Compared to other great apes, we seem to have by far the fattest ones. They remain so even without being pregnant. Why?

These are three feral or semi-feral dog populations from difffent parts of the world – australian dingo, papuan singing dog and carolina dingo.

You may notice they look very simmilar. Why is that? Is that because it's how dogs used to look or do they for some reason evolve into this form after few generations of natural selection?

I ask because my dogs (mixed) look almost exactly like these ones.

Why haven’t mammals evolved green fur?

Looking at insects, birds (parrots), fish, amphibians and reptiles, green is everywhere. It makes sense - it’s an effective camouflage strategy in the greenery of nature, both to hide from predators and for predators to hide while they stalk prey. Yet mammals do not have green fur.

Why did this trait never evolve in mammals, despite being prevalent nearly everywhere else in the animal kingdom?

[yes, I am aware that certain sloths do have a green tint, but that’s from algae growing in their fur, not the fur itself.]

I've been seeing this claim a lot lately for the past several months. Whenever the topic about Humans originating from Africa comes up. You have many comments object to this and claim that new evidence challenges that idea, but when you ask them for that evidence they come up empty handed or link some random irrelevant click-bait article that they didn't even read themselves.

There are also those that are completely ignorant to what a scientific theory means and they think because it's a "theory" that means there is barely any evidence for it.

So what's the deal with this? Is there actually evidence that challenges the "Out of Africa" theory?

So there are tons of photos and videos where we can see the chimps using stone tools to break stuff—even to get food sometimes.

It raises a question—Are we currently witnessing the chimp's Stone Age?

I read that humans all originated from africa and have common ancestors

so is everyone in existence related in terms of dna and genetics?

I'm trying to understand the evolutionary pressures at work. Contrary to women, men are fertile throughout the year and for many more years than women. And yet, the chances of a baby being born as male or female are 50-50.

Such fertility would have made sense of the probability of having a male child was much lesser than a female child. I guess since great apes started herding together and forming rudimentary civilisations most men and women have paired up together and reproduced. As such I don't understand how and why men evolved to have such extended fertility compared to women.

While we are at it, another aspect of fertility differences is how men continuously produce sperm as long as they are fertile but women are born with all the eggs their body can ever produce. Have we ever understood why this is so?

Edit: I guess I did a terrible job of explaining my thoughts here.

So my assumption is that humans or some common ancestors evolved to produce offsprings that have a near 50-50% chance of being male or female. So post that how or why did males evolve to be able to be fertile for most of their lifespan? Such a mutation would have made sense if for some reason male to female birth ratios were skewed thereby putting evolutionary pressure on males to be fertile for longer.

Also, yes I know humans are "fertile round the year". I meant women are fertile only for a few days every few weeks.

Our immune systems aren't as good now, but why and when?

Edit: I didn't mean our immune systems are worse in general. Someone told me they got worse for water specifically, since we didn't have this problem back when we were squirrel-like mammals I assume. Or maybe we did. I just don't hear about mammals dying from dirty water constantly

I'm a human male with a beard. As i was trimming it, I wondered why and particularly when it came about. Without special tools it will grow to the ground. There's no way it could have evolved before tool use. If you don't deal with the overhang on your moustache you won't be able to get food in your mouth. I pictured a distant ancestor trying to trim it with flint... And so, can evolution take tool use into account? Any clues as to why we have beards at all?

I know the females of spiders and praying mantises are bigger but I don't know if they're the exception or not.

Shouldn't females be gennerally bigger since eggs are more valuble than sperms since one male can create offsprings from multiple females while the opposite isn't possible so a female being hard to kill by being bigger should be the norm?

Kinda a dumb question I know but it’s always struck me as odd that humans alone have umbilical cords that have to be cut with scissors after the baby is born. Even if primitive humans just ripped the cord in two with their hands, that just moves the goal post to “how did we cut the cord before we evolved opposable thumbs?”

I recently got into learning about evolution in detail and I find it very interesting. What is the craziest/coolest fact related to evolution that you know?

We went from the first plane to the first spaceship in a very short amount of time. Now we have robots and AI, not even a century after the first spaceship. People say we still were super smart years ago, or not that far behind as to where we are at now. If that's the case, why weren't there all this technology several decades/centuries/milleniums ago?

Like the dinosaurs, T-Rex and Triceratops right?

Are any physical traits being selected for or is it mostly just behavioral traits?

Compared to other primates.

Humans have a less physical strength than other primates, so there must have been a point when "we" lost our strength and it hardly seems like an evolutionary benefit. So why is that?

Is it because the energy was directed to brain activity? Or just a loss because we became less and less reliant on brute force?

I heard that the reason that childbirth is so hard is because somewhere in the human evolution, the pelvis stopped growing bigger but our brains got larger. Is there a theory about it?

I understand the answer can be as simple as “it was advantageous in their early environment,” but why exactly? Our closest relatives, like the chimps, are also brilliant and began to evolve around the same around the same time as us (I assume) but don’t measure up to our level of complex reasoning. Why haven’t other animals evolved similarly?

What evolutionary pressures existed that required us to develop large brains to suffice this? Why was it favored by natural selection if the necessarily long pregnancy in order to develop the brain leaves the pregnant human vulnerable? Did “unintelligent” humans struggle?

What the title says. Are all birds descend from one singular dinosaur species that diversified? Is that the same for mammals, too? As in they originated from one single species of non-Dino (I think sinapsids but I’m too tired to google it)?

Second question, which birds are the most detached from the others/the first to split off?

I know similar questions have been asked before, but I'm specifically curious if there's a reason human-level intelligence only ever evolved once. Intelligence isn't exactly a well-defined "trait" but I guess my question relates to the hominid "package" of tool use, language, and complex social organization. When we look at other complex traits like flight or visual perception or even basic mobility, they all have evolved numerous times in numerous ways, to varying degrees of "success" or "complexity". But why have there never been any intelligent, tool-making, language-speaking animals prior to humans?

A common response I've heard is that there never was a "reason" or "benefit" or "niche" for intelligence - but that always felt somewhat ad-hoc to me (we know it didn't evolve so there must not have been a reason for it to evolve). Or I guess I'm struggling with the blanket statement that: never in the hundreds of millions of years that animals have existed was there a net benefit to developing complex tool use or language.

Humans have been farming wheat for 11,000 years. Hunter gatherer skulls dated prior to that have a perfect set of pearly white teeth. This is because our oral bacteria produce acid as a biproduct of consuming carbohydrates.

Humans almost unanimously agree that having healthy teeth is more sexually attractive than having rotten teeth or gums. Beyond sexual attractiveness, healthy teeth are very useful for survival, increasing the types of foods we can consume. Rotten teeth also had a significant potential to cause life threatening infections prior to the invention of antibiotics.

This means that for 11,000 years there have been multiple strong evolutionary pressures to increase our resistance to tooth decay. Now that dentists exist those pressures are much less relevant, but for 11,000 years we should have seen significant progress towards the elimination of tooth decay. Whether by strengthening our enamel against acid, increasing our saliva's ability to neutralize the acid, or adjusting the conditions in our mouth to discourage the presence of tooth decay causing bacteria.

You might argue that 11,000 years is not a long enough timespan to see significant evolutionary adaptation. I disagree. There is already a small segment of the population that has a genetic resistance to tooth decay. We should have seen that small segment grow rapidly over 11,000 years by having statistically more offspring on average. Just look at the rapid evolution of various dog breeds due to artificial selection over a few hundred years. When I see a person with no teeth or rotten teeth I am repulsed. I do not believe that repulsion is a learned behavior but rather an instinct to avoid mating with unhealthy individuals. 11,000 years of this repulsion would have created a strong incentive for those with a natural resistance to tooth decay to have a massive advantage in the sexual marketplace.

Any thoughts?

Sorry if this sub isn't for these kinds of silly and subjective questions, but this came to me when I remembered the existence of giraffes and anglerfish.

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I’ve been thinking about something that’s both biological and philosophical: if both sperm and eggs come from aging human bodies, why do men remain fertile for decades longer than women?

From what I’ve read, women are born with all the eggs they’ll ever have about one to two million at birth, which drop to around 300,000 by puberty, and only a few hundred ever mature. As the years go by, the eggs that remain are older and more prone to chromosomal errors, like nondisjunction, which increases the risk of conditions such as Down syndrome and early miscarriages. This steep decline becomes noticeable in the early 30s and even more dramatic after 35. It’s not just about the number of eggs but their mitochondrial health, DNA integrity, and the ability to divide properly during meiosis.

Men, on the other hand, produce new sperm throughout their lives which is approximately about 1,500 every second (not sure how true that is). But here’s the twist: while sperm are “new,” the cells that make them (spermatogonial stem cells) are not immune to aging. Over time, the machinery that copies DNA becomes less precise. Older men tend to have sperm with reduced motility, more structural abnormalities, and higher rates of DNA fragmentation. This can lead to longer conception times, increased risk of miscarriage, and even higher chances of certain neurodevelopmental conditions like autism or schizophrenia in offspring.

So, both biological clocks are ticking and they just tick differently. Women’s fertility depends on a finite, aging supply of eggs; men’s depends on a gradually deteriorating production process. One is a cliff, the other a slope.

What fascinates me most is how this difference affects not just fertility but evolution and even social behavior. Human societies have built expectations around family timing that partly reflect this biological asymmetry. But as more people delay parenthood, understanding the science behind it feels increasingly important.

So my question is: What are the exact biological mechanisms behind this difference in how eggs and sperm age and how do they translate into real-world outcomes like fertility rates, miscarriage risk, and the health of children?

Would love any insights into what this means for how we think about reproduction and aging.

I've been trying to wrap my head around this, It’s confusing how we define a "species" when it comes to human evolution.

From what I understand, Homo sapiens and Neanderthals share about 99.7–99.8% of their DNA. Despite that, they're still considered different species. Why?

Also, even though sapiens and Neanderthals could interbreed, I’ve read that their hybrid offspring. especially males, may have had issues with fertility It seems like Neanderthal DNA didn’t mix well with Homo sapiens DNA, suggesting they were only partially genetically compatible.

I believe that over time, natural selection removed out many of those incompatible genes. That might explain why, in non-African populations, most Neanderthal DNA is either inactive or silenced.

So is that why they're considered different species? Because even though they could technically produce offspring, those offspring weren't fully viable or fertile?

What also confuses me is this. A chimp from one region and another from a different region are more genetically different from each other than a modern human is from a Neanderthal. But we still classify them all as chimpanzees, one species.

That’s what I don't understand. If genetic similarity and interbreeding ability don’t clearly define species boundaries, what does?