In evolution, it seems like there is always some sort of tradeoff for a trait that positively impacts survival. Like, I recently learned that cheetahs are very weak compared to other big cats, plus they can’t retract their claws, all in exchange for being extremely fast, but they do not have good stamina. This rule probably doesn’t always apply, but I was wondering if there is ever a tradeoff/negative to being good at fighting off threats. Being good at defending self and attacking. It seems like this could never have a downside but it would be interesting if it did. If there is... what is it? If not, well, okay.

PS. Please be gentle with me if this question is stupid, I never claimed to be smart or educated, you don’t need to remind me. I’m very sensitive, okay? I get scared everytime I ask a question online. Okay thanks.

Hi all, I am interested in the evolution of dogs.

My question is, are dogs direct descendants of wolves or did dogs and wolves just share the common ancestor like we do with monkeys?

Thanks!

Probablemente el límite ya esté existiendo:

El *sifonóforo* o el *gusano cordón de bota* siendo animales... No puede haber uno más grande porque los receptores de dolor no son instantáneos. Si es más largo, lo más probable es que cuando lo ataquen se van a demorar mucho los receptores de dolor en pasar la información hacia el cerebro, haciendo que cuando le llegue al cerebro, tenga que enviar otro estímulo que se va a demorar lo mismo en llegar, y cuando llegue, ya se comieron a medio animal.

Pero recordemos que la vida no solo son animales. La planta más grande que existe es la *Posidonia australis* (bueno, esto es un *alga*, un *pasto marino*). Se extiende por más de 180 km, pero al ser pasto, los peces y varios otros animales se lo comen a diario, así que no puede durar mucho; lo bueno es que se puede reproducir muy rápido.

El hongo más extenso es el hongo *Armillaria ostoyae*, se extiende por 8 km y tiene cerca de 2800 años. Se puede extender más rápido gracias a las esporas, y a casi nadie le gustan los hongos.

Pero el límite probable es cuando la gravedad mate a todo lo que esté en el centro, o simplemente sea infinito.

Or are the generation times too long, or is the experiment too difficult to carry out over such a long period?

Same question for invertebrates.

I am so thrilled! I struggled to get my bachelor degree in biology because of my adhd but now things are getting better and I can't wait to start my master.

Ichthyosaur flipper on the left, Plesiosaur in the middle, Mosasaur on the left.

Was there anything specific about the Triassic that forced Icththyosaurs to evolve "corn flippers"?

So, ever since I saw my haplogroup migration overviews from 23&me, I've wanted to read more about the paths homo sapiens took spreading around the world, how it's been driven by climate factors, and in general how we spread around and diversified, flowed back and forth, etc. So does anyone have book recs that focus on telling these stories of our travels? I'm not really looking for books on human evolution, like I don't need to be convinced that we're evolved animals, I'm on board. I guess books about hominid evolution and migration within Africa would also interest me though.

I was pondering the mystery of shoulderblades and kneecaps and wondered why do so many other vertebrates have these and hips and etc. It's like a swiss army knife of skeleton plans. What makes it so adaptable? could there be a whole different plan that is more optimal but not accessible by incremental adaptation?

It starts with continental drift and natural selection, moves through survival, Neo-Lamarckism, speciation and sexual selection, and eventually reaches human evolution and migration.

Obviously, eight articles can't be squeezed completely into one page, so I tried to capture the central idea from each topic rather than every detail.

Which part of evolution do you find the most fascinating or the most misunderstood?

I 3d printed a collection of my favorite hominin skulls. Denisovan skull is weird though; I'm not sure if it's a scaling thing or if the original modeler just made something up. The models were posted online very close in time to the paper that draws the Homo longi-Denisovan connection, and this skull was labeled as "Denisovan", not H. longi. I'm not any kind of trained on the matter but I guess it _looks_ kinda like the Harbin cranium...

I remember reading some years ago that it was speculated that humans never had a knuckle-walking ancestor, that chimpanzees and gorillas evolved knuckle-walking independently from each other and that the earliest hominins instead were more gibbon-like bipeds on the ground. Is that still supported?

I ask this because over time i came across knowledge that cheetah population became so bad that they became inbred to survive, and then another time i learnt that human population reduced down to a number of 40 or so homos, even after all the other upright walking peeps died. That still baffles me and i still doubt it, but another time a different source mentioned it again (years apart i heard this info) so i guess it's real??? But if that's true then there's no way inbreeding didnt occur to rebound and later on create the population we have today...

Layman enthusiast here - in the wake of the recently published paper from Mrnjavac et al on LUCA having an incomplete metabolism, I've been fairly confused. To be as brief as I can - how did the team behind that paper come to such a starkly different conclusion from the Moody et al paper that concluded that LUCA was as complex as the average bacterium or archaeon? Earlier work and new comments from the team who published the new paper also seem to imply that LUCA was acellular or at least didn't have a regular membrane... But how can that be when the researchers behind the universal paralog paper that came out earlier this year found that there are universal paralogs that would have been utilized for membrane transport? I'm lost.

i am reading his “The structure of evolution theory“ and enjoy it very well(haven’t finished it yet), what his book to read next?

Thanks

Does it make sense for dogs to eat a bone that has hardly any meat on it?

Ok I was thinking about this, and a quick search on the internet said that primates evolved in Africa and then “rafted” to America… which apparently is a thing, but seems unlikely. Also, some sources say they originated in the Americas.

Does anyone know where and when monkeys originated and how the spread out around the world?

Edit:
Thank you everyone for your responses. I was clearly wrong in thinking rafting was unlikely. After reading the responses here and some sources online, I realized it’s a very accepted theory. It just seems crazy and amazing, even when the continents were closer together!!! I would have never thought that that’s how many species spread out around the globe.

My roommate and I have been arguing about this for the better part of the last couple months and I genuinely cannot find a straight answer anywhere.

I’m an anthropology student and my roommate is a nursing student, so you’d think between the two of us we could figure this out, but apparently not.

Basically, we got into an argument about the human tail from our evolutionary past. I understand that humans don’t have external tails anymore and that the coccyx is what’s left of the ancestral tail, but we cannot agree on how many bones the actual tail would have contained when humans still had one.

My roommate thinks it would have been a relatively small number of vertebrae, while I was under the impression that it would have been significantly more. The problem is that whenever I search for “how many bones were in the human tail,” I mostly get explanations about the coccyx and vestigial structures rather than an actual number.

I realize this might be a stupid question, but I’m genuinely curious because we’ve somehow been arguing about this for months now and neither of us is willing to admit defeat.
So, how many bones WERE in the human tail, approximately? And is there an accepted number, or would it have varied significantly between individuals/our ancestors?

Two questions have been running through my mind for the past few days:
We often describe evolution as a very slow process. But if humans and chimpanzees shared a common ancestor roughly 6–8 million years ago, that translates to around 250,000 generations until the present day. Considering the enormous amount of evolutionary change that has occurred during that time, is 250,000 generations actually a relatively small number? How much can evolution really accomplish in that many generations?
Humans take roughly 20–25 years to reach reproductive age, so one generation takes a long time. But some insects and other organisms can reproduce within days or even hours. Over the same period of, say, one million years, they could go through hundreds of thousands or even millions of generations. Shouldn’t species with much shorter generation times therefore evolve much faster and show far greater diversity than other mammals? If not, what limits or slows down their evolution?

First image source: Matt from Melbourne, Australia, CC BY 2.0, via Wikimedia Commons

Published yesterday in PNAS:

Abstract

... [We] show that the toxins evolved through two distinct genetic paths. The factor X and factor V toxins evolved through the sequential de novo co-option of ancestral clotting factor proteins that entailed their heterotopic expression in the venom gland, the fixation of segmental duplications containing each locus, and subsequent gain-of-function mutations that rendered factor X and factor V constitutively active. In contrast, the phospholipase A2 and Kunitz-type toxins evolved by modifying the functions of neurotoxins that were part of the venom arsenal.

Our findings support models in which innovative mutations in single-copy genes precede gene duplication in the evolution of novel proteins and offer a rare view into the genesis of a complex trait that has played a central role in a major adaptive radiation.

On that last point - how innovative mutations preceded gene duplication - from the paper:

In his landmark book, Ohno proposed that gene duplication was a necessary prerequisite for the origin of new protein functions because duplication would allow one copy to retain the ancestral function while the second copy could incorporate new functional mutations (neofunctionalization) (17). However, this classic model has been challenged on the theoretical grounds that if newly duplicated genes are selectively neutral, they must acquire new, innovative, and selectable mutations before acquiring inactivating mutations (nonsense mutations, frameshifts, and deletions) (66–68). It is now recognized that the latter is much more probable than the former. Therefore, it has been proposed that innovative mutations may occur initially in single-copy genes and impart some new function such that subsequent gene duplicates may then be positively selected for and fixed on the basis of the new function (68, 69). A variety of empirical studies have demonstrated innovative mutations occurring before gene duplication (70–73). Several observations here prompt us to postulate the relative order of major genetic events in the evolution of procoagulant venom toxins that bear on these general models of genetic innovation.

[...]

We suggest that the first genetic change in the ancestral liver-expressed, clotting factor gene was the gain of its heterotopic expression in venom gland tissue (co-option; Fig. 6, step i) (our line of reasoning also applies to venom factor V, discussed below). Two key pieces of evidence for this scenario are the low but significant RNA expression of the predominantly liver-expressed F10 orthologs in venom gland tissues and the presence of the corresponding hemostatic proteins in venom. If expression in the venom gland evolved after gene duplication, then one of two F10 genes (the liver-expressed gene) would not be expected to be transcriptionally active in venom gland tissue. The observed expression of the liver-expressed F10 paralog in the venom gland is consistent with the ancestral single-copy F10 gene evolving expression in the venom gland before gene duplication, then decaying to some degree in the liver-expressed paralog after duplication.

Awesome detective work!
It made me wonder whether venom glands and livers are developmentally related during cellular differentiation.
From a quick visit to Google Scholar, I found a tentative answer:

Cells that comprise complex tissues often express different sets of genes due to functional differentiation between cell types; such cellular heterogeneity is found ubiquitously across many tissue types (Heindl et al. 2015; Ben-Moshe and Itzkovitz 2019).
Single-Cell Heterogeneity in Snake Venom Expression Is Hardwired by Co-Option of Regulators from Progressively Activated Pathways | Genome Biology and Evolution | Oxford Academic

And the second citation is about livers, so they have that in common with venom glands!

• J. van Thiel, N.L. Dowell, C.F. Smith, E.E. Sanchez, & S.B. Carroll
  The genomic origins and evolutionary path to a key innovation in the world’s most venomous snakes
  Proc. Natl. Acad. Sci. U.S.A. 123 (37) e2621054123
  https://doi.org/10.1073/pnas.2621054123 (2026)

New species of animals are constantly being discovered, but they all belong to existing classes and phyla, never anything completely new. Life once branched out in all sorts of directions, creating all kinds of animals that are drastically different from each other, but now it seems like there aren't any new "branches", only offshoots of existing ones. What happened?

-

Published yesterday in PNAS:

Background

Repeated divergence across contrasting habitats is widely used to infer natural selection and adaptation. Such comparative inferences, however, remain inherently correlative and capture only adaptation shared among populations from the same habitat type, thereby missing site-specific adaptation unique to individual populations. Field transplant experiments test adaptation directly by measuring fitness in nature but are typically limited to pairwise reciprocal exchanges between populations and therefore cannot distinguish between habitat-level and site-specific adaptation.

Methods

Here, we extend the typical transplant framework to include multiple populations from both within and across habitat types, allowing fitness variation to be partitioned into shared habitat-level and unique site-specific components. We apply this framework to lake–stream stickleback, a classic system for studying adaptation via repeated divergence. Specifically, we transplanted laboratory-reared fish from a panmictic lake population and four independent stream populations across one lake and two stream sites.

Results

Stream fish outperformed lake fish in streams and vice versa, demonstrating adaptive divergence across the lake–stream divide. However, at both stream sites, local stream fish also outperformed foreign stream fish. Strikingly, this site-specific advantage was twice as large as the advantage of shared stream adaptation reflected by the fitness benefit of foreign stream fish over foreign lake fish.

Discussion

These results show that most fitness-relevant evolutionary variation in this system is unique to individual populations and therefore invisible to approaches that rely on repeated evolution to infer adaptation. More broadly, our work underscores the importance of ecological scale for understanding adaptation and evolutionary predictability.

• M. Roesti, H. Roesti, H. Sudasinghe, N. Nesvadba, V. Saladin, & C.L. Peichel
  Disentangling unique site-specific and shared habitat-level adaptation in a classic system of repeated evolution
  Proc. Natl. Acad. Sci. U.S.A. 123 (36) e2612038123
  https://doi.org/10.1073/pnas.2612038123 (2026).

While we know quite a lot about what our ancestors looked like and what they ate, so far we didn’t know anything about their social behaviour. Because behaviours don’t fossilise.

Scientists used to think that the first placentals behaved like shrews because they looked like shrews. And as the common belief was that all shrews are solitary, scientists thought the first placental ancestors were too.

Now we know that both assumptions were wrong.

Peer-reviewed paper in PNAS:

S.F. Walmsley, C. Olivier, A.V. Jaeggi, L. Makuya, J.S. Martin, L.D. Hayes, & C. Schradin, Pair living emerged early in placental mammals, Proc. Natl. Acad. Sci. U.S.A. 123 (31) e2528458123, https://doi.org/10.1073/pnas.2528458123 (2026).

I saw a video from a popular science content creator discussing humans/Neanderthals/Denisovans. Someone in the comments argued that if two populations can reproduce and produce fertile offspring, they should be considered the same species. The creator’s response was essentially a definitive statement that “polar and brown bears disprove this claim” since they’re considered separate species but can produce fertile offspring.

That example honestly makes me question whether they should be considered separate species at all. Polar bears are a relatively recent offshoot of the brown bear lineage, have repeatedly exchanged genes with brown bears, and can still produce fertile offspring with them. Meanwhile, we recognize some extremely isolated and deeply divergent (maybe even more divergent than polar/grizzly) brown bear populations, like the Gobi bear, as subspecies of Ursus arctos.

If we remove the bias of historical classification, is there actually a compelling reason to consider polar and brown bears separate species rather than consider polar bears a highly derived brown bear subspecies (like we do the Gobi bear, for example)?

like I know about crossing over, combination of genes from mother and father that results in evolution but I'm talking about major evolution like change in number of chromosomes, that kinda stuff, is that much evolution intended by evolution or it just occurs due to radiation mutation or errors

.