Evolution debate question. Help needed!
Offline I had someone ask me this question,
Can you site a source which proves that organisms can develop useful mutations? Has it ever been observed, or just inferred by reverse engineering existing species?
I responded by posting a link
http://www.newscientist.com/channel/life/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html
He then said:
Again, my argument is based on sexually reproducing species, but I disagree that what happened with that bacteria is 'evolution'. The genes to metabolise citrate were probably recessive, and since it was beneficial to the species, it became dominant. Just like it is possible but very unlikely for two white people to have a black baby. If it was beneficial in the environment to be black (extremely hot and sunny), the recessive gene would become dominant because if you aren't black you sunburn easily and get heat exhaustion easier. This is not evolution, it's natural selection, and does not produce new species.
Can someone clarify this and if I am wrong can you point me to a better example? Thanks
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http://www.usnews.com/articles/science/2008/07/24/where-is-human-evolution-heading.html
http://ecoworldly.com/2008/10/07/scientists-discover-fish-in-act-of-evolution-in-africas-greatest-lake/
Furthermore, the "gene to metabolise citrate" was most certainly not recessive. Bacteria are largely categorized by what they "eat." Recessiveness doesn't work the way your interlocutor is suggesting. That is, beneficial mutations don't just sit around and wait in hiding until a use for them happens to show up. There would be no reason for such things to propogate. It's elementary math.
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...tell your friend that his original question specified "organisms," and that, whether he likes it or not, microorganisms count as organisms.
Conor
Argh, so many fallacies and misunderstandings in a single paragraph!
First, if his argument is based on sexually reproducing species, and then he goes on to say that the citrate mutation was probably 'dominant' in the bacteria... Argh! He doesn't even know that gene dominance *depends* on sexual reproduction. You have two copies of the gene (sexual; one from each parent), and if one of the copies is dominant, then it overpowers the recessive gene and the dominant characteristic shows up in the organism. But if there's only one copy of each gene in a bacterium (asexual; one copy from the single parent), then there's no mechanism for dominance.
Second, genes don't 'become' dominant. There are alleles (versions) of a gene which either are dominant or they are not. Your friend is confusing dominance with allele frequency. He is basically saying that if conditions favour it, certain allele variations will become more frequent than other allele variations. Guess what! That is the definition of evolution! Change in allele frequency in a gene pool over time.
Third, when they sequence the genome of the pre-citrate and post-citrate bacteria, if they haven't done it already, is your friend willing to concede his argument if they find that indeed there were actual point mutations making step-by-step changes to the genes which enabled citrate mutation? If he is not willing to concede after such a demonstration, then he is being intellectually dishonest both with you and with himself. I guarantee you the researcher involved (can't recall his name, to lazy to find it) is going to milk this discovery for as much data as he can. Wouldn't be surprised if he gets a Nobel if he hasn't got one under his belt already. I guarantee there's going to be genome sequencing going on, and replication of the experiment using intermediate forms of the bacteria. They might even go so far as to take a single bacterial cell which does not contain the citrate gene and reproduce the experiment showing that from a genome without the gene, poof, via random mutation, you get a genome with the gene. Again, change in allele frequency over time *includes* random mutation, it doesn't *require* it.
Fourth, where does your friend draw the line at 'new species'? Get him to state his precise defintion of species and explain how many many *small* changes in allele frequency over time can *not* add up to *large* changes in allele frequency over time. What is this imagined barrier that stops a person who can only step a few feet in a single stride from crossing the continent in *many* strides over a long period of time?
This friend is arguing from a dogmatic position and is not open to honest intellectual discussion. He assumes new species can't be formed because he was taught that in his dogma. And he can't give up the dogma because of his fear of the consequences.
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Thank you, natural, for putting into print that which I was too drunk to elucidate in my post. That post was so dumb, I had to respond somehow, but all I trusted myself to do was post links.
Atheism isn't a lot like religion at all. Unless by "religion" you mean "not religion". --Ciarin
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You do actually have one example in germany of a positive mutation in a human. A german child has had a mutation in the gene that counteracts muscle development. And his muscels are developing faster, and better then normal. This also qualifies as a sexual reproducing species i bleive. And is clearly beneficial.
http://www.abovetopsecret.com/forum/thread61416/pg1
The genetic sequence of organisms certainly does change, by copying errors leading to point mutations (changing one of the 'letters' of the code to another), duplication (extra copies of individual letters or of whole genes inserted during copying, like a 'stuttering' of the copying process), migration (whole genes being copied out of sequence, or even to other chromosomes), and deletions (failed to copy).
Whole chromosomes can be duplicated.
All of these processes have been observed, I believe, and are well established.
They provide all the mechanism required for generating the raw 'new information' the anti-evolutionists prattle on about.
Throw in natural selection, which is inevitable, and that IS evolution, small changes from generation to generation, continuing indefinitely. There would be some broad limit on how much change can occur in one generation - the greater the change, the less likely it is to occur, and the more likely the mutation is to make the organism unviable.
But there is no way for there to be a mechanism at this level to signal that the organism has changed too far from some distant ancestor, which would be needed to block 'macro-evolution', which can only occur over many generations - the genetic code does not have some sort of built-in reference code to measure how much it has changed compared to some hypothetical standard for its species. THAT puts the onus back on the anti-evolutionist to demonstrate how that could work and provide some evidence.
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