Believers in evolution, can someone explain this to me?
The idea of evolution relies on advantageous mutations, right? Which makes sense in theory. But when I think of the mutations required to produce a single working organ, such as an eye, I don’t understand how they could have been passed down successfully. An eye requires so many different parts and attachments to function. How could an organism have all those mutations at once in order to benefit from them? A cornea unattached to the brain would serve no purpose and likely not get passed down. For it to develop attached would require a series of mutations in unrelated sections of DNA. How is that possible, even after millions of years?
Forgive me if I’m missing something big here, or my eye example doesn’t work. I’m no scientist.
In The Land of the Blind, The One Eyed Man is King.
That’s Evolution…
The “what use is just part of an eye” argument has been refuted over and over. “Incomplete” eyes not only are useful, they exist. A light sensitive patch lets the creature tell light from dark, a light sensitive patch covered with transparent tissue is less prone to damage, a patch in a pit can tell the direction of light better, a lens-less pinhole eye can still perceive crude images etc. It’s perfectly possible to evolve an eye step by step.
It happened over a long period of time, with many small steps. It would have started with simple light-sensing… the ability to sense which direction had more light would be helpful in both avoiding predators (which might cause flashes of darkness/shade) and finding potential food (like plants, which need to be in a light-accessible place). Small changes and advances would improve this ability- such as better directional sensing (knowing more accurately which direction has more light), forming simple images, and eventually colors and detail.
So it was a series of small changes, selected for because they were advantageous, that provided an increasing benefit at each step.
The evolution of the eye has been heavily studied, and the Wikipedia article is a pretty decent start.
I’m curious if you’ve researched any of the existing explanations…
But if (as I assume) you find the fanciness of the eye persuasive evidence that there is an Intelligent Designer at work directing genes, what about all the crappy designs, or left over bits and pieces of non-functioning genetic material? Are they not equally persuasive in the other direction?
No. It relies on changes over time. Some are beneficial, some are not. The ones that are beneficial are passed along to successive generations.
Evolution does NOT say all those mutations happened at once. You need to seriously learn what evolution is before dismissing it.
Evolution is small changes over time. Although you can’t imagine the eye springing from a non-eye (neither can anyone else), can you imagine a light-sensitive spot on the skin? Can you imagine the spot becoming more sensitive over many generations, especially if it helped the organism avoid predators or find food? Can you imagine that spot becoming transparent, improving to provide a small amount of focus, so the organism can tell in which direction the predator is coming from and avoid it? Can you imagine this improving over a million years into a receptor that can create images and a brain that can interpret them?
If so, you’ve just described evolution. If not, you need to read up more. We have many examples of this kind of development. Evolution is a fact, not a wild-assed guess.
No one is proposing such a preposterous idea except the Creationists who have developed their own twisted idea of evolution.
How many millions of years do you propose? How did you determine that a X millions of years was not sufficient? Because you didn’t think it made sense? Can you show your math?
You are missing a lot. You are repeating the major misconceptions of those who wish to oppose science. I suggest you start here.
Obviously an organism doesn’t get all those mutations at once, that idea is called saltation.
This is a long-used, exhaustively debunked creationist argument (though the fact that it’s been thoroughly explained millions of times over never seems to prevent anyone from cheerfully using it again) called “irreducible complexity”. Google that term, and you’ll find thousands of people arguing about it. Somewhere in that pile, you’ll find pages and pages of explanation as to why it’s wrong.
If you’re going to argue about evolution, do yourself a favor and at least brush up on the bare bones, so that you know you’re not rehashing incredibly old arguments.
BTW, people don’t “believe” in evolution in any meaningful way. The evidence is there to support the fact of evolution; scientists are studying the methods and intricacies of how evolution works. Scientists believe in evolution the same way they believe in gravity.
To clarify, I was never dismissing evolution. I’d believe in it even if the eye argument hadn’t been refuted. I do confess to not doing my research, though.
Even a light sensitive patch seems complex to have sprung from mutations-- with connection to the brain and whatnot
You do know that there are animals with every step of the “part of an eye” making a successful living nowadays? Even bacteria show photosensitivity.
And that an intelligent falcon would wonder how an eye with only a single fovea and no pecten oculi at all (like mammals have) could function?
This, right here, showsa fundamental misunderstanding about what evolution and science actually represent.
Look at this blog post. The main point is: you don’t actually have to “believe” in science. It quotes, for instance
or
So: if you want to understand a scientific “fact” you actually need to retrace the process that led scientists to it. Or, of course, ask. But when you ask you should bear in mind that the “fact” is the result of plenty of “facts” before it.
The patch does not need to connect to a brain. There are a lot of living things with no brain and no nerves. In fact, there are more living things without them than with them.
And “I don’t understand” is never, ever, ever an argument for anything.
Plants sense and respond to light, and have, I believe we agree, nothing analogous to a mammalian brain.
If you find the biology of evolution difficult to conceive, you might find the chemistry and the physics of it easier to grasp.
Hmmph, not all that intelligent if s/he can’t figure that out.
Oy. Semantics, IMHO. I was going to say “evolutionist” but it sounded a bit clunky. I can imagine a creationist saying they “accept the evidence” for creationism. Either way, it’s constantly debated, I don’t see the harm in using “believes” to reference one’s belonging to their school of thought.
You are referring to the intelligent-design hypothesis of “irreducible complexity”.
Common sense tells us that an eye with no brain would be useless. The reality of evolution often flips the bird to us puny humans though
There is also the argument that something that seems impossible for evolution to build directly could be the result of something else that was built, something more complex, that was re-purposed for the observed function. Sight however I don’t really see falling into this.
However I find the argument that the word ‘belief’ should not apply I find hypocritical, as most people are only taking what they have been taught by others in their decisions, so yes it is a belief, unless they have done the original research. Belief does not mean you can’t change your belief.
Not only as said can eyes help a creature without being connected to the brain, but if the light sensitive cells in question are a mutation of, say, the cells involved in touch then they already have that connection. They’d just be detecting something different.
Keep in mind that any new biological feature is going to have a large amount of preexisting biological hardware to re-purpose and build on. It doesn’t need to start from scratch.
Creatures without brains at all, such as jellyfish, can have light sensitive patch eyes (which are generally single light-sensitive cells). The single-cell eye does have to be linked to the nervous system in such a way that the animal will move differently depending on whether the eye-spot is being stimulated or not, but all that is required to achieve that is a mutation that makes certain nerve cells sensitive to light, so that they fire off action potentials more (or less) rapidly when illuminated than when they are not. If that happens, and if the change in motion when illuminated happens to be advantageous to the animal (e.g., it makes it swim towards better-illuminated waters, where it will find more food) then it will be positively selected for.
The nerve network will be linked to the animal’s muscles already. The most basic function of nerves is to stimulate the muscles to move, and, in the case of a jellyfish, the nerves are arranged in a circuit that provides a regular oscillatory pattern of signals that cause the animal’s muscles to contract rhythmically, in the proper order to produce swimming. If the jellyfish has light sensitive proto-eyes, stimulating them will produce a change in that oscillatory pattern of nerve impulses that will cause the animal to swim in a different direction, perhaps towards or away from the light source (and/or perhaps move more quickly, or more slowly).
Very arguably, at root this is also how all nervous systems, including ours (and including our brain), work. The brain is, most fundamentally, a generator of rhythmic, oscillatory patterns of nerve signals that cause the muscles to move [see, e.g., Yuste et al., 2005 - PDF], and the function of sensory input is to perturb those patterns in such a way that the movements will change in a way appropriate to the situation. Of course in humans (and other animals with actual brains) it is all vastly more complex than it is in a jellyfish, so much so that the underlying rhythmic patterns of our movements are impossible to discern, with so many different complex rhythms interacting in complex ways with each other, and with sensory stimulation, to produce our actual behavior. Nevertheless, it may well be what our brains really do, what they are for. (And maybe it helps to explain things like dancing, and drum solos.)
There is no need to feel dumb for asking this question about the evolution of the eyes, incidentally. The problem of how an organ as complex as an eye cold evolve by natural selection used to keep Darwin himself awake at night. We now know that it can be done, and have a good idea o how it was done, but the answer is by no means an obvious or simple one.