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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: 4, Insightful) by requerdanos on Friday November 09 2018, @02:09PM (23 children)
What do we want? Time Travel!
When do we want it? Oh, it doesn't matter all that much, any one time would be as good as any other.
But this is just a footnote to chaos theory [logosconcarne.com], which contains your answer:
Try again with a million slightly different starting conditions: Gives a million different results.
Replay the tape with the same starting conditions: You watch exactly the same thing every time.
It's a tape. That's how they work. Have you ever watched a tape that had different endings randomly? No. The Titanic sinks, Jack dies, every time. Same ending, without fail. That's what "replay the tape" means. To get a different ending, you have to play a different (section of) tape.
(Score: 2, Insightful) by khallow on Friday November 09 2018, @02:17PM (2 children)
(Score: 4, Interesting) by HiThere on Friday November 09 2018, @05:35PM (1 child)
I'm sure you could get things as similar as an ichthyosaur is to a dolphin. Anything much closer to any particular existing species would be unlikely.
Remember, chaos theory doesn't have quantum mechanics at its base, but chemistry does.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 1) by khallow on Sunday November 11 2018, @06:14AM
I think a far portion of the time, you'd get something that wasn't even DNA-based cellular life. It'd be amazing to get something as similar as an ichthyosaur to a dolphin.
(Score: 2) by c0lo on Friday November 09 2018, @02:29PM
In a restricted system, with some good percentage of configuration impossible (e.g. dead end by extinction), the "surviving systems" will show differences, but the differences may not be large enough for the system to look absolutely unrecognisable.
Have the Lorenz attractor as an example [wikipedia.org]
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 0) by Anonymous Coward on Friday November 09 2018, @02:32PM (1 child)
Magnetic tape? Fucking magnets, how do...
(Score: 2) by requerdanos on Friday November 09 2018, @02:36PM
Sadly, he will never find out how magnets work, judging by the next two lines:
(Score: 3, Insightful) by MichaelDavidCrawford on Friday November 09 2018, @02:43PM (16 children)
While evolution takes the path of increasing the survival of the fittest, what actually causes the genetic change is often background radiation - cosmic rays from the sky, the products of radionuclide decay from the ground.
Also breathing radon.
It would be exceedingly unlikely for the same base pair to get ionized again were we to try to reply history.
Yes I Have No Bananas. [gofundme.com]
(Score: 3, Touché) by requerdanos on Friday November 09 2018, @02:55PM (10 children)
Well, if you replayed history, you would be replaying cosmic rays from the sky, the products of radionuclide decay from the ground, and breathing radon, because they're part of history.
If you only replayed part of what happened, with different conditions everywhere else that influence the result, then you get... different results.
According to a fictional chaos theory expert, "Life finds a way", but in this case I'm not too sure.
(Score: 2) by MichaelDavidCrawford on Friday November 09 2018, @03:18PM (6 children)
-ic.
TFS stated that chaos theory requires identical inputs to have identical results. While some particle interactions will have the same results, many of them won't. Just making the original particle trajectories identical won't make the reaction products identical, it is random.
Not well-understood is that the _distribution_ of reaction products is systematic. That is, if you carry out the interaction enough times, the reaction products will converge to a systematic distribution. For example scattering a photon off an electron onto some photographic film will always produce the same overall image - but microscopic examination of the exposed spots will reveal different speckled patterns.
Yes I Have No Bananas. [gofundme.com]
(Score: 2) by Arik on Friday November 09 2018, @04:04PM (5 children)
Not saying I believe that's true, but I think it explains why Quantum Physics continues to be pretty much ignored by most people. It really does turn the world upside down, if particle interactions are non-deterministic, yet the world that we interact with seems to be extremely deterministic.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Friday November 09 2018, @06:46PM
I think it comes down to the law of large numbers, if you average out enough randomness, you tend to get something that looks predictable.
However, with evolution being driven by mutations (and conditions), and mutations being done at the molecular scale, I think it likely that you end up with race conditions. That is, evolution will go in direction X, unless something makes X bad before it can evolve.
(Score: 2) by MichaelDavidCrawford on Friday November 09 2018, @06:48PM (3 children)
If you repeat the experiment enough times the average of all the results asymptotically approaches deterministic.
The number of particles we can see with all but the very most powerful microscopes is so great that whatever we look at, it's quite close to determinism - but it never really gets there.
There has long been a suspicion that "Hidden Variables" we cannot see cause affects that seem random but really are not if you can examine these hidden variables. However there have been lots of experiments that cannot be explained by hidden variables.
Yes I Have No Bananas. [gofundme.com]
(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?
(Score: 2) by mhajicek on Friday November 09 2018, @03:22PM (2 children)
It depends on whether quantum phenomena are random or deterministic.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by requerdanos on Friday November 09 2018, @04:09PM (1 child)
That quantum phenomena occur with probability instead of certainly is a good point.
I believe that it's an open question as to whether the progression is (primarily) a macroscopic or quantum phenomenon, that is, whether it is dependent upon newtonian rules, or spooky ones.
(Score: 2) by mhajicek on Friday November 09 2018, @05:58PM
As I understand it, in the probabilistic model, every time an atom or particle radiates a particle the direction is random. That means radiation from the sun will have a different pattern every time the "tape" is run, and each DNA strand will be subject to different mutations.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 4, Touché) by HiThere on Friday November 09 2018, @05:39PM (3 children)
You're missing half of evolution theory. You get random variations generated that way, but selection cuts off the ones that aren't sufficiently optimal. Sometimes that means almost optimal isn't good enough. Sometimes it means even optimal isn't good enough. And sometimes the selection is loose enough that several variants survive.
That said, it won't end up being the same, but it's likely to have lots of similarities due to functional constraints.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by bart9h on Friday November 09 2018, @08:16PM (1 child)
The book The Vital Question -- Why Is Life The Way It Is? [wikipedia.org] argues that many important traits of life (as we know it): sexual reproduction, two different sexes, programmed death (by old age), the balance between fertility and immunity to diseases (can't choose both); are all somewhat inevitable, and if there is life elsewhere in the universe, it must have the same fundamental properties, and share these same traits.
Good read, if a bit heavy on the technical side. I highly recommend it.
(Score: 2) by HiThere on Saturday November 10 2018, @01:43AM
Perhaps I'll look it up. (I'd probably need to buy a copy to read it, so this isn't certain.)
OTOH, bdelloid rotifers call into question the inevitability of sexual reproduction. Most theories of why sex say that they should have gone extinct long ago...but they're still around, and fairly numerous (at least in number of "species", the source I read didn't give estimated counts or mass).
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Insightful) by Lester on Saturday November 10 2018, @11:50AM
There are ten eggs in a nest, one has a really good mutation, a mutation that happens 1 in a billion. And then a lizard eats that egg just because it was a few cm closer to it. That mutation is lost forever
Think of a tree where there are multiple branches in each level, some with more probability that others, but nobody guarantees that the one with more probabilities will be chosen, just the best has more chances. Multiply it for the billions of beings in 3.5 billions of years and you are nobody knows where.
(Score: 2) by maxwell demon on Friday November 09 2018, @07:14PM
If you forget to rewind the cosmic environment together with life on earth, I'll predict a rather large deviation in the course of evolution about 65 million years ago.
The Tao of math: The numbers you can count are not the real numbers.