3 ms·

Looks like no one answered this question from the last time around: https://news.ycombinator.com/item?id=24492646 https://news.ycombinator.com/item?id=24492646

mikeyouse 2y ago
Q: Anyway, my problem with the argument is that some mammals obviously survived. Why? We had worse lungs, roughly the same amount of protection against the cold as many small dinosaurs... so what gives? A possible answer from this article (https://www.scientificamerican.com/article/how-mammals-conquered-the-world-after-the-asteroid-apocalypse/ https://www.scientificamerican.com/article/how-mammals-conqu...) The earliest Paleocene scene is dire. There is a fossil locality in Montana dated to approximately 25,000 years after the asteroid hit, called the Z-Line Quarry. It reeks of death. Almost all the mammals that flourished in the region in the Cretaceous are gone; only seven species remain. Several other fossil sites divulge what was happening over the next 100,000 to 200,000 years. If you pool together all mammals from this time, there are 23 species. Only one of these is a metatherian; these marsupial ancestors, once so abundant in the Cretaceous, were nearly extinguished. All told, if you consider the entire Montana fossil record, along with other data from across western North America, the statistics are grim. A paltry 7 percent of mammals survived the carnage. Imagine a game of asteroid roulette: a gun, with 10 chambers, nine of which hold a bullet. Even those odds of survival are slightly better than what our ancestors faced in the brave new world of the Paleocene. This bleak state of affairs raises a question: What allowed some mammals to endure? The answer became apparent when Wilson Mantilla looked at the victims and survivors. The survivors were smaller than most of the Cretaceous mammals, and their teeth indicate they had generalist, omnivorous diets. The victims, on the other hand, were larger, with more specialized carnivorous or herbivorous diets. They were supremely adapted to the latest Cretaceous world, but when the asteroid unleashed disaster, their adaptations became hardships. The smaller generalists, in contrast, were better able to eat whatever was on offer in the postimpact chaos, and they could have more easily hunkered down to wait out the worst of the bedlam. As ecosystems recovered in the earliest Paleocene, many of the mammals that started to multiply were eutherians, the placental antecedents that were once bit players in the Cretaceous. Their tiny bodies, flexible diets, and perhaps faster ways of growing and reproducing allowed them to commandeer open niches and start building new food webs. Around 100,000 years postasteroid a new eutherian appeared in Montana and swiftly became common. Purgatorius, with gentle molar cusps for eating fruits and highly mobile ankles for clinging and climbing in the trees, was an early member of the primate line. It, or perhaps another closely related eutherian, was our ancestor.
- downrightmike 2y ago
  Neat
nonameiguess 2y ago
In addition to the more detailed quoted answer, I believe the surviving mammals mostly lived underground, shielding them from many of the worst effects happening on surface world. Many were blind anyway and did well in the darkness of the clouded surface. Their predators all died off. The biggest remaining threat would have been lack of food, but as the other answer states, they had more flexible diets than dinosaurs and mammals that did not survive.
- downrightmike 2y ago
  They were underground long enough that we lost the genes to repair UV damage.

mikeyouse 2y ago

Q: Anyway, my problem with the argument is that some mammals obviously survived. Why? We had worse lungs, roughly the same amount of protection against the cold as many small dinosaurs... so what gives? A possible answer from this article (https://www.scientificamerican.com/article/how-mammals-conquered-the-world-after-the-asteroid-apocalypse/ https://www.scientificamerican.com/article/how-mammals-conqu...) The earliest Paleocene scene is dire. There is a fossil locality in Montana dated to approximately 25,000 years after the asteroid hit, called the Z-Line Quarry. It reeks of death. Almost all the mammals that flourished in the region in the Cretaceous are gone; only seven species remain. Several other fossil sites divulge what was happening over the next 100,000 to 200,000 years. If you pool together all mammals from this time, there are 23 species. Only one of these is a metatherian; these marsupial ancestors, once so abundant in the Cretaceous, were nearly extinguished. All told, if you consider the entire Montana fossil record, along with other data from across western North America, the statistics are grim. A paltry 7 percent of mammals survived the carnage. Imagine a game of asteroid roulette: a gun, with 10 chambers, nine of which hold a bullet. Even those odds of survival are slightly better than what our ancestors faced in the brave new world of the Paleocene. This bleak state of affairs raises a question: What allowed some mammals to endure? The answer became apparent when Wilson Mantilla looked at the victims and survivors. The survivors were smaller than most of the Cretaceous mammals, and their teeth indicate they had generalist, omnivorous diets. The victims, on the other hand, were larger, with more specialized carnivorous or herbivorous diets. They were supremely adapted to the latest Cretaceous world, but when the asteroid unleashed disaster, their adaptations became hardships. The smaller generalists, in contrast, were better able to eat whatever was on offer in the postimpact chaos, and they could have more easily hunkered down to wait out the worst of the bedlam. As ecosystems recovered in the earliest Paleocene, many of the mammals that started to multiply were eutherians, the placental antecedents that were once bit players in the Cretaceous. Their tiny bodies, flexible diets, and perhaps faster ways of growing and reproducing allowed them to commandeer open niches and start building new food webs. Around 100,000 years postasteroid a new eutherian appeared in Montana and swiftly became common. Purgatorius, with gentle molar cusps for eating fruits and highly mobile ankles for clinging and climbing in the trees, was an early member of the primate line. It, or perhaps another closely related eutherian, was our ancestor.

downrightmike 2y ago
Neat

nonameiguess 2y ago

In addition to the more detailed quoted answer, I believe the surviving mammals mostly lived underground, shielding them from many of the worst effects happening on surface world. Many were blind anyway and did well in the darkness of the clouded surface. Their predators all died off. The biggest remaining threat would have been lack of food, but as the other answer states, they had more flexible diets than dinosaurs and mammals that did not survive.

downrightmike 2y ago
They were underground long enough that we lost the genes to repair UV damage.