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

by David Turell , Friday, October 14, 2016, 19:46 (2962 days ago) @ David Turell

dhw: It is you who keep talking of tiny steps. But maybe there were. Maybe Tikki Jr had slightly more leggy legs than Tikki Sr. Who knows?
DAVID: Once again, the evidence is huge gaps, no tiny steps. We must work with the evidence we have and then hypothesize.

Tikki is new evidence of transitional forms. My hypothesis allows for all eventualities: tiny steps (improvements, as above, not changes of species), transitional forms and saltations leading to new species.

David: You are hypothesizing tiny steps. Fine. There is no evidence. My gaps are the evidence we have, and so I hypothesize from the only evidence we have. That is how jury trials work or logic should work.

Look at this article which discusses Tiktaalik:

https://blogs.scientificamerican.com/artful-amoeba/fish-out-of-water-are-actually-prett...

"The new findings suggest that though the transition from water to land seems extreme, it does not seem particularly hard. Something else must prevent fish from evolving into full-fledged land-dwellers, as seems to have happened only once, giving rise to terrestrial vertebrates like ourselves. But what?

***

"To that end, they sought to see how often the move from water to land has occurred among fish, an iconic transition that seems like it should be hard and rare. To do so, fish must confront many challenges. Breathing, moving, and metabolizing all have to be modified in ways that make them possible in an environment of radically increased gravity and decreased wetness.

***

"Most of the family-level examples, however, were fish out of the water for only a few seconds or minutes, which may not meet the expectations of some regular “amphibious” behavior. Four of the families did have species that spend hours or days out of water: mudskippers, rockskippers, eels, and four-eyed blennies each come from separate families, implying that at least four times, significant amphibious behavior has evolved on Earth, not including, of course, the crucial fifth instance that resulted in us. The closest living relatives of the lobe-finned fish that made this particular transition also include many species today that make at least occasional forays onto land.

***

"What traits do modern amphibious fish share? More than anything, the scientist found that living in the intertidal zone promotes forays onto land. Fish living in the intertidal zone were amphibious much more frequently than would be expected given their overall numbers. With the twice-daily advance and retreat of the sea, and the ubiquity of tide pools that heat up in the sun, starving them of oxygen and forcing fish onto land, the zone seems to be particularly good at making fish terrestrial.

"On the other hand, the tropics seemed to be no better than the polar regions, proportionately, at producing amphibious fish. Nor did freshwater systems produce more amphibious fish than would be expected.

***

"..the authors theorize, drying out is the real challenge: specifically, the problems posed by the dessication of gills, which must remain moist for most fish to breathe. Our ancestors, such as the early tetrapod Tiktaalik, seemed to have been pre-adapted to overcome this obstacle because they possessed, in addition to gills, a primitive lung. (my bold)

"Without this trait or something like it, the forays of fish onto land seem destined to remain a flirtation. Though free to frolic, they must ultimately remain tethered to the water whence they came." (my bold)

Comment: In regard to jumping gaps, note the bolds above. The Tiktaalik come with a pre-adaptive primative lung. It looks like a God saltation to me, allowing the ability to breathe on land while real legs are added in a further gap jump. Walking bass in Florida don't have any type of lung. Hypothesized tiny steps are not in the fossil record. Lets work from what we see in that record to derive a theory of evolution.