February 17, 2010
Chris Venditti
School of Biological Sciences
University of Reading
Reading
Berkshire RG6 6BX
UNITED KINGDOM
Dear Chris Venditti:
My interest is in fertility, which of course means that speciation is something I would like to understand. I enjoyed your article with its intriguing name (Phylogenies Reveal New Interpretation of Speciation and the Red Queen, Chris Venditti, Andrew Meade and Mark Pagel, NATURE vol. 463 no. 7279 January 21, 2010 page 349). You compared a number of ways that evolutionary decent trees might occur with a large number of actual trees including evolving taxa of animals, plants and fungi and came to the conclusion that speciation occurs as a rare random event.
You certainly are not alone. Darwin in his book Origin of Species could only spare one sentence from his need to talk about his beloved pigeons and other obsessions and address the issue. More or less he said, “As for the origin of species it is happenstance, since hybrid infertility never did any species any good.” I’m sure he would have been delighted to know that the matter would still rest there in 2010.
The Red Queen you refer to in your title, the Lewis Carroll character who had to run very fast just to stay where was, is a good metaphor. Obviously natural selection is going on all the time, but mostly species go nowhere. It is more complicated. The various parts of an animals anatomy, not to mention the elements of the internal workings of metabolism, must all be fine tuned to each other. This fine tuning is under the pressure of mutations that tend to degrade them, and the fine tuning must be reestablished by selection. In other words the Red Queen must run in countless directions at the same time. No wonder she gets nowhere.
As it turns out, it is easier for her to manage if the population is small. That way any error can be run down and corrected more easily. I have written a computer program in C language which you will find on the enclosed black CD, which models the phenomenon. It runs on a windows XP platform, to gigs of ram, at least dual processor technology for heat management. The parameters I use are given at the end of the long chart in the Brisbane file.
There is real world evidence for this going on, which you will find on the enclose DVD along with references. No only animals but humans are affected.
There are some hurdles that a single step of evolution must clear. First there must be a suitable mutation. The mutation must be valuable enough so that it increased fitness more than the cost of maintaining it in the population by the elimination of members that do not have it. In other words mutation pressure is increased, conferring a penalty if the new phenotype is to be kept. But if the mutation increased fitness, the population size will increase, other things being equal. An increase in population size means lower fertility. So a well adapted species must consist of a great number of pretty much mutually exclusive communities. Sometimes we see animals going to great lengths to preserve this exclusivity. Penguins march off to mate at some old family haunt that has been buried under ice for eons. Fish cruise the open sea but swim back to their natal brook to spawn.
So the rare speciation mutation arrives with its work half done. Any large population is already subdivided and investing energy in keeping it that way. But the border is not air tight. That must await your rare random event.
Of course once speciation is established the new species can take off and evolve at a gallop. There are the same hurdles to clear of course but at least for a time large population size is not a problem. And even after the population has approached its size limit, there is not the problem of quite so many outsiders wandering in.
I had hitherto rather thought things went the other way. A rare random event led to increased fitness and speciation followed so that the new advantage could be exploited without dragging along the whole population and possibly losing abilities that were working quite well. A fish gets smaller, say, so it can hide better. Now it cannot eat all the same things it used to eat. But it finds new food sources that it could not get before. Obviously there is now selective pressure for speciation to occur.
The issue that makes this of great importance is that as of some time this year people will mostly live in cities. Even those who do not live in cities are in an urban environment. There is an old story from Dorset. A sailor had traveled inland with a basket of crabs. One escaped and was found by the locals. They had no idea what it was, so the got the oldest man in the village and put him in a basket and carried him to see the wonder. Maybe he had seen something like it before. He hadn’t. Nowadays I don’t think you will find many villages in which nobody in living memory has traveled as far as a days walk in or out. Dorset is all within about thirty miles of the sea. Its isolation was probably pretty typical of most of humanity most of the time.
We are living in a time of unprecedented communication. Our gene pool size is excessive everywhere. And fertility is falling everywhere. Speciation being rare, we are not subdivided that way.
It might be too much to ask of you to take an interest in saving humanity by spreading the word on this or helping me to. But you might at least take a moment to think about how it impacts your evolutionary trees. Maybe there is another discovery in it for you.
If you would like to know more, there is much posted at NoBabies.net and of course I would be delighted to offer further clarification or help in any way I can.
Sincerely,
M. Linton Herbert MD
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