the synapsid side of the split between reptiles and mammals. This group encompasses all now-living reptiles as well as birds, and as such is comparable to Goodrich's classification. The main difference is that better resolution of

9315-586: The key manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstition and darkness... The dumbing down of America

9430-729: The largest animals on land, in the water, and in the air. The Mesozoic is sometimes called the Age of Reptiles. In the Cretaceous–Paleogene extinction event , the large-bodied sauropsids died out in the global extinction event at the end of the Mesozoic era. With the exception of a few species of birds, the entire dinosaur lineage became extinct; in the following era, the Cenozoic , the remaining birds diversified so extensively that, today, nearly one out of every three species of land vertebrate

9545-501: The latter group." Sagan's contributions were central to the discovery of the high surface temperatures of the planet Venus . In the early 1960s no one knew for certain the basic conditions of Venus' surface, and Sagan listed the possibilities in a report later depicted for popularization in a Time Life book Planets . His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigated radio waves from Venus and concluded that there

9660-443: The mammalian brain is seen as an oversimplified organizing theme in the field of comparative neuroscience. It continues to hold public interest because of its simplicity. While inaccurate in many respects as an explanation for brain activity, structure and evolution, it remains a commonly used concept as the "neocortex" represents that cluster of brain structures involved in advanced cognition, including planning, modeling and simulation;

9775-469: The model suggests that the interactions between structures are not constructive, but that they are conflicting due to the anatomical separation of the brain. This separation of structures proposed an underlying difference between consciousness and unconscious behaviour and argued that the reason why humans are such intelligent and conscious species is due to the not-so-common neocortex that they possess, unlike most other animals. This detachment contributes to

9890-415: The modern one in that reptiles without an otic notch , such as araeoscelids and captorhinids , were believed to be theropsids . This classification supplemented, but was never as popular as, the classification of the reptiles (according to Romer 's classic Vertebrate Paleontology ) into four subclasses according to the positioning of temporal fenestrae , openings in the sides of the skull behind

10005-679: The motivation and emotion involved in feeding, reproductive behaviour, and parental behaviour. This consists of the cerebral neocortex , a structure found uniquely in higher mammals, and especially humans. MacLean regarded its addition as the most recent step in the evolution of the mammalian brain, conferring the ability for language, abstraction, planning, and perception. The triune brain model argues that these structures are relatively independent from one another, but that they are still connected to each other in some form or another. The model views different cognitive behaviors as caused by three different entities instead of one. The reptilian complex

10120-407: The natural NEO impact threat and the intrinsically double-edged essence of the methods to prevent these threats would serve as a "new and potent motivation to maturing international relations." Later acknowledging that, with sufficient international oversight, in the future a "work our way up" approach to implementing nuclear explosive deflection methods could be fielded, and when sufficient knowledge

10235-416: The observed color variations on Mars' surface and concluded that they were not seasonal or vegetational changes as most believed, but shifts in surface dust caused by windstorms . Sagan is also known for his research on the possibilities of extraterrestrial life , including experimental demonstration of the production of amino acids from basic chemicals by radiation . He is also the 1994 recipient of

10350-534: The oil assets, Sagan together with his "TTAPS" colleagues and Paul Crutzen , warned in January 1991 in The Baltimore Sun and Wilmington Morning Star newspapers that if the fires were left to burn over a period of several months, enough smoke from the 600 or so 1991 Kuwaiti oil fires "might get so high as to disrupt agriculture in much of South Asia ..." and that this possibility should "affect

10465-534: The pallium are considered homologous to the mammalian neocortex. While these areas lack the characteristic six neocortical layers, birds and reptiles generally possess three layers in the dorsal pallium (the homolog of the mammalian neocortex). The telencephalon of birds and mammals makes neuroanatomical connections with other telecencephalic structures like those made by neocortex. It mediates similar functions such as perception, learning and memory, decision making, motor control, conceptual thinking. The triune model of

10580-636: The poor or helping soothe tensions between workers and management within New York City's garment industry. Although awed by his son's intellectual abilities, Sagan's father also took his inquisitiveness in stride, viewing it as part of growing up. Later, during his career, Sagan would draw on his childhood memories to illustrate scientific points, as he did in his book Shadows of Forgotten Ancestors . Describing his parents' influence on his later thinking, Sagan said: "My parents were not scientists. They knew almost nothing about science. But in introducing me simultaneously to skepticism and to wonder, they taught me

10695-440: The possibility of life on Mars and other planets. According to biographer Ray Spangenburg, Sagan's efforts in his early years to understand the mysteries of the planets became a "driving force in his life, a continual spark to his intellect, and a quest that would never be forgotten." In 1947, Sagan discovered the magazine Astounding Science Fiction , which introduced him to more hard science fiction speculations than those in

10810-415: The recently hired astronomer Frank Drake among the faculty at Cornell. Following the denial of tenure from Harvard, Sagan accepted Gold's offer and remained a faculty member at Cornell for nearly 30 years until his death in 1996. Unlike Harvard, the smaller and more laid-back astronomy department at Cornell welcomed Sagan's growing celebrity status. Following two years as an associate professor, Sagan became

10925-448: The reptilian cortex (agenda: territory and reproduction; in humans that translates to power and sex) is out of control, and the amygdala stokes the fear that leads to more bad behavior. Carl Sagan Carl Edward Sagan ( / ˈ s eɪ ɡ ən / ; SAY -gən ; November 9, 1934 – December 20, 1996) was an American astronomer , planetary scientist and science communicator . His best known scientific contribution

11040-465: The sister group Theropsida (now usually replaced with the name Synapsida ). Goodrich's classification thus differs somewhat from Huxley's, in which the non-mammalian synapsids (or at least the dicynodontians ) fell under the sauropsids. Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features such as the structure of the forebrain. According to Goodrich, both lineages evolved from an earlier stem group,

11155-589: The smoke did not produce continental-sized cooling. Sagan later conceded in The Demon-Haunted World that the prediction did not turn out to be correct: "it was pitch black at noon and temperatures dropped 4–6 °C over the Persian Gulf , but not much smoke reached stratospheric altitudes and Asia was spared." In his later years, Sagan advocated the creation of an organized search for asteroids/ near-Earth objects (NEOs) that might impact

11270-525: The space probe Pioneer 10 , launched in 1972. Pioneer 11 , also carrying another copy of the plaque, was launched the following year. He continued to refine his designs; the most elaborate message he helped to develop and assemble was the Voyager Golden Record , which was sent out with the Voyager space probes in 1977. Sagan often challenged the decisions to fund the Space Shuttle and

11385-481: The term " limbic system " to refer to this set of interconnected brain structures in a paper in 1952. MacLean's recognition of the limbic system as a major functional system in the brain was widely accepted among neuroscientists, and is generally regarded as his most important contribution to the field. MacLean maintained that the structures of the limbic system arose early in mammalian evolution (hence "paleomammalian", with paleo- meaning old ) and were responsible for

11500-559: The themes of A Personal Voyage and became the best-selling science book ever published in English; The Dragons of Eden : Speculations on the Evolution of Human Intelligence , which won a Pulitzer Prize ; and Broca's Brain: Reflections on the Romance of Science . Sagan also wrote the best-selling science fiction novel Contact in 1985, based on a film treatment he wrote with his wife, Ann Druyan, in 1979, but he did not live to see

11615-468: The toolmaking of the New Caledonian crow and the language-like categorization abilities of the grey parrot . Structures of the limbic system, which MacLean proposed arose in early mammals, have now been shown to exist across a range of modern vertebrates. The "paleomammalian" trait of parental care of offspring is widespread in birds and occurs in some fishes as well. Thus, like the basal ganglia,

11730-433: The triune theory explored by MacLean and goes one step further. Her theory about human behavior, and the problems we create with that behavior, distinguishes the prefrontal cortex as uniquely different from the rest of the neocortex. The prefrontal cortex, with its agenda of integration, is the part of the brain that can get the other parts to work together for the good of the individual. Hoffmann claims that in many humans

11845-576: The two uneasily cohabiting modes of thought that are central to the scientific method." He recalled that a defining moment in his development came when his parents took him, at age four, to the 1939 New York World's Fair . He later described his vivid memories of several exhibits there. One, titled America of Tomorrow , included a moving map, which, as he recalled, "showed beautiful highways and cloverleaves and little General Motors cars all carrying people to skyscrapers, buildings with lovely spires, flying buttresses—and it looked great!" Another involved

11960-506: The war plans"; these claims were also the subject of a televised debate between Sagan and physicist Fred Singer on January 22, aired on the ABC News program Nightline . In the televised debate, Sagan argued that the effects of the smoke would be similar to the effects of a nuclear winter , with Singer arguing to the contrary. After the debate, the fires burnt for many months before extinguishing efforts were complete. The results of

12075-419: Was 14, his father's work took the family to the older semi-industrial town of Rahway, New Jersey , where he attended Rahway High School . He was a straight-A student but was bored because his classes did not challenge him and his teachers did not inspire him. His teachers realized this and tried to convince his parents to send him to a private school, with an administrator telling them, "This kid ought to go to

12190-671: Was a kind of religious experience. There was a magnificence to it, a grandeur, a scale which has never left me. Never ever left me." When he was about six or seven, he and a close friend took trips to the American Museum of Natural History , in Manhattan . While there, they visited the Hayden Planetarium and walked around exhibits of space objects, such as meteorites , as well as displays of dinosaur skeletons and naturalistic scenes with animals. As Sagan later wrote, "I

12305-1076: Was a member of the SETI Institute Board of Trustees. Sagan served as Chairman of the Division for Planetary Science of the American Astronomical Society , as President of the Planetology Section of the American Geophysical Union , and as Chairman of the Astronomy Section of the American Association for the Advancement of Science (AAAS). At the height of the Cold War , Sagan became involved in nuclear disarmament efforts by promoting hypotheses on

12420-598: Was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA's Jet Propulsion Laboratory , he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962. Sagan was among the first to hypothesize that Saturn 's moon Titan might possess oceans of liquid compounds on its surface and that Jupiter 's moon Europa might possess subsurface oceans of water. This would make Europa potentially habitable. Europa's subsurface ocean of water

12535-426: Was considered controversial, but his rhetorical skill won over the judges and they awarded him first prize. When he was about to graduate from high school, his classmates voted him "most likely to succeed" and put him in line to be valedictorian . He attended the University of Chicago because, despite his excellent high school grades, it was one of the very few colleges he had applied to that would consider accepting

12650-415: Was denied academic tenure at Harvard. He later indicated that the decision was very unexpected. The denial has been blamed on several factors, including that he focused his interests too broadly across a number of areas (while the norm in academia is to become a renowned expert in a narrow specialty), and perhaps because of his well-publicized scientific advocacy, which some scientists perceived as borrowing

12765-482: Was gained, to use them to aid in mining asteroids . His interest in the use of nuclear detonations in space grew out of his work in 1958 for the Armour Research Foundation 's Project A119 , concerning the possibility of detonating a nuclear device on the lunar surface. Sagan was a critic of Plato , having said of the ancient Greek philosopher: "Science and mathematics were to be removed from

12880-414: Was later indirectly confirmed by the spacecraft Galileo . The mystery of Titan's reddish haze was also solved with Sagan's help. The reddish haze was revealed to be due to complex organic molecules constantly raining down onto Titan's surface. Sagan further contributed insights regarding the atmospheres of Venus and Jupiter , as well as seasonal changes on Mars . He also perceived global warming as

12995-462: Was named in honor of his maternal grandmother, Chaiya Clara, who had died while giving birth to her second child; she was, in Sagan's words, "the mother she [Rachel] never knew." Sagan's maternal grandfather later married a woman named Rose, who Sagan's sister, Carol, would later say, was "never accepted" as Rachel's mother because Rachel "knew she [Rose] wasn't her birth mother." Sagan's family lived in

13110-468: Was selected as a notable book of 1995 by The New York Times . He appeared on PBS's Charlie Rose program in January 1995. Sagan also wrote the introduction for Stephen Hawking 's bestseller A Brief History of Time . Sagan was also known for his popularization of science, his efforts to increase scientific understanding among the general public, and his positions in favor of scientific skepticism and against pseudoscience , such as his debunking of

13225-628: Was transfixed by the dioramas—lifelike representations of animals and their habitats all over the world. Penguins on the dimly lit Antarctic ice [...] a family of gorillas, the male beating his chest [...] an American grizzly bear standing on his hind legs, ten or twelve feet tall, and staring me right in the eye." Sagan's parents nurtured his growing interest in science, buying him chemistry sets and reading matter. But his fascination with outer space emerged as his primary focus, especially after he had read science fiction by such writers as H. G. Wells and Edgar Rice Burroughs , stirring his curiosity about

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