Posted on 10/19/2001 11:19:12 AM PDT by Junior
Why? It's not as if an obligation to believe "the truth" exists in a random, meaningless, self-existent universe. And anyone who asserts otherwise has left the scientific ballpark and gone into the subjective realm of morality.
Now, with that said....... I don't think I'm in the crevo list. Any way, a little history.
To: keats5 & JBS (post #25)
Proof of evolution? Let's see... mitochondrial DNA, the cheetah and the "bottleneck effect", carbon dating of fossils and skeletal remains.
No, you "E" folks NEVER do address the cheetah.Todays biologists and 'animal saviors' will swear that "Too small of a population, and the animal group will go extinct."
(Is this not true?)
Yet, "E" people will say that just a mutation will give a couple of breeding pairs that will then grow into a stable population.
There are ONLY two choices:1. the biologists are wrong, or.........
2. the "Evolutionists"
Come on boys: fight it out.
88 posted on 9/28/01 5:50 PM Pacific by Elsie
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Todays biologists and 'animal saviors' will swear that "Too small of a population, and the animal group will go extinct."
(Is this not true?)
Yet, "E" people will say that just a mutation will give a couple of breeding pairs that will then grow into a stable population.
The answer to this is pretty straightforward, actually. Think of your typical boy meets girl scenario. Boy is born with mutation. Boy meets girl without mutation. Boy kisses girl, Boy falls in love with Girl, Boy marries Girl, and has lots of little kids. Boy's mutation gets passed on to a certain percentage of his offspring. If that mutation is more advantageous than others, those offspring will meet more girls and they will make babies, and those offspring will make more, and so on and so forth. Since the DNA of an individual is an amalgamation of the two parents, some, but not all, of the kids will have the mutation, and if it is a good mutation, the kids with it will outhunt and outlive the siblings without it. Thus, at some critical generation, the offspring with the mutation will outnumber the ones without it. As there are a number of mutations out there the successful mutations can get together and have more kids than the unsuccessful ones.
Speciation seems to be defined to occur when enough mutations occur so that when boy meets girl, it turns out that boy is so genetically different than girl that they can't procreate. It's a nice finite boundary, even though it isn't always followed.
Here is some fine print from above.........
At some finite time in the past, life began somehow. (How it began is beyond the scope of the theory, but the observational evidence strongly suggests that only one such beginning on Earth has left descendants to the present day.) As life reproduces and multiplies, mutations occur with small but finite probabilities, causing new genes to be added, and creating new alleles of existing genes. The different alleles confer different traits upon their owners, rendering them more or less successful in coping with their environments. The organisms that are more successful in coping with their environments consequently have a slightly greater probability of passing their genes to the next generation of organisms than do the less successful organisms. This causes allele frequencies to change over time.
Because mutations are random according to their probabilities, there is essentially a zero probability that two non-interbreeding populations will get the same set of mutations. (Even if they somehow do, there is essentially a zero probability that the frequencies of the alleles will end up the same in both populations.) The alleles and new genes available in each population will therefore diverge, with the result that the populations become genetically more distant from each other over time. Eventually, the two populations will become genetically so distant that they lose the ability to produce viable hybrids between them. This is the cause of the origin of species.
God did it. 'Nuf said.
So the evidence seems clear that they are very inbred. But why do some scientists think that cheetahs were reduced to a population of less than seven individuals, about 10,000 to 12,000 years ago.
(can you say NOAH!? I thought you could.........)
They think less than seven individuals, because it has been shown that if a population is reduced to seven individuals and then expands quickly, the offspring still retain about 95% of their genetic variability. But cheetahs have almost zero genetic variability - there's hardly any difference between them.
They think about 10-12,000 years ago, because back then, there was a massive destruction of many different mammalian species, such as mammoths, sable tigers and cave bears. About 75% of all mammalian species died out in North and South America. So this was probably the "disaster" that knocked off most of the cheetahs. Perhaps this disaster was a severe climate change associated with the tailing-off of the last Ice Age.
Whatever the cause, some scientists think that the cheetahs got almost totally wiped out - perhaps more than once. Like true copycats, they then built up their numbers with generation after generation of brother-sister inbreeding.
Once again, cheetahs are very endangered, because we are stealing their land and killing them, so bringing them closer to the brink of extinction.
*shrug* While a species is *likely* to have problems when a population is reduced so far, it doesn't mean that it *will* have problems, or that it didn't hang on through other lean times since then. Just because one species barely survived where others died out tells me that the cheetah must be pretty resilient, and survives well in pretty lean times. Now, if there are 20-30-50 species that show this evolutionary bottleneck, that tells me that there might be a problem. But one? Why is this a problem for evolution again?
Ahh yes, but inbreeding only increases the likelihood of there being non-viable offspring. It doesn't say all of the offspring will turn out to be deformed or non-viable, only some. Look at the Royal Family, after all....they have been pretty inbred over the past millennium, and yet some of their family are still pretty functional. It's a probablilty issue, more than anything. I bet there were a lot of cheetah deaths in the past, and if a person could get the data, I bet it would bring it out...
Despite your insistance, problems with the cheetah do not stick any sort of nail in the coffin of evolution, at most, it may make a Ph.D defense project. It would be an interesting project, too...
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Wasn't trying for nails, just a biologist reply. I don't know if we have any of those among 'the usual suspects'.
I assure you that my answers to your question are not fundamentally different that that a biologist might answer. Despite having a degree in Astronomy, I also do have some background in Biology. Do you have a response to my above statements in 17 and 18?
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