[math-fun] Evolutionary bottlenecks and fat tails
(Distributions having fat tails, that is.) Evolution, as usually presented -- e.g., by Darwin himself -- talks about *gradual* changes happening over hundreds/thousands of generations. As Moore's Law shows, even gradual change, if extended to enough generations, can produce dramatic change when viewed with enough historical perspective. Nevertheless, I contend that the most dramatic evolutionary changes occur at *bottlenecks*, where 80-90-95% of the population is wiped out, and the few remaining individuals have one or more features which might not have had any (or perhaps only a very modest) effect under "normal" times, but suddenly become the only thing that matters for survival. Assuming that the rest of the genes of these survivors are more-or-less independently distributed, then normal day-to-day evolution will continue to weed out "bugs" in the rest of these genes which are more common, while the one or two features that provided survival at the bottleneck are now shared by *all* of the remaining population. For example, essentially all humans have 5 fingers on each hand. This is quite bizarre, as under "normal" circumstances, having 3,4, or 6 fingers would seem to provide about the same survival advantage as having exactly 5 fingers. Suppose that there was a population bottleneck where survival depended upon have *at least* 5 fingers, and all of the survivors had 5,6,7,8, etc. fingers. More normal evolutionary pressures might then have eliminated those individuals having more than 5 fingers, but the gene pool as a whole would "remember" vividly the bottleneck event which wiped out everyone having fewer than 5 fingers. Note that these population bottlenecks don't have to happen very often. Indeed, it is estimated that the last great bottleneck for the human race was perhaps 70,000 years ago. Exactly which features enabled survival in that bottleneck isn't known, but whatever it was, this feature was clearly was a *rare* feature that suddenly became crucially important for survival. This means that really understanding evolution is going to exceedingly difficult, as some of the most important events are also the rarest events.
We need to ask the Moties for help on this ;) On 7 Oct 2018, at 18:49, Henry Baker wrote:
(Distributions having fat tails, that is.)
Evolution, as usually presented -- e.g., by Darwin himself -- talks about *gradual* changes happening over hundreds/thousands of generations. As Moore's Law shows, even gradual change, if extended to enough generations, can produce dramatic change when viewed with enough historical perspective.
Nevertheless, I contend that the most dramatic evolutionary changes occur at *bottlenecks*, where 80-90-95% of the population is wiped out, and the few remaining individuals have one or more features which might not have had any (or perhaps only a very modest) effect under "normal" times, but suddenly become the only thing that matters for survival. Assuming that the rest of the genes of these survivors are more-or-less independently distributed, then normal day-to-day evolution will continue to weed out "bugs" in the rest of these genes which are more common, while the one or two features that provided survival at the bottleneck are now shared by *all* of the remaining population.
For example, essentially all humans have 5 fingers on each hand. This is quite bizarre, as under "normal" circumstances, having 3,4, or 6 fingers would seem to provide about the same survival advantage as having exactly 5 fingers.
Suppose that there was a population bottleneck where survival depended upon have *at least* 5 fingers, and all of the survivors had 5,6,7,8, etc. fingers. More normal evolutionary pressures might then have eliminated those individuals having more than 5 fingers, but the gene pool as a whole would "remember" vividly the bottleneck event which wiped out everyone having fewer than 5 fingers.
Note that these population bottlenecks don't have to happen very often. Indeed, it is estimated that the last great bottleneck for the human race was perhaps 70,000 years ago. Exactly which features enabled survival in that bottleneck isn't known, but whatever it was, this feature was clearly was a *rare* feature that suddenly became crucially important for survival.
This means that really understanding evolution is going to exceedingly difficult, as some of the most important events are also the rarest events.
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The meaning and purpose of life is to give life purpose and meaning. The instigation of violence indicates a lack of spirituality.
This notion seems fairly mainstream among evolutionary biologists --- see for example the remarkably broad-ranging (though somewhat overpowering) course by Robert Sapolsky in Stanford, starting from https://www.youtube.com/watch?v=NNnIGh9g6fA WFL On 10/7/18, Henry Baker <hbaker1@pipeline.com> wrote:
(Distributions having fat tails, that is.)
Evolution, as usually presented -- e.g., by Darwin himself -- talks about *gradual* changes happening over hundreds/thousands of generations. As Moore's Law shows, even gradual change, if extended to enough generations, can produce dramatic change when viewed with enough historical perspective.
Nevertheless, I contend that the most dramatic evolutionary changes occur at *bottlenecks*, where 80-90-95% of the population is wiped out, and the few remaining individuals have one or more features which might not have had any (or perhaps only a very modest) effect under "normal" times, but suddenly become the only thing that matters for survival. Assuming that the rest of the genes of these survivors are more-or-less independently distributed, then normal day-to-day evolution will continue to weed out "bugs" in the rest of these genes which are more common, while the one or two features that provided survival at the bottleneck are now shared by *all* of the remaining population.
For example, essentially all humans have 5 fingers on each hand. This is quite bizarre, as under "normal" circumstances, having 3,4, or 6 fingers would seem to provide about the same survival advantage as having exactly 5 fingers.
Suppose that there was a population bottleneck where survival depended upon have *at least* 5 fingers, and all of the survivors had 5,6,7,8, etc. fingers. More normal evolutionary pressures might then have eliminated those individuals having more than 5 fingers, but the gene pool as a whole would "remember" vividly the bottleneck event which wiped out everyone having fewer than 5 fingers.
Note that these population bottlenecks don't have to happen very often. Indeed, it is estimated that the last great bottleneck for the human race was perhaps 70,000 years ago. Exactly which features enabled survival in that bottleneck isn't known, but whatever it was, this feature was clearly was a *rare* feature that suddenly became crucially important for survival.
This means that really understanding evolution is going to exceedingly difficult, as some of the most important events are also the rarest events.
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To take Henry's example, five fingers go way back before humans. Fingers evolved from fin rays in bony fishes. Five rays is fairly common, but different numbers occur in fish. But among land animals, five is the common number. So the theory is that the first amphibians evolved from fish with five fin bones. It was a "bottleneck" only in the rear view that after moving into the air a huge new ecological field opened up. Brent On 10/7/2018 3:18 PM, Fred Lunnon wrote:
This notion seems fairly mainstream among evolutionary biologists --- see for example the remarkably broad-ranging (though somewhat overpowering) course by Robert Sapolsky in Stanford, starting from
https://www.youtube.com/watch?v=NNnIGh9g6fA
WFL
On 10/7/18, Henry Baker <hbaker1@pipeline.com> wrote:
(Distributions having fat tails, that is.)
Evolution, as usually presented -- e.g., by Darwin himself -- talks about *gradual* changes happening over hundreds/thousands of generations. As Moore's Law shows, even gradual change, if extended to enough generations, can produce dramatic change when viewed with enough historical perspective.
Nevertheless, I contend that the most dramatic evolutionary changes occur at *bottlenecks*, where 80-90-95% of the population is wiped out, and the few remaining individuals have one or more features which might not have had any (or perhaps only a very modest) effect under "normal" times, but suddenly become the only thing that matters for survival. Assuming that the rest of the genes of these survivors are more-or-less independently distributed, then normal day-to-day evolution will continue to weed out "bugs" in the rest of these genes which are more common, while the one or two features that provided survival at the bottleneck are now shared by *all* of the remaining population.
For example, essentially all humans have 5 fingers on each hand. This is quite bizarre, as under "normal" circumstances, having 3,4, or 6 fingers would seem to provide about the same survival advantage as having exactly 5 fingers.
Suppose that there was a population bottleneck where survival depended upon have *at least* 5 fingers, and all of the survivors had 5,6,7,8, etc. fingers. More normal evolutionary pressures might then have eliminated those individuals having more than 5 fingers, but the gene pool as a whole would "remember" vividly the bottleneck event which wiped out everyone having fewer than 5 fingers.
Note that these population bottlenecks don't have to happen very often. Indeed, it is estimated that the last great bottleneck for the human race was perhaps 70,000 years ago. Exactly which features enabled survival in that bottleneck isn't known, but whatever it was, this feature was clearly was a *rare* feature that suddenly became crucially important for survival.
This means that really understanding evolution is going to exceedingly difficult, as some of the most important events are also the rarest events.
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The most dramatic evolutionary changes have come from changes that open up new ecological niches, e.g. hard scales that allow living out of water or kidneys that allowed living in fresh water. Brent On 10/7/2018 10:49 AM, Henry Baker wrote:
(Distributions having fat tails, that is.)
Evolution, as usually presented -- e.g., by Darwin himself -- talks about *gradual* changes happening over hundreds/thousands of generations. As Moore's Law shows, even gradual change, if extended to enough generations, can produce dramatic change when viewed with enough historical perspective.
Nevertheless, I contend that the most dramatic evolutionary changes occur at *bottlenecks*, where 80-90-95% of the population is wiped out, and the few remaining individuals have one or more features which might not have had any (or perhaps only a very modest) effect under "normal" times, but suddenly become the only thing that matters for survival. Assuming that the rest of the genes of these survivors are more-or-less independently distributed, then normal day-to-day evolution will continue to weed out "bugs" in the rest of these genes which are more common, while the one or two features that provided survival at the bottleneck are now shared by *all* of the remaining population.
For example, essentially all humans have 5 fingers on each hand. This is quite bizarre, as under "normal" circumstances, having 3,4, or 6 fingers would seem to provide about the same survival advantage as having exactly 5 fingers.
Suppose that there was a population bottleneck where survival depended upon have *at least* 5 fingers, and all of the survivors had 5,6,7,8, etc. fingers. More normal evolutionary pressures might then have eliminated those individuals having more than 5 fingers, but the gene pool as a whole would "remember" vividly the bottleneck event which wiped out everyone having fewer than 5 fingers.
Note that these population bottlenecks don't have to happen very often. Indeed, it is estimated that the last great bottleneck for the human race was perhaps 70,000 years ago. Exactly which features enabled survival in that bottleneck isn't known, but whatever it was, this feature was clearly was a *rare* feature that suddenly became crucially important for survival.
This means that really understanding evolution is going to exceedingly difficult, as some of the most important events are also the rarest events.
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participants (4)
-
Brent Meeker -
David Makin -
Fred Lunnon -
Henry Baker