Is Evolution Gradual or Punctuated?

Hi @T.j_Runyon,
Thanks for your candid summary.
Looking forward to your story.
I am skeptical about 3 and think an intelligence is required to explain this change.
As to 2. I feel it’s an outdated concept that lost its relevance. I think Common ancestry has explanatory value only in a gradualistic scenario…

What is your take on gradualism… do you subscribe to a gradual continuous evolution or something along the line of punctuated equilibrium?

I see people often speak of gradualism without ever defining it. its always misunderstood. So I need to know how you are defining it

Change happening continuously over time in a step by step (graded) manner.
As opposed to the idea that change happens in bursts with long periods of stability in between (punctuated equilibrium).

Your knowledge of latest in evolution theory is lacking. Why not let a real expert help T.J. - Dr. Swamidass himself.

The term “gradual” can mean different things. For some writers, it means “very smooth”, but another meaning is “stepwise”. We can see this in e.g. the terms graduation, graduated cylinder, etc. – these are referring to discrete steps. Similarly “gradations”. Considering that the raw material of evolution is mutations, at some level, everyone should agree that evolution is fundamentally a stepwise process, not perfectly smooth. The interesting argument, then, is more about how big are the steps.

If one reads Darwin’s works carefully, you will often see this “stepwise” interpretation is the better one, even if the steps are small. And even “large/small” is a relative thing. E.g. long before the Origin of Species, Darwin discusses seeing an earthquake in Chile that lifted the coast a meter (or several meters, I forget). He then assembles evidence that this process has, “gradually”, raised up the Andes so they are thousands of meters high. Most people wouldn’t think of earthquakes as a “gradual” process, but from a deep-time perspective, they are.

Punk eek isnt really opposed to gradualism. It’s just Mayr’s allopatric speciation applied to the fossil record. It’s not about big changes. A lot of the time it takes an expert to tell the changes apart. Stasis is a real phenomenon and its relatively well understood. Things like population size, body size, and stabilizing selection can all contribute to it. I know some people will point to Prothero’s work on the La Brea tar pits and stabilizing selection and say this rules this out but he only looked at a timespan of 40ky. Among other difficulties. Also, the extent of stasis is also overblown as well. We should expect the pattern we see. If everything happened in a phyletic gradualistic way, life wouldve went extinct a long time ago


Why would you read Darwin to learn about today’s theory of evolution. That would be like asking Alexander Graham Bell, how does my smart phone work.

I was discussing the history of gradualism… Darwin is kind of an important figure in the history of Evo bio wouldn’t you say? @Patrick

Sure Darwin is an important figure but really has nothing to do with today’s theory of evolution. Read the latest popular scientific press on evolution theory. Evolutionary Biology is a rapidly changing science with information doubling every two years. Today’s understanding of what evolution is or isn’t is vastly beyond any insights obtained and published by Darwin.

In science, recent knowledge and information dwarfs previous knowledge very fast.

Does He want to learn about the science of evolution? or does He want to explore the cognitive dissonance going on in his brain from what he has learn about the science of evolution?

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I’ll get to this soon. I’m sure @jongarvey will want to join in :smile:. Turns out the answer, as is the case most of the time biology, is “both.”

Also @T.j_Runyon is a scientist in training, and certainly has insight to offer. I’ve often learned from him, especially because he is a paleontologist, and I am not.

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It’s pretty difficult getting to a truly gradual “GRADUAL” evolution, don’t we think?

When I learned that the influence of mutations continues to increase as a struggling population of a given species becomes smaller and smaller … I thought what an amazing roller coaster it is for a population living on a planet like Earth where the climate and water conditions change eon by eon.

Sure … from the human perspective, eons are long periods… but in geological time … the Earth is a constantly moving target.

Compare this to the fruit fly experiment now into the 70,000th generation … in laboratory conditions that don’t really change much at all.

Changes in the environment is what drives big swings in phenotype…

if so, you are talking about lamarck more than darwin.

As far as i understand, In the evolutionary model,the phenotype needs to be there already before the change gives it a fitness advantage that causes it to become established in a species.

So big swings in phenotype need to be available independent of any change… this is very improbable. This is why, there is a case for gradual or a step by step series of incremental changes which leads to a big change.
only problem being, there doesn’t seem to be much evidence for it.


Ugh, no, of course I am not.

I’m talking about the pure mathematics of how fast a mutation can spread in a dwindling population, compared to how fast a mutation can spread in a large population (especially when ecological factors and factors of competition have not yet changed much).

I was referring to the below comment-

Simple enough. A changing environment makes changes in phenotype advantageous, so when they arise as mutations they spread through the population by selection. No Lamarckism required. The bit about declining population size is probably not true.


In which case, it’s not the environmental change driving the phenotypic change.
At best it fixes several mutations that pile up to give rise to different phenotypes that solve different challenges posed by the environment.
At least that what I understand.

Depends on what you mean by “the change”. If you refer to the mutation, then it isn’t. But if you refer to the spread through the population by selection, then it is. I think the latter is clearly what George was talking about, and that’s what I would say too. The environment drives selection.



Ahhh… now I see why you wrote what you wrote.

I promise I will NEVER EVER use that phrasing again.

Buried in that over-simplification was the idea that environmental changes is what starts killing off the individuals of a given population.

So… it is the stressed population that begins to suffer loss in the size of the population. Which … as I was saying above … leads to a population that is more easily influenced by each individual mutation … whether it be good or bad.

I apologize for not realizing it sounded like I was saying the environment DIRECTLY changes phenotype. I reject that idea… except where it is demonstrated by lab work that environment affects either the transmission of genetic material or the expression of genetic material.

It’s all about the genetic material!

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Yeah, this is probably not an important factor in evolution. Note that the most common fate of advantageous mutations is to be lost within a generation. In a large population, the same mutation will occur more often, given a greater chance that one of them will spread. Both stochastic increases and decreases in frequency are more likely in a small population, and that more or less evens out. A large population is actually more capable of responding to selection than a small one, just because drift is less powerful.

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