facts of evolution

[eFestivals]

The purpose of this thread is to discuss what is recognised as true by the science of evolution, not to discuss whether evolution happened or not.

I caught the end of a programme the other day about evolution, and it said (which I'd not heard before) ...

Only one eye has ever evolved.

All living things with eyes share universal DNA which is used in the formation of that eye as an embryo, which shows that in all of time an eye has only evolved once - and every creature with an eye shares the being that evolved that eye as an ancestor.

The differences in some creatures eyes (such as say a human's to a fly's) are things that have evolved on the path each has travelled since that common ancestor.

Anyone else got anything similarly weird and interesting?

[Langdale Wolf]

I predict 25 pages before 6pm on Saturday.

Where are you, worm?

[Rufus Gwertigan]

I am not too versed in genetics as I am the rest of biology, but I would have thought it was obvious that animals with eyes have shared DNA. I am not been flippant there. Humans have shared genes with many organisms including yeast and mice, and that's why they are used as model organisms.

As far as I am aware of DNA evolution, it all started in one big puddle and broke away from there. Therefore many organisms will possess similar sequences.

[worm]

All living things with eyes share universal DNA which is used in the formation of that eye as an embryo, which shows that in all of time an eye has only evolved once - and every creature with an eye shares the being that evolved that eye as an ancestor.

[worm]

As far as I am aware of DNA evolution, it all started in one big puddle and broke away from there. Therefore many organisms will possess similar sequences.

[Rufus Gwertigan]

Each species adapting from the former universal species. If an eye is still apparent across species then it clearly came from a species further back in time.

[worm]

Thank f**k you cleared that up for me. I knew I was missing something in my Biology dgree

[Rufus Gwertigan]

Sorry, I meant to show that I had the same understanding. Perhaps I could just have just said 'agreed'. Felt it needed further affirmation though.

[feral chile]

I know absolutely nothing about evolutionary biology so I cheated and googled - found some interesting stuff about the trap-jaw of ants evolving independently at least four different times in the ants' history.

clicky

[sadwitch]

I recall reading that mollusc eyes are differently arranged in terms of structure than mammalian eyes and this being an example of convergent evolution.

Oh god it's too complicated to talk about and I have a masters.

[pehaw]

I recall reading that mollusc eyes are differently arranged in terms of structure than mammalian eyes and this being an example of convergent evolution.

Oh god it's too complicated to talk about and I have a masters.

[sadwitch]

Yes. The theory most widely accepted seems to be convergence as far as the eye is concerned. Ie it doesn't derive from one common ancestor.

Paired eyes in vertebrates, arthropods and mollusks have long been considered to be classic examples of evolutionary convergence.

[Atlanteanlost]

Evolution may repeat the same variation independently in several species because that variation or adaptation is best suited for survival, and reflects the fitness of the species.

[Rufus Gwertigan]

This is why I was surprised at the example of the eye as something only evolving once unless the programme was talking about a more developmental or genetic angle.

I was going to start talking about developmental genetics but I didn't want to have a nervous breakdown again.

If any potential employers are reading this however:

I LOVE DEVELOPMENTAL BIOLOGY. AND PRESSURE. AND DEADLINES. AND PEOPLE SHOUTING AT ME WHEN IT'S NOT MY FAULT.

Is that Darwin/Attenborough program on yet? I'm concerned because Dave has a history of making inaccurate statements regarding evolution...

[sadwitch]

Right convergent evolution would be the same biological trait evolving in distantly/unrelated species.

Neil said he saw a programme where it said the eye evolved only once.

We were surprised the eye was mentioned as an example of something evolving only once when different eye structures have evolved.

I don't know about mollusc genetics so I can't really comment on whether the same genes are involved in mollusc eye development and vertebrate eye development. I should know about insect eye genes but I seem to have forgotten. Some of the genes involved in eye development are active in both avian eye development and mammalian development and some aren't. It wouldn't surprise me if the same genes were involved but they're all involved in so many things...

Molecular evolution is a bit hardcore for efestivals isn't it?

I am piss poor at explaining evolution even when I understand it which is why I went molecular.

[worm]

You are too easy to wind up mate

[TalkShow Bob]

The thing that strikes me as crazy is this... Apparently the first ever sence evolved was smell. So there were organisms that were floating around [i presume] smelling stuff but they couldn't touch it. If I were to guess I would have gone touch first. These organisms didnt know how big they were, where they were or even if they hit a wall! Crazy.

Edited January 30, 2009 by TalkShow Bob

[krisskross]

in mammels: male = XY; female = XX

in birds: male = XX (well ZZ to be accurate); female XY (ZW)

in grasshoppers it goes weird because there are two types: male Xo neo-XY; female XX or neo-XX

Polyploidy is fascinating (how sad am i). There are a couple of closely rodent species in south america where one has 56 chromosome and another has 102 chromosomes (and another with 96). Its thought that it is the only mammal to have gone through such a genetic event (where the number of chromosomes double) in plenty of years. I think the one with 102 chromosomes is the mammel with the most DNA - the elephant only has 56 and the poor whale only has 44! less than us humies at 46.

[krisskross]

Molecular evolution is a bit hardcore for efestivals isn't it?

[eFestivals]

Don't mean to rain on the parade or anything, but isn't that the same with all things? All animals with brains must have evolved from one organism? All animals with hands must have evolved from one thing? All animals with nostrels must have evolved from one thing? All animals with a sexual organ must have evolved from one thing? You can say it of anything, no?

Isn't that the point of evolution? That we all evolved from one organism?

So that the further the category goes back the more traits that are shared? i.e. humans (self conscious brain, warm blood, sexual organs, colour vision) > mammals (conscious brain, warm blood, sexual organs, vision) > animals (responsive brain, blood, sexual organs, sense) > organism (will, cellular composite, replication, response)

Isn't that what evolution actually is?

Yes, we all ultimately evolved from the same organism, but we have not all followed the same evolutionary path.

Some similar things have evolved independently of each other. Eyes have not.

[eFestivals]

This is why I was surprised at the example of the eye as something only evolving once unless the programme was talking about a more developmental or genetic angle.

I was going to start talking about developmental genetics but I didn't want to have a nervous breakdown again.

If any potential employers are reading this however:

I LOVE DEVELOPMENTAL BIOLOGY. AND PRESSURE. AND DEADLINES. AND PEOPLE SHOUTING AT ME WHEN IT'S NOT MY FAULT.

Is that Darwin/Attenborough program on yet? I'm concerned because Dave has a history of making inaccurate statements regarding evolution...

the guy who was presenting the programme was an evo-devo (developmental evolutionist). He reckoned we'll be able to predict our coming evolution at some point.

(the prog was on bbc4 earlier this week. I can't remember what it was called, but will still be available on iPlayer. The attenbough is on Sunday I think)

Back to the eye .... from genetics they know for certain that an eye has evolved just once for all living things. I can't say i'd ever thought about it, but I would have assumed that due to big differences in some eyes (say a fly compared to a human) that our evolutionary paths had parted before we had eyes, and these different eyes had evolved totally independently of each other. But apparently not.

Edited January 30, 2009 by eFestivals

[t8yman]

Some similar things have evolved independently of each other. Eyes have not.

Edited January 30, 2009 by t8yman

[eFestivals]

Coincidentally, I am currently "reading" Hitchens' "God Is Not Great" audiobook, and two days ago he was discussing this very subject, the evolution of the eye. surely the eye is just a processor of light information (forgive me, I am not a scientist) with lens etc. The eye of a bat may well be based upon the same design of eye as the hawk, yet both eyes have evolved independantly to become completely different in terms of performance, therefore they wont really be the same eye?

he also mentioned a fish that has 4 eyes, both sets of which are different in form and position, one pair on the side of the head, and one pair looking below.

It is a truly fascinating subject, but one that still swamps my tiny brain a little.

yeah, of course what animals/insects/birds/reptiles/etc have now isn't all the same eye, but all creatures with eyes are decended from one common ancestor which first evolved an eye. The differences in eyes now are evolutionary changes to that first evolved eye that we all share.

Edited January 30, 2009 by eFestivals

[t8yman]

yeah, of course what animals/insects/birds/reptiles/etc have now isn't all the same eye, but all creatures with eyes are decended from one common ancestor which first evolved an eye. The differences in eyes now are evolutionary changes to that first evolved eye that we all share.

[eFestivals]

Are there creatures without eyes? I guess there are.

In which case, unless they evolved away eyes they had in the past (is anything known to have done this? I've no idea), these split from the evolutionary path that we share with the creature that evolved the original eye before the evolution of that eye.