Conversations with History - Neil Shubin

[Stauffenbergje]

@Akkritah

Of course, some species survive for very long times, examples are coelacanth and nautilus (called 'living fossils' sometimes), but most do not.

An animal like tik would have serious problems in a slightly more modern world, which contained more efficient land animals to compete with it and/or predate on it. Just because the conquest of land happened, the ecosystems at the water-land boundary changed a lot. And big changes drive evolution into new forms or extinction of old forms.

[keaney42]

JESUS DID IT ALL!!NO EVO

[akkitrah]

At 18:46 Shubin says certain rocks were too young to find Tiktaalik in because there were already quadrupeds. But that assumes Tiktaalik has to go extinct after giving rise to quadrupeds. No reason that has to be.

[akkitrah]

actually a bit earlier 18:30

[Timbul53525253]

If you think about it logically, it would most likely be a pseudoextinction - Tiktaalik as a transitional form would give rise to other better adapted tetrapods which would no longer be identified as Tiktaalik. If Tiktaalik *was* our ancestor, it didn't become extinct per se because we're still here!

[akkitrah]

Yes pseudo E is a possibility.

But Tik could be our ancestor and still be found in rocks Shubin said were too young.

In fact, Tikcould be our ancestor and be living _today_.

Would be wrong to assume Tikt is our ancestor: Just say he lived at the expected time and place and had the right features. Maybe he life no descendants and we are descended from some similar animal that lived somewhere else. There were probably many such animals. Shubin found Tik because it was in accessible rock.

[Timbul53525253]

Agreed - all these are possible scenarios; and Tik is far more likely to represent part of an adaptive radiation than a one-off. The lancelet is still around, too.

And as someone who's done a fair bit of fossil hunting myself, I have no problems with people looking in accessible rocks! :o)

[GuppyPal]

True, but it's more common for animals to evolve or go extinct rather than remain unchanged. It would also be impossible to place Tiktaalik as a transitional species if quadrupeds already existed.

[RabidApe]

cooooooooool!

thanks, ucberkeley!

[CousinoMacul]

This was great! I'd never made the connection before between having a neck and living on land (vs. the water), but in retrospect, it''s so obvious that one has to say "Why didn't I think of that?"

[RabidApe]

I can't remember where exactly, but in one of the "Physics for Future Presidents" classes, Prof Muller said something to the effect of "the most dangerous assumptions [for scientists] are the ones you don't know you're making".

;D