TagliatelliMonster
Veteran Member
Concerns with the morphological discontinuity/sudden jumps in the fossil record were already identified by Ernst Walter Mayr (Mayr was one of the 20th century’s leading evolutionary biologists who was called “the Darwin of the 20th century”). Then the prominent paleontologists Eldredge and Gould confirmed the stasis in the fossil record (The state of no morphological change for most of the geological history) followed by sudden jumps, which gave rise to their punctuated equilibrium theory that proposes rapid events of cladogenesis. Eldredge and Gould confirmed that the gradualism attributed to Charles Darwin is virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species. Mayr later complimented Eldredge and Gould's work and stated that stasis had been "unexpected by most evolutionary biologists"
This was unexpected back then. It is very well understood today.
Also, PE is still gradual. The type of gradualism that PE disproved was the idea of a constant trend of gradualism instead of more "burst like". Before PE, they assumed a constant rate of change through time.
PE has shown us that this rate isn't constant through the ages. It slows down, speeds up, slows down, speeds up, etc. But in both cases (slowed or speed up), change still occurs gradually.
Today PE is very well understood and explained. And it is also very easily demonstrated using a genetic algoritm. Even with a very simplistic one like this right here:
HTML5 Genetic Algorithm 2D Car Thingy - Chrome recommended (rednuht.org)
The original one in flash was a lot better though, but flash is no longer supported. Hopefully the devs will expand on this new one to make it better cause it was loads of fun.
Anyhow..... let's just summarize what PE is about.
It is the simple idea that in periods of environmental stability, species close in on their "local optimum". Meaning that they become so specialized in the niche they live in, that evolutionary processes can no longer offer "easy" pathways towards further improvement. The closer to the local optimum, the more Natural Selection will favor the status quo. The amount of potential beneficial changes will become smaller and smaller.
When a significant change then occurs in the environment, the local optimums shift.
This change can be anything. A meteor impact. Climate change. A desease going rampant. A geological event. Anything that stirs up the balance of an eco system really.
Now, natural selection no longer favors the status quo. The amount of potential beneficial mutations (= mutations that get you closer to a local optimum) goes up. So the rate of change in the population (evolution) speeds up.
But how those changes spread in the population and achieves fixation, doesn't change. It's still gradual. Natural selection selects changes, they are inherited by off spring and so spread throughout the population over generations. Gradualism.
We can easily see this in action in that genetic algoritm I linked.
Leave it open for say 30 minutes (and click "surprise" so that it fast forwards without playing the animation).
You'll see that the top performers will have reached some local optimum. The properties of the top performers will exhibit very little change for the generations to come.
Now introduce an impactful change. In that example, all one can really do unfortunately, is change the gravity. The default setting is earth's gravity. Now put it on Jupiter. Wait another 5 minutes. You'll see noticeable change in the design of the top performer now. Then it will again reach its local optimum for the "new" environment, with little change for the generations that follow.
Now put it on the gravity of the moon. Wait 5 minutes. Now you'll notice BIG change in a short time. And once again it will settle in a new local optimum.
PE in action. It's not rocket science.
In the original version in flash, we would be able to take the population and put it on an entirely different track. For example one that had movable obstacles and alike. That was great. You could first have race cars evolving on relatively flat tracks and then put them on the obstacle one and pretty soon, those race cars would change in snowplow-like trucks allowing them to "scoop" the obstacles away. lol
Last edited: