Evolution or De-evolution?

[Crucible]

Please, elaborate. I would like to hear your detailed explanation of the events (as opposed to just few sentences of general ideas). Keep in mind that possibility of “developmental shifts” and “shift in timing” are genetically predetermined.

That's of course, possible and does occur...but is it necessarily so ? I don't think you've shown that to be true.

Also, I would like a possible explanation of the fact that “in 40 years, no offspring of an extraseasonal mating has survived to adulthood” (http://www.terrierman.com/russianfoxfarmstudy.pdf). Could you offer one?

Sure. Some of what is needed to have 2 good cycles per year is not there yet. One hormone not at the right level, could do that.

[Cat]

Could you, please, elaborate???

[Crucible]

Genetically PRE-determined shifts in timing would be like with different kinds of zebra...different striping patterns emerge.
http://www.bio.miami.edu/dana/dox/zebra.html

...but are all shifts in development genetically predetermined ?
Apparently not. Some are environmentally determined.

[Crucible]

Perhaps a help to understanding how this 2 estrus cycles per year instead of one...could occur.

Suppose there are a bunch of kinds of organisms in an environment where a drought is occurring.

Suppose the genes that do something in kidney cells do something different in reproductive organ cells ( e.g. wrt to estrus )

Suppose dehydration triggers a "signal", that to kidney cells makes them respond with a change. The signal also goes to other organs including reproductive organ cells - and they respond in a different way ( because they are different kinds of cells ).

Suppose a good strategy for reproduction is to breed right after the dry season ends and the rains begin...

Some organisms will end up in a situation where it APPEARS that they time their egg-laying perfectly for the wet season...but they are actually responding to the "dehydration" signal.

A good strategy is to lay eggs or encapsulate, as drought kills the population off.

So having these genetic "means and methods" of accomplishing an "end", built in...is one thing.
The thing which triggers it, which makes it happen... can be environmental ( dehydration ).
It needn't take a change in genetics to change the cycles a bit.

[Cat]

I wasn’t asking how to regulate reproduction to just once a year. Vernalization is the greatest example of such mechanism. I was asking why “out of season” offspring die…

[JackBean]

because they evolved to survive particular season and if they are born into other season, it's not good for them?

[JackBean]

Somewhere, probably in other thread, you wrote that evolution has no direction (and I agree), so how can you ask

So, evolution or de-evolution? Are we moving toward perfection or away from it?

? If evolution has no direction, there's nothing like de-evolution

[Crucible]

It might help if the cause of death was known.
If it's something like a genetic incompatibility within the group for extra-seasonal reproduction, I'd suspect that it would be in one or two forms; every individual having a weakness in varying amounts, but all so far have been under the threshold for living...or that the weakness is in some individuals only ( the ones being bred all show it so far ).

By these two ways, in time some living pups might be produced ..when some pups are above the threshold, or when parents that have more compatible genetics are found to breed successfully.
If one or more extra- seasonal pups ever do survive, they probably will have systems more or more likely to be compatible with producing extra-seasonal pups.
If a pair of parents is found that can produce extra seasonal pups, problem ( for farmer-breeders) is solved that way.

[Cat]

because they evolved to survive particular season and if they are born into other season, it's not good for them?

But in domestic conditions there is no "season", so why do they still die?

[Cat]

Somewhere, probably in other thread, you wrote that evolution has no direction (and I agree), so how can you ask

So, evolution or de-evolution? Are we moving toward perfection or away from it?

? If evolution has no direction, there's nothing like de-evolution

Good point. Not very accurate on my part. What I meant here is popular view of evolution = from simple single cell to complex multicellular organism, from bacteria to human if you will. De-evolution is just an antonym ...

Force of evolution is blind just as you said. Here, however, I was trying to judge the outcome of our evolution...

[JackBean]

like humans evolving into bacteria?

I guess I understand your point

[Cat]

It might help if the cause of death was known.
If it's something like a genetic incompatibility within the group for extra-seasonal reproduction, I'd suspect that it would be in one or two forms; every individual having a weakness in varying amounts, but all so far have been under the threshold for living...or that the weakness is in some individuals only ( the ones being bred all show it so far ).

By these two ways, in time some living pups might be produced ..when some pups are above the threshold, or when parents that have more compatible genetics are found to breed successfully.
If one or more extra- seasonal pups ever do survive, they probably will have systems more or more likely to be compatible with producing extra-seasonal pups.
If a pair of parents is found that can produce extra seasonal pups, problem ( for farmer-breeders) is solved that way.

Crucible, you are making everything too complicated with vague ideas and slippery explanations. I had to read your post several times to be able to understand what you were saying. Please, make sure to present your future ideas more clearly.

The easiest way to address the problem is decide how it could be done. In my opinion, the answer is in epigenetics. When ovulation takes place out of cycle, an assortment of lethal genes are active; when ovulation takes place on time, those genes are epigenetically silenced. Depending on how far from normal cycle ovulation takes place; ultimate effect will vary from miscarriage to death at some point after birth to (possibly in the future) progeny able to reach adulthood but suffering from infertility.

As I said before, I imagine the mechanism is very similar to that of vernalization…