Evolution: driven by extinctions (Evolution)

by David Turell , Saturday, October 17, 2020, 21:04 (1496 days ago) @ David Turell

There seems to be no question about this in Chixculub for dinos and now in the P-T largest extinction ever:

https://www.sciencedaily.com/releases/2020/10/201016114927.htm

"The Permian-Triassic mass extinction killed as much as 95 per cent of life, and the very few survivors faced a turbulent world, repeatedly hit by global warming and ocean acidification crises. Two main groups of tetrapods survived, the synapsids and archosaurs, including ancestors of mammals and birds respectively.

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"But a strong hint for this sudden origin of warm-bloodedness in both synapsids and archosaurs at exactly the time of the Permian-Triassic mass extinction was found in 2009. Tai Kubo, then a student studying the Masters in Palaeobiology degree at Bristol and Professor Benton identified that all medium-sized and large tetrapods switched from sprawling to erect posture right at the Permian-Triassic boundary.

"Their study was based on fossilised footprints. They looked at a sample of hundreds of fossil trackways, and Kubo and Benton were surprised to see the posture shift happened instantly, not strung out over tens of millions of years, as had been suggested. It also happened in all groups, not just the mammal ancestors or bird ancestors.

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"'Birds and mammals have erect postures, with the limbs immediately below their bodies. This allows them to run faster, and especially further. There are great advantages in erect posture and warm-bloodedness, but the cost is that endotherms have to eat much more than cold-blooded animals just to fuel their inner temperature control."

"The evidence from posture change and from early origin of hair and feathers, all happening at the same time, suggested this was the beginning of a kind of 'arms race'. In ecology, arms races occur when predators and prey have to compete with each other, and where there may be an escalation of adaptations. The lion evolves to run faster, but the wildebeest also evolves to run faster or twist and turn to escape.

"Something like this happened in the Triassic, from 250 to 200 million years ago. Today, warm-blooded animals can live all over the Earth, even in cold areas, and they remain active at night. They also show intensive parental care, feeding their babies and teaching them complex and smart behaviour. These adaptations gave birds and mammals the edge over amphibians and reptiles and in the present cool world allowed them to dominate in more parts of the world.

"Professor Benton added: "The Triassic was a remarkable time in the history of life on Earth. You see birds and mammals everywhere on land today, whereas amphibians and reptiles are often quite hidden.

"'This revolution in ecosystems was triggered by the independent origins of endothermy in birds and mammals, but until recently we didn't realise that these two events might have been coordinated."

Comment: Seems quite clear. Of course, we can wonder how God handled this. Did He set up the extinction, or did it happen naturally and He used it to advance evolution? Either or! Note the relationship to the discussion about the size of the food-supplying living bush and the need for calories caused by becoming warm-blooded.