David's theory of evolution PART 1: define evolution (Evolution)

by David Turell , Saturday, June 25, 2022, 17:46 (665 days ago) @ David Turell

The point has come up as to how to define common descent, which originally was based on comparative anatomy and geography, now that DNA as a common code shakes up the standard tree of life:

https://www.sciencealert.com/new-dna-technology-is-shaking-up-the-branches-of-the-evolu...

"As our new research shows, appearances can be deceptive when it comes to family. New DNA technology is shaking up the family trees of many plants and animals.

"The primates, to which humans belong, were once thought to be close relatives of bats because of some similarities in our skeletons and brains. However, DNA data now places us in a group that includes rodents (rats and mice) and rabbits. Astonishingly, bats turn out to be more closely related to cows, horses, and even rhinoceroses than they are to us.

"Scientists in Darwin's time and through most of the 20th century could only work out the branches of the evolutionary tree of life by looking at the structure and appearance of animals and plants. Life forms were grouped according to similarities thought to have evolved together.

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"Sloths and anteaters, armadillos, pangolins (scaly anteaters), and aardvarks were once thought to belong together in a group called edentates ("no teeth"), since they share aspects of their anatomy.

"Molecular trees showed that these traits evolved independently in different branches of the mammal tree. It turns out that aardvarks are more closely related to elephants while pangolins are more closely related to cats and dogs.

"There is another important line of evidence that was familiar to Darwin and his contemporaries. Darwin noted that animals and plants that appeared to share the closest common ancestry were often found close together geographically. The location of species is another strong indicator they are related: species that live near each other are more likely to share a family tree.

"For the first time, our recent paper cross-referenced location, DNA data, and appearance for a range of animals and plants. We looked at evolutionary trees based on appearance or on molecules for 48 groups of animals and plants, including bats, dogs, monkeys, lizards, and pine trees.

"Evolutionary trees based on DNA data were two-thirds more likely to match with the location of the species compared with traditional evolution maps. In other words, previous trees showed several species were related based on appearance.

"Our research showed they were far less likely to live near each other compared to species linked by DNA data.

"It may appear that evolution endlessly invents new solutions, almost without limits. But it has fewer tricks up its sleeve than you might think.

"Animals can look amazingly alike because they have evolved to do a similar job or live in a similar way. Birds, bats and the extinct pterosaurs have, or had, bony wings for flying, but their ancestors all had front legs for walking on the ground instead.

"Similar wing shapes and muscles evolved in different groups because the physics of generating thrust and lift in air are always the same. It is much the same with eyes, which may have evolved 40 times in animals, and with only a few basic "designs".

"Our eyes are similar to squid's eyes, with a crystalline lens, iris, retina, and visual pigments. Squid are more closely related to snails, slugs, and clams than us. But many of their mollusk relatives have only the simplest of eyes.

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"Haeckel's drawings made brilliant observations of living things that influenced art and design in the 19th and 20th centuries. His family trees were based almost entirely on how those organisms looked and developed as embryos. Many of his ideas about evolutionary relationships were held until recently. (my bold)

"As it becomes easier and cheaper to obtain and analyze large volumes of molecular data, there will be many more surprises in store."

Comment: my definition of common descent must use this new approach, based on common biochemicals of which one, DNA, is the common code controlling the whole process. Therefore, gaps in form are of no issue, much to dhw's confusion, since he still is with Haeckel's views. Be sure to see the illustrations to see the marked differences in trees.