Tag Archives: Oligocene

Gould’s Belt

30.3-28.7 million years ago

Logarithmic History has had a lot of geology and biology lately, not so much astronomy. But all is not peaceful in the heavens.

Benjamin Gould is a nineteenth century astronomer who noted that a lot of bright stars in the sky — especially the bright blue stars that we know are very young — seem to fall along a ring tilted at a 20 degree angle to the Milky Way. This ring has come to be called Gould’s Belt. The Belt is an ellipse about 2400 by 1500 light years across where there has been a recent wave of star formation. Our Sun lies within the belt, somewhat off center; the center lies in the direction of the Pleiades.

The Belt began forming maybe thirty million years ago. We’re not sure what happened. A supernova may have set off a wave of star formation, but it would have to have been a huge one. Or it may be that a gas cloud or a clump of dark matter passed at an angle through our part of the Milky Way, and started stars forming with its shock wave. There are features resembling Gould’s Belt in other galaxies. In any case, the Belt is one of the really striking features of our part of the Milky Way.

Whatever its cause, no one disputes its magnificence. Gould’s belt is the most prominent starry feature in the Sun’s neighborhood, contributing most of the bright young stars nearby. Nearly two thirds of the massive stars within 2,000 light-years of the Sun belong to Gould’s belt. If I were kidnapped by an alien spaceship and taken to some remote corner of the Galaxy, Gould’s belt is what I’d look for to find my way back home.

Ken Crosswell. Gould’s Belt.

If you’re in the Northern hemisphere you can look at the sky tonight and see the Milky Way in an arc in the Western sky, stretching from North to South. West of the Milky Way you’ll see some of Gould’s belt, an arc of bright stars running north to south from the Pleiades, through Taurus and the bright stars of Orion, and Canis Major. So tonight look at the stars, and drink a toast if you want to your ape ancestors who were just on the cusp of splitting off from monkeys thirty million years ago.

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The monkey’s voyage

33.9-32.1 million years ago

The Oligocene sees a major diversification of anthropoid primates (monkeys, apes, and humans). Among the anthropoids, the major evolutionary split is a geographic one, between platyrrhines (New World monkeys) and catarrhines (Old World monkeys, apes, and humans). Aegyptopithecus is one of the earliest primates that clearly falls on the catarrhine side of that split (although the split must go back earlier).

At Logarithmic History we traffic in Big Questions, and one of the biggest questions of all is the balance of natural law and accident in making our world. Thus physicists have long hoped to find that the laws governing our universe reduce to just a few fundamental equations, but we saw at the beginning of this blog that they are now confronting the possibility that our universe is just one among many, and that the laws of physics in our universe may incorporate a large dose of historical accident. With the discovery of extra-solar planets, we’re just beginning to get an idea of how typical or atypical our solar system is. And we’ll have a lot of opportunities to ask whether there are Laws of History (an old idea now undergoing a revival in the new field of cliodynamics*) when we move into the historical period later in the year.

The field of biogeography – the study of the geographic distribution of species – has seen some major pendulum swings in this regard. Darwin was intensely interested in questions of biogeography mainly because they could provide support for the theory of evolution. His approach could fairly be called eclectic. From sometime in the second half of the twentieth century however, a lot of biologists thought they could do better than just answering particularistic questions about how species A got to island Z. They wanted to find scientific laws.

Edward O. Wilson was an early pioneer in this area. Along with Robert MacArthur, he developed a theory of island biogeography which was supposed to get the field out of its natural history phase, and turn it into a predictive science. According to MacArthur and Wilson, the number of species on an island is set by a predictable equilibrium between extinction (smaller islands have higher extinction rates) and colonization (remote islands have lower colonization rates). Being a good scientist Wilson actually put this theory to the test by getting an exterminator to “defaunate” (it means what you think it means) some little mangrove islets, and showing that they returned to very close to their predicted equilibrium numbers of animal species after a while.

For the biogeography of continents (and larger islands once part of continents) the quest for scientific laws took a different turn. The discovery of continental drift and plate tectonics encouraged a school of “vicariance biogeography.” Vicariance biogeographers liked to trace current biogeographic distributions to the wanderings of continents. They were highly allergic to explanations involving accidental long-distance dispersal over big stretches of ocean.

Alan de Queiroz, in The Monkey’s Voyage: How Improbable Journeys Shaped the History of Life, provides a highly readable overview of the decline (if not quite the extinction) of the vicariance school in the face of mounting evidence for flukish dispersals as a major factor in biogeography. The dispersal of monkeys to the New World is a dramatic case in point. (Guinea pigs and their relatives are another.) About the only scenario that makes sense involves a raft of trees washing out to sea (most likely from the Congo basin) and eventually delivering a few parched, scared monkeys to the island continent of South America, where they eventually spawned the whole range of species – spider monkeys, squirrel monkeys, howler monkeys, tamarins, marmosets, capuchins – we know today. Sheer accident: change the weather a little, leave the monkeys stranded at sea a little longer, and the whole history of primates in the New World is erased.

* so new my spellchecker doesn’t recognize it.

Ginormous, or The Canseco Conjecture

35.9-34.0 million years ago

The Eocene epoch, which we leave behind, saw super-greenhouse conditions, and tropical forests extending to high latitudes. The Oligocene, starting 34 million years ago, sees a drop in atmospheric COlevels. Glaciers begin forming in Antarctica, and the world cools sharply. There are extinctions in a number of groups (although not on the scale of the Big Five mass extinctions), after which the fauna, at least in Eurasia/North America, starts looking like what we’re used to: versions of horses, deer, camels, elephants, cats, dogs, and many rodent families begin to dominate.

The Oligocene also boasts also the largest land mammal of all time, Indricotherium (or Baluchitherium, discovered 1922), related to living rhinoceroses, but 15 feet high at the shoulders, and weighing as much as three or four African elephants. (The picture below compares them.) Indricotherium was big enough to browse high up on trees. By contrast, living big browsers (giraffes, elephants) use special bits of anatomy (long necks, trunks) to reach that high, and don’t get quite as big.indricotherium

This is still a lot smaller than the biggest dinosaurs, the sauropods. Ginormousness is one of the things dinosaurs are famous for, even though there were plenty of small dinosaurs too. Two things that keep mammals from getting truly huge are probably (1) a different respiratory system, without the extensive airsacs and aerated bones of dinosaurs, and (2) live birth. Gigantic sauropods could lay eggs and produce (relatively) small offspring which grew up quickly, so they didn’t pay as high a reproductive penalty for being big.

There are other possibilities. Jose Canseco, former Major League Baseball player, and authority on being large (he is the author of Juiced: Wild Times, Rampant ‘Roids, Smash Hits, and How Baseball Got Big), published his theory on Twitter in 2013 (February 17-18). “My theory is the core of the planet shifted when [a] single continent formed to keep us in a balanced spin. The land was farther away from the core and had much less gravity so bigness could develop and dominate.” Anticipating possible criticism, he tweeted, “I may not be 100% right but think about it. How else could 30 foot leather birds fly?”

Canseco may not have been the first to come up with this idea. A guy named John Stojanowski wrote to me two years back claiming to have originated the Gravity Theory of Mass Extinction. His main area of expertise is in the design of residential geothermal systems.

The monkey’s voyage

The Oligocene sees a major diversification of anthropoid primates (monkeys, apes, and humans). Among the anthropoids, the major evolutionary split is a geographic one, between platyrrhines (New World monkeys) and catarrhines (Old World monkeys, apes, and humans). Aegyptopithecus is one of the earliest primates that clearly falls on the catarrhine side of that split (although the split must go back earlier).

At Logarithmic History we traffic in Big Questions, and one of the biggest questions of all is the balance of natural law and accident in making our world. Thus physicists have long hoped to find that the laws governing our universe reduce to just a few fundamental equations, but we saw at the beginning of this blog that they are now confronting the possibility that our universe is just one among many, and that the laws of physics in our universe may incorporate a large dose of historical accident. With the discovery of extra-solar planets, we’re just beginning to get an idea of how typical or atypical our solar system is. And we’ll have a lot of opportunities to ask whether there are Laws of History (an old idea now undergoing a revival in the new field of cliodynamics*) when we move into the historical period later in the year.

The field of biogeography – the study of the geographic distribution of species – has seen some major pendulum swings in this regard. Darwin was intensely interested in questions of biogeography mainly because they could provide support for the theory of evolution. His approach could fairly be called eclectic. From sometime in the second half of the twentieth century however, a lot of biologists thought they could do better than just answering particularistic questions about how species A got to island Z. They wanted to find scientific laws.

Edward O. Wilson was an early pioneer in this area. Along with Robert MacArthur, he developed a theory of island biogeography according to which the number of species on an island is set by a predictable equilibrium between extinction (smaller islands have higher extinction rates) and colonization (remote islands have lower colonization rates). Being a good scientist he actually put this theory to the test by getting an exterminator to “defaunate” (it means what you think it means) some little mangrove islets, and showing that they returned to very close to their predicted equilibrium numbers of animal species after a while.

For the biogeography of continents (and larger islands once part of continents) the quest for scientific laws took a different turn. The discovery of continental drift and plate tectonics encouraged a school of “vicariance biogeography.” Vicariance biogeographers liked to trace current biogeographic distributions to the wanderings of continents. They were highly allergic to explanations involving accidental long-distance dispersal over big stretches of ocean.

Alan de Queiroz, in The Monkey’s Voyage: How Improbable Journeys Shaped the History of Life, provides a highly readable overview of the decline (if not quite the extinction) of the vicariance school in the face of mounting evidence for flukish dispersals as a major factor in biogeography. The dispersal of monkeys to the New World is a dramatic case in point. (Guinea pigs and their relatives are another.) About the only scenario that makes sense involves a raft of trees washing out to sea (most likely from the Congo basin) and eventually delivering a few parched, scared monkeys to the island continent of South America, where they eventually spawned the whole range of species – spider monkeys, squirrel monkeys, howler monkeys, tamarins, marmosets, capuchins – we know today. Sheer accident: change the weather a little, leave the monkeys stranded at sea a little longer, and the whole history of primates in the New World is erased.

* so new my spellchecker doesn’t recognize it.

Ginormous, or The Canseco Conjecture

35.9-33.9 million years ago

The Eocene epoch, which we leave behind, saw super-greenhouse conditions, and tropical forests extending to high latitudes. The Oligocene, starting 34 million years ago, sees a drop in atmospheric COlevels. Glaciers begin forming in Antarctica, and the world cools sharply. There are extinctions in a number of groups (although not on the scale of the Big Five mass extinctions), after which the fauna, at least in Eurasia/North America, starts looking like what we’re used to: versions of horses, deer, camels, elephants, cats, dogs, and many rodent families begin to dominate.

The Oligocene also boasts also the largest land mammal of all time, Indricotherium (or Baluchitherium, discovered 1922), related to living rhinoceroses, but 15 feet high at the shoulders, and weighing as much as three or four African elephants. (The picture below compares them.) Indricotherium was big enough to browse high up on trees. By contrast, living big browsers (giraffes, elephants) use special bits of anatomy (long necks, trunks) to reach that high, and don’t get quite as big.indricotherium

This is still a lot smaller than the biggest dinosaurs, the sauropods. Ginormousness is one of the things dinosaurs are famous for, even though there were plenty of small dinosaurs too. Two things that keep mammals from getting truly huge are probably (1) a different respiratory system, without the extensive airsacs and aerated bones of dinosaurs, and (2) live birth. Gigantic sauropods could lay eggs and produce (relatively) small offspring which grew up quickly, so they didn’t pay as high a reproductive penalty for being big.

There are other possibilities. Jose Canseco, former Major League Baseball player, and authority on being large (he is the author of Juiced: Wild Times, Rampant ‘Roids, Smash Hits, and How Baseball Got Big), published his theory on Twitter in 2013 (February 17-18). “My theory is the core of the planet shifted when [a] single continent formed to keep us in a balanced spin. The land was farther away from the core and had much less gravity so bigness could develop and dominate.” Anticipating possible criticism, he tweeted, “I may not be 100% right but think about it. How else could 30 foot leather birds fly?”

The monkey’s voyage

The Oligocene sees a major diversification of anthropoid primates (monkeys, apes, and humans). Among the anthropoids, the major evolutionary split is a geographic one, between platyrrhines (New World monkeys) and catarrhines (Old World monkeys, apes, and humans). Aegyptopithecus is one of the earliest primates that clearly falls on the catarrhine side of that split (although the split must go back earlier).

At Logarithmic History we traffic in Big Questions, and one of the biggest questions of all is the balance of natural law and accident in making our world. Thus physicists have long hoped to find that the laws governing our universe reduce to just a few fundamental equations, but we saw at the beginning of this blog that they are now confronting the possibility that our universe is just one among many, and that the laws of physics in our universe may incorporate a large dose of historical accident. With the discovery of extra-solar planets, we’re just beginning to get an idea of how typical or atypical our solar system is. And we’ll have a lot of opportunities to ask whether there are Laws of History (an old idea now undergoing a revival in the new field of cliodynamics*) when we move into the historical period later in the year.

The field of biogeography – the study of the geographic distribution of species – has seen some major pendulum swings in this regard. Darwin was intensely interested in questions of biogeography mainly because they could provide support for the theory of evolution. His approach could fairly be called eclectic. From sometime in the second half of the twentieth century however, a lot of biologists thought they could do better than just answering particularistic questions about how species A got to island Z. They wanted to find scientific laws.

Edward O. Wilson was an early pioneer in this area. Along with Robert MacArthur, he developed a theory of island biogeography according to which the number of species on an island is set by a predictable equilibrium between extinction (smaller islands have higher extinction rates) and colonization (remote islands have lower colonization rates). Being a good scientist he actually put this theory to the test by getting an exterminator to “defaunate” (it means what you think it means) some little mangrove islets, and showing that they returned to very close to their predicted equilibrium numbers of animal species after a while.

For the biogeography of continents (and larger islands once part of continents) the quest for scientific laws took a different turn. The discovery of continental drift and plate tectonics encouraged a school of “vicariance biogeography.” Vicariance biogeographers liked to trace current biogeographic distributions to the wanderings of continents. They were highly allergic to explanations involving accidental long-distance dispersal over big stretches of ocean.

Alan de Queiroz, in The Monkey’s Voyage: How Improbable Journeys Shaped the History of Life, provides a highly readable overview of the decline (if not quite the extinction) of the vicariance school in the face of mounting evidence for flukish dispersals as a major factor in biogeography. The dispersal of monkeys to the New World is a dramatic case in point. (Guinea pigs and their relatives are another.) About the only scenario that makes sense involves a raft of trees washing out to sea (most likely from the Congo basin) and eventually delivering a few parched, scared monkeys to the island continent of South America, where they eventually spawned the whole range of species – spider monkeys, squirrel monkeys, howler monkeys, tamarins, marmosets, capuchins – we know today. Sheer accident: change the weather a little, leave the monkeys stranded at sea a little longer, and the whole history of primates in the New World is erased.

* so new my spellchecker doesn’t recognize it.

Ginormous, or The Canseco Conjecture

The Eocene epoch, which we leave behind, saw super-greenhouse conditions, and tropical forests extending to high latitudes. The Oligocene, starting 34 million years ago, sees a drop in atmospheric CO2 levels. Glaciers begin forming in Antarctica, and the world cools sharply. There are extinctions in a number of groups (although not on the scale of the Big Five mass extinctions), after which the fauna, at least in Eurasia/North America, starts looking like what we’re used to: versions of horses, deer, camels, elephants, cats, dogs, and many rodent families begin to dominate.

The Oligocene also boasts also the largest land mammal of all time, Indricotherium (or Baluchitherium, discovered 1922), related to living rhinoceroses, but 15 feet high at the shoulders, and weighing as much as three or four African elephants. (The picture below compares them.) Indricotherium was big enough to browse high up on trees. By contrast, living big browsers (giraffes, elephants) use special bits of anatomy (long necks, trunks) to reach that high, and don’t get quite as big.indricotherium

This is still a lot smaller than the biggest dinosaurs, the sauropods. Ginormousness is one of the things dinosaurs are famous for, even though there were plenty of small dinosaurs too. Two things that keep mammals from getting truly huge are probably (1) a different respiratory system, without the extensive airsacs and aerated bones of dinosaurs, and (2) live birth. Gigantic sauropods could lay eggs and produce (relatively) small offspring which grew up quickly, so they didn’t pay as high a reproductive penalty for being big.

There are other possibilities. Jose Canseco, former Major League Baseball player, and authority on being large (he is the author of Juiced: Wild Times, Rampant ‘Roids, Smash Hits, and How Baseball Got Big), published his theory on Twitter in 2013 (February 17-18). “My theory is the core of the planet shifted when [a] single continent formed to keep us in a balanced spin. The land was farther away from the core and had much less gravity so bigness could develop and dominate.” Anticipating possible criticism, he tweeted, “I may not be 100% right but think about it. How else could 30 foot leather birds fly?”

http://phenomena.nationalgeographic.com/2013/02/25/dinosaur-reproduction-not-ancient-gravity-made-sauropods-super-sized/