multicellularity less of an evolutionary hurdle than thought

[cathy]

Last weeks New Scientist (23rd June) had an interesting article to upset creationists. Looking at the evolution of multicellularity in yeast. Unicellular yeast was centrifuged and the next batch of yeast was then inoculated with yeast that had settled at the bottom after centrifuging, ie the stuff that had clumped a little bit. Hence selecting for tendency to group in clumps.

After 60 days, 350 generations, culture line had evolved that had clumped into a sort of 'snowflake' line. Some of those snowflakes then started to behave as if a multicellular organism rather than a clump of unicellular ones. They started to grow bigger and when the reached a certain size, portions broke off to give daughter cells. A few generations later some showed signs or rudimentary division of labour once they reached adult size. Some cells started to undergo programmed cell death leaving weak points for daughter cells to break off. This let them increase the number of offspring yet still remain large enough to sink and increase their survival rates.

As the snowflake lineages were exposed to different selective pressures they evolved. The programmed cell death showed the organism was no longer functioning as a clump of unicellular organisms but as a multicellular one, ie a cell dying for the good of the whole organism.

Most biologists enthusiastic. One crit is that yeast was once multicellular tens to hundreds of millions of years ago, ie many, many more years than 6000 ago and centrifuging could have re-started that. So the researchers are now going to repeat with chlamydomonas. I suspect the creationist literature will be 'overstating' the objection as is their wont, whilst carefully ignoring the timescale. But it was a very interesting article for those allowed to read it without pre-judgements.

[Brian Jordan]

Most biologists enthusiastic. One crit is that yeast was once multicellular tens to hundreds of millions of years ago, ie many, many more years than 6000 ago and centrifuging could have re-started that. So the researchers are now going to repeat with chlamydomonas. I suspect the creationist literature will be 'overstating' the objection as is their wont, whilst carefully ignoring the timescale. But it was a very interesting article for those allowed to read it without pre-judgements.

Note that the authors anticipated criticism and are setting up a further experiment to approach it. Given that the creationists are now swallowing anything but the likes of cats turning into dogs, is this an example of evolution from multicellular to unicellular and back again? Or was yeast condemned to a unicellular existence because it was present on the accursed apple?
Oh, and it's also an ecumenical matter: how do Muslims see the role of wine yeast in the scheme of things?

[a_haworthroberts]

http://www.newscientist.com/article/mg2 ... arity.html

Unicellular yeast were once multicellular? Must be devolution in action - a consequence of the Fall and the Curse.

PS Don't quote me.

[cathy]

I suspect the creationist literature will be 'overstating' the objection as is their wont, whilst carefully ignoring the timescale. But it was a very interesting article for those allowed to read it without pre-judgements.

As predicted its on the Uncommon Descent blog where they are overstating the objection and carefully ignoring the timescale. Oh how surprising.

Yep they point to the fact that centrifuging is not natural (no s~~~ sherlock). Well I think that was cos the researchers were trying to see if it could happen and didn't really have time to wait for natural selection.

Oh and they metioned yeast were once multicellular. Hunted for a mention of millions of years ago. Couldn't find it. Chalked it up to creationist honesty-like real honesty but without the added honesty. Or lying by omission and exageration.

[Brian Jordan]

Yep they point to the fact that centrifuging is not natural (no s~~~ sherlock). Well I think that was cos the researchers were trying to see if it could happen and didn't really have time to wait for natural selection.

Evidently no brewers or wine makers there then, or they could have told them that yeast sediments anyway. Hydrodynamics shows that the multicellular yeasts would hit the bottom first, be it under 1G or many. In fact, a certain professor of fuel technology could have told them that.

[cathy]

Brian wrote: Evidently no brewers or wine makers there then, or they could have told them that yeast sediments anyway. Hydrodynamics shows that the multicellular yeasts would hit the bottom first, be it under 1G or many. In fact, a certain professor of fuel technology could have told them that.

Are creationists allowed to drink wine? Wine is in the bible.

[Brian Jordan]

Brian wrote: Evidently no brewers or wine makers there then, or they could have told them that yeast sediments anyway. Hydrodynamics shows that the multicellular yeasts would hit the bottom first, be it under 1G or many. In fact, a certain professor of fuel technology could have told them that.

Are creationists allowed to drink wine? Wine is in the bible.

Oh dear, on re-reading what I wrote I realise I've stepped into quicksand: sedimentation is quite an issue with creationists, isn't it? I wonder what their professor has to say about that? Woz it a divine centrifuge wot dun it?