Evolution: earliest mammals (Evolution)

by David Turell , Monday, November 18, 2019, 01:13 (1831 days ago) @ David Turell

When the characteristics appeared dinosaurs were still around:

https://www.nature.com/articles/d41586-019-03170-7

"Mammals first appeared at least 178 million years ago, and scampered amid the dinosaurs until the majority of those beasts, with the exception of the birds, were wiped out 66 million years ago. But mammals didn’t have to wait for that extinction to diversify into many forms and species. “These new discoveries document a huge, hitherto-undreamed-of ecological diversity,” says Richard Cifelli, a palaeontologist at the University of Oklahoma in Norman.

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"The latest finds are also offering clues to the evolution of key mammal features. For instance, the keen hearing of mammals is partly down to tiny bones in the middle ear — the malleus, incus and ectotympanic. But in the reptilian ancestors of mammals, these bones were part of the jaw, and were used for chewing instead of hearing. Mammal forerunners, such as shrew-like Morganucodon from 205 million years ago, sported a prototype of the mammal arrangement that allowed for both functions.

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"Another unique trait of mammals is the sophisticated way they chew and ingest food in small parcels, rather than swallowing things whole as snakes and alligators do. To make that possible, mammals evolved a wide variety of complex teeth for biting and grinding food.

"But as babies, mammals are nourished another way — by suckling from their mother’s mammary glands. “Our whole group is named after this incredible biological innovation,” says Luo. Drinking milk is made possible by the ability to suck and swallow, aided by the hyoid bones in the throat and muscles that support them. This apparatus also forms the voice box.

"In July, Luo published a paper revealing a 165-million-year-old vole-sized docodont — a close relative of true mammals — that had the hyoid bones of its throat preserved14. Microdocodon gracilis is the earliest animal known to have been able to suckle like a modern mammal.

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"Much of the constellation of features we think of as defining mammals — complex teeth, excellent senses, lactation, small litter size — might actually have evolved before true mammals, and quite quickly. “More and more it looks like it all came out in a very short burst of evolutionary experimentation,” Luo says. By the time mammal-like creatures were roaming around in the Mesozoic, he says, “the lineage has already acquired its modern look and modern biological adaptations”."

Comment: the same problems that surround the evolution of live birth, the accommodation of skull and pelvic size while a brain is enlarging as evolution goes forward, apply to suckling milk with special arrangements in the infant throat involving the special hyoid bone shape and function to allow suckling without drowning. The problem is designing at the same time changes in two separate individuals, mother and infants. Only design by a designer can accomplish this contemporaneous set of alterations. Darwin theory cannot answer this problem.