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paulmcuk -> RE: Evolution vs. Religion (5/2/2011 12:30:55 PM)
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I'm afraid I haven't taken time to read all the replies so I'm probably repeating what others have said. However...
quote:
If evolution is true, then why didn't every cell continue to evolve?
Because every cell doesn't evolve all the time. Evolution, IS going on all the time, but not in the way you're thinking of it.
It's not the case that all cells are in a constant state of evolutionary flux. However, every time that genes are copied (e.g. when living things make babies) there is a chance that the copy won't be quite perfect (like when you photocopy something, there might be one letter that is a bit smudged). This is cell mutation.
Mutation is a loaded word and sounds bad but it isn't always so. It's just a change from what was there before. Cell mutation happens all the time and doesn't give you super powers. In fact, usually the mutation has no noticable effect at all. However, occasionally the mutation might make a noticible difference. The offsping might be bigger or stronger but it's important not to think of gross mutations like a llama suddenly turning into a giraffe. It's more likely to be quite subtle (a slightly longer beak, say) and might not be visible at all, such as a mutation which increases resistance to certain diseases.
So mutations happen. If the mutations create physical differences in some members of a species and those differences prove to be advantageous, then those born with the mutation prosper more, breed more, and so more of the species have that mutation (possibly completely wiping out the original form or also possibly splitting into two species). The problem with saying why don't sharks or frogs continue to evolve, is that we probably wouldn't know if they were. Evolution is often (not always - see Peppered Moth below) a very slow process. We know that sharks and frogs DID evolve because there are many types of sharks and frogs and the fossil records point to common ancestors. The fact is that they could well still be evolving, but it's a process that can take thousands or millions of years so we'd never notice.
The Peppered Moth is a nice example of evolution in action as it's a species that evolved twice within the space of a couple of hundred years, the changes being observed by humans. These moths were mostly white, which camoflaged them nicely against birch tress in Britain. Black moths were rare because, obviously they stood out on the trees and were easy prey. The mutation that made them black was a DISadvantage so they didn't proser as well as the whites. However, when the industrial revolution started, factories began spewing out so much soot that trees became blackened. The black mutation was suddenly an advantage and within a few generations, the black moths accounted for up to 98% of all Peppered Moths in the worst affected areas. Unfortunately for the blacks, the Clean Air Act was introduced which reduced the amount of soot being spewed out. Trees returned to their natural colour and white moths regained their advantage. Again, within a few generations they were in the majority.
It happens in humans too. The same mutant gene that causes the rather horrible Sickle Cell disease also protects against malaria. In countries with high incidence of malaria, the mutant gene has survived because it imparts greater survivability to the people who have it. Outside of those areas, the gene is incredibly rare because the protection is not needed and all it does is give people a nasty illness. This is why, generally, people of African descent get Sickle Cell while people of European descent don't - the mutation carried an advantage (on balance) in one area while being a complete disadvantage in the other.
There are other cases too. For example there is evidence to suggest that many of the survivors of the Black Death in Europe shared a genetic mutation. More recently, I know of at least one woman in Africa (a prostitute) who appears to have a genetic resistance to HIV/AIDS. She's been exposed hundreds of times and tests on her blood show that, in her, the virus just can't do it's normal trick of inflitrating the body. If there are more like her, their children may inherit Africa.
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