Discussion in 'Biology & Genetics' started by sculptor, Jul 24, 2018.
betting it all on a spin and toss?
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Over billions of years. Punctuated equilibrium is a probabilistic function.
I believe it is related to chaos theory.
There are characteristics that increase survival through disasters, and characteristics that abet radiation into opened niches, and of course the achievement of equilibrium involves Darwinian evolution in the first place - which is not a spin and toss.
(The "punctuation" is a million+ year period of rapid Darwinian evolution).
food security of the tribe Vs cultures of hunting to provide meat.
note stress is mentioned later in the thread. i recal some comment somewhere about a certain amount of stress being considered manditory for some types of brain development ?
i am guessing that with food security via crop rotation etc... this would deliver high carb low mineral (and other trace elements) to diets during times of stress.
i wonder if this has a counter productive effect on reproduction quality(and development).
it draws my mind to the bush meat issue that plagues environmental protections in asian & african countrys, via habitat distruction.
i wonder if the wests ability to produce meat at a more affordible cost can some how counter that assuming the markets were opened and some source of payment could be found.
1. Women with big fat heads tend to be ugly and are therefore at an evolutionary disadvantage.
2. Women with big fat heads tend to be of above average intelligence and thus able to manage contraception better.
Long time teachers who have seen up to three generations pass through their classrooms report that it is the less intelligent who produce more offspring. Each generation is less intelligent than the preceding and smaller headed. Families which have a tradition of sending daughters to university (encouraging them to have careers rather than families) increasingly risk extinction.
Things are worst in England which has tended to export its brighter and more enterprising progeny to populate the empire. This probably explains why English Anglo-Saxons now have lower average IQs than their cousins who remained in colony-free Germany and Denmark. (It is only necessary to take a trip to Germany to observe that the "square heads" have, on average, greater cranial capacity.)
Yeah, in a way.
This graphic from Wikipedia illustrates very nicely what punctuated equilibrium is.
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The horizontal x-axis is morphology. That means body-form. (Small x distances mean small differences in body-form, big distances big ones.) The vertical y-axis is time.
Gradualism imagines that body forms are continually changing, and speciation occurs when these gradual changes bifurcate and different populations start changing in different ways, becoming increasingly dissimilar.
Punctuated equilibrium imagines that changes in body form happen rapidly over short periods of time, so that speciation is sudden and new physically dissimilar populations appear suddenly in the fossil record. Then these new forms might survive relatively unchanged for long periods.
The fossil record provides illustrations of both gradualism and punctuated equilibrium, so both seem to happen.
In both cases, the new morphological variants would have to find new ecological niches where their differences are indeed adaptations and not birth defects. So there's an element of rolling the dice in both cases.
But given that punctuated equilibrium imagines much larger morphological variants appearing more rapidly, the element of risk would seem to be greater.
The question arises: what would explain a sudden speciation event such as punctuated equilibrium imagines? That explanation might perhaps be found in developmental biology. Many of the genes in which mutations can occur regulate fetal development. So a small change in a single gene might cause dramatic differences in how a fetus develops.
Imagine dwarfism genes. A small chemical hiccup, and short legs suddenly appear without all the intermediate leg-length morphological variants that gradualism imagines. Now imagine that there are some niches where dwarfism is a positive benefit, so that these variants enjoy an advantage. If the new variants survive and pass on their genes, a new species might be observed to suddenly appear in the fossil record. And if the new variant is well adapted to its new mode of life, it might not change again for a long time.
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Two ways of looking at the same picture, maybe.
Rescale your Y axes and those two are similar pictures.
Also, the apparent absence of fossil record evolutionary change in times of soft tissue and biochemical selection, or even behavioral changes. Snake venom, say, has evolved quite a bit without the skeleton necessarily changing much at all. Those "equilibria" might look quite different in a graph of dated genome modifications.
And then there's the missing inclusion of population equilibrium in the gradualism picture - gradualism does not axiomatically presuppose that evolutionary change proceeds at one steady rate, and the notion that a large and stable population of well-fitted organisms in a long occupied niche would tend to evolve very slowly compared with colonizers is just recognizing probability - a higher percentage of changes are for the worse, a lower percentage of the better ones successfully spread.
Likewise the notion that the colonizers or new niche occupants might evolve comparatively - comparatively - rapidly. Add to that the observation that evolution itself creates new niches - a great deal of the habitat of this planet is other living things - and we expect bursts of feedback amplification now and again, under gradualism or any other paradigm. Arithmetic.
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