The human eye - how did it happen?

[kyser_soze]

I was bumbling around the Beebs website and came across the planet earth bit about those insect targetting parasitic fungi...

7 rows down, 1 in for HD clip

 

[stdPikachu]

I'd agree that parasites that modify the behaviour of their hosts in order to propagate themselves better are far more interesting, evolutionarily, than the eye (especially the human eye which, as pointed out above, is riddled with hideously obvious errors such as rods and cones being in the wrong place, which is why we have such disastrously poor vision compared to most other mammals.

Anyone got a link to the animated gif of the snail infected by the parasite climbing to the top of a piece of grass and flashing its antanae so as to be better spotted and eaten by birds? From an evolutionary standpoint, it's staggering.

 

[ATOMIC SUPLEX]

fuck the eye

the eye is easy


i'm fucking amazed by the parasitic wasp... how the fuck did evolution make that one

Fuck the the parasitic wasp. . . . A woodpecker has an ear on the end of it's tongue.


I now believe in God because it's too hard to imagine any other explanation.

 

[stdPikachu]

Fuck the the parasitic wasp. . . . A woodpecker has an ear on the end of it's tongue.

I now believe in God because it's too hard to imagine any other explanation.

Well then if you start with that attitude you're going to find evidence for FSM everywhere - there are so many neat tricks in the animal kingdom alone. For instance, the cat family are stunningly adapted predators - normal cats' canines are spaced to fit between the vertebrae of rodents and sever the spinal column in a single bite, with lions and tigers having teeth spacing suited to gazelles and the like. Their skeletal structure means their gait involves one paw falling pretty much precisely on the preceeding footprint, minimising noise and visible tracks. Whiskers grow up to the width of the cats body and then stop, facilitating their ability to squeeze through almost any gap (thanks to their "unattached" shoulder blades). Siamese cats are thought to have learnt to mimic human baby cries in their meow as a way of fostering strong bonds with humans, on whom they are more reliant due to a genetic defect that prevents them from having good night vision.

Pretty much every species has some incredibly cool ability that perfectly suits its way of life simply because that way of life is what led to the ability becoming apparent in the first place. Once you adapt slightly better to a niche, you can exploit it better, hence furthering the adoption of your own adaptations as you out-breed less well adapted creatures in the same niche. Couple this with the fact that this has been going on over time scales that are so colossal that the human mind cannot comprehend them and, to me, evolution looks like the only probably explanation. YMMV, however

 

[weltweit]

... Couple this with the fact that this has been going on over time scales that are so colossal that the human mind cannot comprehend them and, to me, evolution looks like the only probably explanation. YMMV, however

So assuming you started out with basic animals, very basic crawl out of the slime with no eyes, how did human reproduction evolve? what steps were in that process of evolution?

 

[mauvais]

I don't know, but it's a good trick isn't it. It's like when you wake up and some joker's put some roadworks in your garden. 12 billion eyes. When did those get there? I mustn't have been looking.

 

[kyser_soze]

So assuming you started out with basic animals, very basic crawl out of the slime with no eyes, how did human reproduction evolve? what steps were in that process of evolution?

Go and find one of the 00s of books about evolution, seriously. You're talking about 600 million years worth of evolution of life on this planet with that question...

FWIW, humans share a simila reproductive set to all other mammals - it's one of the things that actually defines what a mammal is, so it wasn't just human reproduction, it's mammalian reproduction. Would be useful for you to get a grounding in things like shared stuff first before coming onto something really hard like the brain...

 

[moon]

When I grow up and become a robot...or fembot...or something...
I want a proper eye...like this one
and just one will do...

 

[Jonti]

So assuming you started out with basic animals, very basic crawl out of the slime with no eyes, how did human reproduction evolve? what steps were in that process of evolution?

Google is your friend -- but you may also need a subscription to Nature seriously to get to grips with the question. This from Wikipedia ...

Origin of sexual reproduction
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The most primitive organisms known to undergo meiosis and to reproduce sexually are protists (primitive unicellular eukaryotes) such as those that cause malaria.

Organisms need to replicate their genetic material in an efficient and reliable manner. The necessity to repair genetic damage is one of the leading theories explaining the origin of sexual reproduction. Diploid individuals can repair a mutated section of its DNA via homologous recombination, since there are two copies of the gene in the cell and one copy is presumed to be undamaged. A mutation in an haploid individual, on the other hand, is more likely to become resident, as the DNA repair machinery has no way of knowing what the original undamaged sequence was.[18] The most primitive form of sex may have been one organism with damaged DNA replicating an undamaged strand from a similar organism in order to repair itself.[23]

Another theory is that sexual reproduction originated from selfish parasitic genetic elements that exchange genetic material (that is: copies of their own genome) for their transmission and propagation. In some organisms, sexual reproduction has been shown to enhance the spread of parasitic genetic elements (e.g.: yeast, filamentous fungi).[24] Bacterial conjugation, a form of genetic exchange that some sources describe as sex, is not a form of reproduction. However, it does support the selfish genetic element theory, as it is propagated through such a "selfish gene", the F-plasmid.[23]

A third theory is that sex evolved as a form of cannibalism. One primitive organism ate another one, but rather than completely digesting it, some of the 'eaten' organism's DNA was incorporated into the 'eater' organism.[23]

A theory states that sexual reproduction evolved from ancient haloarchaea through a combination of jumping genes, and swapping plasmids. [25]

A comprehensive 'origin of sex as vaccination' theory proposes that eukaryan sex-as-syngamy (fusion sex) arose from prokaryan unilateral sex-as-infection when infected hosts began swapping nuclearized genomes containing coevolved, vertically transmitted symbionts that provided protection against horizontal superinfection by more virulent symbionts. Sex-as-meiosis (fission sex) then evolved as a host strategy to uncouple (and thereby emasculate) the acquired symbiont genomes.[26]

 

[Barking_Mad]

Well then if you start with that attitude you're going to find evidence for FSM everywhere .......... Couple this with the fact that this has been going on over time scales that are so colossal that the human mind cannot comprehend them and, to me, evolution looks like the only probably explanation. YMMV, however

*waits from someone to mention intelligent design*

oops! too late

 

[stdPikachu]

oops! too late

<voice style="agent smith">It is... inevitable</voice>

Humans do seem to have a remarkable conceit in that alot of them think that if they can't see it happening, it doesn't exist. Can't believe the number of people where I've exaplined "that star could well have blown up a million years ago" to be looked at like I've just done a foot-long line of catnip.

So assuming you started out with basic animals, very basic crawl out of the slime with no eyes, how did human reproduction evolve? what steps were in that process of evolution?

As others have said, there's a million and one textbooks categorising the rise of life over the aeons and both the changes they wreaked on our planet and the changes the planet wreaked upon them. You can even look at things like vestigal hip bones (similar to our own pelvic structures) and atrophied limbs in whales and dolphins as evidence thet they were once land dwelling animals, or the fact that human embryos are almost indistinguishable from lizard, fish and bird embryos as evidence that we share a common genetic history.

But if you're one of those people who wants to see a flawless, gapless fossil record that details every single species and every transition from one form of life to the other (commonly given the misnomer "missing link"), you'll be disappointed.

 

[i-am-your-idea]

Yep, if you don't get laid soon those tape worms are going to run amok.

LOL!

 

[urbanrevolt]

The Blind Watchmaker's good on this, including on the eye.

Like the chat-up line though I reckon anyone using it would not be very genetically fit and would soon die out!