Different in degree or kind: Egnor's take; more on gaps (Introduction)

by David Turell , Sunday, October 23, 2016, 20:11 (2953 days ago) @ dhw

dhw: My hypothesis, in line with the cases we know of, is that environmental conditions caused organisms to make the changes. Here’s a website explaining the advantages of primitive lungs, which obviously have a long history.

1. How did fish evolve lungs? - Quora
https://www.quora.com/How-did-fish-evolve-lungs

DAVID: Sorry, but I've read your article, which is filled with Darwin-speak.

Look at the supposed uses. to me that is Darwin-speak, all suppositions, no proof stated.

I admit I was unaware of current theory re fish lungs and swim bladders. From Berkeley:

http://evolution.berkeley.edu/evolibrary/article/fishtree_09

The available evidence suggests that gills were present in the very earliest fishes — the common ancestor of hagfish and ray-finned fishes. However, lungs — gas-filled organs that serve the function of respiration — also evolved very early on. The common ancestor of the lobe- and ray-finned fishes had lungs as well as gills. So what happened to these lungs and gills? In the lobefins, lungs stuck around, and tetrapods, coelacanths, and (duh) lungfish, all inherited them and use them to obtain oxygen. Coelacanths and lungfish also retained their gills. Modern tetrapods, on the other hand, bear evidence indicating that we once had gills but that these were lost in the course of our early evolution. The ray-finned fishes retained gills, and some of them (e.g., the bichirs, BYK-heerz) also retained lungs for the long haul. But in the lineage that wound up spawning most ray-fins (and in at least one other lineage), lungs evolved into the swimbladder — a gas-filled organ that helps the fish control its buoyancy.

dhw: They categorically inform us that the swim bladder evolved FROM (not to) a primitive lung. It is the primitive lung that is my focus, not the swim bladder.

Note that the lung came first. God anticipating land creatures.

dhw: But I am only quoting this to show that the primitive lung has a history which is always associated with environmental needs. Among the functions listed are enhancing stablility in the water, filtering carbon dioxide out of the bloodstream, oxygenating the blood in hypoxic environments, I don’t know why this should be dismissed as Darwin-speak (whatever that means). I find the link with environmental needs at least as convincing as the hypothesis that your God gave a particular fish a set of almost readymade lungs (just one transitional phase apparently) before it stepped onto the land. (my bold)

The functions are theoretical possible functions, all reasonable. But there is no getting around the primitive lungs came long before stepping on land. To me Darwin-speak.