Comment: That's a softball!

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That's a softball!

I would love to inform you on this one... Most decent comparative anatomy courses spend a few weeks on this very topic, as it is one of the most complete transitions present in the fossil record.

There are two very good examples of extremely "tetrapod-like" fish:
- panderichthys (located in 380 million year old strata)
- eusthenopteron (located in 385 million year old strata)

And there are two very good examples of extremely "fish-like" tetrapods:
- ichthyostega (located in 365 million year old strata)
- acanthostega (located in 360 million year old strata)

There's only one problem... We have salamanders that look like fish... and we have fish that look like salamanders... But where's the half salamander half fish creature?

If such a creature were to have existed, it would have to be located in ~370 million year old strata... in between the above species...

So that's were we looked... and... viola!! Tiktaalik is a half fish half tetrapod that was discovered in 2006.

Tiktaalik is a beautiful transitional fossil. It's a fish with functional wrist joints and non-rigid articulation between the bones of the pectoral girdle and the skull.

In fact... evidence for the transition between fish and land animals is present in none other than... HUMANS! Next time you have an anatomy textbook handy, take a look at the recurrent laryngeal nerve. Most creationists quiver when you mention this structure.

In short, the recurrent laryngeal nerve exits the brain stem, travels all the way down the neck into the thoracic cavity, loops around the aortic arch (main vessel exiting the heart), travels back up the neck (almost to where it started from), and innervates the larynx (voice box). At best, a creationist could refer to this as an "unintelligent design." The extreme example is the giraffe neck, where there is 17 feet of wasted nerve.

The only way to explain this is by taking a look at the anatomy of our fish ancestors. The recurrent laryngeal nerve in fact does take direct root in fish... But in fish, the laryngeal pouch is located in the thoracic cavity, and it is intersected by systemic gill arch (aortic arch in mammals). This format makes complete sense and has been conserved in the genome ever since.

As far as why this evolutionary process would occur... Well, with a basic understanding of the principles of natural selection, drift, mutation, and migration, and the impact of environmental pressures, it doesn't take much imagination to figure out why some individuals having a slight edge over others would have driven such a change.

an idea whose time has come cannot be stopped by any army or any government