Genome complexity:does variation in species drive evolution? (Introduction)

by David Turell , Monday, September 20, 2021, 17:34 (1161 days ago) @ dhw

Using fruit fly wing comparisons, not much:

https://www.quantamagazine.org/mathematical-analysis-of-fruit-fly-wings-hints-at-evolut...

"Persevering until they had perfectly mounted about 2,000 pairs, the scientists then photographed the wings in high resolution and systematically compared the photos in 30,000 places.

"This was no mere exercise in taxonomy. Rather, the study, which was recently published in the journal eLife, has offered an exceptionally detailed look at the variation that can exist within a species. The results begin to resolve a long-standing tension in biology.

"On one hand, despite dramatic mutations in individuals’ genes and diverse environments in which they grow, members of a species develop into strikingly similar creatures. This robustness ensures that almost all individuals are functional. On the other hand, for evolution to occur, members of a species need diverse traits that natural selection can act upon. Those two forces — robustness and evolvability — tug in opposite directions. One wants less variation, and one wants more.

***

"Unexpected simplicity emerged from this rich data. The scientists saw a narrow range of possible appearances for the wings, which mostly diverged in a small set of characteristics. The variation was concentrated near the hinge of the wing and showed up in a few particular spots, such as the shape of the frontmost vein. Moreover, these variable traits were linked: When one of the traits on a wing was far from the average, the other traits usually were, too. This was true no matter which genetic or environmental modifications that fly experienced, implying that these factors individually have very limited influence.

***

"The photos of fly wings offered no clues as to the mechanisms that restrict the possible morphologies that can develop. Rather, the results substantiated the extensive power of these guardrails. Natural selection must mostly act on the significant diversity exhibited in the small number of linked, variable traits, while robustness tightly constrains the rest."

comment: variation in fruit fly's wings is tiny. Darwin theory demands enough variation to allow evolution to advance to more complex forms. If the variations are this tiny, Darwin's theory is constrained. Small species adaptations are changes in degree. A completely new species is a change in kind. That possibility requires new design, not offered by the small variations seen in this study .