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from the only-if-Betteridge-is-not-on-it dept.
How predictable is evolution? The answer has long been debated by biologists grappling with the extent to which history affects the repeatability of evolution.
A review published in the Nov. 9 issue of Science explores the complexity of evolution's predictability in extraordinary detail. In it, researchers at Kenyon College, Michigan State University and Washington University in St. Louis closely examine evidence from a number of empirical studies of evolutionary repeatability and contingency in an effort to fully interrogate ideas about contingency's role in evolution.
The question of evolution's predictability was notably raised by the late paleontologist Stephen Jay Gould, who advocated the view that evolution is contingent and unrepeatable in his 1989 book Wonderful Life. "Replay the tape a million times ... and I doubt that anything like Homo sapiens would ever evolve again," Gould mused, noting that being able to "replay the tape" and give history a do-over would be impossible. Yet since the publication of Wonderful Life, many evolutionary biologists have taken up this challenge and conducted their own versions of Gould's experiment, albeit on smaller scales. In doing so, they have reached different conclusions about the interplay between randomness of mutations, chance historical events, and directionality imparted by natural selection.
[...] Their review of comparative studies of "natural experiments" further illuminated evidence of evolution's predictability. Similar features can independently evolve in multiple species—for example, anole lizards of the Caribbean, which separately evolved traits such as the length of their legs and tails to ease their life in their specific habitats. Yet convergence in evolution does not always occur, as their review shows; contingency can play a strong role in divergent evolution of various traits.
Replaying the tape of life: Is it possible?
[Abstract]: Contingency and determinism in evolution: Replaying life’s tape
[Source]: IS IT POSSIBLE TO REPLAY THE TAPE OF LIFE?
(Score: 2) by Arik on Friday November 09 2018, @07:58PM (2 children)
And this is exactly what we would intuitively expect if our constraints are simply not precise enough, either in the sense of say constraining to 8 decimals when 12 is required, or perhaps as you mention a 'hidden variable' that has not been identified at all.
"However there have been lots of experiments that cannot be explained by hidden variables."
Can you name one?
If laughter is the best medicine, who are the best doctors?
(Score: 2) by MichaelDavidCrawford on Friday November 09 2018, @09:12PM (1 child)
If you have a hot filament that gives off light, then passes through two vertical slits, eventually to strike a photographic film, there will be a pattern of light and dark fringes on that film if you let the experiment run long enough.
Any effort to determine which slit the photon went through will destroy the fringes.
It happens that I spent five months, one hour per week discussing this with Richard Feynmen Caltech. I used to be heavily into the Newtonian idea of the Clockwork Universe.
What finally convinced me was that Dr. Feynman pointed out that this same experiment can be done with electrons if its in a vacuum. If you reduce the the filament's positive voltage so that there is measurable time delay between each electron emitted, you can measure that time interval by measuring the filament's voltage. A phenomenon called Shot Nose will result in an abrupt drop in voltage, which goes quickly back up to the normal level.
You can do things to measure the passage of electrons, such as by placing capacitor plates on either side of the path between the filament and the slits. Actually using that capacitor destroys the fringes.
I have to admit it's been thirty years since I studied this, so my memory is quite hazy, but if you want to come up with an objection I'll do my best to answer it, as I would enjoy brushing up on this stuff.
Yes I Have No Bananas. [gofundme.com]
(Score: 2) by Arik on Friday November 09 2018, @09:49PM
And I think you're right - we can't explain those results by appealing to sloppy measurements. Something else entirely has to be going on here.
However, this really brings us back to an old scientific problem that was never properly /solved/ in a way that many feel satisfying.
That question is what is the nature of light? Is it a wave or a particle?
If it's a particle, we expect it to be as deterministic as our bullets are. If it's a *wave*, however, we expect waves to do things like this. Waves of different frequencies can reshape each other in all kinds of shocking and unexpected ways.
As best I recall my history of science, the ultimate outcome of the debate over this question was something like "it's both a particle and a wave, depending on how you measure it."
I don't claim to have ever fully wrapped my mind around exactly what that means, but it sounds to me like something very similar to imprecise measurement, if not exactly the same. After all, waves are always composed of particles, at some level - waves in the ocean are composed of molecules, mostly H2O but with lots of minorities represented.
But all of them are particles and they have viscosity and experience common movement, and those two qualities together make them behave in ways that are extraordinarily difficult, if not utterly impossible, by reference to their particles as particles alone.
If laughter is the best medicine, who are the best doctors?