Theories about dinosaur extinction
Mass extinction events can seem quite capricious as to what species live or die. generally outcompeted their ancestral for hundreds of millions of years. Ammonoids were lightweight versions of nautiloids, and they often thrived in shallow waters while nautiloids were banished to deep waters. Both dwindled over time, as they were outcompeted by new kinds of marine denizens. In the and mass extinctions, deep-water animals generally suffered more than surface dwellers did, but the nautiloids’ superior respiration system still saw them survive. Also, nautiloids laid relatively few eggs that took about a year to hatch, while ammonoids laid more eggs that hatched faster. However, the asteroid-induced Cretaceous mass extinction annihilated nearly all surface life while the deep-water animals fared better, and nautiloid embryos that rode out the storm in their eggs were survivors. The Cretaceous extinction while and comprise another group of living fossils, although that status is disputed in 2014. was about the only land animal of significance that survived the Permian extinction and it dominated the early Triassic landmass as no animal ever has. It comprised about 95% of all land animals. Why , which was like a reptilian sheep? Nobody , but it may have been the luck of the draw. Perhaps relatively few bedraggled individuals existed in some survival enclave until the catastrophe was finished, and then they quickly bred unimpeded until , for the most spectacular species radiation of all time, at least until humans arrived on the evolutionary scene.
New dinosaur extinction theory causes debate - …
Before the era of mass extinction investigation that began in the 1980s, a hundred hypotheses were presented in the scientific literature for the dinosaur extinction, but it was a kind of scientific parlor game. Scientists from all manner of specialties concocted their hypotheses. But even during the current era of scientific study of mass extinctions, much is unknown or controversial and even the data is in dispute, let alone its interpretation. Dynamics may have conflated to produce catastrophic effects, such as increasing atmospheric carbon dioxide concentration warming the land and oceans to the extent that otherwise stable on the ocean floor and in permafrost would be liberated and escape into the atmosphere. That situation is to the , , and extinctions, as well as helping end the . Today, there is genuine fear among climate scientists that , as global warming continues and hydrocarbons are burned with abandon, which could contribute to catastrophic runaway conditions. Wise scientists admit that humanity is currently conducting a huge chemistry experiment with Earth, and while the outcomes are far from certain, the .
Mass extinction events may be the result of multiple ecosystem stresses that reach the level where the ecosystem unravels. Other than the meteor impact that destroyed the dinosaurs, the rest of the mass extinctions seem to have multiple contributing causes, and each one ultimately had an energy impact on life processes. The processes can be complex and scientists are only beginning to understand them. This essay will survey mass extinction events and their aftermaths in some detail, as they were critical junctures in the journey of life on Earth.
Ken Ham’s Climate and Human-Induced Dinosaur Extinction Hypothesis
Peter Ward led an effort to catalog the fossil record before and after Romer’s Gap, which found a dramatic that did not resume until about 340-330 mya. Romer’s Gap seems to have coincided with low-oxygen levels of the late Devonian and early Carboniferous. If coincided with a halt in colonization, just as the adaptation to breathing air was beginning, the obvious implication is that low oxygen levels hampered early land animals. Not just the lung had to evolve for the up-and-coming amphibians, but the entire chest cavity had to evolve to expand and contract while also allowing for a new mode of locomotion. When amphibians and splay-footed reptiles run, they cannot breathe, as their mechanics of locomotion prevent running and breathing at the same time. Even walking and breathing is generally difficult. This means that they cannot perform any endurance locomotion but have to move in short spurts. This is why today’s predatory amphibians and reptiles are ambush predators. They can only move in short bursts, and then have to stop, breathe, and recover their oxygen deficit. In short, they have no stamina. This limitation is called . The below image shows the evolutionary adaptations that led to overcoming Carrier's Constraint. Dinosaurs overcame it first, and it probably was related to their dominance and the extinction or marginalization of their competitors. (Source: Wikimedia Commons)
Scientists Explain How Asteroid Impact Led To Dinosaur Extinction
In the early 19th century, a dispute was personified by , a British lawyer and geologist, and , a French paleontologist. Their respective positions came to be known as and . Just as , so did uniformitarianism prevail in scientific circles. Under the comforting uniformitarian worldview, there was no such thing as a global catastrophe. Changes had only been gradual, and only the present geophysical, geochemical, and biological process had ever existed. The British Charles Darwin explicitly made Lyell’s uniformitarianism part of his evolutionary theory and he proposed that extinction was only a gradual process. Cuvier was , which contradicted the still-dominant Biblical teachings, even in the . Although Cuvier did not subscribe to the , his catastrophic extinction hypothesis was informed by his fossil studies. But Lyell and Darwin prevailed. Suggesting that there might have been catastrophic mass extinctions in Earth’s past was an invitation to be branded a pseudoscientific crackpot. That state of affairs largely prevailed in orthodoxy until the 1980s, after the was posited for the dinosaurs’ demise. An effort led by a scientist publishing outside of his field of expertise (a ) removed from its primacy. Only since the 1980s have English-speaking scientists studied mass extinctions without facing ridicule from their peers, which has never been an auspicious career situation. Since then, many and mass extinction events have been studied, but the investigations are still in their early stages, partly due to a dogma that prevailed for more than a century and a half, and Lyell’s uniformitarianism is influential. The ranking of major mass extinctions is even in dispute, , and a was recently .