IN THE BEGINING THERE WAS MAN?

[dmaiski]

you have a point in that it can be related to a trait that is beneficial to an organism, good examples of this are long legs, tails(no idea where we lost ours), and muscle strength

 

but there are also plenty of examples of really bad traits that are sexual, like a baboons red butt, a peacocks feathers, oversized antlers(on herbivorous species), bright colours(all the better to see you with), secretion of chemicals(musk, not a good thing when there are predators)

 

but this is getting too complex lets get down to basics (i say sexual bacteria are nice and simple)

lets say you have 1 mutated bacteria

its mutation makes it use 5% of its energy on making a chemical compound to attract more mates (bacteria already make such compounds as a sort of IFF system to identify each other)

5% is a lot of energy to spend on signalling, but it results in the bacteria being positively selected

conversely more fit bacteria, the ones that spend 5% less energy, are not selected for because the chemical marker is highly potent

 

you can argue all day whether it is or is not a beneficial trait for reproduction

but it is not a beneficial trait for survival, 5% for a bacteria is like chopping off your arm, its a fairly bad mutation

if this mutation did not promote mating, it would be selected out very quickly

 

 

[jp255]

but there are also plenty of examples of really bad traits that are sexual, like a baboons red butt, a peacocks feathers, oversized antlers(on herbivorous species), bright colours(all the better to see you with), secretion of chemicals(musk, not a good thing when there are predators)

 

The purpose of post 25 was to make you ask yourself, but are they really bad traits, or can they be good? There are many sexually reproducing species which you would say had bad traits as a result of sexual selection. Do you really think that natural selection would allow such bad traits to fixate in such a large number of species if they really were bad? sure it can happen, but in so many instances that you see today? what are the chances?

 

 

you can argue all day whether it is or is not a beneficial trait for reproduction

but it is not a beneficial trait for survival, 5% for a bacteria is like chopping off your arm, its a fairly bad mutation

if this mutation did not promote mating, it would be selected out very quickly

Overall it is a good trait in the long run then. Survival is only one aspect of evolution, reproduction is just as critical. So you should be asking yourself, what is the net benefit or loss of fitness. Rather than down playing the importance of reproduction.

[dmaiski]

The purpose of post 25 was to make you ask yourself, but are they really bad traits, or can they be good? There are many sexually reproducing species which you would say had bad traits as a result of sexual selection. Do you really think that natural selection would allow such bad traits to fixate in such a large number of species if they really were bad? sure it can happen, but in so many instances that you see today? what are the chances?

 

 

 

Overall it is a good trait in the long run then. Survival is only one aspect of evolution, reproduction is just as critical. So you should be asking yourself, what is the net benefit or loss of fitness. Rather than down playing the importance of reproduction.

 

overall its a bad trait, the species of bacteria will not survive because of that trait when in competition with another species

that 5% energy loss in a bacteria is fatal in the long run, it means it CAN NOT COMPETE with other species

the sexually favourable trait gave it an advantage in the local area(its species) while at the same time giving it a massive disadvantage in the global field (being wherever it's habitat is)

 

that is the point i am trying to communicate to you

and yes this trait will be passed on, because sexually speaking it is highly favourable

(other species do not care how sexy you are, your big red ass is lunch stupid baboon)

not a valid statment because baboons have no real predators

Edited September 13, 2012 by dmaiski

[jp255]

I'm not really sure what you are getting at, but I know that traits have varying fitness depending on the environment. That is obvious.

 

Post 25 was lost on you because you are still going on about bad sexual traits. Show me evidence that they are bad. Pointing out the obvious handicaps of the traits is not enough to categorise a trait as bad. That is what post 25 is saying.

[dmaiski]

that is just a philosophy argument:

if you are being very strict, any trait that lower the competitive advantage of a species is bad

if you are being a bit more liberal, any trait that lowers the species competitive advantage to the point of extinction is bad

if you are being very liberal, no trait is bad because they are, in the end, natural occurrences that are bound to happen

 

i was looking at it from the strict perspective and decided that saying "specific disadvantageous traits that lower the survivability of the individual by lowering the competitive advantage of the species against its major competitors, while still being selected due to a species specific advantage through an increase of the likeness of the trait being passed on by sexual reproduction" could be abbreviated to "bad" and people would understand.

 

 

 

 

I'm sorry I was foolish and optimistic, I forgot that this is the internet...

 

 

[jp255]

i was looking at it from the strict perspective and decided that saying "specific disadvantageous traits that lower the survivability of the individual by lowering the competitive advantage of the species against its major competitors, while still being selected due to a species specific advantage through an increase of the likeness of the trait being passed on by sexual reproduction" could be abbreviated to "bad" and people would understand.

 

 

It is inappropriate to label the trait "bad" because no where in that sentence is the mean fitness of individuals with said "bad" trait compared to the mean fitness of individuals without said "bad" trait. Post 25 was lost on you.

 

Anyway, you need to support that statement with evidence that shows partner choice/reproduction was already biased (and not variable within the population) towards the "bad" trait before the "bad" trait rose to fixation/high frequency as this is practically the only way such a bad trait can rise to fixation (the survival impediment of the "bad" trait would be more than corrected for and instead be positively selected for). Essentially, you'd have to show that the biased "bad" partner choice is free from selection (because it cannot vary in the population) itself because in your scenario it would have been selected against and eliminated early on.

 

In a nutshell, it requires much more than "this bird has an excessively large tail, it is bad" to actually label it as bad. Indirect genetic benefits must be considered, which is what post 25 shows an example of.

 

look up the handicap principle. Non-uniform fitness does exist within populations, and evolution can take advantage of anything that is associated to above average fitness individuals.

[dmaiski]

look up the handicap principle. Non-uniform fitness does exist within populations, and evolution can take advantage of anything that is associated to above average fitness individuals.

 

yes, that is the verry liberal view of "if evolution didnt get rid of it, it must be good"

it would be a great view if evolution was a "perfect" system, without any loopholes

loopholes like pheramones, which allow a "weak" individual, to be extremly sucsessfull at recproduction, even if the other traits the individual posesses are disadventageous

 

but thats too complex an example

(back to that bacteria i was discussing)

the chemical it produces, forces other individuals to reproduce with it

this subverts the process of natural selection, random mating, and spreads whatever traits that individual had,

the benificial ones and the non beneficial ones, throughout the whole species, untill the whole species poseses the mutation for the chemical

if that individual had numerous bad traits, then the whole colony will now posess all those bad traits in high numbers

this will result in the whole colony being selected out by evolution

 

its an example of how a sexualy "good" trait can be "bad" for a population by introducing disadvantegeous traits that come packaged with the "good" sexual trait

and this ignores enviormental selection, in favour of sexual selection, and is not allways beneficial to the species as a whole

also has anyone heared of http://en.wikipedia.org/wiki/Sexual_selection#Exponential_growth_in_female_preference

[jp255]

yes, that is the verry liberal view of "if evolution didnt get rid of it, it must be good"

Except my view means nothing and is irrelevant. I only deem a sexually selected trait "bad" if it has risen to high frequency even if it is not associated to individuals of higher average fitness or if it results in lower average fitness. To me, this is required. I think it is absurd to describe a sexually selected trait as "bad" without trying to detect possible fitness benefits (indirect and direct).

 

You are referring to the Fisherian runaway. Yes this is a possibility, but this is not true for all sexually selected traits. Using your view point based on this to call traits "bad" isn't really appropriate. A more in-depth examination of fitness benefits is required.

[dmaiski]

but i was talking about a specific trait at the start of this post, the SRY region, is a “bad” mutation.

it dropped the fecundity of the whole species by 50% in a single go.

 

it may not have been deadly, but it certainly didn’t do much good

 

and it was a runaway trait(not Fisherian, closer to a viral trait in the way it spread)

 

 

on the upside, its estimated that it will completely die out in 100milion years or less

 

 

 

yes i am using "viral" in an incorect way, but there is no better way to describe it

 

 

[MattyG]

Found this video today. Thought it might be helpful.

 

[jp255]

I can't watch that video right now, but I'll look later.

 

but i was talking about a specific trait at the start

of this post, the SRY region, is a “bad” mutation.

it dropped the fecundity

of the whole species by 50% in a single go.

 

I think we just have very different opinions on what is required in order to call a trait bad. Now you are pretty much contradicting yourself, I thought we agreed that overall sexual > asexual in terms of efficiency. You are not really considering the positive aspects of traits and weighing up the pros and cons of them..

 

 

[dmaiski]

I can't watch that video right now, but I'll look later.

 

 

 

I think we just have very different opinions on what is required in order to call a trait bad. Now you are pretty much contradicting yourself, I thought we agreed that overall sexual > asexual in terms of efficiency. You are not really considering the positive aspects of traits and weighing up the pros and cons of them..

 

 

 

unfortunately, you don't understand the meaning of sexual reproduction

"Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve homologous recombination."

thank you wikipedia

 

nowhere in that definition dose it say that the 2 individuals must be "male" and "female"

in fact most sexual bacteria are all "female" they just reproduce by mixing their DNA together

 

"male" and "female" sexes came about through a rouge mutation, that caused sexual organisms to differentiate into 2 sexes, where 1 was incapable of producing offspring while the other was. since the species was sexual this trait spread to other individuals(and probably killed off a few species in the process, by turning all offspring "male"), this spread was stopped when it was finally locked down to a single chromosome (the Y chromosome, 95% or it cannot recombine at all), and thus "male" and "female" was created

 

 

 

 

[jp255]

nowhere in that definition dose it say that the 2 individuals must be "male" and "female"

Yeah. There are not many species which sexually reproduce without having two sexes though, I don't know of any.

 

in fact most sexual bacteria are all "female" they just reproduce by mixing their DNA together

Horizontal gene transfer is something else entirely.

[dmaiski]

Yeah. There are not many species which sexually reproduce without having two sexes though, I don't know of any.

 

 

Horizontal gene transfer is something else entirely.

sexual reproduction using 2 genders is more conducive for multicellular organisms, prokaryotes use horizontal gene transfer as a method of sexual reproduction because its just easier to do when you are single.

 

i would tentatively say protosists have no gender, but reproduce sexually(im not that good on the nuances protosists biology)

also reptiles... they have no Y chromosome, "sex" is determined by temperature

and plants... natural hermaphrodites(they have both genders)

 

another thing, i would not expect genderless reproduction to persist in nature for long(unless the genderless species was extremely isolated, genetically incompatible, or single celled)

 

sexual reproduction probably arrived in the world 1.2billion years ago near the end of the Mesoproterozoic era so its been around for a long time

a trait for gender, once it arose, would be extremely contagious, since it allows the individual to literally screw everyone over, with minimal energy expenditure.

 

its basic maths form that point on:

same sex reproduction: 1 offspring per individual per cycle

reproduction using a "male" as the genetic contributor and a "female" as the incubator: "male" is capable of fathering 1000 children in the same time period

this would result in colonies becoming all male, and dieing out(initially after trait was created) as the trait would spread throughout the genetic structure of the organism

 

this would go on till 1:1 "male" to "female" equilibrium was reached, by isolating the SRY precursor to the Y chromosome precursor, or some other mechanism

 

ofcource this is in the end just a very good educated guess as to what exactly happened, i wasnt around back then(at least not in multicellular form) to record the events

Edited September 19, 2012 by dmaiski

[CharonY]

Yeah. There are not many species which sexually reproduce without having two sexes though, I don't know of any.

 

 

Horizontal gene transfer is something else entirely.

 

As Ophiolite mentioned, the majority of species reproduce asexually. Bacteria have sex, but do not reproduce in that manner.

On top of that there are species who can reproduce sexually as well as asexually (usually by having different life cycles).

That being said the evolution of sexual reproduction is still an unsolved problems. Most models have trouble find that sexual reproduction actually has a benefit over asexual reproduction. The reason is that it is associated with a two-fold cost.

All things being equal, an asexually reproducing population will grow at twice the rate as a sexually reproducing one (i.e. the sexually reproducing population will only inherit half of its genes to its progeny).

Most assumptions of fitness increase due to increase in genetic variation due to sex do not overcome this barrier (this is presumably why bacteria utilize sex, but not for reproductive purposes).

 

That being said, some newer works offer potential solutions to this problem, but it is far from trivial or being solved conclusively.

[jp255]

Yeah, I understand the point about asexual being common. To convey the likihood that sexual is more efficient in terms of rate of evolution I mentioned the strong correlation of sexual reproduction to high generation time. This is pretty obvious, but you do raise a good point about some species using both mechanisms. However, there are various indicators even within these species that sexual is extremely useful in times of stress. Some species switch to sexual reproduction when under stress, I'd have to look for the link but I think it was yeast I read about.

 

 

All things being equal, an asexually reproducing population will grow at

twice the rate as a sexually reproducing one (i.e. the sexually reproducing

population will only inherit half of its genes to its progeny).

This is a very high cost for sure.

 

Most assumptions of fitness increase due to increase in genetic variation due to

sex do not overcome this barrier (this is presumably why bacteria utilize sex,

but not for reproductive purposes).

 

That being said, some newer works

offer potential solutions to this problem, but it is far from trivial or being

solved conclusively.

 

The way in which sexual and asexual comparison are being done are not that realistic. http://jhered.oxfordjournals.org/content/101/suppl_1/S142.long is an example of a fairly recent paper. Papers like this don't include non-random recombination into the models, which is an advantage of sex. The gene coding for this function has been under very high selection and is one of the fastest evolving genes, citation in the other thread.

 

Allowing for selection of the best recombination pattern allele is an advantage not considered. Maybe this shouldn't be taken into account when considering the evolution of sex though, not sure when non-random recombination evolved.

[dmaiski]

why are you trying to prove that sexual is better then asexual?

they are both good for their own things

 

asexual is good for maintaining a genetically stable colony of cells(did you know?: a human is a fine example of a genetically stable colony of cells)

 

sexual is good for spreading a trait that is useful to your friends(like email, and with just as much spam mail in the mix)

 

 

ive thought of a great technology analogy to this:

think of sexual reproduction as a certain board commonly referred to as "the asshole of the Internets"

think of asexual reproduction as a blog page managed by one person

 

with sexual reproduction, you sometimes get a real gem, that will be spread everywhere(example: caturday(its today btw))

but you also sometimes get real shit that is spread everywhere (a fine example is this http://www.youtube.c...h?v=qmPmIJyi0sc)

 

with asexual reproduction, you have 1 person managing the blog

it varies with their moods, sometimes changes with outside influence

but it is allays "their" blog, no one else has creative rights to it

the rate of change is slow and steady, and usually retains the original ideology

 

 

 

 

also you can make this an analogue of peer-peer sharing against direct downloads

 

it shows the advantages and inefficiencies of both systems

 

go google it, I am not going to try to explain P-P sharing to the unknowing

 

(its just a recipe for pain)

Edited September 22, 2012 by dmaiski

[jp255]

I am interested in the process of evolution. What do you offer to explain the high amount of sexual reproduction among species with high generation times, and the opposite for species with very low generation times (where asexual reproduction is the main mechanism)? Your creative analogies?

 

sexual is good for spreading a trait that is useful to your friends(like email, and with just as much spam mail in the mix)

 

How do you propose I spread my traits to my friends then? Again, HGT =/= sexual reproduction.

[dmaiski]

How do you propose I spread my traits to my friends then? Again, HGT =/= sexual reproduction.

 

WELL GENERALLY SEX...

yoU know meiotic division

tab a goes into slot b, and so on

(sorry, but you really set yourself up for that one)

 

as for species with high generation times... that’s simple

ill explain my logic step by step:

1. im assuming you are referring to multicellular species

2. most of the cells in a multicellular creature reproduce asexually

3. asexual reproduction involves splitting the organism(you know like planaria)

4. sawing something like a human in half is not productive (they generally die)

5. thus you must use a system that allows the organism to reproduce without being sawed in half

(i was just setting the background a bit)

 

now once you acknowledge that:

1. you can acknowledge that asexual reproduction is not conducive to multicellular life

2. sexual reproduction is conducive to multicellular life

3. the long generation times are a side effect of being so big

(you do realize that humans are amazingly, colossally, ginomusly, humongous creatures)

 

now why did the two gender system in mammals evolve?

1. lets say you have a organism that is reproducing sexually without gender

2. and a mutation happens that makes it male (there is no SRY region for female...)

3. this male can then reproduce with everyone in its colony in a single generation

4. and then the whole colony has male, and female genders

5. and the traits proceed to spread, and persist

(also since the SRY came from a common ancestor, and it is extremely beneficial towards the "male" i would guess this development happened very early on in the development of sexual reproduction)

 

 

i think i have explained how i think it could have come about in sufficient detail, but feel free to question.

[jp255]

WELL GENERALLY SEX...

yoU know meiotic division

tab a goes into slot b, and so on

(sorry, but you really set yourself up for that one)

My unborn offspring, which don't exist yet, are my friends? They arn't on my facebook list tho!

 

 

i think i have explained how i think it could have come about in sufficient

detail, but feel free to question.

 

I guess I should have said before, but the I am interested in the explanation which takes into account fitness/selection. That explanation only tries to asnwer how the situation arose, not why.

[dmaiski]

how did this happen... the real answerer is "f**k if I know" (to quote popular language)

evolution is blind, and dose things for unfathomable reasons

 

my best guess is this:

1. lone bacteria began to form aggregates (the aggregates helped the colonies survive)

2. the aggregates individual bacterium in the aggregates began to form codependency on each other

3. the aggregates reproduced asexually (ive already explained why this isn’t that good an idea)

4. the aggregates began to specialize the bacteria in the aggregate into subsections

5. a specialized cell line was derived specifically for reproduction (to allow some control over the process)

6. the aggregates was still asexual

7. the aggregates mutated to develop sexuality

8. the advent of the "SRY precursor" and, everyone gets screwed

9. tada sexual species!!!

 

*3-7 could have happened in any order

**this may look short but probably took at least half a billion years to happen

***this is probably not an accurate representation, contact architect for exact dimensions

****this is a very general representation of one possibility of what could happen, its the one i like, there’s another 100 where this one came from

 

 

[CharonY]

I am interested in the process of evolution. What do you offer to explain the high amount of sexual reproduction among species with high generation times, and the opposite for species with very low generation times (where asexual reproduction is the main mechanism)? Your creative analogies?

 

I am not sure why this is supposed to be relevant. But simply put, sexual reproduction is more time intensive compared to asexual reproduction. Often specialized cells (gametes) have to be produced, then recombination with other cells are necessary etc. etc. Even in simple cells like yeast meiosis takes hours.

During that time other organisms are already done reproducing for a couple of generations. Again, the question is more, why bother with it?

[dmaiski]

i would guess once the trait developed it was impossible to drop, and somehow managed to survive

 

the only way it could be dropped was through complete extinction