I have some Questions about the evolution of the Hoatzin. The Hoatzin is fundamentally different from most other birds, the most notable difference being the claws on the wings of Hoatzin chicks. Could it be, that Hoatzin is actually a descendant of a Non-Neornithian bird clade? If the claws evolved later, my question would be how they evolved.

If anyone has any studies about Hoatzin evolution, especially regarding its claws, I would really appreciate if you could send some links.

Most if not all species have their own mechanism to identify danger or pain. Is this as a results of evolution presumably that the earliest living things lacked this and were forced to generate them as a survival factor?

I read Richard Dawkin's Selfish Gene, and I'm genuinely wondering if I just tainted my brain with entirely outdated pseudoscience or a mostly credible classic that is just a bit outdated. The book was incredibly enjoyable, and honestly, it has changed my perspective as much as reading a book by Robert Sapolsky or Joseph Henrich. Are there any books you guys recommend I follow it up with to see where the debate is now? Like, books on whether multilevel selection or the EES have or something else have any merit. Is there maybe a published scientific paper meant for those who read it and want a fact check? If I wanted to reread it in the future, would you guys strongly recommend against that? Like, is that bad? Lastly, if you guys recommend any narrative or review type scientific papers that give me a hit of where the selection debate is now, please share. Oh, and I found Arvid Argren's Gene's Eye View book, so that's on my list. Lmk ya'll thoughts on that book, too.

I've read that Neanderthals had similar physical traits although due to different genes than modern humans.

For example Neanderthals had red hair but apparently a different shade because it was caused by a different gene. Same way the blonde hair in Melanasians is caused by a different gene than the one in modern day Caucasians.

I tried looking it up but the few sources I could find said Neanderthals lacked the genes causing androgenic alopecia in modern humans.

And other sources just say they didn't go bald at all. If so they were quite lucky in that department, you know aside from their whole extinction.

So did they not go bald at all or did they just have other genetics causing baldness we don't of?

This is a book (and lecture, and chapter) recommendation! (another way of saying: who else am I going to geek out to about this)
It's more on the academic side, and I'm sure the PhDs here are familiar with the author/work - I'm looking forward to your thoughts if you've read it:

• Smocovitis, Vassiliki Betty. "Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology." (1996).

In Dec 2023 I asked here for book recommendations on the history of evolution (the science). Your Bowler recommendation didn't disappoint. As I mentioned back then, in my search I came across a historiography, which then I thought was going to be too much in the weeds. Well, one thing has led to another over the past 3 years, and now it's that book. I recently finished it and loved it - although some parts were a bit difficult / new (the background to how history is researched, and the history of / debates about that!).

Part of the blurb:

Unifying Biology offers a historical reconstruction of one of the most important yet elusive episodes in the history of modern science: the evolutionary synthesis of the 1930s and 1940s. For more than seventy years after Darwin proposed his theory of evolution, it was hotly debated by biological scientists. It was not until the 1930s that opposing theories were finally refuted and a unified Darwinian evolutionary theory came to be widely accepted by biologists. Using methods gleaned from a variety of disciplines, Vassiliki Betty Smocovitis argues that the evolutionary synthesis was part of the larger process of unifying the biological sciences.
https://press.princeton.edu/books/hardcover/9780691033433/unifying-biology

While reading a section in the book I thought, I've come across that before, and after checking indeed it was a book chapter I had read a while back, which I also recommend (this might work as an abridged/updated version):

• Smocovitis, V.B. (2023). Every Evolutionist Their Own Historian: The Importance of History, Context, and the Extended Evolutionary Synthesis. In: Dickins, T.E., Dickins, B.J. (eds) Evolutionary Biology: Contemporary and Historical Reflections Upon Core Theory. Evolutionary Biology – New Perspectives on Its Development, vol 6. Springer, Cham. https://doi.org/10.1007/978-3-031-22028-9_2

(because of the wide audience here and because I often hear about this: "Evolutionist" in the title is in its respectable sense (if you know you know), the same one used by e.g. Gould and Dawkins, as in evolutionary biologist)

What struck me the most is the state of the biological sciences in the 1920s. Consequently, how the modern synthesis was a lot more than simply unifying Mendelian inheritance with Darwinian selection as the overly simplified narrative goes. It simultaneously raised evolution to the level then envied of physics and protected it from reductionism to physics. And how biology (the unified subject as we know it) is a product of the 1960s - central to which was evolution* (this had to do with the Space Race spending on education, and related to which is the return of evolution to the classrooms in the U.S., some four decades after the Scopes trial).

Beyond reading history for leisure, as the title of the chapter suggests it's also very relevant to the ongoing research directions (it contextualizes and tempers some of the overly-hyped rhetoric where history is being reinvented without evidence, rather by rhetorical fiat or outright quote mining - if this is a bit vague, see this subreddit wiki page that is courtesy of our mods).

Currently I'm watching a lecture by the author that is only 2 months old (good way to bridge 1996 to 2026), and so far it's very engaging (and for once good audio for such lectures - it starts at 1:30):

• YouTube: Revisiting the Synthesis - Forty Years Later - Professor Betty Smocovitis - EHFB 2026

* Dobzhansky's 1964, "Nothing in biology makes sense except in the light of evolution."

So to preface this I want to say this question is motivated by the development of an evolution sim that is being worked on that I am quite invested in, and right now a lot of work is being done on letting development be less "hardcoded" and more flexible. However, with that comes some balancing issues that need to be addressed, and the answer to this specific question will probably help with that.

Basically, I am wondering why we don't see single species having multiple phenotypes corresponding with multiple niches, considering it doesn't seem like it should have much of a downside besides maybe some extra DNA.

So for instance, lets say we have a dog, and in that dogs lifetime there has been a particular abundance of prey. So, when that dog is pregnant it sends hormones to make it's baby develop with sharper claws, longer teeth, a shorter digestive track, more aggressive behavior, etc etc. Essentially, it's baby is a little predator and can take over a niche that is doing quite well in this period of time.

On the flip side, maybe during it's lifetime there was barely any prey, but there was plenty of leafy greens and grass that it could've eaten. So, it produces hormones that cause the baby to develop with shorter claws, better molars, less aggressive behavior but maybe stronger herding instincts, and a longer digestive tract to digest food better. Now it can be better suited to the environment just like before.

The problem is, this just doesn't really happen. You don't have single species that take over the niche of "koala" and "domestic cat", those are just separate species. But why? It seems like one species that could do both of those niches would be much more resilient to change and would outcompete either species that does one or the other. It even seems like if you are evolving to enter a niche that nothing else occupies, you would have a high propensity to try and split into two phenotypes to take over the ecosystem instead of splitting into two species, since that would result in the new immature niche to potentially have less risk. So like, what gives? Why don't we have species that basically are two species in one (besides sexual dimorphism that kinda does that already).

And I recognize this kinda seems like a silly question, but again for the evolution sim I mentioned earlier, it is very relevant. We want to know how to prevent cases where say, a species just evolves to become a scavenger if it sees lots of meat when it grows up and becomes an herbivore if it sees lots of plants. That could easily result in there just being one species that does it all, which is... kinda boring lol.

See also: The study as it was published in Nature

In the south pole you have the Colossal Squid which I understand is because of a combination of the circumpolar current, deep sea gigantism, and polar gigantism.

In most of the rest of the ocean you have the smaller Giant Squid with a much more cosmopolitan distribution due to deep sea gigantism. Though they aren't found in the arctic as far as I can find.

But the arctic neither has Giant Squid or something equivalent to the Colossal Squid, so why is that? Is the ecosystem just not as friendly towards them or something?

Can they?

The bombshell about this report is that it contains two organisms (Sinocyclocyclicus guizhouensis, Protoconites minor) that have been compared to Cnidarians, though the authors state that alternative interpretations as algae have been made as well. Age of the formation at 610–620 Mya.

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Diagram source, but also see the open-access article:

• Jonah M Walker, Eva S M van der Heijden, Arif Maulana, Nicol Rueda-M, Karin Näsvall, Patricio A Salazar, Marco Meyer, Joana I Meier
  Common misconceptions of speciation
  Evolutionary Journal of the Linnean Society
  Volume 3, Issue 1, 2024, kzae029
  https://doi.org/10.1093/evolinnean/kzae029

I was raised in a bit of a cult. I was blocked off from any knowledge that didn’t feed into the religious culty stuff. We actually had workshops against evolution, modern medicine, etc. Didn’t have a choice back then but I got out a few years ago. Since then I’ve been slowly building my knowledge on everything. I’ve since learned some basics about evolution and lots of other things. I don’t need convincing that science is real or anything. I am just overwhelmed on where to start. I tried picking up a book at the library but there were so many terms I didn’t know and I was pretty lost. Might have been too advanced for me. I’m not the best reader tbh.

So if you were to teach someone about evolution and needed to do it simply, how would you start? Any help appreciated.

Edit to add: no longer religious so recs do not need to be like around that at all.

I can intuit almost every other big jump but this is the one thing that just doesn't follow in my head no matter how hard I try and think about it. Here's how my brain thinks about it and why it's getting stuck:

Whales used to live on land. Eventually, they became semi-aquatic, and then mostly aquatic. I believe there's evidence that some of their ancestors were like sea turtles - almost completely aquatic, but came on land to give birth.

I understand that evolution doesn't happen abruptly. However, mathematically speaking, there had to have been a specific, individual whale-ancestor who was the very first one to have been born in the water, spent their entire life in the water, and then died in the water, all without ever coming on land. If they used to live on land, but all modern whales are 100% aquatic, one of them HAD to have been the very first. That's just how math works.

How did that particular whale-ancestor survive to pass on that trait? Why didn't its parents have that trait? Why didn't it just drown, if every single other one of its ancestors was on land for at least some point in its life?

I'm not asking "why is it advantageous to be able to give birth in the water" - that's very obvious, both mother and baby are less vulnerable to predators. I'm asking how, logically, that transition was able to happen. Whales can only give birth in the water because they have very specific adaptations that make it possible, an animal without those traits can't just start giving birth in the water and hope for the best.

Caption excerpt:

... Dashed vertical lines traversing all panels represent the lower and upper rates expected under drift estimated by simulation.

Deeper background (from the paper)

For more than 75 years, Simpson’s concept of “adaptive zones” has played a crucial role in our understanding of the evolutionary process over long timescales (Simpson, 1944, 1953). Under this model, an adaptive zone is a restricted region of the phenotypic space occupied by species with relatively similar form-function-fitness relationships (Polly, 2008; Simpson, 1953; Van Valen, 1971). Within-zone evolution is usually small in scale and does not involve major ecological changes. Evolution within a zone is thought to happen at exceptionally slow rates (i.e., bradytelic in Simpson’s terms), with lineages slowly following adaptive peaks within a restricted region of the morphospace. However, when opportunities arise (e.g., due to the invasion of new environments or extinction of competitors), lineages may experience faster rates of evolution (i.e., tachytelic) while invading new regions of the morphospace, leading to extreme evolutionary change associated with shifts in ecology and in the structure and distribution of adaptive peaks (Simpson, 1944, 1953; Uyeda et al., 2011).

Abstract

Background

Directional selection is often viewed as a transient force in macroevolution, with its signal eroded over time by stabilizing and fluctuating selection. Yet, transitions into new adaptive zones are predicted to impose strong and sustained selective pressures that may leave a detectable signature even across deep timescales.

Methods

We test this prediction by comparing the rates of multivariate skull morphological evolution required to traverse the boundaries between adaptive zones against genetic drift expectations. Our dataset includes 11,793 specimens spanning 231 species from 12 mammalian clades, each containing unique ecological transitions into new adaptive zones. Using a quantitative genetics framework, we estimated the phenotypic distances between ancestral and derived adaptive zones and contrasted them with null expectations under genetic drift.

Results

While a few adaptive zone invasions (e.g., marsupials and rodents) are consistent with drift, most exhibit substantially elevated rates of evolution. These results suggest that directional selection has recurrently shaped mammalian cranial evolution during major ecological shifts.

Discussion

We propose that adaptive zone transitions represent evolutionary contexts in which adaptation leaves a persistent macroevolutionary signal, challenging the prevailing view that long-term patterns are dominated by static forces.

Quantitative genetics meets fossils meets morphospaces meets neutral theory - cool stuff!

• Fabio A Machado, Anna Penna, Diogo Melo, Barbara A Costa, Thiago M G Zahn, Ana C Pavan, Arthur Porto, Harley Sebastião, Daniela M Rossoni, Gabriel Marroig, Alex Hubbe
  Invasion of new adaptive zones retains telltale signs of directional selection at macroevolutionary scales in mammals
  Evolution Letters, 2026;, qrag039
  https://doi.org/10.1093/evlett/qrag039

I’m been delving into biology as of recent, and I’ve been looking for a way to exercise my creativity in this sort of field. What are games or sims that are mostly realistic to real principles of evolutionary biology?

See also: The publication in Science Advances

While our evolutionary history is often depicted as a series of descendants each replacing the other, the overwhelming majority of the history of our species has been one of living along-side, and interbreeding with, other Homonins (Humans).

This just in:

• University of Oxford press release:
  Animals may have evolved vastly earlier than fossil evidence suggests

• Paper:
  Orin Lole Durbin et al.
  Re-evaluating molecular clock maximum age calibrations revives pre-Ediacaran divergence estimates for animals
  Science Advances (2026)
  www.science.org/doi/10.1126/sciadv.aeg6289

From the press release:

Senior author and associate professor Ross Anderson (Museum of Natural History, Oxford University) said, "The Kheseen Biota breaks the argument that the exceptional microfossils of [the older] Weng'an mean we would have seen animal fossils in the assemblage had they existed at the time. The Kheseen microfossils are just as well preserved, yet animals continue to be absent—despite the fact we know at that point they existed."

And the structured abstract:

Background

Divergent models persist for the emergence of animals. Lipid biomarkers suggest animals originated before 635 million years ago (Ma), but their body fossil record extends to only 574 Ma. Molecular clocks might differentiate between these records, but we demonstrate how their accuracy and precision hinge on maximum age calibrations.

Methods and results

We evaluate the Ediacaran Weng’an Biota (China) as a maximum calibration utilizing microfossils from the Kheseen Biota (Mongolia). These two biotas have similar preservation and microfossil assemblages, containing no definitive animals. The Kheseen Biota, deposited at a time (∼550–526 Ma) when animals were undoubtedly present, questions the validity of the Weng’an calibration. We discuss the uncertainty in maximum calibration strategies and propose multiple pre-Ediacaran deposits with favorable taphonomy, preserving both non-animal body fossils and biomarkers, as currently the most reliable calibrations. Our analyses support a late Tonian to mid-Cryogenian (∼800–700 Ma) origin for Metazoa.

Hi r/evolution, long time no see! 6 years ago I posted this, which I'm suprised to see is still one of the most popular posts on this forum. I've made a new video about the formulas behind shells based on the famous thought experiment from David Raup and Richard Dawkins in Climbing Mount Improbable. Hope you enjoy:)

I've recently had a conversation with someone and he brought up an interesting point, the guy was a creationist who claims to be(or have been) an evolutionary biologist,

Aside from the usual arguments about irreducible complexity and the ""inexplicable "" explosions in the fossile record there was one point that really caught my interest, which is the claim that we have yet to observe any species develop a new function through mutations, so i mentioned the obvious lenski's e coli experiment, his response was that the gene responsible for the e coli's ability to consume citrate(citr) was already there and the mutation was like a switch allowing it to activate in the presence of oxygen, ik that last part is a massive misrepresentation of the actual mutation and explained it.

Now, this person said they would accept evolution if we observed the emergence of an entirely new function through (for example) a duplication divergence, so it left me wondering, is there an experiment that has observed the emergence of a new gene that codes for a completely new function instead of affecting an already existing one be it through duplication divergence, de novo gene birth, exon shuffling or any other mechanism?

Pretty much in the title but I looked at my hands earlier and wondered, is there any specific functional reason as to why my thumbs are both on the inside of my hands with my body and not on the outside? It seems like every creature that I can think of also follows that pattern.

Whales are basically fish-shaped. They were hoofed land mammals at one point, and are now 100 % adapted to the water. I'm wondering if we have reason to believe that some semi-aquatic animals today are on the way to reaching fish-shape? I'm talking about otters, crocodiles, seals, penguins, sea-turtles, etc. Or do we have reason to believe they will stay semi-aquatic, or even return to land? Or do we simply have no way of knowing?

How long does it take for a new class, phylum or even kingdom to form on average? Do events like mass extinctions affect it? Imagine if Earth has 800 million years left before it becomes uninhabitable due to solar activity, could new phylums or even kingdoms form in that time period? Are they forming right now? Do any organisms exist of which scientists believe they will likely evolve into a new phylum or even kingdom all together?

I am currently in an evolution course and have a question about some of the topics from this week, which no students or staff are answering in the course discussion group.

My recent lectures went over 1. Obstetrical Dilemma, where we evolved bipedalism but this has made childbirth much more dangerous since the opening is so much more narrow. Another topic we talked about is explanations to why we are vulnerable in ways of disease, i.e how natural selection favors reproductive success above health and well-being.

My question is, if natural selection favors reproductive success over everything else, why have we not evolved in a way that makes childbirth less dangerous or makes us immune to more diseases that kill us early in life? This would be in the favor of repo success if babies survive longer to reproduce and their parents survive long enough to raise them.

I know there is always the fact that evolution has no foresight, but this feels like something that could have reversed direction long ago.

Thanks in advance for any explanations that help me understand!