Evolution Question #1
As I have indicated elsewhere, I am an agnostic about almost every major subject, not just “god”. One subject in which I am definitely at a loss for finality is Evolution by Natural Selection. Lord knows, there’s plenty of evidence in support of Mr. Darwin’s contentious theory, but I remain unconvinced. Interestingly, just as I pointed out that I have read atheists’ writings claiming that there is no such thing as an “agnostic” - we are all really uncommitted atheists - I have encountered precisely the same idiotic evaluation from evolutionary scientists (Richard Dawkins being the most notable). ANY doubt about Natural Selection apparently renders one a Creationist, nothwithstanding protestations and explanations to the contrary. There are only two possible positions, apparently. It is amusing but pathetic that the world’s brightest people sometimes lose all capacity for critical thinking when outside their domain and can be as prejudiced and imbecilic and “with us or against us” as the average lout in a bar fight.
Aside from two philosophically objectionable aspects of the theory - its absolute nature and the fact that it’s pithy premise -”survival of the fittest” - is such a laughable tautology - there are a few things that prevent me from embracing Natural Selection as the single explanation for the existence of every organism that ever lived. This is one of the more interesting and perplexing ones, in part because, having posed the question to scientists, I have yet to receive any answer, much less a compelling or even plausible one.
Evolution speaks of “species”. Now that word, in itself, is problematic for scientists for a number of reasons, but it is workable for this discussion. We all know that a Komodo Dragon is not a Hedgehog, after all. There are various definitions for “species” but the common element of these definitions that intrigues and befuddles me is this: an organism is a member of the species with which it can produce viable offspring. Horses can produce horses only with other horses. Breed a horse and a donkey and you get a mule - an animal that cannot, in turn, reproduce anything. All fine.
So, my Evolutionary Question Number One is: With whom does the first member of a species reproduce?
To explain:
We have “Blues” and “Blue-Grays”. Blues mate and produce Blue offspring till the cows come home and everyone is happy. One day, a Blue gives birth to an animal - a Blue-Gray - that cannot mate with any Blue to produce a viable child - i.e. a child that can, in turn, go on to produce babies. So, clearly, that Blue-Gray baby will die leaving no children, so no new Blue-Gray species. However, sometimes that doesn’t happen - obviously - or there would only be one species on earth. If new generations of Blue-Gray are created, how?
There seems to me to be only two possibilites.
1. As above, the Blue-Gray species never comes into existence because the first one - the proto-Blue-Gray, as it were - dies with no offspring - because there is nobody to mate with. Or,
2. At exactly the same time and place in history, several Blues give birth to offspring having precisely the same genetic Blue-Gray mutations that rendered them unable to mate with Blues but also making them able to successfully mate with each other.
Yikes! How many mutations would that entail and what is the probability of such a phenomenon - even once, much less the billions and billions of times it must have happened to account for every species that ever existed? Perhaps a mathematician could help me here, because intuitively I would think the odds against it would be something on the order of one in the number of atoms in the universe.
If I am missing something obvious here (which I often do) and you have the answer - the exact mechanism - I’d love to hear it.
Postscript: The above actually provides an answer to the old unanswerable “Which came first; the chicken or the egg” question. Can you see it? It’s obvious.
Posted in Science and Religion
January 15th, 2008 at 5:34 am
It sounds like you’re asking about speciation which doesn’t really take place like you cite in your example of the Blue-Gray.
Wikipedia has a decent article covering the different kinds of speciation along with examples of each.
The basic idea being that if an offspring is born with a mutation that prevents it from producing viable offspring then your option 1. is the outcome. However what usually happened in speciation is that part of a population of the same species is somehow separated or isolated from the rest of the group and begins to diverge due to different environmental factors. Over the course of generations the genetic drift in each population continues to grow until at some point if the groups were to be reintroduced they would be incapable of creating viable offspring or possibly reproducing at all.
Sticking with your example. What if your Blue-Gray had a mutation that didn’t affect it’s ability to reproduce but instead gave it increased lung capacity (or really any advantage in the water). So because of this mutation it’s able to hunt for food better in the water than the rest of the population. But it still breeds with the general population passing on it’s genetic mutation to offspring. Which are able hunt better in the water and catch more food. In time rather than replacing the land hunters the water hunting Blue-Grays stop mixing with the rest of the population and just stick with their own group. The populations while maybe technically able to produce viable offspring do not. Run the clock of a few millenia and the genetic drifts go in different directions leading to two populations that have now become so vastly different that they can no longer reproduce.
So in answer to your original quesiton about who does the first of a new species mate with… There is no ‘first’ of a new species that loses the ability to produce viable offspring. It occurs gradually usually through segmentation of a population and then genetic divergence.
http://en.wikipedia.org/wiki/Speciation
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jtwurth:
Thank you for taking the time to write such a lengthy and reasoned response. I am familiar with the mechanism you describe but have always found it unsatisfying. (hence, “Evolution question Number 1″)
“…two populations that have now become so vastly different that they can no longer reproduce.”
Vastness of differences are irrelevant. This is a question of a single, deadly, defining difference. Vastly different lung capacities or eyeball complexities can be achieved in an almost continuum like manner. But viability?
Pekingese and Rottweilers are vastly different but are dogs nonetheless, and though mating a male Rottweiler with a female Pekingese might produce an offspring that it is impossible for the mother to carry to term, that miscarried offspring would still be a dog and theoretically viable.
“There is no “first”… It occurs gradually usually through segmentation of a population and then genetic divergence.”
A specific trait exists or does not exist in the individual. Survival enhancing mutations (increased lung capacity) are passed from one individual to another within the group - parent to offspring - not from individual to group. A parent may have a lung capacity of of 2 liters and its offspring, 2.000000001 liters. Fine. A parent is 100% viable but the offspring is only 99.99999999% viable? Of course not. The specific trait/mutation in question (non-viable reproduction), by definition cannot be passed on and cannot be achieved in stages.
I am sorry, but how there can be a 2nd, 10,000th or 50,000,000th of anything without there having been a 1st still remains beyond me.
John
January 16th, 2008 at 12:25 am
Thanks for your response. I have a better understanding of the question your asking but unfortunately lack the expertise to answer it. I’ve been looking for more information online in regards to the question you ask and I keep arriving at the same point which seems to be unsatisfying to you. However, I applaud your natural skeptical, questioning nature which I think we need more of in this world. As long ask you’re not a skeptic who denounces scientific findings only to substitute them for unsound ideas for which there is no evidence. Based on what I’ve read from your posts I don’t think you are.
I hope you can find an answer to your question. I do feel that the evidence in support of the theory is quite powerful and well supported and while I’m not a biologist and haven’t found the answer yet I have difficulty believing it hasn’t been dealt with and answered sufficiently.
Cheers,
Jason
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Thanks for responding again. Frankly, I must confess that, though still not convinced, you have made me reconsider the genetic drift explanation. There may be something in there, though whatever mechanism I consider, I still bash my head against the “1st member” problem at some point.
Again, thanks for your response and your mail. I love nothing so much as a
good verbal punch-up over a subject that has no meaningful effect on either
party’s day to day life. It is invigorating.
Cheers,
John
January 16th, 2008 at 5:50 am
If I understand you correctly, you agree that the genetic makeup of a species may drift over time. If a species is divided into two groups, those groups may drift in different ways, eventually becoming separate species (as happens with ring species).
It is true that one viable mutation (such as gene duplication) will likely not make a child incompatible with its parent. But many of these may make it incompatible with its great, great grandchildren.
By analogy: language changes over time. There is no point at which parents and their children are suddenly unable to communicate with each other. And yet Latin became both French and Spanish — two languages that are no longer compatible.
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Hi.
Thank you. This is the best explanation I have yet encountered. I had not considered reproductive mutation as a cumulative process - one which could easily account for lack of viability between two previously connected populations.
That said, though this explanation is indeed persuasive, it is, like others I have encountered in the theory generally, inductive and for me not 100% compelling. It would, of course, be closer to that if there were experiments demonstrating it, say using a short-lived species such Drosophila melanogaster over hundreds or thousands of generations. Perhaps such studies have been done and if you are aware of any I’d appreciate your directing me to it or them.
Thanks so much.
You’ve got me thinking.
John