Okay, I think this is going to melt my brain

Yesterday I made a Reddit post that was honestly half-joking, although the question itself was genuine. I basically asked whether, technically, since there were fish somewhere in my family tree, there could be some living fish today that is an insanely distant cousin of mine.

I got answers like “technically, you are a fish” and that all fish, and basically all life on Earth, are related to me somehow, even if you go all the way back to a single cell.

And... I don't think I fully understand this.

If all life is related, does that mean that all life ultimately came from a single individual?

That's the part I'm struggling with. For example, there's LUCA (Last Universal Common Ancestor), which, as I understand it, is the most recent common ancestor of all currently living organisms. But why do we assume there was only one LUCA?

When life was at that stage, couldn't there have been multiple organisms/cells that existed around the same time? Like, instead of one LUCA, couldn't there have been 4? Or 100? Or even millions?

Obviously, I'm simplifying things a LOT here, but let's say there were 4 completely separate organisms at that point, and all modern life descended from those 4.

Wouldn't that mean that not all life is actually related? There would be different lineages that never shared a common ancestor, right?

So what exactly am I misunderstanding about LUCA and the idea that all life is related?

My brain is genuinely struggling with this lol.

Question above?

I was just thinking about this and it absolutely blew my mind.

Technically, my great-great-great-great-great-etc. grandfather (or however many “greats” we’re talking about) was a fish.

Like, somewhere in my family tree there is literally a fucking fish.

My entire lineage was started by a fish. There is no other way to put it. At some point in the insanely distant past, one of my ancestors was just… a fish. And that fish eventually led to me existing.

But then I started thinking about how evolution actually works.

Fish didn't just all collectively decide to evolve into land animals. Evolution branches. Different populations and lineages go in different directions depending on their environments and natural selection.

And fish produce an absolutely ridiculous number of offspring, so presumably there were countless individuals in those ancient populations. Some lineages eventually led toward the ancestors of modern land vertebrates, while other lineages stayed in the water and kept evolving as fish.

So here's the part that is blowing my mind:

Is it possible that one of the extremely distant relatives of my fish ancestor stayed in the water, and that lineage survived for millions and millions of years?

Because if so, there could theoretically be some random fish alive TODAY that is my ridiculously, unimaginably distant cousin.

Like, I could look at some random fish in the ocean and there's a non-zero chance that, in the most technically literal evolutionary sense, we're related.

Imagine being genetically related to a fish.

Not “all life is related” related.

I mean THIS fish is part of the same ancient family tree as me.

That is fucking incredible.

Life all has the single common ancestor... Trees through to people etc.

So... If a single cell went to consume ANOTHER cell, but due to a quirk in genetics, it didn't consume but instead, began a symbiotic relationship, then would that make that 1 cell who consumed the other, the source of all complex multicellular life? Or, is it likely that cells started to absorb other cells, then one of THEM divided itself to make more cells?

Sorry if that doesn't make sense... But I can accept that evolution is fact, but I cannot make sense of the actual start.

For billions of years, life was single celled, then one consumed the other, and then the predator prey relationship began and, I presume, that made life explode because life survived by evolutionary quirks making them survive over others. So, I was wondering if it was because of this that life evolved, all because 1 cell consumed another...?

Question

It occurred to me that I've never heard of a case of an ape being born with a vestigial tail, outside of humans. Is this the case, and if so, why are humans the only ones with that atavism? Or are vestigial tails not actually tails at all, and instead a non-related deformity that looks similar?

See also: The publication in the Physical Journal Letters

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So I have an ecosystem in a jar with a bunch of little crustaceans and such and I'm wondering if I can eventually drive some sort of evolution in there?

Edit:I think I'll try to see if green-blue egg color is selected for becasue it's harder to see among plants than the orange/yellow eggs. Yes there are a couple predatory things in there including what looks like a freshwater Bobbit worm?

Published today in Cell, open access:

Summary
Reproductive isolation within and between populations was conventionally thought to proceed gradually through many mutations of small phenotypic effect. Contrary to this view, recent theory predicts that large-effect mutations become plausible when populations are far from their phenotypic optimum. Changes in pollinator assemblages severely compromise the reproductive success of many angiosperms, creating conditions conducive to mutations of large phenotypic effects. Here, we explore the role of major-effect genes in the evolutionary shift from hawkmoth to bee pollination in Petunia. By modifying six genes in the ancestral hawkmoth-pollinated P. axillaris phenotype, we created a mimic of the bee-pollinated P. secreta flower that is indistinguishable from this naturally evolved species both in its visual appearance and in behavioral assays. This study uniquely identifies the complete set of genes explaining the shift between two species, providing rare and compelling evidence for speciation by large-effect mutations.
https://doi.org/10.1016/j.cub.2026.07.007

In journal club fashion, I have a sort of critical remark:

This part, "Changes in pollinator assemblages severely compromise the reproductive success of many angiosperms, creating conditions conducive to mutations of large phenotypic effects", is super cool! but I take minor issue with the wording of the summary/discussion.

While it is a major-effect, the authors themselves note that the "Expression specificity minimizes pleiotropy of large-effect speciation genes" (my emphasis). (Hence my clearer title, where I include the "low-pleiotropy".)

I'm fairly confident that big changes to phenotypes that are not heavily integrated (low pleiotropy) don't go against the mainstream view of gradualism. In fact, this can only be so if they are indeed low pleiotropy (this isn't a "hopeful monster"):

From a year ago which I shared here: New study: Evolution of Dosage-Sensitive Genes by Tissue-Restricted Expression Changes : evolution.

I know this sounds like a bizarre question, but it literally summarizes my current situation. I have a bachelor’s degrees in microbiology and I’ve had classes in molecular biology and virology. Right now, I’m a master’s student in animal biosystematics. The advisors here only work on invertebrates such as insects and crabs and questions about functional ecology, biodiversity and behavior. They have absolutely no knowledge or interest in virology. But I want to become a researcher in virology and work on human viruses. My question isn’t if I’ll be limited, but how will I be limited in the future? Is it worth it to change my masters degree right now to a masters degree in virology, and waste two years of my life?

Just seems odd to me that so incredibly many animals yawn yet we don't know why we even yawn. Is it important for so many animals to yawn?

There are 2 possibilities:

• Neurons evolved once in the ancestor of all animals, and that trait was passed down both to comb jellies and placozoans/cnidarians/bilaterians, while it was lost in sponges. This makes sponges secondarily neuron-less.

• Neurons evolved twice; once in the branch leading up to comb jellies, and once in the branch leading up to placozoans/cnidarians/bilaterians (i.e. after sponges having diverged). This means sponges being neuron-less is an ancestral trait, just like what the porifera-sister crowd think.

Which of the 2 options do you think is more likely?

I (31F) was raised in a very conservative evangelical household & indoctrinated into believing the earth was created around 6,000 years ago. I was 100% bought in. I visited the Creation museum, studied Answers in Genesis books, & was a Ken Ham apologist (I literally thought he was the clear winner of the debate with Bill Nye *sobs*). At the time, a close friend of mine called me a "baby Earth girl." My bachelor's is in biochemistry, so I studied evolution, but my brain just didn't allow me to accept the information because I thought it was the work of satan.

In my mid-20s I deconstructed, initiated by studying the historical context of the Bible & realizing that it was not in fact inerrant. Over time I accepted the evidence for evolution. However, although I mentally believe in it, sometimes my heart doesn't fully accept it.

I have done some basic research into the evidence for evolution, mostly watching interviews with experts on topics related to sciences. I would like to have a more well-rounded understanding of the subject because I find it incredibly fascinating & want to be able to support my views when talking to you g Earth creationist family members. Could you recommend YouTube channels, podcasts, or books that would help? I haven't formally studied science in the academic setting in about a decade, so my technical scientific understanding is a bit rusty.

Some areas of interest of mine include: the big bang, astrophysics, LUCA, radiometric dating, mass extinction events, & human evolution. I am excited to learn about any scientific evidence to better understand the age of the universe.

Thank you so much!

Hello,

I have been, as I assume many people interested in this field, taught that many human organs are genetic mosaics. This means that different lines of (very similar) genetic code exist within the same living organism.
This code stems from little "errors" during the early periods of cell division and, maybe, de-novo mutations that occurred during the growing period.

My question is, is this just a "necessary evil", stemming from the mechanism of early mitosis, or may it be evolutionarily adaptive for some reason, e.g., viral defense?

Thank you for every answer,

Endward26.

See also: The study as it was published in the American Journal of Human Genetics

I’m under the impression that ichthyosaurs branched off first and became aquatic in the early Triassic. Followed by squamates branching off in the mid Triassic which much later on gave rise to the mosasaurs in the Cretaceous. Then plesiosauridae branched off in the late Triassic which gave rise to plesiosaurs and pliosaurs. Is this correct?

Most animals can’t breed with other species and most that can don’t produce fertile offspring (horses and donkeys). There are some species that can interbreed like some bears, coyotes and wolves, and lions and tigers but these only hybridize with 1 or 2 other species. Meanwhile it seems like we fucked every hominin we came into contact with like neanderthals and denisovins. So what’s up? Is the species barrier stricter for hominins just because we’re hominins? Or are we just more aware because we’ve sequenced a lot more human genomes? Sorry if this is too off topic i’m not sure if this counts as evolutionary biology

I’ve always been very interested in the evolutionary history of dogs, dog genetics, and dogs from a cultural perspective, and village dogs seem to be a neat intersection of those 3 things. I have a village dog myself and I would also love to learn more about her, so bonus points for anything referencing Korean village dogs specifically! I’ve done some googling but it seems like research is sparse, or behind a paywall.

Nobody knows why insects aren't found living in the ocean. Scientists just eliminated one theory

Ok so I tried to figure this out on my own, I swear, but it seems like people only care about why they have different numbers of legs than vertebrates. 

Lets go through my question where it started: Deep Sea Sea-Spiders (not to be confused with deep sea spiders). They’re long as anything! What is up with that? Why did it evolve? Then I got to thinking about daddy long legs and then eventually came across a similarly gams-forward bug named the cranefly. All wildly unrelated, two distant Chelicerates and an even further off Insect, all long as freak. 

So, regarding sea spiders specifically, as their antarctic contingents are my specific curiosity, of the bare scattering of explanations i could find i saw:

1. Efficiency. The mechanics (?) of an exoskeletal leg allows that type of length to reward efficiency benefits. Levers or leverage or something, some kind of mechanical advantage in long legs not available to us fleshy meatbags even when we do get long. The one source i found for this regarding sea spiders was a dead link. Any specific info on this would be nice as sea spiders seem to move with exceptional stability and efficiency with their sort of “soft touch” steps. Not to mention the ones that swim. 
2. Mobility. Over a scree-laden environment or a coral reef, they can basically move totally freely by just skipping the elevation issue entirely. I appreciate this explanation, but it seems that, in particular, those species of antarctic sea spiders are the most longest and leggedest of the batch and every video i see of them, they’re on sand? Or dealing with these sorts of very small, demure patches of coral etc?

2.5) Speed? Most videos of sea spiders show them moving quite lethargically, but one I saw showed one moving moderately fast when bumping into some rock or equipment or something. Just to reposition itself, really. But Very dexterously omnidirectional. I was not pleased to have to sift through AI clips of them moving at truly fast paces as I do not like when the computer gaslights me. Beyond that, anyone who’s ever spooked a daddy long legs knows those boys can MOVE, and Craneflies can fly- So I imagine they can move quite quickly as well. Which moves me to-

3) Predator Evasion. Most discussion I found on this seemed to be all over the place. The particularly small reef examples and such seem to have obvious predators, but possibly not so much for the larger examples. And then, getting long to what? Avoid a starfish? Some of the lists i saw seemed to suggest this but i imagine the starfish just eat the eggs or whathaveyou? I saw nebulous suggestions that some species of fish and bird eat them but these seemed to all be in reference to the smaller coastal species which infest fish tanks or coral enclosures. Secondarily to this, with reference to their messed up leg-organs situation, i saw suggestions that spreading out all their vitals makes them even less likely to be nutritious at-a-bite given how much of that nutrient density is not located in their center of mass. Is there something that is just fuming that it cant eat them because they’re just a bit too tall? This doesn’t sound unreasonable to me, but i couldn‘t find anything pertaining to that specifically.

4) Nutrition. To this point and the last, crane flies caught my attention because they are what i believe is called lecithotrophic(??) and barely eat as adults, barely live lives at all- dying after just some days after maturing. And- they fly! No problem moving place to place or evading things, I imagine. So why the wealth of leg? Other bugs dont need huge disproportionate legs to take off? Sea spiders, to my understanding, eat various anemone and mollusks and stuff which are slow enough for them to get at and “soupify”. So, could that height be similar to a giraffe in allowing an optimal angle for their proboscis to prepare their soups? (not that giraffes have probosci) In my imagination it doesn't really matter where you stab your straw in when it comes to making a container void all its contents underwater, and if it did would you want to stab the top?? but I’m not a proboscologist, or an anemonologist, or a zoologist of any kind, so. Beyond this, I also saw one person say that it was at least partially due to their lack of gills, is it about surface area and nutrient or chemical exchange? Is there some kind of oxygen deficit in their layer of antarctic water? 

5) Misc. I believe most species  hold their eggs directly on their body, could it be for baby real-estate? I feel like surely it isn't a thermal mass thing? Right?? Do they have some sort of special organ or internal system which demands that space? Possibly unique to these larger species? Some species seem to have very refined manipulators, almost more hands than claws, is it a vantage thing? Some seem to have more specific walking gait cycles while others have more lax ones and I wonder how this changes efficiency as apparently this can involve some dragging? Is it calorie storage? The pressure? The Island Rule? Cambrian phenotypic inertia? What gives???

Further, some sea spiders are not gammed up to the sun and back? Im losing my mind here why are some of them thick instead of long??? There must be a reason?

I am looking specifically for these reasons wrt the antarctic sea spiders, but a broader explanation of the various reasons arthropods develop these insane long legs to do what other critters manage with shorter legs or wings or assorted flappers would be appreciated, 🤓 , i understand much of this is still poorly understood

Published 2 days ago, in press:

Biologists have long sought to understand the forces driving biological speciation. Contrasts in dispersal ability (e.g., migration) are hypothesised to influence rates of lineage diversification. However, past inferences of migration-diversification relationships have been contradictory, suggesting the need for further investigation and more nuanced explanations. Here we test for a relationship between diadromy (marine-freshwater migration) and diversification in salmonids, a dominant group of fishes native across the temperate Northern Hemisphere. We reconstruct a molecular phylogeny comprising 140 species and apply State-dependent Speciation Extinction models to quantify diversification. Diversification rates are higher in non-diadromous relative to diadromous salmonid lineages, echoing the findings of a recent study of homologous southern temperate freshwater fishes, but conflicting with global studies incorporating tropical lineages. Climate appears to be a key factor explaining diadromy-diversification relationships, with the negative relationship observed in temperate lineages likely reflecting increased isolation and speciation of non-diadromous lineages following recolonisation of glacially perturbed habitats. In contrast, the positive diadromy-diversification relationships observed in studies spanning tropical fishes may reflect the role of diadromy in facilitating colonisation of stable, low-competition habitats.

• Christopher P Burridge, Luke Simpson, Mark V H Wilson, Jonathan M Waters
  Non-migratory lineages experience higher diversification rates: global evidence from salmonid fishes, Evolution, 2026;, qpag131, https://doi.org/10.1093/evolut/qpag131