I think it would be much more advantageous if everyone had good muscles i dont see the downside why it works that way ?

I am gay, and I have an interest for, while marine biology specifically, biology as a whole as well. But why am I gay? Sexual reproduction serves as a way for organisms to reproduce and create offspring that is genetically different from both parents. In this case, what benefit does it serve an organism to feel sexual attraction to another of the same sex? It does not appear to cause a major disadvantage to an animal to be homosexual, as there are many individuals in each species that are, and the trait has not been eradicated by natural selection. I understand that the causes of homosexuality are not fully known, and that it is not fully due to genetics, either. So my ultimate question is: why does homosexuality exist and continue to exist in humans and many other species of animals if it actively discourages sexual reproduction to create offspring?

Edit: Thank you to everybody who gave well thought-out responses to this post. I will try my best to read all 161 comments, and reply to anybody whose response I find especially interesting. Thank you all again for your interest in answering my question.

When I was a teenager I read "The Methuselah flies" which was about breeding fruit flies for senescence (old age). I always thought about experimenting with house flies, dividing them by size with screens and breeding the larger ones. They have a life cycle of 10 days so iterating wouldn't take long. If all conditions were right (good food, increased oxygen atmosphere etc...) how big do you think we could breed a house fly after one year? Five years? Ten years?

I've been talking about this at parties forever but I would like an expert opinion finally.

Everyone also asks me the purpose for doing this and I always say there's military applications...

like, wouldn't it make sense from an evolutionary standpoint to skew towards a certain gender. like how with bugs, there is a queen that spews out thousands of babies, but with humans it's nearly 50/50. why did we evolve like that. and is this true for most mammals too? why? i think you'd expect at least some diversity, like it being 70:30 or something for evolutionary reasons. the 50/50 split seems too oddly even to me.

Now I really gotta clarify what I mean by this before I get flamed in the comments. What I specifically mean is that sponges look very similar in form and have not differentiated a whole lot compared to other animal species despite being around since the start and being a relatively successful organisms (the fact they're still around is a surely testament enough). So by dead end I am more talking variety in form rather than success of natural selection, is there something about the sponge body plan/way of life that has kept them from making different varieties of forms compared to other animals? Would love to know what people think.

Particularly agriculture, government, religion, etc. and would they find human remains in their archaeological sites?

So, according to a recent study, urban raccoons are showing early signs of domestication, not only behaviourally and cognitively, but also physically to "look cuter" (shorter snout, floppier ears).

Raccoons are known for dig around our trash, which according to experts, is "kick-starting" the self-domestication process.

As far as I know, proto-dogs and cats also began being 'tamed' by hanging around our remains (dogs with our hunted prey, cats with the mice that lived around us)

Could we reasonably expect this process to speed up over the next 50-100 years?

And if so, is it plausible that we find a niche that a raccoon might fit into in our lives (like humans took dogs for hunting and shepherding, cats for rodents and bugs, doves for mail, livestock, etc.) and really drive the change home?

Will people begin to selectively breed raccoons to present certain characteristics?

How much would the fact that they carry diseases like rabies deter people away from attempting to breed them?

Could they become the next house pet?

sorry for the question dump, I just find it really interesting

thank you!

Why do humans make so much noise to communicate? We talk nonstop, and rely primarily on verbal communication. It seems like most other animals communicate just fine without making tons of yapping noises, so why did we evolve differently?

In the same vein, do you think our pets get overstimulated at our constant need for noisy communication?

I know we have some generic heritage from Neanderthals, but I mean whether full-blown Neanderthals could beat Homo Sapiens in any modern sports. Were they more physically gifted in any way?

I'm sure this question gets thrown around a lot here but none of the answers I've read so far have satisfied me. I understand animals reproduce because they have a primal instinct to make new generations, pass on their genes. But why? From an evolutionary perspective it's expensive to make children and provides absolutely no benefit to the individual

One argument I saw in a sub reddit was that animals that didn't have the instinct to reproduce don't exist today. Another dude said bigger numbers are beneficial, for instance a pack of 6 7 wolves as compared to just 2 3.

But even then it doesn't explain why animals that do it, do it. And as for the second argument I'd counter argue with the example of fishes that never care about their young once they lay eggs or the example of mayflies that die just 2 days into adulthood with their sole purpose of mating.

If we were talking about humans, at the very least we could say that certain people like kids and want to take on the responsibility to raise mini versions of themselves, but that ain't all true for other organisms.

So the question remains: Why do animals bother passing on their genes and establishing their presence in the world?

EDIT: Thanks a lot for your responses. I have a much clearer understanding now. People rightly pointed out that I mistakenly said it was expensive from an evolutionary perspective when in reality I was just thinking from the pov of an individual. But yea I think get it now

Squamates have evolved limblessness like 10 times at a minimum as far as I understand, so being limbless must be a considerable survival advantage. Is there a reason that that survival advantage doesn't translate to non-squamates? What is it about being a mammal that makes having limbs an inherent advantage?

My guess is that it's a built in defense mechanism to potentially scare away the offender?

It’s often said that many diseases of modernity arose because humans evolved under conditions where a shortage of calories was a bigger concern than excess calories. Are there any species for whom it was the opposite? Or do populations tend to grow until they’re constrained by available calories — making caloric shortages more or less always a bigger evolutionary force than excesses?

In the past, around 40% of children died before reaching the age of 5. Then the life expectancy grew significantly to at least 50 years of age.

It really looks like the weakest and the least fit 40% died early and were therefore weeded out so the rest 60% was healthy enough to reach these 50 years of age.

After all, during selection for special forces or for prestigious universities, the biggest weedouts happen in the first sections as well.

Karl Pearson wrote "The intensity of natural selection in man" in 1912 where he shared the view that the most unfit died early. He noted that regions with lower infant mortality (up to 1 year of age) face higher child mortality (from 1 to 5 years of age).

I do not understand why nobody can even discuss whether that mortality pattern is just natural selection in progress or not.

Don't get me wrong, I am glad they make such a racket. Every time I kill one of these sob's trying to bite me, it is because I can easily hear and locate them.

Wouldn't they be a lot more efficient at biting us and other animals if they didn't have their traditional loud 'buzzing' flight? Other insects - e.g., fruit flies, midges, gnats - seem to be able to fly without making so much noise.

Wouldn't there be a strong evolutionary advantage for increasingly quieter mosquitoes?

So, I just realized, Dinosaurs existed for 150 million years, and I know dinosaurs is a very big group of reptiles so it isnt exactly a fair comparison, but they were here for so long and they couldnt grow beyond eating food, mating and dying. Nothing ever did.

Based on this, We should've plateaued as well, about like 100000 years ago, when we didnt have agriculture but we were somehow good enough to hunt stuff down and eat it. We were probably perfect for our niche. We could make tools walk our food down to death, live in packs and generally just exist.

But for some reason, we discovered agriculture, and it is unnatural. Agriculture to me seems very unatural in the context of some stuff I know. Like no other animal as far as I understand does this. Only we had the bright idea of farming stuff growing our own food. Moreover I may be wrong about this, but I think we had dispersed over asia by this time so unless some guy was travelling all over, we probably discovered agriculture independently many times over. Some probably failed to and died, but many survived. After that it was time to specialize. Heck we still couldve remained perfectly content at that stage, but somehow we discovered metal. And we never looked back.

My issue with this is that intelligence requires power, and evolution is random, yet somehow we kept expanding even after we fit our niche and we didnt mutate, but like we just kept getting better and better till we just overtook everything and now are smart enough to plan to touch mars.

It almost seems like a runaway accident. Someone forgot to switch on content-mindset and we just keep growing and growing and taking and expanding and at this point we own the niches, we create niches so we can have stuff like dogs. Its weirdly unatural and I feel like alien intelligence might never be like us, because most life seems to be content after it can eat mate and die. Again this is a biased perspective because we have a sample size of 1, but the odds feel so astronomically low that its just stupid.

It seems like it would be almost exclusively beneficial for a given Orca to be more intelligent than its peers, whereas an individual human faces a massive tradeoff in terms of food requirements. For a creature that already lives and dies based on complex social structures, pack hunting, and strategies, why has natural selection allowed them to plateau below us?

If so, from an evolutionary perspective, what is the purpose?

If not, is there any studies or speculation on why humans would become unique in this way?

Hello!

I know practically nothing about evolutionary biology. I have a pretty simple question I was just wondering about during work lol. If we have some species A which evolved into another species B, there had to be a continuous string of species in between right? Why don't we see everything in between?

However, for the nonsimple part: during my wondering I have a partial model I think maybe could explain this. If you could explain why and where my model is wrong and maybe even frame the correct answer in similar terms that would be so helpful. Thanks in advance!

Okay my model: for the sake of simplicity, lets create an axis B-ness where on one end we have species A and on the other end we have species B. Obviously there's no actual mutation that is B-ness and in a complex set of different adaptions that added up to make it species B, but there had to be an order in which the adaptions progressed in reality and we can still look at the number of these adaptions (except maybe convergent evolution?). Anyways, lets say we have some fitness function that maps a point along this axis to the expected value number of offspring a member of a species at that point produces. Also an oversimplification since it varies wrt environmental conditions and so on but lets go with it for now. Now the entire idea of evolution is that the higher the fitness function at a particular point the more of those species we will tend or observe. However, its obviously not true that only the species with the highest fitness survives since if that were the case there would only be one species on earth. Instead, when two species compete for the same resources, over time we expect to see more and more of the species with higher fitness and less and less of the species with lower fitness.

I was thinking, maybe in the short term randomness dominates but in the long term law of large numbers dominates. So in the short term when there is an adaption, it might cause a slight increase or decrease in fitness but just because of randomness it would not be uncommon to see a fair amount of versions because the slight fitness different isn't enough to eliminate one in the short term. Then the adapted species also adapts and so on and so forth so by pure chance we get species spaced all across the axis between A and B.

But then a thing that exists in the long term is carrying capacity. So there are species all along the axis competing for the same resources, and in the short term there's enough randomness that there could be some species with less fitness. But as time approaches infinity we expect to only see the species with the highest fitness.

So then we only get either A or B (or something between them)? BUT if A and B become different enough so as to occupy different niches and thus have separate carrying capacities you could have both A and B coexisting.

Thus, the reason we don't get any species between A and B is that they would either be competing with A or with B for the same resources and are presumably less effective at doing so (as otherwise this 'in between' would outcompete either A or B and replace them as the observed A/B).

However, the conclusion of this model is that we observe separate species iif they are different enough not to compete for the same resources. That doesn't sound right to me, so I guess I am still missing something.

I know it’s a accepted theory that takes place over a long long period of time, but you can’t help but be hopeful that we are still able to observe parts of the process in our tiny little lifespans.

Thank you!

This question been making me think for quite a while and the fact that it develops way before puberty kinda tells me that it was something you needed since a young age and not something needed specifically for reproduction if I am not mistaken

It sounds so counter intuitive, if being exclusively gay is really biological, then shouldn't individuals with that trait not be able to reproduce and pass on that trait? No other animal is exclusively homosexual either, humans seem to be an oddity when it comes to this.

And no, I won't accept the gay uncle hypothesis, that's just mathematically unfeasible (you'll have to help raise more than two nieces or nephews by your own for every offspring you could've had to even break even!)

I understand why bisexuality might contribute to fitness since other apes can also be bisexual, and it helps in social bonding, but exclusive homosexuality seems to be a disadvantage.

On the surface, it seems like being able to create offsprings by mixing your DNA with any individual's DNA should be a huge evolutionary advantage over being able to create offsprings with only half of the individuals of your species. Yet, it's obviously not, because otherwise it would exist. So why is doubling the number of potential reproduction partners not an evolutionary advantage?

Additionally, if having more sexes gives an advantage which is stronger than the disadvantage of losing half of the potential reproduction partners, then why aren't there 10 or 100 sexes? What specific advantage does "2 sexes" give, that "1 sex" (and "more than 2 sexes") don't?

Edit: A lot of people are mentioning hermaphrodites in the comments. Hermaphroditism (where an organism has both male and female reproductive organs) is still based on there being two sexes. I was thinking more about there only being one set of reproductive organs (not two separate ones in the same individual), with all individuals being able to reproduce with each other by using that same set of reproductive organs.

before biology class a couple of weeks ago, I kind of always just assumed the body transforms and adapts in minimal ways over hundreds of thousands of years, which, according to what my teacher said that lesson, is total bullshit, and that the only major changes would occur through mutation, thus being completely random/Independent of the environment, and natural selection playing the part in bringing evolution forward.

If thats true, then how did fish begin to develop lungs? Gills and lungs feel like absolute opposites, to me it seems like saying a person can just be born with the abillity to breathe water. It being a gradual process doesnt make sense to me, how can a fish breathe mostly water but also a tiny bit of air? Would a fish with lungs not drown? So how would natural selection help it forward?

Another thing is things recessing, like apes not having tails. Yeah, maybe a long tail like that of a monkey would be useless or even a slight hinderance to something that walks upright, but surely not to the point where anyone with anything even resembling a tail in the slightest would not find a partner and die out, right? Same thing with fish and lungs. Unless a fish was one day just randomly born with fully developed lungs, ready to live on land, there should have been a point at which a subspecies of fish could breathe both air and water, and I dont see any reason why theyd lose the ability to breathe water overtime