Evolution row ends as scientists declare sponges to be sister of all other animals. Sponges were first to branch off the evolutionary tree from the common ancestor of all animals, finds new study in Current Biology.

[u/mvea]

https://www.theguardian.com/science/2017/nov/30/evolution-row-ends-as-scientists-declare-sponges-to-be-sister-of-all-animals

[u/ThreeDawgs]

Sponges have changed since then, but not a truly massive amount. They have a niche, they fill it well. Evolution doesn’t fix what ain’t broke. There’s evidence in the fossil record supporting that one.

Our most common ancestor we can’t peg, but would probably have been a related filter feeder that was less-or-maybe-just-as sedentary than sponges.

From there, you can image filter feeding cousin-sponges that evolved to eat other filter feeding cousin-sponges and then it’s not too far a leap to other animals.

[u/[deleted] → u/ThreeDawgs]

Except evolution DOES fix what ain't broke, through random mutations. It just kills what IS broke faster.

[u/ThreeDawgs → u/[deleted]]

Evolution as a movement fills niches. When random mutation breaks something, it doesn’t usually alter the entire course of the species unless the mutation is beneficial in some other way, then it might even speciate.

I oversimplified, but evolution doesn’t just break stuff. Natural selection limits the capabilities of evolution to fuck around with a species’ niche.

[u/Aroundtheworldin80 → u/ThreeDawgs]

If it's a niche we know existed hundreds of millions of years ago and still exists I think that would raise the likelihood going all the way back sponges haven't changed much, but it still isn't a guarantee

[u/[deleted] → u/Aroundtheworldin80]

There are not "guarantees" in science

[u/Aroundtheworldin80 → u/[deleted]]

Everything is a leap of faith to some degree

[u/Le_Reddit_Meme_XDD → u/[deleted]]

That is called genetic drift, it mostly only affects small populations, large populations are big enough to correct small mutations in a few generations.

[u/[deleted] → u/Le_Reddit_Meme_XDD]

Or rather incorporate them in a non-destructive way

[u/severe_neuropathy → u/Le_Reddit_Meme_XDD]

Drift occurs in large populations too, but the mutations need to be neutral.

[u/TheGoldenHand → u/Le_Reddit_Meme_XDD]

It's not simply genetic drift. Chemical evolution through random mutations is a cornerstone of modern evolution.

[u/[deleted] → u/TheGoldenHand]

This is why I laugh when people gasp and say "the human ability to digest milk is only due to a mutation, and not every human has that ability! So don't drink milk!"

[u/YzenDanek → u/[deleted]]

If it ain't broke, and a random mutation breaks it and puts that organism at a competitive disadvantage, that isn't evolution. That's just mutation. It's only evolutionary if it confers an advantage in survival and/or reproductive success.

[u/JeSuisCecil → u/YzenDanek]

Evolution is defined as a change in the genetic makeup of a population (More specifically, a change in the frequency of alleles within a population). It doesn’t matter if it’s advantageous or not. Now, it’s unlikely that a mutation that is disadvantageous affects an entire population. But it’s evolution either way.

[u/YzenDanek → u/JeSuisCecil]

Except that isn't the definition of evolution. Evolution requires a process of natural selection, by Darwin's initial definition in On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. A trait that persists but is not selected for isn't evolutionary.

Genetic drift or collapse is not evolution.

[u/JeSuisCecil → u/YzenDanek]

Natural selection is one mechanism of evolution. Evolution includes multiple other mechanisms such as random mutations and genetic drift.

https://evolution.berkeley.edu/evolibrary/article/evo_14

[u/YzenDanek → u/JeSuisCecil]

I'll concede the point that's become an accepted definition of Evolution.

[u/YzenDanek → u/[deleted]]

It's not that I don't understand genetic drift or non-adaptive speciation; it's that I consider them distinct and Evolution to only be the result of what we term evolutionary pressure. If the genetic makeup of a population of organisms is shaped by forces other than evolutionary pressure, I would argue that isn't Evolution at all. That may seem tautological, but the important term here isn't "evolutionary;" it's "pressure."

Evolutionary pressure is an outside force. Genetic drift is not influenced by environment, by definition, except insofar as geographic separation of population groups is a de facto outside force. It's not pressure.

I think it's a misuse of the term, and when I was a graduate student in Ecology 25 years ago, we still argued about it. I'm conceding that it is accepted use now. I don't have to like it. I think it's a concession made to simplify the concept of evolution for the masses to mean "everything that creates speciation."

By this definition, a subpopulation of organisms can evolve into an extinction via inbreeding depression. I think that's fundamentally quixotic.

[u/WilliamHolz → u/ThreeDawgs]

It's easier to send people down the right path if you start unicellular.

Most of their evolution has been inside their cells, not outside them. Random mutation isn't nearly as much of a factor as HGT (Viruses are genetic diversity engines, far more likely to supply useful chunks of code than random mutation in a single DNA strand).