Why don't we evolve into microbes?

[ecoo]

That is the reason I thought that being a microbe is better as one can adapt very quickly to the environment. (For example, the common cold virus).

It may be "better" in your terms, but the tree of life branches off to many different directions.
Microbes have survived for a long time, but I believe so can humans. Us Homo sapiens are pretty new compared to microbes.

We're already humans and not microbes, so let's be happy about that. :D

 

[Yashbhatt]

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

 

[SteamKing]

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

You can't really say that since adaptations take many generations to develop and produce individuals which are noticeably different because of such adaptation. In humans, a generation is generally reckoned to be about 20 years, and fewer than 10 generations have elapsed since genetics was recognized as a science, much too short a time for significant adaptation to become apparent.

Humans have been adapting to their environment since Day 1, as can be seen by the variety of fossil humans discovered over the last century and a half. H. erectus isn't just an older version of the modern H. sapiens, but quite a different creature altogether. Certainly, if you saw a live specimen of H. erectus walking down a street, you would have no trouble discerning that this individual is not the same as other humans, just shorter and stockier.

 

[Ryan_m_b]

That is the reason I thought that being a microbe is better as one can adapt very quickly to the environment. (For example, the common cold virus).

Evolution doesn't work by deciding on the best possible adaptation to an environment and then changing a species into that. If an organism has traits that enable it to reproduce more than others then that trait will dominate. It's not about the bets possible configuration, it's about survival.

Also as an aside microorganisms are well adapted to their environment which is very different to human environments.

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

Organisms don't adapt themselves either in an evolutionary sense, species do. It's an interesting discussion to what extent natural selection has been curtailed in humans but we still experience sexual selection, genetic drift and gene flow. Or to put it another way there are many processes by which evolution occurs other than natural selection.

 

[Yashbhatt]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

 

[Ryan_m_b]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Mutations can be negative, neutral or positive. Negative mutations decrease the chances of reproduction, neutral have no effect and positive increases the chances. If a mutation is positive then over time (how long depends on how positive it is aka weak or strong) it will proliferate through the species as organisms with the mutation reproduce more.

Whether or not a mutation is negative, neutral or positive is mostly down to the environment which provides context. It's the environment which determines what mutations will spread, e.g. A mutation that makes an organism red in colour will increase its chance of survival if it is in a red environment so it can be camouflaged. The appendix, along with most vestigial organs, could decrease in size and eventually disappear as they cost energy to produce and maintain which is a waste. But if the amount of energy wasted is negligible then it's not going to effect reproduction and so they'll stick around unless some other factor arises.

 

[bobze]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Tails aren't free to make. Think about it from a cost-benefit analysis.

 

[thorium1010]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Think of it another way , analogy like a person who hits the gym to build muscle size, does it frequently and will increase his muscle size. But once he stops it it will return to previous size , before he started his training.

It may not be a good analogy , but extend this over long periods of time , where the populations of a species has no more use for the particular organ , body tries to conserve energy over that period of time by simply eliminating or decreasing its size.

 

[Yashbhatt]

Now I get it. Thanks for explaining guys.

 

[Ygggdrasil]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

There's also the fact that it is easier to break something (a loss of function) than to improve something (a gain of function). Thus, if a certain function is not required, over time random mutations will tend to degrade the function.

 

[Hornbein]

Why does the arrow of evolution always point in the direction of complexity?

It's a good question. It doesn't always, but that is the general trend. It is possible that in the future things will reverse, if conditions change to favor it.

In the past one hundred years popular music and other entertainments have evolved to be much simpler.

 

[Yashbhatt]

Really? You don't think the winner of Pop Idol, or the X-Factor lack success in finding mates?

If it's all about reproducing, then there shouldn't exist any people with low sex drive by now, should they?

 

[Borek]

If it's all about reproducing, then there shouldn't exist any people with low sex drive by now, should they?

1. Just because they don't leave progeny doesn't mean similar combination of genes are impossible in the next generations. Compare with hemophilia.

2. In the case of men that's more complicated, but in the case of women it is perfectly possible to be completely passive, have sex just because of the social obligations, and leave progeny despite having no sex drive at all.

These things never want to be simple (which is why they are fascinating to research; sadly, they look simple, so people think they understand them, but then they find something that doesn't fit and they are sure they just falsified the whole idea).

 

[Yashbhatt]

1. Just because they don't leave progeny doesn't mean similar combination of genes are impossible in the next generations. Compare with hemophilia.

2. In the case of men that's more complicated, but in the case of women it is perfectly possible to be completely passive, have sex just because of the social obligations, and leave progeny despite having no sex drive at all.

These things never want to be simple (which is why they are fascinating to research; sadly, they look simple, so people think they understand them, but then they find something that doesn't fit and they are sure they just falsified the whole idea).

What you mentioned is correct but a person with more sex drive tends to mate often and produce more offsprings. So, isn't that a survival advantage?

 

[Ryan_m_b]

What you mentioned is correct but a person with more sex drive tends to mate often and produce more offsprings. So, isn't that a survival advantage?

Things are rarely so clear cut. For starters libido might not even be strongly inherited, in which case it would not experience a strong selective pressure. Whether or not one has a high or low libido might be primarily down to environmental factors which either have a long term effect (i.e. they caused a lasting change at some point in your development) or could be transient (i.e. job stress). It's also extremely likely that sexuality and sex drive are the phenotypic result of a huge range of genetic factors (as well as the aforementioned environmental). The capacity for sex drive could be inherited but not necessarily a specific level.

Even if libido was strongly inherited there are possibilities for why it might be a disadvantage. The hormonal differences between high and low libido people might be detrimental to health meaning that in the long term less offspring are produced. I'm not saying that's true, just offering it as an example of how you have to consider a range of scenarios.

 

[Yashbhatt]

That's quite complicated.

 

[SteamKing]

What you mentioned is correct but a person with more sex drive tends to mate often and produce more offsprings. So, isn't that a survival advantage?

Yes, up until he gets the bill for supporting all his offsprings. Then, it's a decided disadvantage. Plus, he must keep all his baby mamas separated from one another lest it become a deadly survival situation for him from them.

 

[Borek]

But there is an obvious grain of truth in the idea.

I have read in several places (I believe I should be able to dig the original reference if that's necessary) that woman in general tend to be more promiscuous around ovulation, and are more attracted to macho types. There is an obvious advantage to that - kids of a successful wanderer (sorry, I can't think of a better English word) are more likely to be wanderers themselves, and to spread their genes widely. At the same time being less promiscuous and more faithful at other times keeps the supporting male close by, and makes the progeny more likely to survive.

The deeper you dig, the more fine print you find.

 

[Ryan_m_b]

But there is an obvious grain of truth in the idea.

I have read in several places (I believe I should be able to dig the original reference if that's necessary) that woman in general tend to be more promiscuous around ovulation, and are more attracted to macho types.

A lot of studies on the behavioural effects of the menstrual cycle, particularly with regards to sex drive and mate selection, are very dodgy methodologically speaking. Here's one meta-analysis that shows that the notion is unsupported:

Meta-Analysis of Menstrual Cycle Effects on Women’s Mate Preferences
http://emr.sagepub.com/content/early/2014/03/24/1754073914523073.abstract

This doesn't surprise me in the least. When it comes to evolutionary psychology there's a lot of bias masquerading as science as various groups (often inadvertently) just try to gather data to fit cultural ideas and place a far too heavy emphasis on explaining behaviour through biology.

 

[Borek]

A lot of studies on the behavioural effects of the menstrual cycle, particularly with regards to sex drive and mate selection, are very dodgy methodologically speaking. Here's one meta-analysis that shows that the notion is unsupported:

Meta-Analysis of Menstrual Cycle Effects on Women’s Mate Preferences
http://emr.sagepub.com/content/early/2014/03/24/1754073914523073.abstract

Thanks. I am not following these things closely, so my knowledge is based on popular science books, not on the original research. In my defense, authors like Matt Riddley (Red Queen) or Cindy M. Meston and David M. Buss (Why Women Have Sex) look credible, and I am more than sure it was either in one of these books, or in both.

This doesn't surprise me in the least. When it comes to evolutionary psychology there's a lot of bias masquerading as science as various groups (often inadvertently) just try to gather data to fit cultural ideas and place a far too heavy emphasis on explaining behaviour through biology.

Plus one on that. I am sure there are behavioral/psychological things that can be explained as evolutionary traits, but I agree the idea is often abused.

Unfortunately it is a loaded subject so I guess both sides play dirty tricks, instead of cooperating to find out what the reality is. Sigh.

 

[Yashbhatt]

Yes, up until he gets the bill for supporting all his offsprings. Then, it's a decided disadvantage. Plus, he must keep all his baby mamas separated from one another lest it become a deadly survival situation for him from them.

That's only for humans and not other animals.

 

[SteamKing]

That's only for humans and not other animals.

Yes, but in Post #49, persons were specifically mentioned, not animals. It's also not clear if animals have what is known as a 'libido', or if they are simply responding instinctively.

In any event, if a given population of a certain species of animals overpopulates, there are often dire consequences. The local supply of food can easily be outstripped by the expanded population, leading to starvation and increased mortality for those animals and others. Hardly a long-term survival strategy. If the animal population must migrate in search of food, additional risk may be introduced, in the form of increased predation, movement to less suitable environs, increased incidence of disease from animals weakened by starvation, etc.

This is often seen with deer populations in and around urban areas of the US. Local predators are driven out by human habitation, the deer are treated as non-threatening wildlife (the 'Bambi' effect), the local inhabitants may even wittingly or unwittingly provide food for deer living nearby, and fewer people are willing or able to hunt the deer. As a result, the deer will increase their numbers over time since there are fewer natural checks on their population growth, providing increased hazards to unwary people by straying into roadways or near homes looking for food.

 

[Hernik]

That's only for humans and not other animals.

I can't think of a single species of animal with low sex drive.

Henrik

 

[Yashbhatt]

It's interesting as well as saddening to see that what we think of various emotions, loyalty etc. are not as amazing as we think of them but are actually there because evolution favors them.

 

[Ryan_m_b]

I can't think of a single species of animal with low sex drive.

Henrik

Animal sexual behaviour is extremely varied, as is parenting. Reproduction may occur at specific seasons, parental care might be involved in small numbers of offspring or not in many (so called R/K selection) and libido is not a constant factor but varies across development and in different environmental factors (libido drops off with age and can be affected by factors such as stress for example). Comparisons to humans are difficult due to the role sex has in socialisation (same applies to some primates).

Either way were really getting to the point where we're going around in circles. Getting back to basics: complex behaviours are rarely strongly associated with one trait which can be out under strong selective pressure. From now on it would be best if members start posting citations to research on this matter, paying very careful attention to the credibility of the papers (evolutionary psychology is a very controversial field).