THE ORIGIN AND MASS EXTINCTIONS OF SPECIES

BY KONSTANTINOS MARITSAS
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Foreword

Once upon a time, there was a King, who wanted to learn the history of all people around the world. And so, one day he gathered the wise men of his kingdom and ordered them to write the history of all people. The wise men immediately started writing. They worked day and night continuously for twenty years. Finally, they gave the King a history of all people on Earth, consisting of one hundred thousand huge volumes.

The King, however, was old and he would not be able to read all the volumes before dying. He ordered them to shorten the story into fewer volumes. The wise men immediately started to work. They worked all day and night for another twenty years. Finally, they submitted to the King a history of all people on Earth, consisting of one thousand huge volumes. The King, however, was even older and would not be able to read all the volumes before he died, and so he ordered them to shorten the story into even fewer volumes. The wise men immediately started to work. They worked night and day for another twenty years. At the end, they submitted to the King a history of all people on Earth, consisting of only one book. But the King was about to die. So he asked: “Won’t someone be found who can tell me the story of all the people on Earth, before I die?” Then the wisest of all approached him and whispered in his ear: “They were born, suffered and died. This is the story of all the people on Earth, my King.”

With the exception of people,

today on our planet, there are about ten million species of animals and plants. And the whole history of the Earth had seen the amazing existence of over 4.5 billion species of plants and animals.[1]

What is the history of all species that had lived on Earth – does the above tale describe the history of the 4.5 billion plants and animal species: they were created (out of nothing), suffered (natural selection), and died, disappeared?

In fact, extinction appears to be the ultimate fate of all species: 99.9% of all the species that ever existed are now extinct.[2]

The same tale we can tell about the species:“Once upon a time, there was a King, who wanted to learn the history of all species around the world. ... Then the wisest of all approached him and whispered in his ear: ‘They originated, existed and were extinct. This is the story of all the species on Earth, my King’.”

For all the people around the world we can say that they were born, lived and died.

For all the species around the world we can say that they originated, existed and were extinct.

If the wisest one knew the 2nd Law of Thermodynamics, he would say to the King: “Around the world things always tend to go from bad to worse.”[3]

After birth comes death, after origin comes extinction, dear wisest one, dear King! This is the fate of all living beings.

Extinction is a normal part, the end of existence. Species come and go continually - around 99.9% of all those that have ever existed are now extinct. This normal loss of species through time is known as the background rate of extinction – the 2nd Law of Thermodynamics. It is estimated to be around one (1) extinction per million species per year. The vast majority of species meet their end in this way.

Sometimes many species disappear together in a short time. Occasionally extinction events are global in scale, with many species of all ecological types – plants and animals, dying out in a relatively short time all over the world. This is a mass extinction.There is no exact definition of what is mass extinction. The loss of 40% to 50% of species is about the norm.

Till today we now recognise that there have been five (5) mass extinctions. The first of these was about 540 million years ago, at the end of the Neoproterozoic era, when the Ediacaran animals disappeared. Some palaeontologists also identify the late Cambrian as another time of mass extinction.

Three further mass extinctions punctuate the Palaeozoic era. The late Ordovician, between 450 and 440 million years ago, saw substantial losses among the dominant animals of the time: trilobites, brachiopods, corals and graptolites. The late Devonian mass extinction, beginning around 375 million years ago, was another long and drawn out affair. Armoured fish known as placoderms and ostracoderms disappeared, and corals, trilobites and brachiopods suffered heavy losses. The Palaeozoic ended with the enormous end Permian mass extinction.

Another 50 million years or so passed before the next mass extinction, at the end of the Triassic. Fish, molluscs, brachiopods and other marine groups saw substantial losses, while extinctions on land opened the way for the dinosaurs. They dominated for 135 million years before being wiped out in the most recent extinction, the Cretaceous-Tertiary (KT).

The explanation of the background rate of is easy. The common pattern is the 2nd Law of Thermodynamics.But what about the mass extinctions? How can we expain the the mass extinctions? Is there any common pattern or not?

Given how important mass extinctions are to understanding the history of life, it may seem surprising that no one was much interested in the idea until the 1970s. Of course, the great Victorian palaeontologists such as Richard Owen and Thomas Huxley were aware that dinosaurs and other ancient creatures were extinct, but they did not see any role for sudden, dramatic events. Following Charles Darwin, they argued that extinction was a normal process: species originated at some point by splitting from existing species, and at some point they died out.

In the 1980s, as the Alvarez hypothesis gained ground, it seemed reasonable to assume that all mass extinctions were caused by impacts:

The Alvarez hypothesis (Impact Theory).

The general perception with the public regarding the extinction of the dinosaurs is that they were wiped out by a meteorite impact. This theory has inarguably become the most famous and highly publicized cause for the disappearance of the species 65 million years ago. Its popularity has caused it to be universally accepted as the only viable theory to explain the disappearance of the dinosaurs. In 1980, Luiz Alvarez, a Nobel prize winning physicists, teamed up with his son Walter, a geologist, and presented the meteorite impact theory. They had conducted research on clay layers found at the K/T boundary in the Umbrian Apennines (Gubbio section) in Northern Italy, and then matched their results to data from clay layers in New Zealand and Denmark. The Alvarez's research studied abundances of rare earth elements (REE) in the clay layer. They discovered anomalies for a few of the REE: although one stood out, a large positive anomaly in the abundance of Iridium (Ir) in the clay. Iridium is found in minute quantities on the Earth's crust. Its average crustal abundance is ~0.3ppb (parts per billion). In the upper mantle its further depleted; whereas its slightly enriched in the lower mantle. However, its believed that the core is enriched in Ir and other REE. In the clay layers in Italy, the Alvarez team found abundance 2 to 3 orders of magnitude higher than expected on the surface. They calculated the abundance of Ir in the clay in Italy to be 9.0ppb or higher. This value did not correspond at all with surface abundances of Ir. So the Alvarez’s pinned the cause on a meteorite impact. This was principally due to two reasons:

Ir is relatively abundant in meteorites.

The isotopic composition of Ir in the clay represents that of a meteorite and not the crust.

They also found chromium isotopes which had similar composition as carbonaceous chondrites. The clay layer was dated to be 65Ma and it corresponded to the extinction of animals which were observed in the sedimentary. The Alvarez pinned the cause of the extinction on the meteorite impact. This theory came to be known as the “Alvarez hypothesis”.

There was one thing missing in the “Alvarez hypothesis”: an impact crater or site. The Alvarez’s had shown that the meteorite had to be 10 km in diameter which would have created a ~150-200 km wide crater. The Alvarez had failed to find any craters that would have matched the age or the size. Ten years later, Alan K. Hildebrand and Glen Penfield found it. They discovered the Chicxulub crater site in the Yucatan Peninsula and dated it to be around 65 Ma. The discovery of the impact site, along with debris in the sedimentary record in North America, provided the proverbial “smoking gun” and much needed credibility to the “Alvarez hypothesis.”[4]

Though there have been numerous “discoveries” of craters and other impact signatures coinciding with the other mass extinctions, none has stood up to scrutiny. It now seems that the KT event was unique - the only mass extinction caused by an impact. In fact, we now think that there is no common pattern, each mass extinction had its own unique cause.

Another idea that was fashionable in the 1980s was that mass extinctions are periodic. Some palaeontologists claimed to have found patterns in the fossil record showing a mass extinction every 26 million years, and they explained this by suggesting that a “death star”, dubbed Nemesis, periodically swings into our solar system and perturbs the meteorite cloud. But Nemesis has never been found and evidence for this pattern is now widely doubted:

The 27 Myr periodicity in the fossil extinction record has been confirmed in modern data bases dating back 500 Myr, which is twice the time interval of the original analysis from thirty years ago. The surprising regularity of this period has been used to reject the Nemesis model. A second model based on the sun’s vertical galactic oscillations has been challenged on the basis of an inconsistency in period and phasing. The third astronomical model originally proposed to explain the periodicity is the Planet X model in which the period is associated with the perihelion precession of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated to mass extinctions, a trans-Neptunian super-Earth planet has been proposed to explain the observation that the inner Oort cloud objects Sedna and 2012VP113 have perihelia that lie near the ecliptic plane. In this Letter we reconsider the Planet X model in light of the confluence of the modern palaeontological and outer solar system dynamical evidence.[5]

How the species became extinct is easy to explain; how they appeared, however, is difficult. Were they created only once? Personally I cannot imagine the mechanism for creating new species, except in terms of the primary creation of the Meccano set, as understood by François Jacob, as a result of zero probability:

The living world is, rather, like a sort of Meccano set.[6]

Equally, I cannot imagine the creation of inanimate matter except the primary creation of the Big Bang, again because of zero probability (the principle of the conservation of matter). And species that have managed to slip out of natural selection (man), they exist and will exist! Will today’s ten million animal and plant species have the same fate?

The ordinary questions of the scientists interested in this field are lying in the search for common causes and patterns that may lead to a general theory of extinction. The most frequent arguments are related either to bad genes or to bad luck. Whatever were the causes, it is logic to give an idea on each of the five major mass extinctions in the fossil record.[7]

That is the purpose of the book – to identify and explain life and death, origin and extinction. But the main purpose is to explain the mass extinctions with one hypothesis and one common pattern, one common impact.


[1]Prof. Nikolov, T. (Проф. Николов, Т.).(1994). The Long Path of Life (Дългиятпътнаживота).Sofia (София): Bulgarian Academy of Science (БАН), back cover.

[2]Leakey, R. (2008).The Origin of Humankind.New York: Basic Books. p. 58.

[3]Hawking, St. (1990).A Brief History of Time: From the Big Bang to Black Holes. New York: Bantam Books.., p. 102: “A precise statement of this idea is known as the Second Law of Тhermodynamics. It states that the entropy of an isolated system always increases, and that when two systems are joined together, the entropy of the combined system is greater than the sum of the entropies of the individual systems.” And on p. 144: “In other words, it is a form of Murphy’s Law: things always tend to go wrong!”

[4] From: http://hoopermuseum.earthsci.carleton.ca/saleem/meteor.htm.

[5]Daniel P. Whitmire. Periodic mass extinctions and the Planet X model reconsidered. arXiv.org>astro-ph> arXiv:1510.03097 (from: https://arxiv.org/abs/1510.03097).

[6]Jacob, Fr. (1998).Of Flies, Mice, and Men. Cambridge, Harvard UP.p. 83.

[7]Elewa, Ashraf M.T. (Ed.). (2008). Mass Extinction.Springer.p. 2

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