Sljslj

It seems to me that humans just don't evolve physically anymore (mentally maybe, possibly even "devolving" mentally at this point). I have a feeling if you were to hop in your time machine (you can borrow mine if you don't have your own) and travel 40,000 years into the past, you would encounter beings physically identical or nearly so.
So is our understanding of evolution completely off? Or is it that we have no need to evolve anymore? If the latter is true, what might bring us to the point that evolution is once again necessary?
It's an interesting thought and I just wanted to see what the great mind at MB (all three of them) have to say about it.

Guybrush

No offense, but I think yours might be - at least slightly! As a biology student, I see no real mystery here and I think the notion that there is or the idea that humans have stopped evolving stems from misconceptions about evolution.

What is evolution? What is it you think drives evolution? Who do well in evolution and who get weeded out and why? Some kind of answers to those questions will solve much of the mystery.

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Neapolitan

If plants and animals evolve in response to the changes in the biosphere; like a change in climate, maybe an introduction or disappearance of flora and fauna that would totally alter their way of life, thus creating a change of their position in the food change or eating habits, like evolving to elude beig eaten, or evolve to be harder, better, faster, stronger plant and/or animal etc. So if plants and animals evolve because they have to adapt, human don't have to the changing world around them humans can alter the habitat they live and create tools, instead of adapting on the genetic level like plants and animals, so why would they have to evolve - it would be a mute point.

Cheetas are lean mean hunting machines, they evolve to run fast, and take out their prey, on the other hand human don't have to evolve for speed they can just create say a bow and arrow right to hunt and kill, right? That would deminish the need to evolve into a fast running species or some subspecies of super fast humans who can chase after prey, while the rest of the species would live a more sedentary lifestyle as like being hunter/gathers or into some kind of husbandry.

Some scientist once siad that the human race could not survive as a species if it wasn't for their intellect. He point out that humans aren't the fastest, or the strongest, and without the domiciles they know how to build, and the clothes they know how to make, the human species would not be suitable to live all over the world like they actually do.

So in short it's human's intelligence that stops us as humans from evolving.

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Guybrush

Sexual selection is roughly the same as assortative mating which means we don't pick our partners at random. We are attracted to some people and others .. not so much. We are selective when it comes to partner choice, the people we want to have children with. People we find attractive have qualities which typically makes them "fit", for example good mothers. You prefer a lady who has some boobs and tush to one which looks like a plank. Likely, boobs and ass is good if you want to give birth to and then raise a child. Attractiveness of the face (symmetry and so on) can be indicators of how fit people are in other traits, a sort of general quality indicator. Smell (sweat) is thought to give knowledge about the properties and quality of the person's immune system.

There's little basis for saying sexual selection plays a greater part now. At least I think so! If other selection pressures are higher, say food is sparse and there are more diseases (not saying that would be the case some tens of thousands of years ago, but), then finding a partner who is healthy and able could be arguably even more important.

Sexual selection is generally thought to have been extremely important in our evolutionary history. Some use it to explain why we are as kind and social as we are. The sex who has the most parental investment, the females, get to be choosy with the kind of males they want to have sex with. F.ex if you're gonna be pregnant for 9 months and then raise a baby after, you'd want a man who's loyal to you, kind and helps raise the child. Still, if it wasn't for this sexual pressure on men, it should make more sense from a selfish point of view to cheat as much as possible because as a man, you can potentually have children with very little investment. The investment is potentially as little as the sperm load you ejaculate and the energy spent courting and having sex.

So, some biologists believe a lot of our social aspects have evolved from sexual selection pressures on men from women. Some even hypothesize that women's gossiping is a way to exchange information about the quality of potential partners. "Have you heard? Lisa is so upset. She had an argument with Ben and he hit her!"

Needless to say, a statement that says sexual selection is more important now than before (when before?) is just a statement which is vague, non-specific and currently without support.

That's well and fine, but it seems a little naive to me. The rough history of man I've heard is that we started walking on two which freed our hands which is important as we're tool users and we switched from a diet based on plants to a diet based on meat. You get a lot more energy per pound of meat and you don't need a huge stomach to digest enough to keep you going. You also don't have to spend most your day foraging and then resting as you digest, something other plant diet apes have to.

Basically, we switched to a source of nutrition which allowed our brains to grow big and we had our hands free and we also got a lot of free time on our hands. When you don't have to spend all day getting food, you can spend it developing culture.

The people you talk about who lived in locations of plenty, I'm not sure what species of man you're talking about, but if they had a culture (could switch off being nomadic and choose to settle), then I'm thinking they were probably already self-aware and had been for a long time.

Even Coco was self-aware!



You should read my post on the previous page. I wrote a set of criterias which have to be fulfilled for there to be no evolution.

A quick comment still, you think we don't have to evolve in the same "arms race" as the fish we eat and the chickens we kill. This is true, we don't. But how about the viruses, bacteria and range of parasites that still infect us on a daily basis? We're talking here about organisms and evolutionary particles which have a very short generation time which means they evolve incredibly fast in this arms race against us.

We don't stop evolving. You seem to think it's something animals do because they "need" to. They don't, it's a consequence. I keep saying it is, but I'm not sure people get what it entails. Basically, it's not something we choose to do. It's not something we can turn off. Evolution will continue to happen as a consequence unless we can turn off the causes. If life as it is was constant and could not vary, not even mutate, from generation to generation, then there would be no evolution. However, hereditary variability is an integral capacity of life as it is and evolution comes with it. It can be slow, it can be fast, but the main point is it's happening.

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duga

Well, that's the beauty of science, isn't it? If you are not convinced, you don't have to believe it. I don't see how your scenario is much different...the hominids I was referring to encountered a place with plenty of food including animal life to ingest. Hunting in scarce lands is still a mentally exhausting endeavor, so it would make sense that the mental development I was referring to wouldn't have happened unless animal life was readily and easily available.

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Dom

Nice Daft Punk reference.

From my understanding I don't think we are evolving at anywhere near the pace of other animals due to the fact that we change our surroundings to suit us, rather than changing to suit our surroundings.

Natural selection happens as the ones with the more advantageous mutations are more likely to survive and therefore breed, passing their genes on. With humans, there are all kinds of things we've made to make mutations to survive unnecessary; e.g. in other animals, a creature with a genetic condition would likely die before it passes the genes on, so the conditon slowly dies out. In humans, medical care allows people with these conditions to survive and pass their "bad" genes on (I'm not saying we should kill everyone with genetic conditions, don't get me wrong).

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Sljslj

I don't claim to be an expert, but I'm pretty sure I understand natural selection. Is the reason that people haven't changed genetically because we have no need to?; because we have been the heirarchy species for a long time and "survival of the fittest" is no longer applicable? Or am I once again off?
I don't mean to avoid your questions, tore, but I honestly don't know how to answer them without sounding like an idiot or a ****.

Barnard17

Out of curiosity, how fast do you think evolution actually happens?

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Guybrush

Well, defining evolution is a bit hard but it's obviously an important thing to do if you want to say whether it happens or not. A lot of ecologists for example might say that evolution is a change in allele frequencies from one generation to the next. For humans, this happens for every new generation so then it's a question of how much. I understand however that you think that humans are not changing as quickly physically as we used to and then I guess you would have to compare. Do you know if we have evolved slower physically the last 100 000 years than we did the 100 000 years before that? You are also focusing on morphological and mental traits, but what about all those genes that you can't really tell that easily?


Evolution is a process of cause and consequence where those who are fittest - those who pass on their genes the most - add more to the human genetic makeup for the future and those who don't pass on their genes, well .. they don't! There are many ways to be fit, but to put it into some kind of perspective, I can make a simple example :


Imagine that there's a plague which kills people, for example cholera. The chances of dying from cholera is quite high, but if you have a specific genetic mutation, your chances of survival are much higher. The reason is the mutation causes a slight change in some ion pumps in your stomach cells which normally just renders these stomach cells less effective and people who have this mutation have more irritable bowels. However, when they are infected with cholera, the same mutation protects them somewhat from the harmful effects of the cholera bacteria which also have an effect on the operation of these ion pumps.

Before cholera occurs, most people don't have the mutation because having it has a slight negative effect on fitness. Diarreah doesn't make people pass on their genes more successfully after all .. But after cholera has occurred, people who had this mutation were much more likely to survive and then the mutation did add to their fitness and did make it much more likely for them to pass on their genes. The occurrence of the mutation after cholera has taken place in the human population is much higher than it was before. The genetics of the human population have changed somewhat and now they are more cholera resistant on the whole than they used to be - there's been some evolution taking place. Because the mutation is not beneficial in a cholera free environment, the frequency of that mutation might change again in the future until it's as rare as it was before the first cholera plague.


The example should be reasonably simple to understand. For a while, there's one selection pressure (cholera) which favours one trait (a mutation). When that pressure is gone, the trait is not favoured anymore. The point is that evolution of specific traits and most likely the sort of changes you are talking about happens as a response to selective pressure. What the pressure is and how strong it is varies with where you are in the world, what your situation is. Different genetic makeups do well in different environments, for different sexual preferences, diseases and so on. Evolution is just a consequence of natural selection. It doesn't stop when it's reached some sort of goal!

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bungalow

evolution is a constant process, it doesn't just shut on and off.